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Αρχειοθήκη ιστολογίου

Κυριακή 26 Ιουνίου 2011

Αυτόματος επαναλήπτης

This circuit will be of interest to the radio amateur and anyone posessing two radios, (one of which must be able to transmit i.e. a transceiver). It is a self powered (audio derived) repeater circuit for receiving a signal and re-transmitting it via the other radio.



Notes:
This little circuit can turn two hand-held radios into a makeshift repeater. Any radio will work fine as Radio 1, but Radio 2 must be a Yaesu, or some other type that also goes on the air when its microphone input is shunted with 1-2 kiloohms.

As soon as a radio signal opens Radio 1's squelch circuit, a tiny amount of energy stolen from the audio signal turns on the MOSFET and it conducts as long as the audio is present. While it conducts, Radio 2 is on the air, retransmitting the content supplied by Radio 1 through C1 and P1.

The BS108 has a conveniently low G-S threshold voltage. The other components' characteristics are not critical, but it would be wise to stay close to the values shown in the picture, or at least take them as a starting point for testing.

Πομπός μεσαίων

An AM voice transmitter with variable tuning. The antenna circuit is also tuned and transmits via a long wire antenna. Please Note. It is illegal to transmit on the AM wavebands in most countries, as such this circuit is shown for educational purposes only.



Notes
Please read the disclaimer on this site before making any transmitter circuit. It is illegal to operatea radio transmitter without a license in most countries. This circuit is deliberately limited in power output but will provide amplitude modulation (AM) of voice over the range 500kHz to 1600kHz with values shown. You can input values in the calculator below, remember to change drop down box to picofarads for capacitance and microhenries for the coil. The coil is fixed at 200uH, the capacitor values can be varied and resonant frequency found by using the calculator below.

Tuned Circuit Resonant Frequency Calculator

Capacitance:
Inductance:
Resonant Frequency:





Coil Data

If winding your own coil then you may find Martin E Meserve page very helpful:
Single Layer Air Core Inductor Design

An alternative is to use a toroid core of appropriate material. Toroid's come in different sizes and colours, see the sample below.

A T130-2 core requires approximately 137 turns of 36 SWG wire.
Mike Yancey has a very useful Toroid calculator on his webpage, link below:
Toroid Calculator

Circuit Notes
The circuit is in two parts, a microphone pre-amplifier built around Q1 and an RF oscillator circuit (Q2). The oscillator is a standard Hartley oscillator which is tunable. Tank circuit L1 and C1 control frequency of oscillation, the power in the tank circuit limited via emitter resistor R1. The transmitter output is taken from the collector, L2 and C2 form another tuned tank circuit and help match the antenna. L1,L2, C1 and C2 may be salvaged from an old AM radio if available. The antenna should be a length a wire about 10 feet or more. In the schematic I have shown coaxial cable to be wired to the "longwire" antenna, the outer coax shield returned to ground. Ground in this case is a cold water pipe, however even without a ground and coax cable a signal should still be possible.
L2 and C2 not only help match the antenna to the transmitter, but also help remove harmonics and spurious emissions in the transmitter circuit caused by non linearity in the transistors.

Q2 needs regenerative feedback to oscillate and this is achieved by connecting the base and collector of Q2 to opposite ends of the tank circuit which is achieved by C4. C3 ensures that the oscillation is passed from collector, to emitter, via the internal base emitter resistance of the transistor, back to the base again.

Emitter resistor R1 has two important roles in this circuit. It ensures that the oscillation will not be shunted to ground via the very low internal emitter resistance, re of Q2, and secondly raises input impedance so that the modulation signal will not be shunted.

Q1 is wired as a common emitter amplifier, C7 decoupling the emitter resistor and realizing full gain of this stage. Bias of this stage is controlled by R4,R5 and R3. The microphone is an electret condenser type microphone, R7 setting operating current of the ECM and C6 providing DC blocking. The amount of modulation is controlled by the 10k preset resistor PR1 which is also the collector load. The preamp stage is decoupled by R6, C8 and C10. This ensures no high freqency feedback from the oscillator gets into the audio stage. Some electrolytics capacitors have a high impedance at radio frequencies, hence the use of C10, a 10n ceramic to bypass any oscillator frequencies.

Δέκτης μεσαίων

This is a compact three transistor, regenerative receiver with fixed feedback. It is similar in principle to the ZN414 radio IC which is now replaced by the MK484. The design is simple and sensitivity and selectivity of the receiver are good.




