[JMS] Info needed on 90800 transmitter

Sat, 8 Nov 2003 16:15:08 -0800 (PST)

Jim:
Many many thanks to you (someone who I consider a "legend" in the ER authorial ranks). I do recall you writing an article for ER on Millen equipment but due to my current deployment, my "stuff" is currently in storage and I'm limited to my time getting at the old ER's. I just acquired the 90800 about a month or so ago along with a matching nice condition Variarm VFO. I'd like to put them both back on the air.

I'll start by acquiring a small rack mount cabinet and bolting all of this stuff in. Also, looks like I'll be punching holes in metal to make a power supply. Thanks.  73 de Cal, N6KYR. 

JAMES T HANLON <[email protected]> wrote:
Cal,

1) The original coils for the 90800 are in the 430XX series. The proper coils for 80 meter operation are the 43082 in both the 807 and 6L6 plate sockets. The cathode coil for 160 meter crystals doubling in the plate of the 6L6 is the 43680. If you use 80 meter crystals and go straight through in the 6L6, you set the cathode coil switch to "out."

2) The Key terminal, "K," on the ceramic terminal strip is wired to key both the 6L6 and 807 cathodes together. 

3) I just use a bnc connector mounted in a bracket that I hang off of one of the screw holes in the chassis. You may need to supplement the number of turns on the link to achieve the desired loading. 

4) The manual calls for a high voltage supply between 500 and 750 volts. It doesn't specify the total current draw - there is a voltage divider network that derives voltage for the screens and 6L6 plate. 200 ma should be plenty. Limit the voltage to 600 if you intend to modulate the 807. You will also need -45 volts for grid bias on the 807 - I use five, nine-volt transistor radio batteries in series. And of course you will need 6.3 volts at 1.8 amps for the filaments.

Jim, w8KGI

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