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[TenTec] Fixes for the 555 Scout.

To: <tentec@contesting.com>
Subject: [TenTec] Fixes for the 555 Scout.
From: rohre@arlut.utexas.edu (rohre)
Date: 24 Apr 1998 11:46:19 -0500
It really seems some have problems with the Scout and some of us do not.

Mine is about 3 years old, and does not have the problems listed.

Actually, a couple of the problems are NOT problems, but design issues of the

No. 1. Hiss in the audio and whine from the CPU.  You are using too low an
impedance headphones or external speaker.  Mine does not have this problem on
the internal speaker, nor with use of phones.  BUT, my phones are military
15,000 ohm impedance headsets MADE for communications use, not HI FI.  Get a
real pair of communications phones, even the 2000 ohm, old 1950's ham phones
and you will have clear audio, as you will not turn up the volume enough to
hear the whine.  For cushions on Military hard phenolic phones, go to drug
store, (chemist in U.K.), and get some of the sponge pads for Ladies powder
Cut holes in the middle of a pair, and use double sided tape to fasten to the
side of the phones that rests on ear.

No. 2.  PTO, all PTO's are firm tuning devices, ie a slug of some mass is
being moved inside a coil.  A different knob is a good alternate.  Many
catalogs with knobs out there in the industrial electronics world and in the
surplus establishments.

Frequency stability does not jump on mine.  There are a couple of cap changes
in the archives of the list that may help this under microprocessor frequency
correction of the PTO.  If the PTO lube is getting old and stiff, or there is
too much drag on the knob, perhaps touching the case might cause something. 
Other causes might be inadequate grounding for RF, (bond rig and tuner and
power supply to proper grounding.)  Make sure the power supply is stiff
enough, ie can deliver enough current at proper voltage.  Scout MUST have the
13+ volts for best results.  Mine operates on Gel cell at 12 volts, but will
drift when the regulator drops out at 11 volts.  Thus, if you are using a AC
to DC supply of 13 volts and still have drift, check the regulator of both the
Scout and the supply.

No. 3 of the design not problem issues:  The keyer needs a back up source of
power to remember its setting.  One thing that should be possible is to place
a back up battery on the microprocess through a diode network that will float
a keep alive voltage on the micro so its memory is retained when main power is

Short of that, leave power on! Or use an external keyer with battery backup of
speed memory.

I think some hams lose sight of the design goal of the Scout/Argo:  SIMPLE. 
It is a rig with a lot of nice features, and does the basics of ham
communications cost effectively and does not have extra confusing controls and
features seldom used.  But the Scout has room inside and schematics and theory
of operations in the manual and CAN be modified.  I know of instances of mods
for 10M Satellite band, (extra band module and change its crystal).  Also,
external power control to a front panel pot on aux panel under case.  And
there are other areas where old fashioned ham ingenuity could shine.

Great idea to add speech processing, I have been thinking of putting a
processor on mine.

Another ham on this list has a novel suggestion, to use the add in board space
of the noise blanker for more mods.  Like most other Yaecomwood noise
blankers, the one on Scout is pretty limited in noise reduction.  Who will be
the first to cram internal DSP processor into that board area?

73, Stuart K5KVH

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