Circuit Notes
All general purpose transistors should work in this circuit, I used three BC549 transistors in my prototype. The tuned circuit is designed for medium wave, but the circuit will work up to much higher frequencies if a different tuning coil and capacitor are used. I used a ferrite rod and tuning capacitor from an old radio which tuned from approximately 550 - 1600kHz. Q1 and Q2 form a compound transistor pair featuring high gain and very high input impedance. This is necessary so as not to unduly load the tank circuit. Q1 operates in emitter follower, Q2 common emitter, self stabilizing bias is via the 120k resistor and the tuning coil. As Q2 operates in common emitter its base voltage will be a Vbe drop higher than ground or about 0.71V in my test sample. The voltage at Q1 base will be this Vbe drop plus the voltage drop across the 1k resistor and Q1's own Vbe drop, this amounted to 1.34V from base to ground in my test circuit. For audio amplifiers, Q2 collector would be biased near half supply voltage, however the input signal levels at RF are tiny, typically 50uV appearing across the coil being amplified by Q2 and being about 5mV RF across the 2k2 load resistor.

The 120k resistor provides regenerative feedback,between Q2 output and the tank circuit input and its value affects the overall performance of the whole circuit. Too much feedback and the circuit will become unstable producing a "howling sound". Insufficient feedback and the receiver becomes "deaf". If the circuit oscillates,then R1's value may be decreased; try 68k. If there is a lack of sensitivity, then try increasing R1 to around 150k. R1 could also be replaced by a fixed resistor say 33k and a preset resistor of 100k. This will give adjustment of sensitivity and selectivity of the receiver.

Transistor Q3 has a dual purpose; it performs demodulation of the RF carrier whilst at the same time, amplifying the audio signal. Audio level varies on the strength of the received station but I had typically 10-40 mV, this is audio voltage, not RF signal level. This will directly drive high impedance headphones or can be fed into a suitable amplifier.


The tuning coil, L1 can be salvaged from an old AM receiver, or to make your own wind about 50 to 60 turns of 26 SWG enamel coated copper wire over a 3/8 inch ferrite rod about 3 inches long. This will create a tuning inductor of about 200uH. AM stations are directional so rotating the rod (or whole receiver) should allow nulling of some signals whilst boosting others.
If you are in an area of weak reception then an external antenna may be required. Wind about 4 or 5 turns (indicated as 4 or 5 T on the schematic) of 26 SWG wire onto the ferrite rod, close to the main winding and connect one end to a cold water tap or ground connection. Use several feet of flexible wire as an antenna.


The frequency coverage or tuning range is controlled by L1 and VC1. If VC1 is fully meshed (closed) then its capacitance will be about 500pF. The resonant frequency is given by:

where F is frequency in hertz, C capacitance in Farads and L the inductance in Henry's. With a meshed 500pF variable capacitor and 200uH coil the lowest frequency works out to be:

When the vanes are open a small capacitance is still present (about 40pF). The coil connections add a slight amount of stray capacitance which may be 7 or 8pF. With 48pF capacitance and a 200uH coil, the highest frequency will be about 1624kHz. Some variable capacitors, have built in trimmers to adjust the highest frequency. For any coil and capacitor that tunes too high, a 50pF trimmer may be added in parallel with VC1 to control the highest tuneable frequency.


The coil details below were kindly submitted and tested by David from Germany and tunes 500 - 1700kHz with a 500pF capacitor. Construction is shown below 35 turns of 32 SWG enamel covered wire are wound 30mm from one end of a 10mm diameter ferrite rod. Now a paper sleeve about 20mm wide is looped around the ferrite rod. The coil is continued winding a further 40 turns, the start of the 36th turn being approximately 50 mm from the same end of the ferrite rod on the paper sleeve see image below.



The MW coil described above results in an inductance of approximately 200uH. If coupled with a 500pF capacitor (full mesh) will tune to about 500kHz and open mesh (about 43pF) tunes to 1700KHz. This covers the top part of the MW band used in North America and some European Pirate stations. If desired a LW coil can also be made on the same rod, this is 330 turns of 32SWG wire starting 70 mm from the same end of the ferrite rod.


All connections should be short, a veroboard or tagstrip layout are suitable. The tuning capacitor has fixed and moving plates. The moving plates should be connected to the "cold" end of the tank circuit, this is the base of Q1, and the fixed plates to the "hot end" of the coil, the junction of R1 and C1. If connections on the capacitor are reversed, then moving your hand near the capacitor will cause unwanted stability and oscillation.

Finally here are some voltage checks from my breadboard prototype.This should help in determining a working circuit:-
All measurements made with a fresh 9volt battery and three BC109C transistors with respect to the battery negative terminal.

Q1 (b) 1.31V
Q2 (b) 0.71V
Q2 (c) 1.34V
Q3 (b) 0.62V

Q3 (c) 3.87V

Finished Receiver
A finished receiver made on veroboard is shown below. This one is built by David in Germany and has received all medium wave stations in David's locality.


