Λίνεαρ με τη λυχνία YC156

This particular amplifier deck project started almost thirty years ago. Around 1973, the original chassis was modified to use a 4CX1000A. The YC156 triode is the third tube type to be used in this chassis. Why? Well, I was always unhappy with the 4CX1000A, and, I always wanted a tube with handles! This photo might show you why. That's a 4CX1000A, a YC156, and a 4-400A for comparison.

The following photos show the progress as I stepped through the conversion. This one shows the chassis after all the 4CX1000A parts have been stripped off. The large hole just behind the load capacitor was where I mounted the modularized tube socket and associated components. This approach made it easier to change tube types.

This next photo shows a new aluminum plate installed for the YC156 to mount to. This tube bolts right to the chassis, no socket to mess with. The small holes are for air flow from the lower pressurized compartment to the tube anode. Also shown are the filament transformer, the turns counter for the roller coil, and what passes for a band switch.

The hardest part of this project was dealing with the sheer physical size of this tube. There was no room for the proper chimney to mount, so I had to improvise. G10 fiberglass-epoxy board was used to fabricate a square box. The square shape was necessary because of the limited space. The plate choke consists of #26 wire close wound for 4 inches on a 1 inch diameter G10 form. The wire ends are held in place with Scotch #27 tape. The whole thing was given several coats of MIN-WAX exterior urethane spar varnish.

This one shows the bottom of the chassis. An EMI filter on the AC line is in the upper right. The bias circuit is in the upper left corner. A temporary cathode pi-net for 40 meters is dangling on the end of the coax. This will be replaced with a multi-band board later. The blower is small. Much smaller then I would like. However, if I can believe the Eimac data sheet and my manometer, I can dissipate 1800 watts continously at 50 degrees ambient temperature and not exceed any seal max temperatures. More than enough for 1500 watts out. HI!

Here is a top view of the business end. The roller coil is all ceramic insulation with multiple rollers for the tap point. I have not had any contact arcing or localized heating, so far. A roller coil would not be my first choice for a serious amplifier, but in this case, it's a good deal. I plan to experiment with different tube operating conditions and the roller coil will allow me to change match impedance and Q without re-winding the coil. The "bandswitch" is small because all it has to do is select the correct cathode network relay and loading cap padder. The anode DC blocking cap is made from four TV type 20kv 500 pf, ceramics. These work pretty good as coupling caps, but not so good as tank components. All tank interconnects are made from 1/2 inch copper strap. Most of the connections are made with copper or brass bolts and nuts, although a few had to be soldered.

And finally, the front panel. The layout was determined by the location of holes used in the past. The dark areas are painted aluminum plates covering up excess holes. If I ever finish this experiment, I might fill the extra holes with Bondo and repaint. Since this project has been ongoing for all these years, I doubt if I'll live long enough to have to worry about that!

Κατασκευή με 3 λυχνίες 4-400A

Like all my amplifier projects, this one started out as a "what if?" For several years I had been using an amp with two 4-400A's in parallel, triode connected, in a grounded grid mono band 40 meter chassis. The chassis was an experiment that was never quite finished. It used cross flow cooling similar to the Heathkit method and proved to be very reliable. Although I could get 1500 watts out with the pair of 4-400A's, it took a lot of drive at the anode voltage I was running. At this level of output, I was seeing some output compression. After with this for a while, the "what if" process started up and the idea of running three tubes in parallel came to be. I had plenty of broadcast "pulls" and three spare sockets on hand. The biggest obstacles were filament supply and cooling. With a total of 45 amps current required to light all those tubes, both the transformer and the filament choke were cause for concern. I found a transformer capable of that current in my "Junqe Box" but when connected to three tubes through a typical filament choke, the voltage across the tube pins was less than the minimum required by the tube manufacturer. Eventually, a choke was wound with 10 gauge wire wrapped with teflon tape (for heat resistance) that was sufficiently low resistance to  minimize the voltage drop.

Cooling was assured by having two muffin fans blowing across the tubes and tube sockets. The sockets are mounted on a sub chassis which is mounted to the main chassis with threaded rod standoffs. Here's what the underside of the sub chassis looks like:



Notice the coax for the cathode RF drive and the ugly filament choke! Control and screen grids are connected directly to the chassis with copper strap. Many years ago I gave up on the idea of monitoring grid current in this type of grounded grid amplifier. I always ran what ever drive I needed to get the output power I wanted regardless of what the grids were doing, so why bother? You can't hurt the tubes in normal operation and as long as you stay out of compression, you can't "overdrive" them.

All of my HF amps are installed in a rack which provides selected RF and HV lines and also provides what metering is required. This makes it easier to build each individual amp. The HF amps are all built behind 19 inch rack panels. The entire chassis for this amp was fabricated from salvaged aluminum sheet. All of the components were also acquired from swap meets or salvaged equipment. Some of the parts date back to old TV sets I salvaged out in the early 60's! A few parts are from old WW II military units acquired and salvaged out through the years.

Monobanders are really simple to build. Here's a photo looking from top left:



In the upper right is a small filament transformer which provides the DC center tap for the cathode return. The 0.25KVA filament transformer is just below it. The diode string provides a small amount of cathode bias. The two muffin fans pull air in from the right side of the chassis and exhaust it out the left side. I wanted to use two larger size fans but I just couldn't squeeze them in the space I had available. In any case, they seem to be able to cool things adequately. Top center and top left are the resistors and relay for the filament in-rush current limiter circuit. Left center at the coax connector is the pi-network input matching circuit. The anode RF choke is salvaged magnet wire wound on a piece of teflon rod. Notice the parasitic suppressors. I had hopped that I could build this thing in a way which would not require them. The last three amps I built didn't need them and I thought I was on a roll. Oh well! It turned out this thing made a great 190 MHz oscillator. No science was involved in the suppressor design. Since no 10 meter operation was contemplated, I didn't have to worry about too much inductance so I just made them "big enough"!

Looking at it from top right:



Air variable caps are used for both output tune and load functions. No need for an expensive vacuum variable in this application. A couple 100 pF doorknob caps are used  to increase the load capacity. No screens are on the fans in this photo. I didn't have the right kind of hardware cloth handy and didn't want to hold up the project. If an when I ever get some, I might put it on. Probably never happen!

