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Collins 70H3 PTO > VFO?




 
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Author Topic: Collins 70H3 PTO > VFO?  (Read 529 times)
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Carl WA1KPD
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« on: December 09, 2020, 02:04:04 PM »

I recently acquired one of these and would like to make it into a VFO to feed 6AG7s and the like.
Google has not been much help. Has anyone done this?
TIA
Carl
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Carl

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Pete, WA2CWA
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« Reply #1 on: December 09, 2020, 07:07:21 PM »

I thought the PTO was self contained - i.e. you supply the necessary voltages and it puts out a signal from 1.5 to 3.0 MHz. You need to develop a frequency readout and possibly a mixer to take the PTO signal to a frequency range useful in the ham bands. Obviously, for 160 meters, it's good to go as is except for frequency readout.
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« Reply #2 on: December 10, 2020, 12:50:53 PM »

I use one with a 6L6 doubler circuit to drive a Gates BCI-T on 75.  The filaments in the pto are in series.  I rewired them for 6.3 volt operation. It works really well, very stable.  For a frequency readout, a pickup wire near the output coil feeds a digital freq. counter.
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Carl WA1KPD
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« Reply #3 on: December 10, 2020, 01:01:39 PM »

Roy,
Thank you
I assume you feed the output after the 100pf cap diretl to the grid of the 6L6.
Did you hook up the 28 VDC for the oven?
Carl


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Carl

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« Reply #4 on: December 16, 2020, 02:45:51 PM »

The output fed to 6L6.  Did not connect the oven. The output of the 6L6 goes to a 6146 amp stage then to the Gates rf  driver tubes.
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