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I've built many transmitters over the years, but this one was definitely the most fun! It uses a 6AG7 crystal oscillator to drive an 807 final. The oscillator design is directly out of any 1960s ARRL Handbook, and the basic design for the final came from one of my favorite project books, '104 Ham Radio Projects for Novice and Technician' (TAB Books, 1968). The note and keying are about as clean as you're likely to hear from a homebrew rig.
I originally built this rig in 1998. It started out with a 6V6 in the oscillator, but I rebuilt the oscillator section in the autumn of 2003 and changed the tube to a 6AG7. In early 2004, I modified the circuit so as to allow VFO operation.
I used as many vintage parts as possible during construction to ensure that the finished product would have a 1950s look. The oscillator and PA tank coils are wound on 1-1/4' diameter red bakelite 5-prong coil forms from an unknown manufacturer. The tube sockets and coil sockets are steatite with silver-plated contacts, probably made by E.F. Johnson. The steatite crystal socket and 807 plate cap are James Millen parts. The plate current meter is war-surplus item made for the U.S. Navy by Westinghouse. The PA grid tuning capacitor is a vintage Hammarlund. The PA plate and loading capacitors were made by E.F. Johnson. The plate choke is an old Heathkit part. The handles on the front are WW2 U.S. military surplus. The enclosure is a 1950s Bud hinged-top steel cabinet with black wrinkle finish.
The aluminum chassis was made for me by Walt Martin, KB5HOV, out of 1/16' aluminum. I made the shield around the oscillator out of two aluminum Bud box lids, held together at the corner by some scrap angle brackets. Other than fabricating the chassis, I did all of the metal work and painting myself. I guess the only thing keeping the rig from looking totally 1950s authentic is my use of Dymo labels instead of vintage water-slide decals (and that's only because I haven't found any yet!).
I power this transmitter with a Heathkit HP-23A power supply. With +750 VDC on the PA plate and +260 VDC on the oscillator plate, output power is about 65 Watts.
Below are several photographs of the finished transmitter:
At the very bottom of the page, you will find the schematic and parts list for the 807 CW transmitter. I suggest you read the following text carefully first, before you spend any time with the schematic. There's some good information here, and some important safety information that you must not skip.
Notes:
- Plate current at maximum output power should be in the vicinity of 110 to 120 mA with a high B+ supply of about +750 VDC.
- You can use anything from +500 VDC to +800 VDC for the high B+ supply. Power output, of course, will be a function of plate voltage.
- You can use anything from +200 VDC to +300 VDC for the low B+ supply, but don't exceed +300 VDC because the maximum rating of the 6AG7 is +300 VDC.
- You can either build your own power supply or buy a commercially-made supply.
- If you want to buy a power supply, two great candidates are the Heathkit HP-23 and HP-23A. Use the 6.3 VAC output for the tube filaments, not the 12.6 VAC output! I recommend that you set the Low B+ selector to the 250 VDC position because the +300 VDC setting will probably run higher than +300 VDC at today's higher AC line voltages. You can also use the HP-23B, HP-23C, or PS-23, but you'll have to wire the tube filaments in series and use a 12 Volt pilot lamp bulb because those later models don't have 6.3 VAC filament outputs. The older Heathkit HP-20 will also work, as long as you wire it to put out 6.3 VAC for the filament voltage. The much older Heathkit UT-1 will work, although the High B+ is only +600 VDC, so your transmitter output power will be substantially reduced. As with the PS-20, be sure to wire the filament output for 6.3 VAC. The Heathkit HP-23 and HP-23A supplies are quite common, easy to repair, and don't cost an arm and a leg, so they're really a good choice. Other vintage power supplies should work fine, too, as long as they meet the voltage and current requirements for this project.
- If you want to build a power supply, refer to older editions of the ARRL Handbook from back in the 'vacuum tube days'. Make sure that your chosen power transformer can supply enough current to power the oscillator and power amp. Look for one that can put out at least 150 mA. If you have a large enough chassis and cabinet, don't be afraid to build the power supply into the transmitter.
- You will find the tube pinout information in any older edition of the ARRL Handbook, GE or RCA Vacuum Tube Manual, etc. If you don't have an old Handbook, GET ONE. They're readily available on eBay and at hamfests. Until yours arrives, you can pay a visit to your public library. They should have one.
