>
> Here is the mod from QST to reduce drift in the Scout when using an outboard
> key or keyer.
> > The mod was described in July 1994 QST by W5UXH. It allows the FLS to
> > operate continuously when an external key is used. I tried this mod and
> > it does make a dramatic improvement. Before the mod I had a lot of drift
> > during warmup when I used a straight key.
> >
> > Here's how to do it:
> >
> > Disconnect the two wires (white and red) from the key jack. Solder these
> > two wires together and insulate them with sleeving. The white wire is
> > the TUNE function, and the red wire is a keying input to the processor.
> >
> > Connect a new wire from the key jack to the wire that comes from the
> > logic board connector 59 to the control board connector 7. There are two
> > pins on these connectors but they are connected together. This wire
> > carries the keying output from the processor to the T/R circuit. I made
> > this connection at the control board because it is easier to get to.
> >
> > When you make this mod, the key jack input goes directly to the T/R
> > circuit, bypassing the processor. Therefore, the processor thinks its in
> > receive mode and it runs the FLS continuously. The author of the mod
> > speculated that the RIT might not work properly, but I found that the
> > RIT works fine. The only quirk is that with RIT turned on, the frequency
> > displays the receive frequency with any offset during receive, but when
> > the key is down it displays the transmit frequency, so you will see the
> > display jump between the two frequencies during keying.
The following mod has been on the Ten Tec reflector in one form or
another. I believe that it originally came from Wayne Montague.
> >
> > Another mod related to stability is to replace one of the 15 pf N1500
> > caps in the PTO with an NP0 type. The original caps are two 15 pf N1500
> > (negative 1500 ppm/deg) temperature compensating caps in parallel. Also
> > in parallel with them is a 10-15 pf NP0 (zero temp. coefficient) cap.
> > This is apparently too much compensation for some PTO's. I'm still
> > experimenting with these caps.
> >
> > I recently read that a small fan on the heat sink will cut down on
> > drift. I haven't tried this myself. The major cause of drift is heat
> > from the heat sink creeping along the chassis side panel into the PTO.
> > So, cooling the heat sink or reducing power will reduce the warmup
> > drift. There may be more exotic ways to do this, like adding a copper
> > strap inside the rig as a thermal shunt to conduct heat away from the
> > PTO, or finding a way to thermally insulate the PTO. These are science
> > projects for another day.
> >
> > I hope this is the info that you're looking for.
> >
> > 73,
> >
> > Bob WB2VUF
> >
> > Mail wrote:
> > >
> > > Hi Bob:
> > >
> > > Can you tell me what the QST fix was for the drifting Scout? I
> > > collect
> > > mods for the Scout and can not locate this modification.
> > >
> > > Ed 73 K7DXV ewell@cvc.net
> > >
> > > ----- Original Message -----
> > > From: "Bwana Bob" <wb2vuf@qsl.net>
> > > To: <tentec@contesting.com>
> > > Sent: Monday, March 17, 2003 8:50 PM
> > > Subject: Re: [TenTec] Field Day GOTA Station - Scout Drifting!
> > >
> > > > Strange... so many different experiences. My Scout will toggle up and
> > > > down about 10 Hz (just barely noticeable) as the FLS corrects the PTO
> > > > when using the internal keyer, but with a straight key it had a fast,
> > > > steady drift, which was really bad until it warmed up. I think that heat
> > > > from the final was creeping along the chassis side rail and heating up
> > > > the PTO. Putting in the mod described in QST fixed the problem, although
> > > > I'm still tinkering with the temperature compensation caps.
> > > >
> > > > Maybe there were a couple of versions of Scout software that handled the
> > > > FLS differently. I wish Ten Tec would publish service bulletins.
> > > >
> > > >
> > > > Still, I've used the Scout portable on vacation and field day with great
> > > > success.
> > > >
> > > > The only time mine drifted on SSB was when I had a loose and corroded
> > > > crimp connection at the vehicle battery. Now I solder all lugs onto the
> > > > power cables and I am replacing the fuses and holders with auto types.
> > > >
> > > > 73,
> > > >
> > > >
> > > > Bob WB2VUF
> > > > Bill Nicolson wrote:
> > > > >
> > > > > Hi Guys,
> > > > > I guess "drifting problem" was not a good selection of words to
> > > > > describe
> > > the
> > > > > Scouts much documented transmitted frequency step problem.
> > > > > The processor corrects the freqency for changes in the PTO and when
> > > running
> > > > > high speed CW (over 15 wpm) the CW note changes on TX. I have heard it
> > > on
> > > > > almost every scout I have worked. Its not enough of a change to move
> > > outside
> > > > > of the passband of a narrow (250hz) RX station but definitely a pitch
> > > change
> > > > > occurs. And I have heard it on both 555 & 556 models. Its still a
> > > > > great
> > > > > rig!!
> > > > > Bill K2rig
> > > > >
> > > > > ----- Original Message -----
> > > > > From: "Ronnie Zoerb" <r.zoerb@worldnet.att.net>
> > > > > To: "Ten Tec Reflector" <tentec@contesting.com>
> > > > > Sent: Saturday, March 15, 2003 11:21 AM
> > > > > Subject: [TenTec] Field Day GOTA Station - Scout Drifting!
> > > > >
> > > > > > Sorry to hear about your "drifting problem" Bill. Have not
> > > > > > experienced
> > > > > that
> > > > > > with my 2 TT # 555 Scouts or either of the 2 TT # 556 Argos. Doubt
> > > very
> > > > > > seriously you could pick them out of a crowd as long as sufficient
> > > voltage
> > > > > > is supplied.
> > > > > >
> > > > > > I believe a Scout or Argo either one would make an excellent FD GOTA
> > > > > > station for CW or SSB. Very much under rated and reasonably priced
> > > > > equipment
> > > > > > that is built to last in the field, mobile or on the bench.
> > > > > >
> > > > > > IMHO. 73 Ron KI0II
> > > > > >
> > > > > > _______________________________________________
> > > > > > TenTec mailing list
> > > > > > TenTec@contesting.com
> > > > > > http://lists.contesting.com/mailman/listinfo/tentec
> > > > >
> > > > > _______________________________________________
> > > > > TenTec mailing list
> > > > > TenTec@contesting.com
> > > > > http://lists.contesting.com/mailman/listinfo/tentec
> > > >
> > > > _______________________________________________
> > > > TenTec mailing list
> > > > TenTec@contesting.com
> > > > http://lists.contesting.com/mailman/listinfo/tentec
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