25L6 QRP 160/80/40/30 METER CW TRANSMITTER

Description

I make to these to order so please allow 7 to 10 days for shipment.
Listed as used because now and then I may send a tested used tube, antenna BNC or 1/4" used key jack. Better than 90% of the components are either new or nos.
This is a quirky little novelty QRP transmitter. Since 160 meter crystals are hard to come I have provided a simple vfo circuit for that band only. The vfo can be used in lieu of crystals on 160, or you may use either the standard FT-243's or 49U QRP crystals on any band.
Attempting to use vfo control with this circuit, for 80 meters and higher, will not work because when you get much above 2 mhz in frequency the tone begins to take on a saw tooth waveform, which is not acceptable on air.
In the 160m vfo mode, because it uses only one tube with no buffer stage between the oscillator and antenna, you get a nice sort of sing-song mellow cw tone, akin to the old copper coil Hartley MOPA transmitters.
There's no voltage regulation, but after a warm up of 20 minutes or so you will get very little vfo frequency drift.
No switches to throw when going from vfo to crystal control. Just pull out the coil and insert a crystal for the desired band, along with a blank jumper crystal holder that is plugged in behind the crystal in use. This is just a pin to pin jumper wire technique that I thought of and it works quite well. One of these, along with several crystals will be provided with this package.
You may use a 6V6, 6U6, 6W6, 12V6, 12W6, 25W6, 12L6, 17L6, 25L6, 35L6 or 50L6 tube in this circuit. The pin-outs are all the same, so there's nothing to change but the tube, with appropriate filament voltage applied. The best performers are the 'L6 versions. I will send a 25L6 unless you specify otherwise.
With about 50 volts for the plate B+ I get around 600 to 650 milliwatts RF output, depending on the band in use. You can go as high as 75 volts for the B+, which will produce over 1 watt output.
The PA tank circuit employs a parallel/series configuration, like the old Paraset Spy radios used. I like this circuit because it seems to be more forgiving when using random length wire antennas. SWR is not that critical with this arrangement. But like the standard Pi-network it has both plate and antenna loading controls. In most cases I can get this circuit to load into a random length wire with an earth-ground counterpoise (ground rods, cold water pipe, etc.).
Once you get the tuning set properly this little transmitter keys well. In most cases I can use the small QRP China crystals and achieve nice cw keying tone.
You will receive QRP crystals and coils for the 80, 40 and 30 meter cw bands, along with the vfo and tank coil for 160m operation (only one crystal per band, 80, 40 & 30m).
A hand sketched schematic, along with the power supply wiring harness will be provided with this purchase. No power supply is included. You will need both a filament and B+ supply. An exception would be if you want to use a 50L6 tube, then you could just use one 50 volt supply for the operating voltage. Just let me know if you want a 50L6 in lieu of the 25L6. No extra charge.
So this little rig uses the old world nostalgic analog circuitry, which can be a lot of fun to operate for us hams who remember the radio days of the 1950's and beyond.
SHIPPING TO THE UNITED STATES ONLY.