- Trimmer capacitor C1 should be adjusted for the least amount of crystal 'chirp'. Although a value of 8 - 50 pF is shown in the parts list, anything in that general range will work fine.
- Feel free to install several different types of crystal sockets, wired in parallel, so that you can use different holder types. The most common ones will be the ol' faithful FT-243 and the more modern HC-33/U, and you might want to include one of those big ol' sockets for BC-610 crystals. Alternatively, you can make up some adapters, which is what I did. Having more than one socket type means that you'll have more chances of finding crystals that you can use. Don't bother with those tiny little HC-18/U and HC-25/U crystals (the kind used in CB radios, scanners, and so on). They aren't designed for the kinds of voltages that this transmitter will present to them.
- SW1 is the 'XTAL / VFO' switch. Setting the switch to the 'VFO' position converts the 6AG7 oscillator into a buffer stage. The 0.01 uF capacitor that is switched into the circuit kills the tendency for the 6AG7 to oscillate.
- SW2 is the 'Spot / Send' switch. In the 'Spot' position, it allows you to key just the oscillator so that you can find your signal with your station receiver. In the 'Send' position, the PA becomes active as well.
- The oscillator stage is the classic 'Grid-Plate' oscillator from the ARRL Handbook. For best performance, the ARRL recommends that you stick close to the component values shown in the parts list for the oscillator stage. I've found their recommendations to be correct.
- When you choose your fixed-value capacitors, be mindful of the DC and RF voltages which could be present in the circuit! I suggest you use caps with at least a 1 KV rating for those parts whose ratings aren't otherwise specified.
- I recommend that you make the 80m and 40m coils interchangeable so that the rig will work on both bands. There are several ways you can go with this. You can use vintage plug-in coil forms, which require a matching socket (you'll find 4-, 5-, and 6-pin styles out there). You can use octal tube sockets and tube bases (salvaged from some old 'dud' tubes). You might get lucky and find some vintage ceramic James Millen jack-bars which will allow you to use B&W or Air-Dux coil stock. Just use whatever you can find, but be sure you can find enough to handle the number of coils you intend to use (two per band!).
- If you find coil forms that are some diameter other than 1-1/4', that's no problem. You'll just have to re-calculate the coil parameters. You'll find the formulas for calculating coil parameters in any ARRL Handbook (how's your high school algebra these days?). No, I will NOT help you do this. If you don't already know how, then you need to learn how. I'm not trying to be a 'meanie'. If you plan to build equipment like this, you'll have to know this stuff anyway.
- If plug-in coils aren't your thing, you can always come up with some kind of band switch arrangement. You'll need to be able to switch both the oscillator and PA tank coils. You could use separate switches or a multi-deck switch for this.
- No, I don't know where you can buy these parts, so please don't ask. You'll have to scrounge for them, just like I did. Where should you look? Hamfests, surplus stores, electronic parts catalogs, other hams' junkboxes, eBay auctions, For Sale listings on QRZ.com, QTH.net, and the Usenet newsgroups, and so on. I often buy other hams' old homebrew projects and old military surplus equipment and strip them for parts. Hunting for the components for a project like this is a big part of the fun! Besides, nothing truly rewarding ever comes easily. The harder you work for something, the more it will mean to you in the long run.
- You'll need some means of switching your antenna between your receiver and the transmitter. Go figure it out.
- Don't try to use your typical electronic keyer with this cathode-keyed circuit unless your keyer has a keying relay or a really stout keying transistor that's rated for high voltages and high currents.
- Tuneup is simple. Set C7, C14, and C15 to mid-range. Connect the transmitter to a suitable antenna or 50 Ohm dummy load. Plug your Morse key into J3. Apply power to the transmitter and let the tube filaments warm up for a minute or two. Set SW2 to 'Spot' and hit the key. Tune in your oscillator signal on your station receiver. While listening to the receiver, adjust C7 for the loudest signal. Let off the key. Set SW2 to 'Send' and hit the key. Watch the plate current meter and adjust C14 for the LOWEST plate current (known as the 'dip'). Adjust C15 to bring up the plate current by 10 to 20 mA, then dip again using C14. Repeat this alternating process until you're loaded to 110 to 120 mA output. You can watch your Wattmeter also. When bringing up C15 no longer increases your power output, you're fully loaded and there ain't no more power gonna come. In any case, C14 will always be your last adjustment of the PA stage. If your keying sounds chirpy, you may need to touch up a bith with C7.