More of David's radio work can be seen in my Pics section in the Practical Pages.

PCB Layout
The following single sided PCB layout was created with Kicad, a free open source schematic and PCB drafting program. Its available for both windows and linux, the image below is a 3D (enlarged) view of the component side. The copper layer (solder side) is the dark green layer on the bottom of the board.



The top view (component side) of the PCB board is shown below. This is without the 3D components, the silk screen (drawings on the component side) allow for size of physical components.



The image below is an actual size (1:1) copy of the copper layer. Note that this is reverse so the veropins appear now on the left hand side at the top. Remember that this is the lower (solder) side, by viewing the top image you should be able to match up the positions of all components.



Finally you may not like my layout and prefer to create your own. The follwing am_rec.zip file, contains the schematic, component list and pcbnew diagram in one convenient zip file.

Download all files for kicad am_rec.zip

More Construction Tips
The following tips come from Austin Hellier in Queensland, Australia and may assist with building this project. Generally speaking, matrix board construction (spread out a bit) seems best. Recently, when I ran out of it, I was forced to use an 8 x 2 way tag strip arrangement, which suffered from several problems. Feedback howls and 'motorboating' were prominent until I moved the tuning coil and capacitor apart, but even then, there were still some feedback problems, as I also used a 100k 'A' tapered pot as the feedback control. I think that there's probably too much stray capacitance with this method of construction. also, some of the longer (180mm) ferrite rods of better quality material, seem to cause this overloading, as they tend to generate a larger, more powerful EM field around the rod. Smaller rods will probably work better with the more compact plastic boxes or cases that constructers tend to use.




More of Austin's radio work can be seen in my RF Pics section in the Practical Pages.

Reducing C1 from a 0.1uF cap to a smaller 0.047uF cap helped a lot, but the final 'fixit' occurred with the placement of the removed 0.1uF cap across the c and e terminals of transistor Q2. These and the above methods have allowed me to fix the two most recent AM receivers that I made last week, with no residual side effects at all. Both units can receive ten out of eleven local AM stations here in Brisbane, Queensland, Australia, and with all parts new, cost around $12 to $15 AUD, depending on which shops you buy them at.

When I was down south in Wollongong some years ago, I made up my very first 'AM Receiver' cct, and picked up stations 1ZB and 2ZB, across the Tasman in New Zealand! If I use this circuit with a loop antenna of any appreciable size, I can also pick up 4RK up in Rockhampton (I live in Brisbane myself,) and 531 AM, a NSW radio station down near Coffs Harbour - quite a few kilometres in either direction. Station frequencies and locations for Brisbane and the rest of Queensland can be found at www.ausradiostations.com.

Λίνεαρ 60 βάττ



The 60 Watt linear amplifier is simple all solid state circuit using power mosfet IRF840. The IRF series of power transistors are available in various voltage and power ratings. A single IRF840 can handle maximum power output of 125 watts. Since these transistors are used in inverters and smps they are easily available for around Rs: 20/-.
The IRF linear amplifier can be connected to the out put of popular VWN-QRP to get an output of 60 Watts. The circuit draws 700 ma at 60 Volt Vcc. Good heat sink is a must for the power transistor.

Alignment of the circuit is very easy. Connect a dummy load to the out put of the circuit. You can use some small bulb like 24V 6Watts as the dummy load. I have even used 230V 60Watts bulb as dummy load with my IRF840 power amplifier working at 120Volts. Adjust the 10K preset to get around 100 ma Drain current. I used gate voltage of 0.8V with my linear amplifier. A heigh gate voltage can make the power transistor get distroyed by self oscillation. So gate voltage must be below 2V and fixing at 1V will be safe.

Bifalar transformaer T1 is wound with 8 turns 26SWG on 1.4 x 1 balun core.
The coil on the drain of IRF is 3 turns 20 SWG wound on 4 number of T13.9 torroids (two torroids are stacked to form a balun core). The RFC at the Vcc line is 20 Turns 20 SWG wound on T20 torroid.

Ενισχυτής λίνεαρ 10 βάττ

Introduction

It is quite easy to get a watt or more with very simple equipment, but to get more than 5 watts becomes a little more difficult. This article describes a 10 watt linear amplifier that is capable of delivering over 15 watts into 50 ohms and uses cheap plastic transistors that are used in CB equipment. If you have difficulty in finding 2SC2078 then lift the lid of your CB set to find a suitable alternative. The bias generator transistor, TR4, is marked TIP31 in the circuit diagram, but here you can use just about anything that will fit. You could even use another 2SC2078, if you had money to burn, but more practical components would be TIP41, TIP3055, MJE3055. All that matters is that it will pass up to 1 Ampere and have the correct base details in a TO220 case.


