12AU7 QRP Transmitter from W0BVT

 The first triode section of the 12AU7 is a XTAL. oscillator transmitter, and the second triode is the choke-coupled modulator.  B+ voltage can be selected form a little hand-crank generator, or the Eico bench power supply.  When using the hand generator 100 mw's of power or less can be expected...with the bench supply at 150 volts, slightly more.  Audio input was from a universal 12AX7 pre-amp. and D-104 microphone.  The D-104 talk bar was taped closed so I could hold the generator down with the left hand and crank with the right hand...while talking!   Only about 50 to 60 percent modulation was possible, and results were improved when using my sweep tube linear amp., which increased output power to more than 1 watt.  

W0BVT's O1A transmitter

Attached is a picture of the two tube O1A transmitter I used on the PW net this morning.  I simply modified the 6L6 rig from a couple of weeks ago and replaced the 6L6's with O1A's.  One tube is a crystal oscillator, and the other tube is a Heising modulator.  Output power is about 200 mw's with the plate voltage at 100 volts, filament voltage was 5 volts.  I could only get about 20% modulation and that is likely the reason only a few stations could copy me.  Suffice to say, band conditions were not great this morning, but I was pleased with the reports I got. 

QRP HF SWR Meter

Here is a link to a nice QRP SWR Meter
http://www.zs6kmd.za.net/pdf/QRP%20SWR%20Meter.pdf

W0BVT's 6L6 Heising Modulated Rig

The attached picture is the 6L6 XTAL. oscillator, 6L6 Heising modulated transmitter used on the net today.  I usually monitor the output with my bench scope but didn't have it on today.  The modulation envelope is greatly effected by antenna loading and adjusting the tank circuit, typical of a simple one tube oscillator transmitter.  I suspect that would be the reason one sideband was more attenuated.  Other obvious compromises are only being able to modulate the carrier at 50%.  In my quest for simplicity it's always interesting to see what can actually work.  The tank coil was marginal as well, shades of the Elmac AF-67, eh?  

One Tube Regen

Here is a really neat little "one" tube Regen receiver from my friend Dale AE0S, picture attached.  It uses a 1625 tube, the only voltage required is 12 volts D.C. for both the filament and plate supply.  It will tune from about 3 mhz. to 7.4 mhz,
Dick, W0BVT

W0BVT's 5763 QRP rig.

This is a picture of Dick's H.B. QRP XMTR that he used on the net today.   It uses a 6C4 XTAL oscillator, 5763 PA and a 6AQ5 modulator.

K0ASK's Retro-75

Bob fired up his Retro-75 for the first time today, 3/26/12.  He was heard by all members of the PW Net.