[Boatanchors] Located cause of Viking Ranger Parasitics

[Philip Atchley]

Hi.
A few days ago I posted a message concerning "Parasitic Oscillations" in my
Ranger (original version with keyer unit) on 10 Meters when in "Standby"
mode.  I "thought" that the problem was in the V4 multiplier stage as
probing around that area affected the parasitics somewhat.  That really
didn't make sense to me because the cathode of that tube is opened up in
standby.  But I completely rebuilt that stage with all new ceramic
capacitors, resistors etc anyway.  NO JOY!

I DID NOT suspect the final stage (6146) because on page 7 of the owners
manual, section 14d2 under "Operate switch" it states that the final is
"disabled" in the standby position.  Well, it really isn't, there is still
apparently at least some plate current flowing (and yes, the clamp tube has
been replaced, twice).  Anyway, I finally traced the parasitic to the final
tube for sure since bringing anything (even a plastic tool) anywhere near
the Grid and/or the hot end of RFC L7 really drives the parasitics bonkers
in the receiver.  Tuning the final also has a drastic affect on it (at first
I didn't think it did but didn't spend a lot of time looking there).

NOW FOR THE KICKER!  The man we originally got this rig from (this rig is on
permanent loan to me from the present owner) told me when I overhauled it
about 4 years ago that it had once been modified with an additional
multiplier tube etc so that the 11 Meter position was actually on 6 Meters.
He said that the rig had been put back to "original" configuration.   Well,
not quite as we'll see below!

Upon doing a very close examination of the output stage, Pi tuning network
etc there is one VERY apparent difference.  Instead of the usual last two
turns on tank coil L11A, one turn has been removed and cut off short and
wound into a small 2 turn coil about 1/2 inch in diameter instead of the
proper "almost" 3 inches diameter.  The apparent 6 Meter tap had been
removed but the coil was not rewound back to the proper configuration.  The
pictures in the manual are a little hard to make out but it is VERY apparent
that this is NOT the correct configuration for the coil.  It probably also
explains why the AUX coupling switch had to be in the 6 position instead of
the recommended 7 position for proper loading on 15 & 10 Meters!!  Less
inductance in the coil would require extra capacitance.

NOW comes the big job of trying to find some proper wire and rewinding that
coil.  I "think" I can get by with just redoing the last turn though it may
be easier to redo both of the last turns than trying to splice two wires
together where the turns are close.  At least the plastic spacers are still
there in good condition, than God!

A couple questions:

1.  I think that final coil "may" be wound with silver plated wire though
I'm not sure.  I realize "normal" copper wire may have a little additional
loss, but do you think I can get by with it ok?  Also, would it be better if
I just "tin" the wire with a soldering iron?  I know at RF skin effect is
important and I think that plain copper wire would have lower loss that a
solder tined wire?

2.  Anybody know what gauge wire this coil is wound with?  I probably won't
have a sample when I go to the store.


73 from the "Beaconeers Lair".
Phil, KO6BB

In daily combat with QRM & QRN.
We may lose a battle but we'll win the war!
beaconeer@elite.net
Merced, Central California
37.18N  120.29W  CM97sh



---
avast! Antivirus: Outbound message clean.
Virus Database (VPS): 11/28/03
Tested on: 11/29/03 9:54:37 PM
avast! is copyright (c) 2000-2003 ALWIL Software.
http://www.avast.com