Circuit


The amplifier has a wide bandwidth, from 1.8 MHz through to over 30 MHz. The drive level required is only about 2 - 5 mW under 14 MHz, rising to 10 mW at 30 MHz. You can therefore make a good QRP CW rig with nothing more than this PA and a simple crystal oscillator. I can achieve 12 watts out of mine using a 10-turn loop around my Grid Dip Oscillator! I can get over 15 watts from my Marconi signal generator, but above about 12 watts it is being over-driven an may not be very nice to look at on the spectrum analyser. The circuit was designed to be as clean as possible. Here is a view over the completed PCB (sorry the photo is so crappy):

The circuit was originally designed to accompany my phasing-type SSB exciter, but it can be used to amplify almost any HF signal from 2mW in the HF band. Note that there is needed a Low-Pass filter between the amplifier and antenna. This is a requirement for ALL transmitters.
L1 matches a 50-Ohm input to the 10-Ohm input impedance of TR1. The output of TR1 is coupled via T1 to TR2 and TR3 bases. T1 also transforms the impedance to the very low input impedance of these two transistors, so the secondary winding must be quite thick wire.
TR2 and TR3 amplify the signal even further, up to about 12-Watts. They are in a push-pull configuration so T1 secondary and T2 primary must both be symetrical. T2 increases the output impedance to 50-Ohms.
TR1, TR2 and TR3 all have a 330R and 10n between the collector and base terminals. This is needed for stability and is a crude form of neutralising. Without these components then the stages would almost certainly oscillate or generate spurious signals. An additional 180pf capacitor from both TR2 and TR3 collectors to ground (not shown in the circuit diagram) give the amplifier an even cleaner output signal. The 68pf capacitor across the output may be increased if you never use the 30MHz band. It, too, increases the stability and helps to keep the harmonic content low. My spectrum analyser did not show any significant spurious or harmonic outputs from 0 - 100MHz when driven at 10-watts continuous, 14MHz. All spurious outputs were better than -60dBm (-70dBc), which I though was pretty good!
TR4 is nothing more than a high-current constant voltage series regulator using a 3v3 Zener diode for stability. It provides the base-bias voltage for TR2 and TR3. The 1K thermistor is thermally coupled to the tinned-copper heatsink to reduce the bias a little when the PA gets hot. More about the thermistor later.


Alignment

To align, set the 1K0 potentiometer to minimum resistance, apply power to the 'PA-12v' and 'DV-12v' terminals whilst monitoring the current drawn by the 'PA-12v' connection. The current should be next to nothing. Increase the potentiometer until the current rises to about 50 - 100 mA. That's it!


Coils

I invariably receive loads of e-mail asking me all about the coils I use. "What was the relative humidity when you wound ..." and "I don't understand what a ferrite bead looks like ...". Ok, so to answer your questions:
L1 is 6 + 6 turns 28 - 36 SWG wire on two "small" ferrite beads super-glued together - side-by-side. The two windings are connected in series to form a single 12-turn coil with a centre-tap. The two ends of the coil are input to the amplifier and ground. The centre-tap is connected to TR1 BASE via a capacitor.

L2, L3, L4 are all about 10 turns 28 - 36 SWG wire on a single ferrite bead. If you use thick wire then only 4 or 5 turns will do. You just can see one of the coils in the above picture (top). L5 is just an 18 SWG link fed through a ferrite bead. If you have a bead with a hole big enough to take a turn or two then by all means add a few turns (it just makes the hammer that bit bigger when smashing eggs).
T1 is 6 turns 24 SWG wire on two large ferrite beads superglued together - side - by side like a pair of binoculars. Use larger beads for this, I used two large ferrite slugs (8mm Dia.) robbed from an old valve IF can. The secondary that feeds the final amplifier pair are 1 + 1 turn 18SWG enamelled wire. It looks like this:

T2 has always given people a lot of problems. It is just 3 + 3 turns 18SWG wire on a large twin-hole ferrite slab or even a "Pot-core", as I have used. All work equally well. The secondary winding is 16 turns 22 SWG. It is not the material that matters, but the physical size of the ferrite. If the ferrite gets hot then it is too small. You could stack 2 or 3 1/2" ferrite rings on top of eack other - twice, then place the 2 tubes formed side-by-side to form another binocular ferrite shape, all held together with superglue. Here is the last T2 I used, and the one I shall continue to use.