Looking from top rear:

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Along the rear apron left to right  RF input, AC mains input, HV input, and RF output. Most of my recent amp projects have an AC connector salvaged from old computer power supplies. I used to always step on the dangling line cord, now the line cord stays in the rack. The tank coil is wound from #10  bare copper wire. The first coil I made was from 1/4 inch copper tube. It was a thing of beauty but didn't fit well in the space allocated. The 10 gauge is good enough for 40 meters and is somewhat easier to work with. The rear chassis cover is made in two parts. The bottom piece stays put and has all the connectors on it. The top piece is easily removed for modifications. Notice I said "modifications" instead of maintenance? I seldom do maintenance, because by the time the thing breaks, I'm tired of it and want to modify it into something else! The input network and the output coil can be changed in a matter of minutes if need be and I can have this on 80 or 20, whatever, quite easily.

Smoke test:



Here the amp chassis is placed in the rack and powered up for some testing prior to final assembly. This is at full power output running a string of fast dots. The bright orange spot on the left most tube is an artifact of the photograph, they all run the same color in reality.

Covers on:



As you can see here, the left side of the chassis is covered with a sheet of perforated aluminum. All other surfaces are sealed so that the air flow is from right to left across the tubes and other components that require cooling. I was worried about hot spots, but it seems to work OK.

In the rack:



The finished 40 meter monobander is placed in the rack right above the 4 x 813 amp deck. Some day I'll have to finish the detail work on that one! But that's another story!

Like all my amplifiers and most everything else I build, I have no documentation! Don't ask, you won't get a schematic because I don't have one. All the RF stuff is right out of the text books and uses commonly available computer software to do the calculations. I just wire it up as I go and try to make it look like an amplifier. I do this for fun, not to prove I'm a world class RF engineer.

Ενισχυτής με 2 λυχνίες 4-400A

This deck started out many years ago as a class C AM kilowatt. By the time I got it, it had been poorly converted to a Grounded Grid linear. I completely rebuilt it using most of the original components and chassis parts. The astute observer will note the ubiquitous TV doorknobs as anode coupling caps, vertical mounting of the vac variable, and, of course, the traditional burnt resistor parasitic suppressors. The chimneys are Coleman lantern parts. I wouldn't do that again, but at the time, it was a cheap way to go. 4-400A's are a good choice for a TCGG low cost amp project. This one has worked out so well, the design has been stable for many years. The only mod made since the original reconstruction has been the addition of a soft-start circuit for the filaments. Note the relay and resistors attached to the chassis with RTV.

Ενισχυτής με 4 λυχνίες 813

This amp project was an exorcise in cheap! The design criteria was to use only components in the "JUNQUE BOX". Turned out I had to purchase a transformer and a half dozen resistors, but everything else was parts on hand. Even the chassis was constructed from salvaged aluminum sheet. The plan was to make it bandswitch 160 through 40, but a problem with the bandswitch has caused it to be fixed tuned on 160 for the time being. If I can find an inexpensive turns counter, I will change the air variable out for a vac variable and solve the switch problem. Note the absence of any form of parasitic suppression devices. The 813's are very well behaved. I doubt that you could make them oscillate above 35 mhz even if you wanted to. I don't believe there is a better choice of tubes for an inexpensive, easy to build, utterly reliable amplifier. No tube matching is required. If I am reading the date codes correctly, one of the tubes is pre-war (WW II) and the other three are scattered through the '40's. This amp project is far from finished, but it is cute enough to warrant it being shown off!

2 λυχνίες 3-500Z για τα 80 έως και τα 10 μέτρα

( NOTE: Please do not ask for schematics or a how-to for this amp. This article is meant to give you ideas for your own custom design. Every bit of documentation in existence is presented in this article. I build them as I design them and keep no notes!)

This was another "junque box" project and had several objectives, some rather unique. I started thinking about this design when it became obvious that I needed to re-build my old trusty 2 x 4-400A amp. That amp deck had never been upgraded to cover the WARC bands and was a drive hog. With a 100 watt exciter, it wasn't possible to achieve a full 1500 watts output (at the available anode voltage).

So the first objective was to create a design that would produce a minimum of 1500 watts output on all bands 80-10 with less than 100 watts of drive power (and use the existing power supply).

The second objective was to wind up with an amp deck that integrated into my existing facilities with a minimum of effort and to be easy to use in my HF operating environment. This meant that the tubes selected had to be "instant on" and precluded the use of the Russian triodes or 8877, etc.

Third was a self-imposed mandate to NOT buy anything to build this amp. I have been gathering and saving components for 50 years, time to use them up! If some of the parts in the photos look old and crusty, it’s because they are! Included in the final design are parts from TV sets, salvaged military and commercial radios, computers, and various other electronic devices. Some date back at least 50 years!

Fourth was to make the thing "look better" than most of my projects. I always start with good intentions but after all the "mods" and "improvements", my projects usually look like the junk they were made from.

The fifth (but not last) objective was to try out some circuit "tricks" and "do-dads" that have been on my list of improvements needed on some of my other amps.

The first step in any amp project is the selection of the major components. Using the above objectives as a guide, I rummaged around in the old "junque box" looking for the right parts. I had a NIB pair of Amperex 3-500Z's so that part was easy. I also had a pair of Eimac air system sockets that I had picked up over thirty years ago so that was a match. Digging deeper produced a chassis, some coils and caps, a few switches and a bunch of smaller parts. A long time was spent placing the possible parts on the chassis and moving them around for the best compromise layout. Several times it was necessary to toss a component back in the "junque box" and look for a better fitting part.

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Here’s a photo of the top of the partially assembled chassis.

In the above photo, you can see the tank components, tube sockets, filament transformer, and fans. The black object just in front of the filament transformer is an air duct which directs the air flow from one of the two fans down into the chassis bottom. I was worried about cooling the tubes during RTTY operation and this was the solution I came up with. It provides ample air flow while meeting all the necessary mechanical requirements.

