[Johnson] Two sugjects: Johnson Signal Sentry. Possible source of TVI?

[Philip Atchley]

Hi!
I have a Johnson "Signal Sentry" here that I'm using with my Ranger and
Hammarlund HQ-110 (too bad Johnson didn't make Receivers ;-).  I digress.
Anyway, last night I was going to use it for SKN (straight key night) and
found it "not working" on 40M.  When I did the "hookup" I'd tested it OK on
10M.  It turns out I wasn't getting sufficient signal pickup to trigger the
relaxation oscillator on the 2 foot wire I was using as an antenna, even
though it was enough "antenna" to pick up a couple of the local radio
stations in the headphones (an excellent "Xtal" set).

Johnson had recommended either using it with the probe output on their
"Matchbox" or skinning the insulation off a section of coax, spread the
braid to make it "leaky" and wrap some turns of wire around it.  I find that
distasteful as I don't wish to damage my coax jumpers!!

My alternate approach is to put a PL-259 Tee on the TX side of the coax
switch, poke a little screw in the extra side and wrap the insulated pickup
wire around the screw as a "gimmick" capacitor.  I expect that'll work just
fine. especially at the 40 Watt level where I don't need to worry about
arcing so much.  Also, I suspect that at HF the small impedance "bump" won't
be noticeable in actual performance.

ALSO, to get away from the "antenna pickup" of local stations I replaced the
funky pin plug on the Signal Sentry with a Small RCA jack to allow coax
right up to the pick-off point on the relay.  (I kept the original pin jack
in case it's ever desirable to put it back original).

Now, one final observation.   (Is anything EVER final?)  Johnson went to a
great deal of trouble to make the Ranger "TV Friendly", shielding, filtering
of all entrance leads, shielding of meter etc.  I've read that often Various
TR switches are a great source of TVI as they rectify the transmitted signal
then radiate the harmonics out through the antenna.  It would seem to me
that this Signal Sentry, as it comes from the factory would do the same
thing.  The pickup signal first hits a tube diode rectifier.  The unshielded
pickup lead that Johnson suggests (has to be unshielded because of the pin
plug) would make a GREAT antenna at VHF TV frequencies.  It's not too much
of a factor here because all the local TV is on UHF and most people are
either on Cable or Dish anyway.  But it does seem like there could have been
a problem in the past.

73 from the "Beaconeers Lair".
Phil, KO6BB

DX begins at the noise floor!
beaconeer@elite.net
Merced, Central California
37.18N  120.29W  CM97sh