Re: {Collins} 32S3 Question about Loading / SWR



Jim,  There is a strange mish mash of things going on here.  First, those
cross needles are a reflection of what is going on after the tuner, and not
before...  although the Power Out needle, of course, relates to the output
of the 32S-3....  But, let's think in terms of "Tuner indicates power
delivered to the antenna and reflected to transmitter by the antenna (As
tuned)".

I would say you have for sure some kind of antenna or cable issue after the
tuner.   That is for starters.

Now, let me say that doing what you are doing and adjusting Tuning and
Loading on your 32S-3 at the same time you are adjusting your tuner is a
GIANT recipe for disaster.  I will categorically tell you that you should
never do that - ever.  And hope that those reading this listen up too.

First of all, a well maintained 32S-3 will swing (tune) well over a 2:1 VSWR
circle and come close to 3:1...  That is exactly what a Pi Network is for...
VERY FLEXIBLE... so, if your antenna is better than 2.5:1 on the frequency
of interest, just put the tuner in "DIRECT" mode, and use the needles for
power, but as long as the VSWR indicated is less than 2.5:1, you could just
live with it and tune up the rig using the regular procedure.  The LOAD
Control will just NOT wind up at the 50 Ohm set point when you are
finished...  It will wind up one way or the other a nominal amount, and the
direction of the out of position LOAD control depends on the sign of the
imaginary part of the impedance of the antenna.  As long as you are not up
against the stop on the load control one way or the other, then just load to
230 mA and keep it dipped while doing this and you will be fine.

But, let's say you want to use the tuner to flatten the VSWR.  Then, either
use an antenna analyzer (highly recommend you have one) looking into the
antenna THROUGH the tuner and set the tuner to 50 Ohms and J - zero (50 Ohms
REAL) or tune up the 32S-3 to a very low power (say 10 watts and enough to
get cross needle action, and tune the tuner for minimum VSWR. You just have
to get it close.  You do not have to be at exactly 1:1 VSWR.   The loss in
that little bit of cable between the tuner and the transmitter is zip and
the VSWR on the antenna cable is still what it started out to be..  Then
connect the 32S-3 to the tuner and tune it like you were tuning into a Dummy
Load.  The tuning of the 32S-3 will wiggle the needles, but it will not
change the 1:1 VSWR as tuned by the tuner unless you have a bad cable or
antenna. DO NOT NOW CHANGE THE TUNER AT ALL - EVER.

To close the Antenna discussion, I would get an analyzer (borrow if you have
to) and check that antenna and cable to the tuner.  Wiggle and poke and find
out, for one thing, if it is now stuck in some higher VSWR failure mode
since the tuner wound up so far off.

Now, re your 32S-3.  First, there is no built in protection of any kind
except the plate voltage fuse on the 516F-2.  First, you have - I believe -
misspoken when you say " adjust the PA Tuning control and Loading lever to
get a grid current down to around 100mA; the Load lever then was set about
3/8" to the left of the 50 ohm mark."  You, I am sure meant 100 mA Plate
Current.

If you got the tuner to read 1:1 VSWR after the "event" and retuning and you
still could only get 100 mA of Plate Current with the LOAD control off
nominal, then - assuming the output of the tuner was 50 Ohms, then something
is wrong with the transmitter.

I smell a rat here and you need to be very careful or you will do more
damage.

I believe your original issue may have been with the antenna.  This in turn
really messed with the 32S-3 and may have damaged it.  I just worked with a
guy that had a very similar situation (turned out the onset was caused by an
intermittent RF cable to the amp and then to the tuner) and the wildly
varying failing load to the transmitter damaged both his tuner and the
transmitter.  At least you do not have an amp n the equation. He blew his
amp also.  So, I wound up rebuilding his 30L-1, his tuner (actually went to
the mfg.) and his 32S-3 which was mortally . wounded.

Bottom line, you must - at this point - isolate your variables and see where
the culprits are.

Short answers to your questions:
1. No, and the problem could be many places if there is one.  See above
comments and below recommendations.
2.No.   If you tune into a dummy (50 Ohms and close to 1:1 VSWR) and then go
to an antenna raw, you must retune using the same process you did on the
dummy. If you have pre-tuned your antenna tuner to 50 Ohms real (1;1 VSWR)
and then go from the dummy tuning state to the antenna through the tuner,
you should see no to minimal change and be OK.
3. Yes to the first sentence but see above. This is in fact a way to
"Pre-Tune your tuner at a low power.  Then leave it alone.  Going to high
power does not change your antenna impedance (if it does your antenna is
REAL SICK) and the tuner is just doing an impedance transformation from what
the antenna is to 50 Ohms.  You will have to retune the PA a bit when going
on up in power out and the higher operating current of the PA.
4. Sounds like you may have an intermittent somewhere.  If you power down
and the power back up, you should not have to retune, but always check the
Dip (TUNE) in Plate Current.BUT, if that were my setup, I would not operate
it one more minute until I tried to find out what happened.
 

I suggest the following. I assume you have aa dummy load.  Try tuning the
transmitter into a good known 50 Ohm dummy load and operating it for some
length of time to see if it holds and tunes and loads normally.  Move around
in frequency from where you were when the issue occurred to where you are
now at 7.123 MHz.

Put an analyzer on your antenna and wiggle all cables and check all
connections and make sure your antenna is good and stable and that it is not
showing an abnormally high VSWR.

Then, take a gross check of the tuner function and readout by hooking the
antenna port to your dummy load, put it in "TUNE" mode and see where the
controls wind up when you tune  the dummy to 50 Ohms as indicated on the
antenna analyzer hooked to the transmitter port. You should be able to tune
the 50 Ohms to read 50 ohms.  Then put it in DIRECT mode (no tuner function)
and make sure your 50 Ohm dummy reads 50 ohms through the tuner.
  
