[Johnson] Two sugjects: Johnson Signal Sentry

[Philip Atchley]

Glen et al.
Thank you for the suggestion.  Since it was quick and easy to implement I
took one of my precious genuine Amphenol tee's and modified it as you
suggested.  Only, rather than drilling out the metal, it was easy to remove
the insert by unscrewing the center pin and cutting it off so that it
wouldn't reach the pin of the PL-259.  However, I still couldn't get enough
drive to the Signal Sentry to turn it on.

I suspect that this may be due to the fact that the Ranger is only 40 Watts
output while perhaps they expected it to be used with something a little
larger.

So, I tried the gimmick capacitor idea I mentioned.   With about 3 loose
turns around the screw inserted into the Tee it still wouldn't trigger (and
yes, I tried a new trigger tube).  So, I took the gross approach.   I
soldered a 36pF/1000 V silver mica capacitor to the screw head and inserted
it into the Tee.  Connected the center of the coax from  the SS to the other
side of the capacitor.  I figured out it's reactance to be about 140 Ohms at
29MHz, about 2.3K at 1.9 MHz.  This gave me positive keying of the sidetone
from 160M through 10M.  It didn't seem to affect the tuning/loading of the
Ranger at all, though I do have some tuning/loading anomalies that I will
discuss in another post.

The ONLY problem I see that might occur with this arrangement is if I end up
with a series resonant circuit between the 36pF capacitor and the RF choke
to ground in the Signal Sentry.  If that does occur, it just might burn out
the RF choke, I'll have to wait and see (Johnson DOES NOT give the value of
that choke so I could calculate it).

73 from the "Beaconeers Lair".
Phil, KO6BB

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

----- Original Message -----

> A simple solution is to make what is called an
> "iso-Tee".  To make one, use a "normal" UHF "T"
> connector that has the male connector on the stem of
> the "T" and has two female connections.  Using a drill
> bit that is the same diamter as the hole in the
> insulation of the connector, drill out the "fingers"
> of one of the female sides.  Make sure that you get
> all the way to the bottom of that side.
>
> Connect the male side to the transmitter and the
> antenna connection to the "good" side of the "T".
> Then using a length of coax with the "normal" UHF male
> on the end plug this into the modified side of the
> "T".  Make sure that the plug doesn't come in contact
> with any metal.  If it doesn' then trim the center pin
> of the UHF plug slightly so that no connection is
> made.  Connect the other end of the length of coax to
> the monitor.
>
> This type of arrangement has been used for decades to
> tune VHF and UHF duplexers with "normal" signal
> generators while the transmitter is in operation.  The
> basic fact is that there is a very small capacitor
> created between the modified "T" connection and the
> center pin of the coax connector inserted into the
> modified "T".
>
> Glen, K9STH
>
>
>
> --- Philip Atchley <beaconeer@elite.net> wrote:
>
> 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.
>
> =====
> Glen, K9STH
>