Opinions of GSB-100...

[Joe Buch]

At 19:12 3/22/98 -0800, you wrote:
>Hello all (including Kevin!),
>
>Having just arranged to purchase that GSB-100, I would like to gather
opinions of it.

I used one for about nine years in the late 60's and early 70's.
Maintaining the balanced modulator and phasing adjustments for decent
sideband suppression was a continuing hassle.  You will probably need a
good narrow band receiver and a low distortion 1.5 kHz audio oscillator to
do the alignment properly and periodically.  There is a plug-in audio phase
shift network, made by B&W as I remember, which if OK should permit
sideband suppression of about 20dB when the rest of the stuff is aligned
correctly.  Optimum suppression usually occurs at only one audio frequency
so the results on a complex signal like the human voice will usually be
somewhat worse.  I had a guy down the road from me measure my opposite
sideband on voice as being down only about 10 dB after I thought I had it
optimized.  This was the only problem I had.  It's not really a problem if
you stop and think about all the boatanchor folks who are perfectly content
running zero dB opposite sideband suppression.  They just call it AM and
carry on.

The rig never ate sweep tubes but I was careful not to make the final
plates glow red.  Pretune using low drive levels and you should be able to
make the tubes last forever.

The GSB-100 has grid-block keying as I remember with a nice CW keying
characteristic.  I think the VFO operated in the 5 MHz range and used old
ARC-5 BC-458 parts which produced a reasonably stable signal for that era.
I used the radio on CW and worked lots of barefoot DX from southern
California during the sunspot maximum.  I bought the radio second-hand in
1965 from the original owner, Tom O'Harra W6ORG, the guy who sells the ATV
transmitters and downconverters; I got rid of it in 1974 so my memory is
now a little vague.

Beware, like most rigs of this era, the radio requires a high impedance
microphone.  I used a replacement crystal element mounted in an old upright
telephone which I still have.  The element cost me about $.50.  Mouser
still sells an equivalent crystal element.  An old D-104 should also work
well.

You will also need an antenna change-over relay or a Johnson Matchbox with
a relay in it unless you elect to use a separate receive antenna.  Again,
my memory fades but I am nearly 100% sure the GSB-100 supplied 120v AC to
control such a relay when transmitting.  If you use the Matchbox relay, be
careful not to get across the 120v AC on the rear terminal strip.  Ralph
Nader was still driving his Corvair when this stuff was first sold.
Today's product liability lawsuits would soon put anyone selling this kind
of equipment out of business and in the poorhouse.

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Joe Buch                                |  @  @ |     |  @    |
Amateur Radio N2JB                      |       |_____|       |
joseph.buch at dol.net                     |    @  @ /-\ @   /-\ |
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