Thermistor (*1K0)

The thermister is connected between the BASE of TR4 and the copper ground- plane on the top-side of the PCB. It's purpose is to reduce the bias voltage to TR2 and TR4 when they heat up a little. This reduces the standing (no-signal) current to the original setting and prevents "thermal stroll-away" (it begins slowly). In my case I used a 1K0 thermister in series with a 330R resistor. The 330R resistor damps the effect of the thermistor by lowering it's dynamic range. The thermistor is placed in direct contact with the tinned-copper heatsink for the power transistors. If you have problems with the idle current (no signal) whether hot/cold, then reducing the 330R and reseting the bias current will lower the "hot PA current". Increasing the 330R will increase the "hot PA current". The PA standing current should be the same, no-matter whether TR2 and TR3 are hot or cold.


Construction

The PCB is constructed on double-sided copper-clad board, but only one side is etched. During assembly, insert each component with reference to the component overlay. If there is a red circle with a green cross over a hole, then the component lead must be soldered both top and bottom. If there is no cross/circle then the top-copper should be countersunk a little with a 3mm drill bit to remove copper from the edge of the hole. This is clearly shown in this picture:

The decoupling capacitors in the circuit are somewhat "diagramatic". I really used the first cap I put my hands on, and there are only two types of decoupling capacitors; BIG ONES and small ones:

BIG - An electrolytic somewhere between 10uf and 10,000uf
small - A ceramic cap somewhere between 1nf and 330nf
I was fortunate enough to get my hands on a load of ultra-miniature low-voltage electrolytics in a rectangular plastic case. Use whatever you have got to hand, it is all the same and the decoupling component values are all VERY FLEXIBLE. You will notice that in the circuit I show the places that must be decoupled, but on the real board there are quite a few more. You cannot really have enough decoupling. I love it!


PCB

A PCB foil drawing is available. Sorry about the quality, but I drew it around the year 5BC (5 years Before Computers). At that time I used pens and drafting film to draw all my circuits. Download the PCB foil for the ten watt PA (38,712 bytes). The size of the copper foil is 134mm x 72mm, but I also have about 1cm extra as a border all the way ariound the board for mounting the complete PCB.
The last point is that the heatsink is made of 0.5mm tinned copper plate, bent into an L shape so that it fits under the three power transistors. I have shaded the bottom of the L in red on the component overlay. The vertical part of the L is connected to a much larger aluminium heatsink, for example, the metal case of your transmitter.

Κατασκευή χειριστηρίου CW

Δίχως τη παραμικρή αμφιβολία, η φαντασία μερικών ανθρώπων δεν έχει όρια!

Καθώς έψαχνα στο διαδίκτυο για να βρω κάποιο CW κλειδί τύπου «πεταλούδα» που να είναι πάση θυσία, μικρή, ελαφριά και μαλακιά, έπεσα σε κάποιες ιδιοκατασκευές τόσο σε «πεταλούδες» όσο και σε «κάθετα» χειριστήρια τύπου straight. Μόλις όμως είδα κατασκευή χειριστηρίου πάνω σε δισκάκι CD, δε σας κρύβω πως μου άνοιξε η όρεξη! Η συγκεκριμένη κατασκευή φιγουράριζε στη παρακάτω ιστοσελίδα: http://www.eham.net/articles/7114 με τίτλο, AG4RQ's Homebrew Single-Lever CW Paddle. Με μια ματιά βλέπουμε ότι πάνω σε ένα δισκάκι CD, το οποίο εκτελεί και χρέη βάσης, στηρίζουμε ένα λαμάκι που το βρίσκουμε από κουτί Η/Υ. Το λαμάκι στηρίζετε πάνω σε μια βίδα, μονωμένη από το δισκάκι με μονωτική ταινία, λίγο καλώδιο κι ένα καρφάκι τύπου mini jack, συμπληρώνουν τη λίστα με όλα τα υλικά που θα χρειαστεί κάποιος για να φτιάξει ένα … κανονικό (straight) κλειδί για CW. Ανακυκλώνοντας ένα παλιό ή άχρηστο ή «καμένο» δίσκο CD, ένα λαμάκι που μπορούμε να το βρούμε ακόμα και από τη πίσω πλευρά του κουτιού ενός Η/Υ και δυο βίδες, έχουμε ένα πρώτης τάξεως CW κλειδί για το shack ή και για τις εξορμήσεις μας στην ύπαιθρο! Μόλις συγκεντρώσουμε τα υλικά, σε 15 λεπτά της ώρας θα είναι έτοιμο προς ... χρήση. Τόσο απλά, τόσο γρήγορα!



VHF και UHF Slim Jim antenna

Απλή, εύκολη, οικονομική κεραία για τη μπάντα των 2 μέτρων και των 70 εκατοστών.

