TPU Clues

BEP · August 04, 2009, 12:44:01 PM

My opinion only....

If 180 is from a TPU it is a result not a drive frequency. To much info points to two drive freeks. One around 2500Hz and the other in the high 15k to low 16k range. With these I get a result tone around 4900Hz. The 4900 isn't steady. It drifts in and out about 180 times a second.

I believe the slight vibration reported was this coupling at around 200Hz.

There still may be a third freek. If there was and it was higher yet, the video camera wouldn't record it. Who knows? Maybe the 15-16 kHz was also a result and not a drive freek?

One thing is sure... we need to stop thinking in dipole antenna terms. This is a traveling wave situation and it is going in a circle therefore pi must be a factor.

What do you get when you divide horizontal sweep by pi? About 5kHz.

Grumpy · August 04, 2009, 12:53:52 PM

What sort of the waveform might the 180kHz be to effect the tv screen like we see in the video?

BEP · August 04, 2009, 01:20:01 PM

Quote from: Grumpy on August 04, 2009, 12:53:52 PM
What sort of the waveform might the 180kHz be to effect the tv screen like we see in the video?

I've made the exact interference pattern while sending CW on 160 meters. Could be almost anything.

Unlikely the videoed TV used a reactance tube controlled horiz. oscillator so AFC with dual diodes was probably used. If so, the interference signal may have been forcing the sweep frequency too high or low. This would cause a periodic blanking and split the frames. The diodes would rectify anything injected. So, a wave form gues is just a guess.

Come to think of it... the 180kHz calculated could just be a limitation of the TV circuits. The signal causing it could have been almost anything above the standard retrace. The AFC may have been cutting in at that rate.

BEP · August 04, 2009, 01:38:38 PM

BTW:

This is something that couldn't be done with SS unless you used true mosfets. I would expect true metal-oxide semi-conductor Fets were still abundant during the SM hayday. They aren't now but are coming back into vogue.

Quote from: BEP on August 04, 2009, 01:20:01 PM
reactance tube controlled horiz. oscillator

It is amazing how low you can resonate a circuit by varying the grid voltage on such a tube pretending to be a capacitor.

Grumpy · August 04, 2009, 03:58:34 PM

what if something was retriggering it?

Quote from: BEP on August 04, 2009, 01:20:01 PM
I've made the exact interference pattern while sending CW on 160 meters. Could be almost anything.

Unlikely the videoed TV used a reactance tube controlled horiz. oscillator so AFC with dual diodes was probably used. If so, the interference signal may have been forcing the sweep frequency too high or low. This would cause a periodic blanking and split the frames. The diodes would rectify anything injected. So, a wave form gues is just a guess.

Come to think of it... the 180kHz calculated could just be a limitation of the TV circuits. The signal causing it could have been almost anything above the standard retrace. The AFC may have been cutting in at that rate.