Apr 08, 2014 807 and 6L6GC TUBE POWER AMPLIFIER / HYBRID CIRCUIT Phinoy itho hehe. D-Lab dual 807 Tube guitar amp project Creature. Cayin CS-845A Type UK Integrated Valve Amplifier Unboxing - Audio. Direct-coupled Single-Ended (SE) 6V6 and 6V6GT Tube Amplifier Schematic with ECC83 Driver Stage. From the book Build your own Audio Valve Amplifier by Rainer zur Linde. Dainius Zokas Valve Amplifiers. Quad Valve Amplifier Mini Audio. Nov 29, 2011 I intend to use 807 beam tetrodes in a push-pull circuit triode connected with B+ 425V. The data sheet specifies Vg2.
This project involves LETHAL power supply voltages. You must use great care when working with this circuit. Never forget that death is a permanent condition! Any homebrew project like this might involve troubleshooting a live circuit. If you don't feel comfortable working with high voltages, then you should either forget about messing with tube-type equipment, or get friendly with a local ham who is experienced with this stuff and ask them to assist you and teach you what you need to know (this person is known as an 'Elmer', and every ham, new and old, should have at least one!). I recommend the latter. Never be afraid to ask for help! It's much better to feel stupid for asking than to BE stupid and get yourself killed because you didn't ask!
Single-Ended 807 Tube Amplifier I have stated in the past that my mate Don makes an amp a month. This month Don has completed an 807 amp based on a schematic designed by Matt from the USA and the same as I built a short time back. I took a short listen and thought it OK but a.
If you use plug-in coils, you MUST turn off the power to the transmitter and allow the power supply filter caps to discharge completely before you change coils! A good way to quickly discharge the filter caps is to switch off the power supply, switch the transmitter to the 'Send' mode, lock your key in the 'down' position until your signal has disappeared completely from your station receiver, then wait another 30 seconds.
It seems really silly to me to even have to mention any of this, but I just know that some knothead would kill himself changing coils if I didn't!
BACK
| 807 | |
|---|---|
|
Three 807s and an early 6L6,
Left, British Emitron brand 807 |
|
| Classification | Beam-power tetrode |
| Service | Class-A amplifier, (single-ended) Class-AB amplifier, (push–pull) Class-C amplifier, (radio frequency) |
| Cathode | |
| Cathode type | Indirectly heated |
| Heater voltage | 6.3 |
| Heater current | 900 mA |
| Anode | |
| Max dissipation Watts | 25 W |
| Max voltage | 600 V |
| Socket connections | |
| American 5 Pin, (UY) Pin 1, Heater |
|
| Typical class-A amplifier operation | |
| Anode voltage | 300 V, (600 V) |
| Anode current | 83 mA, (40-75 mA) |
| Screen voltage | 250 V, (300 V) |
| Bias voltage | -12.5 V, (-29.5 V) |
| Anode resistance | 24 kΩ |
| Typical class-C amplifier operation | |
| Power output | 24 W, (plate dissipation = 16.5 W max) |
| Anode voltage | 475 V |
| Anode current | 83 mA |
| Screen voltage | 300 V (screen dissipation = 2.5 W max) |
| Bias voltage | -50 V |
| Typical class-AB amplifier operation (Values are for two tubes) |
|
| Anode voltage | 400 V (AB1), 600 V (AB2) |
| Anode current | 90-119 mA (AB1), 90-240 mA (AB2),(zero to max signal) |
| Screen voltage | 300 V (AB1), 300 V (AB2) |
| Bias voltage | -45 V (AB1), -25--30 V (AB2) |
| References | |
| Philips Valve Data Book, Philips Electrical Industries, 69-73 Clarence Street Sydney, Radio Valve Application Division, 1958 Radio Valve Data, Eighth Ed. Iliffe Books Ltd., London, 1966 |
|
807 tube pinout diagram
The 807 is a beam tetrodevacuum tube, widely used in audio- and radio-frequency power amplifier applications.
Audio uses[edit]
807s were used in audio power amplifiers, both for public address and Hi-Fi application, usually being run in push-pull pairs in class AB1 or AB2 giving up to 120 watts of usable power. The plate voltage limit is 750 volts and the screen grid limited to 300 volts. Because of the 300 volt screen grid voltage limit, the 807 cannot be triode connected for high power applications. Failure to observe this precaution will cause screen grid failure. Less commonly a single 807 was used in a pure class-A, single-ended audio output stage delivering about 10 watts.