Εισαγωγή:
Αγαπητοί μου φίλοι σε αυτό το άρθρο θα σας παρουσιάσω μια πολύ εύκολη, οικονομική και αποδοτική κεραία την οποία μπορείτε να χρησιμοποιήσετε σα κύρια ή σα βοηθητική κεραία για το σταθμό σας, τη Slim Jim.
Τη κεραία Slim Jim τη γνώρισα λίγο πριν τα μέσα της δεκαετίας ’80 και μπορώ να πω με σιγουριά πως δεν είναι μια κεραία που περνάει απαρατήρητη! Τα πλεονεκτήματα που έχει αυτή η κεραία είναι, ότι δε χρειάζεται τεχνητή γη (radials) για να δημιουργήσει ένα ομοιογενές πεδίο γύρω της, ο λοβός της είναι κυκλικός (Omni directional), με ότι συνεπάγεται αυτό, έχει πολύ χαμηλή γωνία ακτινοβολίας 10 μοίρες πάνω από τον ορίζοντα (αυτό είναι και το σημαντικότερο πλεονέκτημά της), είναι κλειστού βρόγχου, παρουσιάζει ικανοποιητικό κέρδος – απολαβή, πολύ καλό εύρος, είναι εύκολη στη κατασκευή και οικονομική ταυτόχρονα ενώ δεν απαιτούνται δυσεύρετα και εξειδικευμένα υλικά για την υλοποίησή της. Τι άλλο να ζητήσει άραγε κάποιος από μια κεραία;


Υλικά:
Για να κατασκευάσουμε τη κεραία Slim Jim θα χρειαστούμε τα παρακάτω υλικά:
Ένα κομμάτι μήκους περίπου 153 εκατοστά από ανοιχτή γραμμή - leader line 450 Ohms, η γνωστή τυποποιημένη του εμπορίου είναι ιδανική, ένα κομμάτι σωλήνα PVC μήκους 2 μέτρων και εσωτερικής διαμέτρου 2 εκατοστών, όσο δηλαδή και το πλάτος της ανοιχτής γραμμής, ένα connector SO-239, καλώδιο RG-58 μήκους 1,5 μέτρο, μονωτική ταινία και δυο – τρείς ώρες από τη ζωή μας!

Κατασκευή:
Πρώτα απ’ όλα μετράμε και κόβουμε την ανοιχτή γραμμή στις διαστάσεις που μας δείχνει το σχηματικό της πρώτης εικόνας. Γυμνώνουμε και τα τέσσερα άκρα για να τα κολλήσουμε με ένα απλό κολλητήρι. Στη μία πλευρά και μετρώντας από κάτω προς τα πάνω λ/4, κάνουμε ένα μικρό κόψιμο 2 εκατοστών. Το τελευταίο στάδιο για τη κατασκευή της κεραίας έφτασε! Μετρώντας και πάλι από κάτω προς τα πάνω 10 εκατοστά σημαδεύουμε και απογυμνώνουμε το σημείο το οποίο θα είναι και το σημείο τροφοδοσίας της κεραίας που μόλις φτιάξαμε! Ναι η κεραία είναι έτοιμη και απομένει να τη στηρίξουμε, περνώντας τη μέσα από το σωλήνα PVC που έχουμε. Σε αυτό το σημείο απογυμνώνουμε τη μια πλευρά από το καλώδιο RG-58 και κάνουμε μια τρύπα στο σωλήνα PVC σε απόσταση 60 εκατοστών από όποια άκρη – τέλος θέλουμε. Η διάμετρος της τρύπας θα είναι όση και η διατομή του καλωδίου RG-58, αφού αυτό θα περάσει μέσα από αυτή. Εδώ χρειάζεται λίγο προσοχή! Λοιπόν θα περάσουμε μέσα από την τρύπα του PVC την απογυμνωμένη πλευρά από το RG-58, από έξω προς τα μέσα και με κατεύθυνση προς τη κοντινότερη έξοδο του σωλήνα. Τώρα βάζουμε τραβώντας τη από πάνω με ένα σχοινί τη κεραία μέσα στο σωλήνα έως ότου το σημείο τροφοδοσίας έρθει στο ίδιο σημείο – συναντηθεί με το απογυμνωμένη άκρη από το RG-58. κολλάμε πολύ καλά στο σημείο τροφοδοσίας και αυτή τη φορά τραβάμε αργά και πολύ προσεκτικά το ... RG-58, από τη πλευρά που βγαίνει από τα πλάγια του σωλήνα, έως ότου η κεραία μπει όλη μέσα στο σωλήνα.

Αφήνουμε τη γραμμή τροφοδοσίας RG-58 να φύγει προς τα κάτω για 10 εκατοστά και μετά τυλίγουμε τέσσερις κολλητές σπείρες (στροφές) γύρω από το σωλήνα κάνοντας ένα απαραίτητο RF CHOKE το οποίο θα σταθεροποιήσουμε με τη μονωτική ταινία που έχουμε. Απογυμνώνουμε και αυτή τη πλευρά από το RG-58 κολλάμε το θηλυκό connector SO-239 και η κεραία είναι έτοιμη για δοκιμές και συνομιλίες!