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In this next photo, we are looking at the back of the partially assembled chassis:

In the rack where this amp will reside, there is no clearance on the top of the cabinet. Air must be taken in from one side (or the back) and exhausted out the other side. The chassis base I had “in stock” was only 3 inches high so that prevented a fan from being mounted below. The duct was needed to allow the fan which cools the tube pins to be placed above the chassis where there was room to mount it.

On the right you can see the screened exhaust port. In operation the ducted fan pressurizes the bottom and forces air past the tube pins. The other fan moves a lot of air across the tube anode seals. Both air streams exhaust out the right side. The fans are speed controlled, more about that later.

The sides, top and bottom of the cabinet are made from salvaged aluminum sheet cut to size. The chassis base is a commercial Bud product that I had “in stock” as well as the 19 inch rack panel. The pieces are screwed to ½ inch aluminum angle stock.

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Here’s a shot from the side:

In this shot, you can see the feed-through caps which the cathode network relay control lines pass through. The small coax is RG-142/U and connects the PI network to the output connector located below the chassis. Both this coax and the HV lead (seen between the tube sockets) caused me some grief. I wanted to drop them straight down but there was no easy way to do that due to components below the chassis. They had to be routed across the top to a place where I could pass through without mechanical interference.

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This view shows the top of the chassis with the tubes installed. Except for a few minor components, it is complete:

The silver plated inductor on left is the 10 meter tank coil. It actually has one turn too many for optimum "Q" but since it worked out OK, I just left it as was. The edge wound inductor used for the remaining bands actually has one or two turns too few for optimum 80 meter tank "Q", but it too worked out OK so I left it alone as well. The edge wound inductor actually has a lower measured Q than a same size same inductance coil wound from heavy wire or tube. It was used it because it was on hand and it was very easy to install the band taps with the matching clips.

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Here's a close up of the tubes. The parasitic suppressors are copied from the Eimac 3-500Z data sheet and had to be replaced after the first time 10 meter operation was attempted. The inductance was way too high. I wound new inductors with approximately half the inductance and replaced the metal film resistors with Ohmite OY's. The small inductor you see just above the left hand tube is used for the "L" network for 10 meters. This compensates for the high output capacitance of the tubes and layout. Without the "L" network compensation, the tank "Q" on 10 meters is too high.

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Moving on to the bottom of the chassis:

 This photo was taken before the cathode matching network board was installed. Top left is the adjustable power resistor used for the filament inrush current limiting. Below that is a 6.3 volt filament transformer connected as a line boost. The filament voltage at the 3-500Z pins was right at the low end of the spec, so I put in the boost transformer to raise it to the middle of the spec, allowing for minor live voltage variations. Below the boost transformer, you can see the hole and air duct for the top mounted fan.

If you look closely at the tube sockets, you can see that the grid pins do not run directly to the chassis. They are bypassed to RF ground with three different sized capacitors on each pin.  There is a 250 pF Unelco mica UHF capacitor connected between the pin and a copper strap bolted to the chassis. These are the same capacitors that are used for solid state UHF amplifiers and have extremely low stray inductance and a series resonance in the microwave region. In parallel with each of the Unelco caps is a 1500 pF disc ceramic cap and a 0.01 uF disc ceramic cap. This configuration eliminates all the usual problems associated with bypassed grids and is RF-wise equivalent to a direct ground connection. Having the grids DC isolated from ground makes bias and metering much easier.

At the lower edge of the image, there is a 28 volt transformer which provides power for the fans, the control board, and the cathode network relays. This transformer has AC power applied at the same time as the filament transformer.

Unlike all the rest of my amp projects, this control board has multiple functions. Usually I make separate modules for the filament inrush limiter, bias, etc. This time I thought I had my act together enough to put them all on one board. This proved to be a mistake and in the future I will put each function in it's own module.

Filament inrush current limiting is accomplished with a power resistor in series with the line side of the filament transformer. A set of relay contacts shorts out the resistor after a preset time delay. The value of the resistor was adjusted to have the initial inrush current be the same as the secondary inrush current. Next time I will use two stages to get better control of the inrush current.

The relay coil is supplied from the 28 volt supply through a series resistor and a parallel capacitor. The relay is a "TV power" type and has a 9 VDC coil. The capacitor value was selected to allow enough time delay for the filaments to reach equilibrium before the realy energizes shorting out the current limiting resistor.

The 28 VDC supply is a positive ground supply. I did that to make the grid bias circuit easier. With the grids above DC ground it made sense to have a grid bias system instead of the usual cathode bias arrangement. The bias regulator consists of a common adjustable three terminal regulator and a darlington pass transistor configured as a shunt regulator. It has sufficient voltage adjustment to allow the Eimac or the Amperex tubes to be used. It will handle several amps of grid current.  The grids are routed to the bias supply through a 1.0 ohm resistor. Leads from that resistor are brought out to jacks on the rear panel allowing grid voltage and current to be measured. I do not normally monitor grid current during operation.

The two fans are 28 VDC muffin fans. Each one will provide sufficient air through the two air system sockets to meet Eimac's cooling requirement for 500 watts dissapation for each tube. With two of them running the noise level is pretty high. It turns out that with only the filaments running on the tubes a lot less air is required for cooling so I decide to slow the fans down when max air flow was not required. The DC type fans allow the speed to be easily reduced by simply reducing the applied voltage. A series resistor is placed in the 28 VDC line and switched out with an opto-coupled relay. The tube cathodes are returned to ground through three 3 amp diodes. Not only do these povide some measure of safety bias in the event of a bias supply catastrophy, the small voltage across them triggers the opto-coupled relay. The fans go to full speed anytime current flows through the tubes and drops back to slow speed when the tubes are not conducting.

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The next shot shows the cathode matching network board in place:




A printed circuit board was contemplated for this module and rejected due to the fact that it would be a one of a kind board. I could not justify the time and expense required for that. A piece of double clad copper board was cut to size and the relays glued to it dead bug style. Not only is dead bug cheaper, it allows shorter leads between the coils and caps and has lots of ground plane to connect to. The relays are SPST 9 volt coil jobs that I had procured some time ago for another project and didn't use. Each pair of band related relay coils are connected in series and routed to the proper band switch position. The -28 VDC source supplies power through an appropriate dropping resistor for 18 volts across the series coils.

