[QRO] ssb refresher course needed

[Dave Haupt]

Ron,

I think you should be commended for your efforts to
ensure that your own house is in order.  All too
often, these QRMing issues turn into political
squabbles, then bickering and in some cases lawsuits.

Make sure that the idling current on the TL-922 is at
spec.  I don't know the spec for that particular
amplifier, but Eimac's recommendation for the 3-500Z
is for 50-60mA per tube, depending on anode voltage
(lower current for 3.5kV on the anodes under load, and
higher current for 3kV on the anodes under load). 
I've seen some amplifiers where the owner chose to
alter the bias circuit to reduce the "heat" by
reducing this idle current (zero signal anode
current).  The result is more IMD.

I don't know if this is possible on the TS-430, but
I've heard of hams moving around the carrier osc and
mixing frequencies in a rig so that the SSB signal is
"tilted" in frequency away from the other net or
operation.  I don't know whether the complaining net
is higher or lower in frequency, but that is a
possibility.

In theory, having another ham a few miles away listen
carefully to your signal, and having him move 3kHz one
way or the other, you should get a good idea of
whether you have a problem or not.

During one of my "tests" with a local contester, we
chose 15 meters when the band was dead.  We're about
10 miles apart.  Barefoot, I received him roughly
S9+10dB, and with the amplifier, S9+20dB.  While he
used his voice keyer to transmit "CQ CONTEST" over and
over, I tuned my RX up 3kHz.  Before we discovered the
ALC issue, I could hear "buckshot" more or less at the
start of every syllable.  After adjusting things so
the ALC was working right, I could hear what I would
describe as "barely detectable coherent noise" right
at my local noise floor.  That suggests something like
65dB down in what you would call the "next adjacent
channel" (borrowing a term from the cellular
industry).  That would be clean, by anybody's
standards.  You might try something similar.  

Given the atmospheric absorption on 75 meters, I've
always figured that for SSB, it's a band that needs
amps if you want to participate in the normal
operations.  Because of a very busy schedule, my
hamming has to be confined to occasional, short QSOs. 
CW DXing fits that bill quite well!

Short of having a spectrum analyzer available, I agree
that it would be a challenge to measure your signal
bandwidth directly in the shack.  If you know someone
who has an Icom 746 or 756, maybe the bandscopes on
those rigs can be employed as an analyzer, at a
distance?  I'm not sure what their capabilities are,
but if I knew someone with such a radio, I'd be
tempted to try it as a spectrum analyzer.

73 and good luck,

Dave W8NF

--- rb <rbig@bellsouth.net> wrote:
> Dave---many thanks for your response on this topic. 
> Everything you said
> brought back what I always THOUGHT the case to be.
> 
> The huge problem with SSB and/or final amp combos is
> that there are very
> complex dynamics at work.
> 
> The real problem I'm wrestling with is to find out
> if my transmitted SSB
> signal is excessively wide (and yes, the 3khz is the
> standard, not the law).
> 
> To give you a brief synopsis, I am a participant in
> a 75m SSB net.  For some
> reason (it could be that another net has moved close
> to "our" freq in recent
> times), I've been getting squawks from the other net
> guys that my signal is
> badly interfering with their net ops.  The other net
> is 2khz below ours.
> 
> The guys in my net are way down in South Florida.  I
> am in Pensacola.  The
> guys in the complaining net are in Birmingham AL. 
> Birmingham is very close
> (200 mi) to me.  I have a very good antenna system,
> and run approx 1300PEP
> or so to cut through the hash to South Florida.
> 
> Our normal net practice is to come on and ask if the
> freq is clear twice
> before we begin the net.  The complaining net comes
> on after ours starts (or
> at least I don't hear their signals until after our
> net starts).
> 
> One thing I want to do, for sure, is ensure that my
> signal is reasonably
> clean.  I just ran a two tone test, at power, and
> the trapezoid is
> "perfect".   However, that doesn't deal with signal
> width, which is one of
> the complaints I've had.
> 
> The guys on the complaining net say my signal is too
> wide (they're 2khz
> down, so that's going to be hard to deal with).
> 
> Before it goes any further, I want to be sure if I'm
> OK or not (frankly, I'm
> morally certain that my signal is just fine, as I've
> had probably 10
> disinterested guys check it and report back that
> 2khz was the limit out that
> they could hear me at all.  I'm using a Kenny TS-430
> xcvr driving a TL-922A;
> these are known to be clean rigs).  However, I would
> like to be able to base
> it on some kind of scientific rather than anecdotal
> evidence.
> 
> One thing I'm in the process of trying to do is to
> get an OO station to give
> me a signal quality report.  Don't know if they'll
> do that or not.  Still
> checking.
> 
> The other thing I'm wondering about is if there is
> any practical way to do
> this in my shack.  Don't think so, but don't know.
> 
> The only other thing I can do to try and mimize my
> interfering with the
> other net is to reduce power.  It will take a trial
> and error iterative
> process to see what I can still QSO my net with, and
> yet not interfere with
> the complaining net.
> 
> If this won't work, I'll simply have to give up
> meeting with my net, as
> there isn't any reason to get a big squabble going
> over this issue.  And, I
> shouldn't be interfering with someone else, anyway. 
>  I don't want to get a
> turf squabble going.
> (I forgot to add that 1 and 2 khz up from us is
> clobbered at our net time
> most nites of the week, so moving up a click or so
> doesn't seem to be a
> viable option.
> 
> Thanks for your help.
> 
> 73 de Ron, K5BDJ
> 


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