RF uses[edit]
The 807 is fully rated to 60 MHz, derated to 55% at 125 MHz in Class C, Plate-modulated operation, thus they were popular with amateur radio operators (radio hams). In this application a single 807 could be run in class-C as an oscillator or amplifier which could be keyed on and off to transmit Morse Code in CW mode. For voice transmission on AM a final amplifier with one or more 807s, up to about four, could be connected in parallel running class-C. Connecting multiple 807s in parallel produced more power to feed to the antenna. Often the modulator stage (simply a transformer-coupled audio amplifier for A.M., with the secondary of its output transformer in series with the anode supply of the final amplifier), was also constructed using 807s. Many hams found multiple paralleled 807s a cheaper alternative to a single larger valve, such as a single 813, as many military surplus 807s became available cheaply after World War II. In Australia 807s are affectionately referred to as 'stubbies' because they are almost as ubiquitous as that common Australian beer container.
The class C operational values in the info box at the right are for anode modulated A.M. operation; for CW operation a maximum anode voltage of 600 is permissible, whereby the anode current increases to 100 mA and the anode/plate dissipation rises to 25 watts. The screen voltage is the same, at 300, but its dissipation rises to 3.5 watts.37 watts of R.F. power is produced from 220 mW of drive but only a 50% duty cycle is allowed. The maximum allowable negative control grid, g1 excursion allowable is -200 volts and average control grid current is 5mA in both A.M. and CW modes.[1]Later versions could be used on CW with a supply voltage up to 750 V and a current of 100 mA to produce 50-55 watts of output power.
Portable Audio Amplifier Schematics
Differences from 6L6[edit]
The electrically similar 6L6 was not favored by hams because high transient voltages on the anode when operating in class C could cause a flashover between pins 2 and 3 on the octal base, whereas the 807 had the anode connected to a top cap, physically distant from all the base pins.
Derivatives[edit]
The 1624 (VT-165) is an 807 variant with a directly heated filamentary cathode operating at 2.5 V, 2 A.
The 1625 (VT-136) is an 807 variant with a 12.6 V heater and a 7-pin base. These tubes were used as RF power amplifiers in some of the SCR-274 and AN/ARC-5 'command set' transmitters of WW2. Postwar, 1625 tubes flooded the surplus market, and were available for pennies apiece. Surplus 1625s found some commercial use, notably the use of a pair as modulator tubes in the Heathkit DX-100 amateur transmitter.
The HY-69 is an 807 variant with a 5-pin base and a directly heated filamentary cathode operating at 6.3 V, 1.6 A.
The 5933/807W is a ruggedized military version of the 807. It uses a shorter, straight-sided T12 bulb, which provides better element support for improved microphonics and shock/vibration resistance.
Tube Audio Amplifier Schematics
The ATS-25 is a military version with ceramic base.
807 Amplifier Schematics
The Г-807 (G-807) is a Soviet/Russian version. The 6П7С (6P7S) is similar to Г-807, but with an 8-pin octal base.
The 807 also found some use as a horizontal output tube in early TV receivers, particularly those manufactured by DuMont. The 807 design (with some 'value engineering' to reduce production cost) was the basis for the first application-specific horizontal sweep tubes such as the 6BG6G and 6CD6G. The redesign mainly involved the omission of some of the internal RF shielding, and the substitution of a bakelite Octal base for the micanol or ceramic 5-pin.
In turn, these low cost sweep tube derivatives found some use as RF power amplifiers in homebrewamateur radio transmitters in the 1950s.
Slang[edit]
Ham operators in the US sometimes use the term '807' to refer to bottles of beer due to the shape of the tube.[2][3]
See also[edit]
- 6CA7 / EL34
References[edit]
- ^R.C.A. Air-Cooled Transmitting Tubes, Technical Manual TT3, R.C.A. Manufacturing Company Ltd. Harrison, New Jersey, 1938
- ^'Ham Speak – Know the Lingo'. QRZ.com. Retrieved 9 May 2012.
- ^Midwestern Journal of Language and Folklore. Department of English and Journalism, Indiana State University. 1978.
...amateur slang such as handle (the name of an operator), lid (a poor operator), rig (radio set, equipment), 807 (a can of beer – from resemblance to a now obsolete transmitting tube), and XYL (ex-young lady: wife).
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