Για τη μπάντα των 70 εκατοστών – UHF θα διαιρέσουμε όλες τις διαστάσεις με το 3 και ... έτοιμη η κεραία!

Μη ξεχάσετε να ταπώσετε τη πάνω τρύπα για να μη μπαίνουν νερά όταν βρέχει.

Τη συγκεκριμένη κεραία τη χρησιμοποιώ τα τελευταία 2 χρόνια με πολύ καλά αποτελέσματα.

Η κεραία παρουσιάζει εξαιρετικό εύρος, bandwidth.

Αυτό ήταν και ελπίζω να ήταν κατανοητή η περιγραφή ιδιαίτερα στο επίμαχο σημείο της σύνδεσης κεραίας και γραμμής τροφοδοσίας.
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SLIM JIM Antenna for UHF 70cm BAND

Ακλουθώντας τα πιο πάνω έφτιαξα και μια για τη μπάντα UHF. Μετά από αρκετό ψάξιμο στα αρχεία μου (#@!@$#$%&^$#@* = αυτά ήταν … μπινελίκια ) ναι, βρήκα τις φωτογραφίες με τη πειραματική έκδοση των UHF που είχα φτιάξει αλλά δυστυχώς δε τη κράτησα για λόγους καθαρά εργονομικούς!

πατάμε πάνω στη φωτογραφία για μεγέθυνση.

PLL FM 50mw





Parts:
1x BH1417 - Stereo PLL Transmitter IC (Case SOP22)
1x 7.6MHz Crystal
1x MPSA13 - NPN Darlington Transistor
1x 2.5 Turns Variable Coil
1x 3.5 Turns Variable Coil
1x MV2109 - Varicap Diode

1x 6-DIP Switch
ANT - 95 cm copper wire
Technical Specifications:
Input Voltage: 7-15V
Transmission Frequency: 87.7 - 88.9MHz, 106.7 - 107.9MHz (200kHz steps)
Transmitter Output RF Power: 50mW
Audio Frequency: 20 - 15KHz
Audio Input Sensitivity: -10dBV
Audio Input Voltage: 1.0V (recommended)
Separation: 40dB
Power Consumption: 20mA
Dimensions: 83x45x15mm






About 50mW BH1417 Stereo PLL FM Transmitter



This is an excellent Hi-Fi Stereo PLL FM Transmitter, the audio source can be the computer, sound card, game consoles, CD, DVD, MP3, stereo mixer for stereo audio signal modulated emission transmission, the board also contains two mic amplifier, with the common receiver can achieve high-fidelity FM stereo radio FM stereo transmission. Suitable for the production of stereo wireless speakers, wireless microphone, wireless headphones, CD, MP3, DVD, PAD, notebook computer and other wireless audio adapter development and production.

ROHM's new Japan has BH1417 is one of the most simple and practical integrated circuits, which combines phase-locked loop circuit, stereo encoder circuit, transmitter circuit, as well as other additions. Pre-emphasis circuit, limiter circuit and low pass filter can significantly improve the sound quality. The total harmonic distortion up 0.3%, stereo separation to 40dB, RF output level is 100dB. BH1417F is an excellent new IC chip, this circuit improves signal to noise ratio (S / N) of pre-emphasis circuit to prevent signal over emphasized limiting circuit, the control input signal frequency low-pass filter circuit (LPF), generate stereo stereo composite signal modulation circuit, FM transmitter phase-locked loop circuit (PLL) component. BH1417F excellent frequency characteristics, it can achieve 40dB of isolation, transmitted sound quality is similar to local FM radio stations.

External power is filtered by 78L05 5V DC regulated output for BH1417 chip. DIP switches M1, M2 turn on dual microphone amplifier, microphone MIC1 the sound signals into electrical signals by the C3 sent by the V1, R6, R7 microphone amplifier circuit composed of enlarged RP1 adjust the volume by the C5 to C6 into BH1417 later by the left channel signal input. DIP switches D0, D1, D2, D3 used to set the firing frequency. BH1417 Stereo FM carrier signal from the output of the first 11 feet, coupled by the C36 into the V3, R21, L3, C37 composed of high-frequency power amplifier, amplified signal coupled through C38 to launch transmitting antenna ANT1.

BH1417 FM Transmitter chip includes a lot of features in one small package. It comes with pre-emphasis, limiter so that the music can be transmitted at the same audio level, stereo encoder for stereo transmission, low pass filter that blocks any audio signals above 15KHz to prevent any RF interference, PLL circuit that provides rock solid frequency transmission (no more frequency drift), FM oscillator and RF output buffer.

