Heathkit HX-20 Transmitter, HR-20 Receiver

[VE3DDY]

Does anyone know of mods to improve stability and selectivity etc on these rigs?
Other mods for Audio quality etc would be greatly appreciated as well.
Jim VE3DDY

[WD5JKO]

Jim,

  These are SSB rigs, and the specifications don't look too bad for the vintage. I wonder what you are specifically looking for, and whether you are suffering from age related equipment problems, or maybe just looking for some tweaks to the Heath design.

http://www.heathkit-museum.com/ham/hvmhx-20.shtml
http://www.heathkit-museum.com/ham/hvmhr-20.shtml

Jim
WD5JKO

[VE3DDY]

Jim,

  These are SSB rigs, and the specifications don't look too bad for the vintage. I wonder what you are specifically looking for, and whether you are suffering from age related equipment problems, or maybe just looking for some tweaks to the Heath design.

http://www.heathkit-museum.com/ham/hvmhx-20.shtml
http://www.heathkit-museum.com/ham/hvmhr-20.shtml

Jim

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I;m looking for specific mods on improving stability of the VFO's and selectivity on the Rx.
I came across a mod by W4NUT in Dec '65 of 73 which described swapping out the 6146 for a 4X250 etc but the current 50 watts output is sufficient for me.
Jim VE3DDY
 
WD5JKO

[WD5JKO]

Jim,

   It looks like those rigs you have are rare.

In general you can stabilize the oscillators by regulating the filament voltage, and add a small quiet DC fan. This combination should help with line voltage excursions causing drift, and reduce drift from temperature buildup in the VFO area. You can also play with temperature compensation of the oscillator components. If the rigs have any crystals, they too will drift if they are in an area that heats up. Here you could find s suitable PTC thermistor that transitions around 50C, and attach to the crystal as a heater making a poor mans crystal oven.

Going further, you could try one of the many Huff & Puff VFO stabilizers that are available. Here are some links:

http://www.cumbriadesigns.co.uk/x-lock-TR7.htm

http://www.hanssummers.com/huffpuff/library.html

http://members.ziggo.nl/cmulder/drake.htm

My vote is the XLock..I use one here on a Lakeshore band Hopper VFO:



Jim
WD5JKO

[W1LO]

I assume you have a good cable set for the power supply.   A schematic of the cables would allow me to get my pair on the air.  They will look great next to my Comanche, Cheyenne pair and my Warrior amp. I love the look of the Heathkit "chrome line"!   Warren , W1LO.  buzzard.buzzard@gmail.com