The PI matching networks are designed for a Q of 2 and are constructed with small torroid cores and small silver mica capacitors. Several small value caps are put in parallel to give the correct capacitance. Load resistors were temporarily connected from the tube cathodes to ground and the individual matching networks are adjusted for best return loss (SWR) by squeezing/spreading the turns on the torroids and/or altering the value of the capacitor on the tube side ot the network. Because the correct torroid material and silver mica caps are used, the network efficiency is very high. If a builder tries to shortcut by using slug tuned coils and/or ceramic caps, the input efficiency will suffer and more drive will be required. An input SWR of 1.1:1 or less is obtained across all 8 bands except for the top end of 80/75. That band is just too wide!

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The next photo shows the completed amp deck installed in the rack:

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 And the full rack with some of my other HF amp decks. Top one is the 3x4-400A deck for 40 meters. Next is the 4x813 deck used on 160. Below the meter panel is the 2 x 3-500Z deck and bottom is the YC-156 deck. At the very bottom is a HV supply (for the 6 meter GS-35B amp not shown here).





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And here is the 2 x 3-500Z deck in the rack from behind:



At the time of this writing, this amp has been in operation for several months. It produces at least 1500 watts output, key down CW, for 65 watts drive power from 8-10 meters. It is stable, easy to tune, and quiet during RX periods. It fits my requirements quite well and I consider it to be a success. Although I did a few unconventional things in the design, the results have proven the usefullness of thinking "outside the box" when designing a custom amp.

Addendum: Since the amp requires only 65-70 watts drive for optimum performance, and since I can never remember to turn down the power on the exciter, I made up a 1.5 dB attenuator and placed on the input.


With the attenuator in place, I can leave the exciter run at full 100 watts output and not worry about overdrive. The resistors are 3 watt metal film and the assembly can run 100 watts input power key down. The return loss from 1.8 through 55 MHz is more than 30 dB.

Κάθετη κεραία για τα 160 μέτρα

This is a 90 foot tall top loaded vertical for 160 meters. It is constructed from aluminum irrigation tubing and has four sets of four guys each. The top guys also serve to support the top load wires.  It has a "temporary" wire  stub about 68 feet long  hung off the side to provide operation on 80 meters. More details are pictured below.

The  most important part of any vertical antenna system is the ground. I like to put the radials in the ground before putting up the antenna so that the antenna and guys are not in the way. This is the implement I used to form shallow trenches for the radial wire to lay in. The local farmers use these to form corrugations in the field for irrigation water to run through.

Here is one of the shallow trenches formed prior to inserting the radial wire. The orange baling twine is streched out between the vertical base and far end of the path I want the radial to take. That gives me a guide to follow with the tractor. I tried to insert the wire in the ground as I pulled the trench but there were too many rocks. Wound up inserting each wire by hand. I figured that I walked about 18 miles putting in the radial system.

Construction was started by first  locating and pouring five concrete piers for the guy anchors and base. All five are similar except the guy anchors have rings instead of a threaded stud. After the cement work was done, conduit was placed in the ground for the coax and control cables. You can see the conduit in the upper left of the photo. Next the radials were placed in the ground using the implement shown above, and terminated in a ring around the base. The green wires are used for connection to the tuner box to be installed last. The wires are all soldered to a ring formed from copper wire. When all the soldering is completed the ring was painted with several coats of common PVC pipe cement and then sprayed with Krylon paint to weatherproof the solder joints. There are 82 radial wires, each 100+ feet long.

The mast is constructed from 4 inch irrigation tubing. The guy lines are fastened to the mast with a "wheel line" hub clamp. Using a clamp allows adjusting the placement of each guy set to minimize mecahnical resonances. When the mast was first stood up, I watched as the wind caused vibrations. The mast was then lowered and the position of each clamp was adjusted. The distance between each guy set is now different and vibration is minimal. The guys are temporary baling twine. I used it to establish the proper lengths and when the design was stable, changed to Dacron.

The base insulator was made from pieces of PVC pipe. I turned various pipe fittings on my small lathe and used PVC pipe cement to bond them all together. The 1/2 inch diameter hole is for the hinge pin. The first insulator was made from ABS. The ABS got brittle when the temperature dropped way below freezing and cracked. So far the PVC has not failed.

The mast is fabricated from aluminum irrigation tubing. The bottom 40 foot is 4 inch diameter, 0.075 inch wall tubing. The next 30 feet is 4 inch diameter, 0.05 inch wall tubing. The top 20 feet is 3 inch diameter, 0.05 wall tubing. I tried a couple different approaches to splicing the sections together before it became obvious that more internal support was required to keep the tubing from collapsing under severe load conditions. This splice was made from PVC conduit. The pieces were turned on my small lathe and make a snug fit inside the two pieces of 4 inch tubing. It didn't need to be made from insulating material but that's what was handy. A sleeve made from a 1 foot long piece of 0.05 wall tubing to fit over the outside of the joint. Sheet metal screws through the tubing and into the  PVC keep the whole thing together and provides electrical continuity.

A base was formed from 4 inch steel "C" channel. The pieces were welded to form hinge points for the mast and gin pole. The base plate is bolted to the cement footing. 1/2 inch diameter bolts form the hinge pins. In this image, the tubing on the left is the gin pole in the lowered position and the antenna is on the right in the raised position. The black base insulator is the old ABS insulator that failed after this photo was taken.

The gin pole is a single 40 foot piece of 0.075 wall tubing. Although difficult to see in this image, the 90 foot vertical is on the ground to the left with all guys in place. The top of the gin pole has a guy on each side, a triple line pulley system to the rear, and four guys to the mast. As the pulley system pulls the top of the gin pole down, the vertical is raised up. This is a one man operation. I wanted to get a photo of the thing half raised but couldn't figure out how to hold the rope and run the camera at the same time!

