Not to the Halls of Montezuma or the Shores of Tripoli but to a city about 40 Miles from my QTH... Los Angeles. We'll have to see how that unfolds.
I have great respect for the United States Marines Corp having served with them in Regimental Landing Team 4 at Chu Lai. I guess this raises many questions as a Marine Deployment is very serious business. We are all thinking was this necessary or just a photo op in the quest for relevance. We all sort of know the answer.
Changed out the AGC circuitry on the HW-32A and while some improvement it did not resolve the low receive issue. I noticed some excessive heating in the 12VDC power supply to the rig filaments, and I pulled the final tubes as I suspect a possible short in the finals. That is unrelated to the low signal level detection.
With the finals out of the circuit and No HV supplied, I tested some of the transmit functions. The VOX works and with an external receiver using a 1-foot antenna I could hear the HW-32A running only the driver (12BY7A). It was clear and no distortion and both sidebands work.
This last test is significant in that we have some proof that the transmit only and common functions work. It was at the end of the day, so I only did a listen test and what I need to do is look at the actual waveform from the 12BY7A. A snoop loop wrapped around the 12BY7A tube has been used in the past and that will be the first attempt. Film at 11PM.
I had a curious observation and not clear as to why. There are actually test points on the HW32 circuit board. One of those test points is on the output of the heterodyned signal.
In the photo above we see V13 and V14 and L3. The secondary side of L3 feeds the Cathode of the Receive Mixer V8B through a chunk of shielded cable and just to the right and mid-cable is the Letter "C". This is a test point. So, I hooked my scope probe to this point and saw a waveform and the frequency was about 16.5 MHz. This is validation of the heterodyne operation and in the correct range. L3 also feeds the transmit mixer not shown.
Now the curious part as I tuned across the signal from the signal generator which was on 14.25 not connected to the circuit and about 5 feet away suddenly the S Meter read 20/9 (that is what it should be). Now remove the scope lead and back to S5. It is repeatable. I also note an increase in background noise. Removing the scope lead and substituting a wire with a clip lead (From Parts Candy, FB stuff) the same result.
THIS is telling me something but what is it saying. I need to noodle through that a bit.
Go back to V8B and this is in reference to a recent post on Hackaday about a 1-tube SDR receiver. I am having trouble seeing how that receiver works from what is described in the hackaday post.
But I could see if we took a 12AX7 which is two Hi-Mu independent triodes and using V8B as an example we could feed a quadrature LO into the cathodes and using a splitter (FT-37-43 Core) feed RF into the grids we could produce and I and Q signal streams to feed a computer sound card and we are off and running. That would be a single tube SDR Receiver.
We could have a 2nd 12AX7 used only transmit and then it would be a two-tube low level SDR transceiver.
Them that know can make it go.
73's
Pete N6QW