Recent content by piepermd

The HP unit provides the RF, and the Arduino the LO.

It was OK with the tubes removed but no test equipment, but when I set up for the tests it acted strangely when bringing up the Variac. Usually when I switch on the Variac that feeds the radio power supply the beginning voltage is about 0.4 volts and it increases very rapidly as I turn the dial...

OK, I’ll give it another go.

Did you see that instead of re-installing the 216 varicaps I placed a fixed value 22 pF cap across those three RF stage coils? With that value and up to an additional 10 pF from the trimmers I should be able to receive 126 MHz as my test RF. I am going to modulate it with a 1 kHz test tone. So...

I was just getting set up to do the tests and removed the VTs for the harmonic generator and harmonic oscillator to disconnect those stages. When I brought it up to power, I detected a bit of electrical smell and immediately shut down. I replaced the 9002 and 9003, re-powered, and now all is...

The 218 trimmers are all still installed

So I need to tune coils 222, 223, and 224?

The 216 and 217 mechanically variable capacitors have been removed and would be a pain to reinstall. Can I put a fixed value capacitor across the coils, selected to approximate resonance at the calculated inductance of the coil and use the 218 trimmers to adjust? For the RF coil I estimate an...

Great, thanks. For the first tests of magnitude of the AVC voltage I don’t need to apply any tuning capacitance, correct?

LO at 225 and carrier at 221, correct? Or would it be better to inject carrier at 222?

OK, very good. What should be the range of the RF signal input at the front end as AVC is measured? A few microvolts up to one volt? Should the LO be set to the same signal level as the carrier? To which coil should I apply the carrier signal?

T Thanks, Tom. Good to have you back on board!

My multimeter has a 7.8 MOhm input impedance. Do I just use 11/7.8 as the multiplier? What should I use as the source of the low impedance reference voltage?

That’s easy, because the AVC line goes right out to the Cinch-Jones connector pin.

Many thanks for your reply! I am finishing the power supply for the receiver so I can make some tests. I have cleaned and deoxidized all of the tube pins and sockets after testing the filaments for continuity and applied voltage to the heaters and they all glow. Once I have the B+ voltage online...