开云体育

• 12 KW CCS ON 160-15M....USING THE 3CX-6000A7..... PART 16

Here all the various tank coil taps are completed. Adjustable SS spark gap installed across the vac load cap. After this video was done, the 2nd adjustable SS spark gap was installed across the vac tune cap. Spark gap across the load cap protects the load cap. Spark gap across the vac tune cap protects the vac tune cap AND the bandswitch.

There is also a.... '.7 uh pre-coil'...... that is wired between output of plate block cap assy....and the hot side of the C1 vac tune cap. The anode to grid C + stray C (lower anode fins to chassis) and this .7 uh pre-coil form the step down L network. This transforms the 1600 ohm plate load Z (7200 vdc loaded @ 2.5 amps) down to just 361 ohms @ 21.225 mhz. Then a lower, loaded tank Q can be used for the PI network on 15m. That L network also has a lesser effect on all lower bands. IE: 939 ohms @ 14.175 mhz. 1419 ohms @ 7.150 mhz etc, etc.

The original target value for the pre-coil was .6 uh. (which would have transformed the plate load Z down to just 483 ohms @ 21.225 mhz). Trying to tap a tubing coil is tough enough as it gets.

With the temp 1600 ohm resistor from anode to chassis....and analyzer on output side (and the pair of RJ2B's relays externally powered on), the swr was 1:1 after tweaking the tune + load to the calculated values for each band = jives with the spreadsheet / GM3SEK software. Previously, both the vac tune + load caps were mapped out, with pf vs turns counters....and a cheat sheet made up.

On a similar note, once the tune + load caps tweaked for 1:1 swr, the caps are left alone....and the upper / lower freqs for the 2:1 swr points are noted down. 160 khz wide on 160m, 310 khz on 80m, 600 khz on 40m, 800 khz on 20m, and 1 mhz on 15m.

So far, so good. All measurements for the adjustment of the tune + load caps were done with the top lid on.



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