In this image, the gin pole is in the lowered position. The side guys are the orange baling twine. The four rasing guys on the mast are black dacron. The yellow rope is part of the two line pulley system. It was later changed to a three line system to allow raising the mast with less effort on my part. The rope is tied off to a board. Not shown in the image is the tractor parked on the board! This was later changed to a pemanent concrete anchor point. The four raising guys are tied off after the mast is raised. Another set of full length guys are used to secure the mast from the "forward" direction

This is the tuner box at the base of the vertical. There are four open frame relays used to switch in different "L" networks. Only two are used now, for 160 and 80. The relays and network parts are mounted on a sub-chassis so that it can be easily removed and modified in the shack/shop.120 VAC is provided for soldering irons and test equipment. In the lower left the bottom of the mast can be seen in the shadow. You can see part of the stand off insulator for the bottom end of the 80 meter side mounted stub.

Κάθετη κεραία για τα 160 μέτρα

This antenna is designed for stations having a difficult time putting a decent signal on 160M from small or CC&R'd lots. It is a 25 ft. vertical antenna, made from three 10 ft. PVC sections bolted together, and 1/2 wavelength of antenna wire helically wound around the PVC sections.  A capacitance hat is on top, and the antenna is fed with a 50 - ohm feedline. Total cost for all parts is less than $90 (2009 prices) and assembly is pretty simple.  Construction time is about 10 hours.

Introduction

"My lot size is too small". "I suffer from CCR-itis". "I can't compete with the Big Guns".
"I don't have the time. Too complicated". "Too expensive". Sound familiar? It's easy to become a Topband curmudgeon - avoiding putting up a 160 meter antenna because it may be more work than fun. Well, if you're having a difficult time putting a decent signal on 160 meters, here's a possible solution to get you up and running on the "Gentleman's Band", while leaving all those "excuses" behind.

Background

My first exposure to a Helically Wound Vertical (HWV) was Gary Ellingson's 1972 QST article for a 75 meter antenna.1 (See note 1 at bottom) His unique "no loading coil" approach eliminated the need for guying and produced more equal voltage and distribution resulting in a better radiation pattern. I first tried this antenna design while living in Pennsylvania years ago with reasonable results for local QSOs using low power.

For many years, I dropped the HWV approach in favor of dipoles or inverted-Vs for 80/75 meters, but became interested again when reading about Jack Swinden's (W5JCK) clever "broomstick with a Top Hat" portable antenna design.2 He used 1/2 wavelength of wire for a targeted resonance frequency of 3.800 MHz and emphasized the importance of carefully calculating and measuring the # of turns around the antenna. Jack's meticulous attention to construction detail was inspiring, and this became my second homebrew HWV project. My FT-847 at 100 watts with this portable little antenna was a fun combination for field day and short trips. There's always something satisfying about a homebrew antenna that generates memorable QSOs.

Overcoming My Excuses

I'm an avid contester, but had no antenna for 160 meters. In fact, I was a bit cynical about ever being able to put up an effective 160 meter antenna from my rather small California city lot. My NCCC contesting buddies, however, convinced me that I was missing out on some big time fun with the ARRL 160 Meter, CQ 160 Meter, and Stew Perry Topband Challenge contests. No more excuses. It was time for me to get on the Topband Train too.

A review of the literature on 160 meter antenna designs leads to the usual discussion of dipoles, inverted-L's, T's, V's, loops, deltas, and verticals. After thinking about my own QTH constraints I found myself revisiting the HWV option and settled upon a design often discussed but not often deployed in the US: a helically wound vertical antenna using PVC tubing.

An early version of this type of HWV antenna for 160 meters was the "rubber duckie" antenna developed by Joe Moraski, KY3F, in the early 1990s.3 This antenna was constructed using two 10 foot sections of 4 inch PVC pipe joined, two lengths of 140 feet of #18 wire, and wound at 1 turn per inch over each 10 foot section and the wires connected at the center joint. Then a "top hat" of 1/2 inch mesh dry wall screen one foot in diameter and four feet long was added at the top of the antenna.3

However it appears that most HWV antennas for 160 meters have been homebrewed in the UK, where the limitations of "small gardens" are common. In 1980, Frank Lee, G3YCC (SK) described his wire-wrapped fiberglass antenna for 160 meters4, based on an original design by Alan Wells, G4ERZ5. More recently, Phil Sidwell, M0VEY, describes his Topband homebrew helical, including a fairly elaborate earth ground system.6 This type of antenna appears to have gained widespread popularity throughout the UK and Europe.

Wire Wisdom

There is no hard-and-fast formula for determining the amount of wire needed to establish resonance in a helical antenna. The relationship between the length of wire needed for resonance and a full quarter wave at the desired frequency depends on several factors. Some of these are wire size, diameter of the turns, and the dielectric properties of the form material.

Experience has indicated that a section of wire approximately one half wavelength long, wound on an insulating form with a linear pitch (equal spacing between turns) will come close to yielding a resonant quarter wavelength. Therefore, an antenna for use on 160 meters would require approximately 260 feet of wire, when spirally wound on a support.7 Add other possible challenges like narrow bandwidth, poor feedpoint impedance, radiation resistance, efficient top hat capacitance, mechanical constraints, sufficient ground radial system - and you could easily become a Topband curmudgeon. But then you'd miss out on building this fun antenna - which really works!

To try and get a first approximation on a final HWV design, I used modeling software developed by Reg Edwards, G4FGQ.8 His program models and predicts the performance of a helically wound vertical antenna, mounted immediately above a ground plane, top capacitance-loaded with a vertical rod or whip. Enter these variables: height/diameter of the helical coil + # turns & diameter of wire + length/diameter of end-loading rod, and you get back theoretically useful data: 1/4 wave resonance frequency, length of wire needed, helix wire pitch, capacitance/inductance data, feed-point impedance and expected bandwidth.

