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Old 4th Apr 2020, 3:38 pm   #11
Jon_G4MDC
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Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
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Default Re: Kenwood TK-359 VCO adjustment.

Yes can clearly see 2pole and 3 pole helical resonator filters.
In Pye sets that used to be a 2pole between Ant & RFamp then 3 between RF Amp and Mixer. The slugs in these were a polythene type material as seen here.

I think the other 3 adjustments are more likely what you are looking for except I'm not sure what it is lurking down the holes in the casting. Are all 3 the same?
Trimmer capacitors or potentiometers I wonder. It doesn't look like inductor cores...

2 capacitors and 1 pot might be good. 2x VCO adjustments and TX peak deviation maybe.

Do you have an RTL-SDR dongle? (the ones that were used for Digital TV but which can also tune VHF / UHF)
Makes a good poor mans spectrum analyser even if you can only span max of about 1MHz.

One of these with a bit of wire for antenna, placed near the chassis, would enable you to find the VCO quite easily and
then you can watch what happens as you tweak. You will see it pull to a fixed frequency when you hit lock. This way you might get away
without having a testpoint to measure tuning line Voltage.

(Later added: A further thought, the fact that the dielectric trimmers for what I called a 2pole filter are some way apart might mean that actually they are the VCO adjustments. Then they could be single resonators 1 TX 1 RX maybe... On reflection I think you already concluded this. )

Last edited by Jon_G4MDC; 4th Apr 2020 at 3:54 pm.
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