Now, use the analyzer to preset your tuner to whatever frequency you will be
using for an air test with a friend and tune the antenna to 50 Ohms.

Only when you have check everything independently and then some on-air
testing, would I go back to normal net operation.  There was a problem
somewhere, and IT WILL COME BACK unless you find it.  Twisting all the band
switches and function switches to clean them on the 32S-3 no way should have
changed the VSWR of your antenna or made that tuner come up so strange..

Tell me what you find after you run the tests.

Bill

Bill Carns, N7OTQ (Trustee K0CXX)
Past President, Collins Collectors Association
Founding Board, Collins Radio Heritage Group
Editor, Signal Magazine (Retired)
Wimberley, TX
512 618 2762  (Cell)
512 847 7010  (Home)


 

-----Original Message-----
From: Collins [mailto:collins-bounces+wcarns=austin.rr.com@xxxxxxxxxxxxx] On
Behalf Of Jim Ewing via Collins
Sent: Sunday, October 22, 2017 7:49 PM
To: collins@xxxxxxxxxxxxx
Subject: {Collins} 32S3 Question about Loading / SWR

This is a basic set of issues, probably, and apologies if it sounds unversed
to those who have operated tube equipment for a long time and are
comfortable with it.

I have read the 32S3 Manual, and have searched the CCA reflector archives
for about 2 hours and still have not found the answers - perhaps because I
don't know how to search properly.

That said, here is the problem.  When doing a CW QSO this afternoon on 40m,
using my 32S3 barefoot in combination with my 75S3b (not as a transceiver
but rather driven by its own VFO), the 32S3 would suddenly stop outputting
power; it would just cut out.  That is, on the manual tuner I am using, the
cross needles would go to zero, from time to time, and the guy on the other
end would not hear me.  Then, after a break in sending, I would get power
out again for maybe 20 seconds before the 32S3 went flat again.  The person
with whom I was QSO'ing also told me that when my signal got through, it had
chirp.  (I was reading him at 599, and he the same with me.)

During tuning, I had adjusted my manual tuner during the Tune / Lock Key
tuning procedure so that SWR was around 1.0.  The tuner during this time was
connected to my 80m full wave loop antenna.  During Lock Key, I had adjusted
PA Tuning and the Loading lever to get a grid current of 230mA at the dip.
I had found it hard to get grid current down to 230mA and where the Loading
lever ended up was right at the 50ohm mark.

I then got off the air, sent an apologetic email, and moved to a slightly
different frequency to try the tuning procedure again.  But first I
exercised the Band switch and the Emission switch slowly, about 10 times
each.  Then, when I went to Tune on the 32S3, I noted that the tuner, with
its same settings as before, was giving me an SWR reading higher than 3.
So during Tune, I adjusted the tuner to get an SWR of 1; it required that I
move the inductor setting 2 taps, and also considerable adjustment on both
capacitors.  I then did the Tune/Lock Key procedures on the 32S3 using these
new tuner settings.  I then found that I could, during Lock Key, adjust the
PA Tuning control and Loading lever to get a grid current down to around
100mA; the Load lever then was set about 3/8" to the left of the
50 ohm mark.

Using these settings, with grid current at or below 100mA, I found I could
successfully call CQ multiple times, and send series of dits and dahs, and
for a longer period of time than before I lost power in my QSO mentioned
above, without the 32S3 cutting out.  At a grid current of  about 95mA, I
was seeing about 100W on the tuner needle, with SWR less than one.

Questions:

1.  What likely caused the 32S3 to cut out on me?  Is there some protection
circuit that cuts out when the amplifier tubes get too hot or grid current
gets too high, or when the 32S3 sees an SWR that is too high, or if the
amplifier is overloaded in some other way?  Or is the problem more likely
the Band switch and/or the Emission switch, since after I exercised them the
SWR on the tuner changed?  Or something else?

2.  Am I doing things correctly when I do the Tune/Lock Key procedure with
my tuner coupled to my antenna, and not to a dummy load, to give me an SWR
of less than one?  (Manual says on p. 2-1 that tuning into an antenna of SWR
<2:1 is OK, but I fear that if I did Tune/Lock Key procedure with the tuner
in dummy load position, then the 32S3 would see a different SWR when I went
to the actual antenna for actual operation, so that the tank circuit
capacitors in the 32S3 controlled by the Loading lever would then be meshed
too little or too much.)

3.  Am I doing things correctly when I adjust the tuner to get an SWR of 1
while the 32S3 Emission switch is in the Tune position, so that the 32S3
sees 50ohms with an SWR of ~1?  I think Tune puts out only a fraction of
actual power you use on the air, and that Lock Key is closer to what you use
on the air.  Intuition raises to me the question that resonation of the tank
circuit in the 32S3 controlled by the Loading lever is not independent of
the resonation of the tank circuit in the tuner, so that changing output
power might change how the tuner and 32S1 tank circuits resonate and thus
require readjustment of one or both of tuner and 32S3 loading.  So will I
need to retune the tuner and do the equivalent of the Lock Key procedure
when I actually go live on my antenna at 100W?

4.  I have tuned the tuner and the 32S3 for a 7.123MHz CW net tomorrow a.m.,
and it does not seem to be cutting out now when I call extended CQ's for a
while.  If I power them down now (both on a variac), will the same settings
work tomorrow morning, or do I need to retune then?

5.  On 40m, how many KHz VFO change before I have to tune the 32S3 again?
And then, do I need to do both Tune and Lock Key?

Thank you, and apologies for any obvious things I should know or should have
learned from my researches.

73,

Jim Ewing
N4TMM
Atlanta, GA
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