There are 14 possible transmission frequencies with 200KHz increments that users can select with a 6-DIP switch. Lower band frequencies start from 88.7 up to 89.9 MHz, and upper band frequencies start from 107.7 up to 108.9 MHz.

BH1417 can be supplied with 4 - 6 voltage and consumes only around 30mA, providing 20mW output RF power. BH1417 provides 40dB channel separation which is pretty good, although older BA1404 FM Transmitter chip provides slightly better 45dB channel separation.

BH1417 is only available in SOP22 IC case so this may be an inconvenience for some folks. On the other hand, because the chip is smaller than regular DIP-based ICs it is possible to fit the entire transmitter on a small PCB.

BH1417 chip may also be used a stand alone stereo encoder. The advantage of that is that you have full freedom of using a transmitter & amplifier of your choice. You will still have a pre-emphasis, limiter, stereo encoder and low pass filter in one small package because very few external components are required for these blocks. PIN 5 is MPX output that can be directly connected to an external FM transmitter through a 10uF cap.


BH1417 Block Diagram



Main blocks of BH1417 chip are; pre-emphasis, (audio level) limiter, stereo encoder (MPX), PLL circuit, oscillator and RF buffer.



Frequency Selection / Calibration


Frequency selection is very straight forward. Simply select transmission frequency at which you would like to transmit, set the combination for 6-DIP switch and BH1417 will immediately tune to that frequency. If you can't hear the transmitted audio signal on your FM receiver then re-adjust 2.5 turn variable coil until you can hear the signal.
As a test to see how PLL is working you can use a laboratory power supply to vary the voltage supply from 4 to 6V. While doing that BH1417 will automatically vary the voltage for MV2109 varicap diode making sure that there's no frequency drift.

S1
S2
S3
S4
Frequency
ON
ON
ON
ON
87.7 MHz
OFF
ON
ON
ON
87.9 MHz
ON
OFF
ON
ON
88.1 MHz
OFF
OFF
ON
ON
88.3 MHz
ON
ON
OFF
ON
88.5 MHz
OFF
ON
OFF
ON
88.7 MHz
ON
OFF
OFF
ON
88.9 MHz
ON
ON
ON
OFF
106.7MHz
OFF
ON
ON
OFF
106.9MHz
ON
OFF
ON
OFF
107.1MHz
OFF
OFF
ON
OFF
107.3MHz
ON
ON
OFF
OFF
107.5MHz
OFF
ON
OFF
OFF
107.7MHz
ON
OFF
OFF
OFF
107.9MHz



Frequently Asked Questions



This is list of answers to questions that I have received through an e-mail so far. If you should have any other questions please don't hesitate to e-mail them to me.

What is the range of BH1417 Stereo FM Transmitter?
Range of the transmitter depends on many factors.
a) Length and type of the antenna (the longer the better, copper will radiate radio waves better than aluminum)
b) Supplied voltage (6V Max power output)
c) Weather conditions (clear skies & no humid, greater distance)
d) Elevation above the ground (the higher the better)
e) Line of sight (no buildings or trees, greater distance)
f) Whether external amplifier is used

I would like to be able to transmit the music to greater distances. Can you provide any suggestions on how to modify the circuit?
You can connect an external amplifier based on the common 2N3866 / 2N4427 RF transistors. Please keep in mind that it is illegal to operate higher power transmitters in most of the countries without the proper license.

Ενισχυτής Linear FM 700W με λυχνία 3CX800A7








Πομπός FM 20-30W με λυχνία EL504











'Ενας αρκετά ισχυρός ραδιοπομπός για όλους τους λάτρεις των FM και της ΕL504 λυχνίας.
Ο πομπός χρησιμοποιεί την γνωστή ΕL504 πέντοδο λυχνία ισχύος η οποία xρησιμοποιούνταν παλαιότερα στην βαθμίδα εξόδου της οριζόντιας απόκλισης (Υπερυψηλή τάση) της TV.

Παρ' όλα αυτά <<εργάζεται>> πλήρως και σε κυκλώματα αυτοταλάντωτων ραδιοπομπών FM και ΑΜ με ισχύες εξόδου της τάξης των 30W με ιδιαίτερα αρμονική λειτουργία,αλλά και σε βαθμίδες εξόδου πομπών διάταξης PUSH-PULL (2 λυχνίες) με ισχύες τής τάξης των 100W.

H συγκεκριμένη κατασκευή είναι αυτοταλάντωτη με ανοδική τάση 360V, ενώ η ΕL504 <<εκτελεί>> χρέη ταλαντώτη και ενισχυτή ταυτόχρονα.
Η διαμόρφωση επιτυγχάνεται με δίοδο varicap BB105.