Version 1.0 -- A Learning Experience

Based on the success of several UK designs, and to test G4FGQ's software, I decided to put together my first 160 meter HWV. I wrapped 20 feet of 1.5 inch diameter PVC tubing with 1/2 wavelength of #22 stranded wire spaced 0.25 inch apart, and used a 6 foot vertical rod for top capacitance. In short, this proved to be an unacceptable solution: high resonant frequency, very small bandwidth, low feed point resistance, poor radiating efficiency, insufficient mechanical strength, and overall poor performance. But this first version gave me a chance to really think through the construction variables more carefully, and after discussions with other Topband buffs, a better overall design emerged.9

Version 2.0 - Looking Better

The remainder of this article describes the construction and performance of a very simple but effective HWV antenna for 160 meters. In a nutshell: The antenna is made by telescoping three 10 foot PVC sections together, helically winding it with 1/2 wavelength of antenna wire, attaching a capacitance hat to the top, and feeding it with a 50-ohm feed line against 8 ground radials. The entire construction can be easily completed in just one day using very simple tools.

Construction Details:
Step 1. PVC Painting
The antenna is made from three 10 foot sections of readily available PVC tubing in three diameter sizes: Top Section = 1 inch, Middle Section = 1 inches, and Bottom Section = 2 inches. To make this antenna environmentally & stealth friendly, the three PVC sections were spray-painted green by suspending each 10 foot section from two pieces of nylon rope between two branches of a convenient backyard tree. Brown paint would work just as well.
Figures 1 and 2 show a PVC section before and after painting. All three 10 foot sections were allowed to thoroughly dry before proceeding (see Figure 3).

Figure 1. PVC Before

Figure 2. PVC After

Figure 3. Painted PVC Pipes

Step 2. Bottom Section: Coax, Antenna and Ground Connections

Refer to figures 4 and 5 below for the following:
The bottom 2 inch PVC section is prepared for both ground and coax connections by drilling the necessary mounting holes. A PVC cap is placed on the bottom of the 2 inch diameter PVC tube, and then, using a felt-tip marker, a circle is drawn around the PVC just above the border between the bottom cap and PVC section. This "marker" ensures that subsequent drilled holes will clear the bottom PVC cap.
Coax Connection: The PVC cap is then removed, and then holes are drilled for the SO-239 connector and 4 attachment screws. The SO-239 hole is centered about 2 inches above the marker (see Figure 4).
Bottom Antenna Binding Post: One 1/8 inch hole is drilled for the antenna binding post, placed 2 inches above the marker. A red binding post was used for the antenna connection.
Ground Binding Posts: Two 1/8 inch holes are drilled for the ground posts, each placed 1 inches above the marker. Black binding posts were used for ground connections.
Summary: The 3 binding post holes (i.e., 1 antenna + 2 ground) are placed equidistant from each other around the PVC section. The antenna post and ground posts are staggered by about inch to avoid any possibility of shorting (see Figure 5).

Figure 4. SO-239 Connector

Figure 5. Binding Posts & Internal Wiring

Step 3. Wiring: Coax Connector and Antenna Post

One end of a 4 inch piece of #14 wire is soldered to the center connector of the SO-239. The other end is then soldered to either a spade or ring lug. The wire is then pushed through the prepared SO-239 hole in the 2 inch PVC tube, and the SO-239 connector secured to the PVC tube using only 3 of the 4 mounting holes. The free end of the insulated wire is connected to the inner section of the red antenna post using the spade or ring lug. After securing the antenna post a binding nut, the connection can be soldered (see Figure 5).

Step 4. Wiring: Coax Connector and Ground Post

A 6 inch section of #14 insulated wire is soldered (or crimped) to spade lugs on both ends.
One end is connected on the outside of the PVC to the remaining SO-239 screw and secured to the PVC. The other end of the #14 wire is connected to the closest black ground binding post on the outside of the PVC.
Inside the PVC, another piece of #14 wire is attached between the 2 ground binding posts.
This essentially connects both ground binding posts and the coax base together. Check to be sure the antenna and ground connections inside the PVC are clean and not touching each other. Braided coax, such as RG-58, can also be used instead of the #14 wire for ground post connections. At this point, the SO-239 and all binding posts should be tightened and secured.
For extra strength and protection, the binding posts can also be glued to the PVC, both inside and outside (see Figure 5)
Step 5. PVC Mast Preparation and Assembly
The Top, Middle, and Bottom sections are assembled using a high-tech solution: duct tape. I actually used Gorilla Tape10 for wrapping because it uses two layers of adhesive and two layers of fabric backing to make it much stronger than standard duct tape.
First, the 1 inch diameter PVC tubing is shortened from 10 feet to 7 feet 6 inches by cutting off 2 feet 6 inches from one end. Duct tape is then wrapped around the tubes as follows:
For the Top Section (1 inch diameter tube) = Two wrappings. First wrap = 2 inches from bottom of tube. Second wrap = from 9 to 11 inches from the bottom of the tube (see Figure 6).
For the Middle Section (1 in diameter tube) = Two wrappings. First wrap = 2 inches from bottom of tube. Second wrap = from 22 to 24 inches from the bottom of the tube (see Figure 6).

Figure 6. Wrapped With Duct Tape

The 3 PVC sections are then telescoped together. When assembled, the Middle Section will extend 24 inches into the Bottom Section, and the Top Section will extend 11 inches into the Middle Section. Its important to use enough duct tape to ensure a good fit between the PVC sections.
PVC Sections - Overlap
The next step in PVC assembly is to further secure the "joints" with a bolt and nut. The lower joint (between the Middle and Bottom sections) is secured by drilling a inch hole through both PVC sections about 12 inches from the top of the 2 inch diameter Top PVC section, and using a 3 inch bolt, nut, and washer to fasten the sections together.
The middle joint (between the Middle and Top sections) is secured by drilling a similar hole, about 6 inches down from the top of the 1 inch diameter Middle PVC section, and using a 2 inch bolt, nut, and washer to secure the joint.

Top Antenna Binding Post

(Shown above) Similar to the Bottom antenna post previously mentioned, a Top antenna post is prepared by drilling a 1/8 inch hole one inch from the top of the Top PVC section. A red-capped binding post is attached to it, using a nut and glued to secure it. The helically wound antenna wire will be connected to this post, which will also be the antenna to-capacitance hat attachment point.

