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AK4YG -- Kenwood TS-820S 30M WARC mod info

THINGS YOU NEED TO KNOW:

• This is based on the article from Feb 1983 QST, available as a PDF from the ARRL online archive.
• You should do this mod in four stages. First, get receive working on 30 meters. Next, get the driver coil working on 30 meters. Next, build and test the relay control board. Finally, do the modifications to the output circuit and install the relay control circuitry.

STAGE 1:

This is documented very well in the QST article. A couple of points:

• You need a very small diddle stick for adjusting the PLL and the antenna and mixer coils. You can buy a 1/4" hardwood dowel at the hardware store and carve one that will work, or you can buy one on eBay, Amazon, Mouser, or elsewhere.
• The mod specifies a HC-18, 3rd order 15.500 MHz crystal. This isn't crucial -- an HC-49S crystal (the short one) on the fundamental works just fine.

STAGE 2:

• If you use the same coil forms I did, you need a hexagonal diddle stick for adjusting the core. You can carve one out of a dowel or buy one.
• Adjusting the coil/capacitor with a grid dip oscillator or an antenna analyzer outside the radio will not work. A rule of thumb: get the coil/capacitor combo to resonate at 10.250 MHz with the slug at about the halfway point, then remove 20% of the turns. On a J.W. Miller 23A014-2 form (equivalent to the one they mention in the editor's notes at the end of the article), I needed 20 turns of 30 AWG wire (from Radio Shack works fine) to resonate outside the radio with the 56 pF cap, and 16 turns to resonate inside the radio. The reason for this is that the additional capacitance from the drive capacitor will bring down the resonant frequency. If you want to test if you have it right without turning on the radio, you can put a GDO loop (or a loop of 3 turns of hookup wire attached to an antenna analyzer) around the coil while it's in the radio (make sure the bandswitch is set to JJY/WWV and the drive control is at the halfway mark).
• You can test whether this part of the mod works before you modify the finals. Hook up a dummy load or 50 ohm resistor to the antenna terminal and set the SG switch to off. Turn on the radio, let the tubes warm up, set the meter to ALC, set the carrier control just past the halfway point, put the radio in TUN mode, tune to 10.125 (or 10124.2 really), turn on the 25 KHz marker, adjust the drive control to peak the S-meter (should hit S9 if you've done Stage 1 correctly), put the radio in send mode, and adjust the core of the new driver coil to peak the meter. As you get close to the right adjustment, you may have to back off the CAR control to keep the meter from pinning.

STAGE 3:

You can use 2N4401 / 2N4403 transistors here rather than what the article specifies.

A 1N4007 diode works fine for the diode here.

You can use an Omron MY4-DC12(S) relay from Mouser here.

STAGE 4:

Adding the additional switch contact is easy per the directions in the article.

I gave up at this point and did not finish the mod. Perhaps I'll buy some longer / narrower tools and try it again. With regular tools, and without removing the plate and load capacitors, it is incredibly difficult to disconnect the wires to the loading capacitor terminals, let alone strip them, solder them, and put heat shrink over the connection. If you have better tools, smaller fingers, or more aptitude than I do, this part may not be so bad for you.

73,
Ben (AK4YG)