There was also a mod described in QST that helped with the drift issue.
I'll forward it to you if you like. Actually I didn't have much trouble
with the keyer, but when I used an external straight key I had a rapid
and severe drift as the heat from the final warmed up the PTO. The QST
mod keeps the FLS circuit active during transmit with an external key.
It just involves moving some wires around.
Bob WB2VUF
Stuart Rohre wrote:
>
> Some Scouts can benefit from having adjustments to the NPO type caps to set
> minimal drift in CW mode. See the manual for why a PTO drifts in the Scout.
> The computer can only correct it up to about 25 wpm code speed, unless you
> pause periodically in sending, (which most folks would do anyway). That
> gives time for the PTO to be corrected for any heat drift. Otherwise there
> will be a step correction at first pause. If you adjust the NPO type
> compensation to minimize drift from normal heating, you do not have to
> correct the PTO as often.
>
> Just adding a fan blowing on the heat sink when running 50 watts will help
> the PTO stability some have found. I guess it keeps conducted heat from the
> front of the radio here the PTO is.
>
> Other mods are to place a pot for the fixed resistor that sets RF gain, and
> to place an outside pot to adjust power, replacing the on board bottom
> facing trimpot. Use of flat cable allows the 3 pot leads to be run out the
> back of case between lid and back wall to a bracket mounted pot. Another
> version makes the mike gain a fixed resistor and uses that 10 k pot to
> replace the power pot.
>
> If you mainly run SSB, you will not need to do anything to the PTO about
> thermal (normal) drift of the LC circuit. The computer will correct. It
> only comes up in CW because the computer also runs the keyer, and there is
> not enough time at speeds above 25 wpm to do both. However, who runs 20
> plus words per minute without pauses? I think it is more of a possible
> concern than a real concern, as the instructions point out the simple fix,
> pause in your sending.
> 73,
> Stuart K5KVH
>
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