Step 6. Helically Winding The PVC
With the sections assembled and fortified, the antenna is ready to be helically wrapped with wire. As previously mentioned, experimentation with HWVs has shown that a half wavelength of wire is often needed for quarter wave resonance, assuming the turns are evenly spaced. At a desired resonance frequency of 1.825 MHz, 256 feet 5 inches of wire is required for a 160 meter vertical, using the formula 468/freq. For this first version of the antenna, I chose #22 insulated wire for the antenna I had a good supply sitting in the garage.
Using our kitchen table, which measures 5 feet long and a coffee can with 2 large screws protruding from sides at the top and bottom 180 deg apart (to keep the wire from falling off the can as it was being wound), my XYL "unwound" the wire from the supply spool, while I wound it onto the coffee can. 50 times across the kitchen table = 250 feet + an additional 6 feet 5 inches did it. The wire was cut, adding a few extra inches for experimentation, but keeping the 256 feet 5 inch point marked.

Figure 9. Wire Wrapping

Wrapping begins by first attaching the antenna wire to the Bottom Antenna Binding Post of the 2 inch PVC section using a spade or ring solder lug. The wire is then wound from bottom to top, being careful to keep the "winding pitch" as consistent as possible, and avoiding the bolts near the two PVC joints. A spacing of about inch seemed to work well. Wire wrapping is not a difficult step, but does require a bit of patience. Its best not to rush this part of the project. Duct tape is helpful here every few feet to keep the windings secure (see Figure 9). In a later version of this antenna, I hot-glued the antenna wire to the PVC for even better protection.
The end of the wire at the top of the antenna is then soldered to a spade or ring tongue and attached to the Top Antenna Binding Post with the red cap at the top of the 1" PVC section.
Option For Portability: Its possible to make the antenna portable by cutting the antenna wire at the two PVC joints. Then, after removing wire insulation, alligator or "quick disconnect" clips are attached to the antenna wire ends. The antenna can then be pulled apart, moved, re-telescoped together, and the full antenna wire length restored by simply connecting the antenna clips together.
Step 7. Top Cap Preparation: Capacitance Hat
There are several designs for a suitable HWV capacitance hat to provide capacity termination and reduce noise. At first, I chose the "circular hat" design described by Jack Swinden (W5JCK), where six 12 inch brass rods are spaced equally around a PVC cap, and soldered together.2 However, I eventually settled on a simpler "square hat" design using two 36 inch brass rods spaced 90 degrees apart, and connected together with #14 gauge copper wire.9
Either of these methods work well. The "square hat" design is described next.
The square hat construction begins by drilling four 1/8 inch hole 90 degrees apart in the 1 inch PVC cap, about 1 inch from the bottom. An additional 1/8 inch hole is drilled next to one of these holes. The brass rods are inserted into the cap, forming an "X". A pair of pliers is helpful here, as it will be a snug fit, which is what you want.
Next, a 6 inch piece of #14 insulated wire is stripped on one end, and soldered to a spade or ring lug on the other end. The stripped end is slipped through the remaining 1/8 inch hole and wrapped securely around the "X" junction of the two brass rods inside the PVC cap, where everything is securely soldered (see Figure 10). The brass rods are tied together externally by connecting them together with #14 gauge bare copper wire in two places: the tips of the rods and also midway between the rod ends the and PVC cap. The bare copper wire is soldered to the brass rod at all 8 intersections, to complete the "square hat" (see Figure 11).

Figure 10. Inside Top PVC Cap

Figure 11. Completed Square Hat

Finally, the PVC cap is attached to the Top Section of the antenna, and the capacitance wire secured to the Top Antenna Binding Post using the spade or ring lug. For maximum result, its important to have a good electrical connection between the antenna wire and capacitance hat.
Step 9. Bottom Cap Preparation
The bottom cap is used to support and protect the antenna. A inch hole was drilled in the center of a piece of scrap plywood (about one foot square). Another inch hole was drilled in the bottom of the 2 inch PVC cap. The threaded aluminum rod was trimmed to 12 inches,and run through the bottom PVC cap, and then through the plywood (see Figure 12 below). Nuts and washers were attached on the threaded rod inside the cap and also on the other side of the plywood. When tightened, only 2 inches of rod was left inside the cap, to ensure that the antenna and ground wiring in the bottom section of the mast would not be disturbed (see Step 2). About 10 inches of threaded rod was left sticking out from the bottom of the plywood (see Figure 13). The plywood base serves as a stabilizing platform to ease final installation of the vertical. By gently standing on it and pushing, you can easily drive the 10 inches of threaded rod into the ground.

Figure 12. Bottom Cap on Plywood

Figures 13. Showing Threaded Rod and bottom cap mounted.

Step 9. Erecting The Antenna
After the PVC sections were bolted together, and completely wire wrapped, the capacitance hat was attached to the top of the antenna, including the capacitance wire-to-antenna binding post connection. The antenna is now ready for final installation (see Figure 14). The bottom 2 inch PVC cap/plywood base was set in the ground at its mounting location. Bracing the bottom against the ground, the antenna was carried to the PVC cap/plywood base and carefully set into the PVC cap. One person can carry & mount the antenna but its a bit easier with two folks (see Figure 14 below).

Figure 14. Ready To Erect

Figure 15. Installed and Neighbor Friendly

My QTH required bracing the mast to my back fence and securing it at the 6 foot point with nylon rope. To keep the vertical, "vertical", a section of nylon rope was also attached at 12 feet using a convenient tree limb and the rope secured at ground level. Final guying/bracing will depend upon your antenna placement.
Radial Wires: This antenna does require some ground radials. Of course, use as many as your QTH allows. I started with four 1/4 wavelength ground radials cut for 160 meters and have expanded that number now to eight, using #16 stranded insulated wire. Spade lugs are soldered to ground radials which are then attached to one of the two ground posts. Because of the geometry of my property, my radials cover only a 180 degree arc but they work pretty well.
Initial Readings: After attaching a 6 foot piece of 50-Ohm coax, an MFJ 249B antenna analyzer showed resonance close to 1.790 MHz. The antenna wire was adjusted at the bottom to bring the resonance closer to 1.830 MHz. Running 500 watts through this antenna without a tuner showed a 50 KHz bandwidth, with <2:1 SWR. With a tuner, the antenna can be adjusted anywhere from 1.800 to 1.900 MHz with an SWR under 2:1.
Version 3.0 - Update
After a few months of use, I took down the antenna and decided to fortify the antenna wire by hot gluing it to the PVC. While on the ground again, the entire antenna was re-wrapped using 4-conductor #18 wire stranded wire I had a good supply sitting in the garage. At each end of the antenna the ends of the 4-conductor wire were twisted and soldered together before wrapping and attaching to the Top and Bottom antenna binding posts. I also added two elevated radials around the fence line
Although I have not done any side-by-side comparisons, this updated version of the antenna appears to "hear" better, and feedback on the air tells me that I have a somewhat stronger signal. However it is not necessary to use 4-conductor wire with this antenna. A single conductor works just fine, and is easier to wrap around the PVC tubing.
On-The-Air
So how does this Helically Wound Vertical for 160 meters perform? From the West coast,its a solid performer throughout the North America. I have worked all 50 states, Canada, and Mexico during the last year with it, almost all confirmed via LoTW. I was awarded First Place, Single Operator, Low Power for the Santa Clara Valley section in the 2007 ARRL 160 Meter contest. In the 2009 CQWW 160 Meter contest, I worked 46 states and 7 countries using 600 watts in just a few hours of operating. For DX, with limited operating time, I have worked 30 countries. Overall, this antenna plays well to the Far East, South Pacific, Eastern Russia, Caribbean and Central/South America. Europe is the most difficult region to reach from my location, but thats generally true for most West coast stations.
Am I the loudest signal on the band? No. Can I compete in pileups with folks having better antennas or higher power? No. But am I having fun on Topband using a homebrew antenna that generates memorable QSOs. You bet!
There are some obvious improvements that can be made to increase overall on-the-air performance with this type of antenna. They include, among others:
-Installing more ground radials in a full 360 degree pattern
-Using a remote tuner at the antenna feedpoint to reduce coax losses
-Running legal-limit power
-Adding beverage antennas for improved reception
Antenna Summary
A Helically Wound Vertical is not "the" perfect antenna for 160 meters, but for a small lot, or where CC&R's are strictly enforced, this easy-to-build vertical is a good alternative to an inverted-L or dipole. During the last year, I have helped other hams around the country get on the air with this HWV design for 160 meters.11
This unsolicited comment from Armand Sun, K6IP, is typical of the feedback I've received:
12 "I finally put up the HWV antenna and I'm happy to report that it works FB. Mine has two feed options: ladder-line or coax. I'm currently feeding with ladder-line and one elevated radial from leftover wire on the spool and the results are excellent! It takes a KW from 1.8 - 1.9 MHz. I painted mine olive drab with black #14 wire so it's pretty stealthy. I would imagine brown would be good too. Sometimes the traditional designs just don't blend well with the existing antenna farm. A Helically Wound Vertical is a good option for small lots or for those with antenna restrictions. Thanks for the design. It was fun to build and just what I needed for a Topband solution."
So, no more excuses for Armand -- or Me. Now how about you?
John Miller, K6MM
Published in QST, June 2009, pages 32-36.
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Notes
1G. Ellingson, WA0WHE. "A Helically Wound Vertical Antenna For The 75-Meter Band," QST, Jan1972, page 32.
2J. Swinden, W5JCK.
(a) http://w5jck.com/broomstick_antenna/80m_helical_antenna.html
(b) http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=19786
3J. Moraski, "The Rubber Duckie 160 Meter Antenna", HF Antenna Book, published by CQ Magazine, edited by Bill Orr, W6SAI, 1996, p. 615.
4F. Lee, G3YCC. "A Practical Antenna for 160 Metres"
http://www.zerobeat.net/g3ycc/ant1.htm
5A. Wells, G4ERZ. http://topband.blog.cz/0612/a-practical-antenna-for-160m-by-alan-g4erz
6P. Sidwell, M0VEY. http://uk.groups.yahoo.com/group/topband-helical/
7 The ARRL Antenna Book, 21st Edition, 2007, p. 6-38.
8R. J. Edwards, G4FGQ. (a) "Model and Predict Helically Wound Vertical Antennas".
http://www.smeter.net/antennas/helical-modeling.php August 2, 1997; (b) "Very Short, Helically Wound, Monopole Antennas", http://www.smeter.net/antennas/short-helical.php,
May 19, 2006
9 I am especially grateful to Jon Sims, N7ON, for sharing his ideas and experiences with me. J. Sims, N7ON Personal communications, January 2006.
10 Gorilla Tape. http://www.gorilla glue.com/tapes.aspx
11 A downloadable construction manual is posted on my website here:
http://k6mm.com/antennas/160M.pdf
12A. Sun, K6IP. Email communication, January 29, 2009. Quoted with permission.
Parts List
Home Depot or Lowes
10' length, 2" diameter schedule 40 PVC
10' length, 1-1/2" diameter schedule 40 PVC
10' length, 1" diameter schedule 40 PVC,
1" diameter PVC end cap,
2" diameter PVC end cap,
1/4" x 3 1/4" threaded bolt, nut, washer
1/4" x 2 3/4" threaded bolt, nut, washer
1/4" x 1 foot threaded aluminum rod,
3 foot length brass rods (2 required)
4 1/4" diameter nuts, 4 1/4" diameter washers,
Rust-Oleum PVC Spray Paint (dark green or brown)
Radio Shack
2 packets, multipurpose posts,
1 packet, crimp-on spade or ring tongues,
1 packet, alligator clips
Misc
500 foot roll insulated stranded wire (you can use 14, 16, or 18 gauge)
Roll of your favorite ground wire for radials (insulated or un-insulated)
Duct tape or Gorilla tape (2" wide)
SO-239 chassis mount coax socket + mounting screws/nuts
Tools
Soldering iron, solder, glue/glue gun, hacksaw, drill, 1/8" drill bit, 1/4" drill bit, felt-tip marker