[TowerTalk] Terminate unused ports on remote antenna switch?

[k1ttt.dave at gmail.com]

Ok, the supported 2 vertical configuration won't work in your case as it is
designed to have a 1/4 wave spacing between the verticals... it also calls
for 50 ohm phasing lines instead of the normal 75 ohm for the 4 vertical
case.  I would be very careful about what you do with the phasing box as you
may damage it with the wrong impedances if you use high power.  As I said
before the comtek boxes are designed for nominal 100 ohm loads when using
all 4 verticals, but only 50 ohm loads on 2 ports with the others open for 2
verticals.

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://wiki.k1ttt.net
AR-Cluster node: telnet://k1ttt.net:7373


-----Original Message-----
From: TowerTalk <towertalk-bounces at contesting.com> On Behalf Of Raymond
Benny
Sent: Wednesday, August 11, 2021 04:04
To: Wes <wes_n7ws at triconet.org>
Cc: Tower Talk <towertalk at contesting.com>
Subject: Re: [TowerTalk] Terminate unused ports on remote antenna switch?

I did not detail my situation at all, sorry.

And, I do understand not needing to terminate the unused port on a remote
coax switch.

In my case, I am building an 80m 4 SQ TX antenna system. I have a Comtek 80m
4 sq phasing controller switch and remote box, and have 2 of the diagonal
verticals working independently.

Soon, I plan to connect the two verticals so to get correct 2 way phasing
and matching. And,  so I don't possibly mess anything else I plan connect
1kw dummy loads to the the ports that do not have a corresponding antennas.
In doing this, no matter where phasing box is set, there should be no
possible damage anywhere.

However, I do like the idea using high wattage incandescent bulbs. They are
less critical to weatherproofing.

Knowing my full situation now, are there any other thoughts or ideas?

BTW, I have done much research on designing and building of my 80m 4 sq tx
antenna system. There is a lot to read. The two most beneficial for
building; first, is a write by Gary,  WA60, on their rebuild of the 80m 4 sq
at N6RO, a very big west coast contest station. 2nd, is a write up for
1:1 baluns by Jim, K9YC specifically for 4 sq antenns systems.

Tnx and 73,

Ray,
N6VR/W7YA


On Tue, Aug 10, 2021, 6:29 PM Wes <wes_n7ws at triconet.org> wrote:

> Bingo.
>
> Wes  N7WS
>
>
> On 8/10/2021 6:22 PM, Earl Morse wrote:
> > Terminating multiport devices in their characteristic impedance is
> desired
> > when those ports are still part of the circuit.  In the case of the
> antenna
> > switch, which disconnects the undesired ports and either just leaves 
> > them hanging or shorts them to ground, termination with a dummy load 
> > doesn't really do anything except to prevent you from transmitting 
> > into an unused port that is either open or shorted and not properly 
> > terminated.  It
> would
> > probably be cheaper to use a switch with the proper amount of 
> > connections rather than buying dummy loads for each unused connection.
> >
> > It is common to terminate unused ports in various multiple port 
> > devices
> but
> > really doesn't apply to the coaxial switch as the unused ports are 
> > physically disconnected or shorted or both.
> >
> > Earl
> > N8SS
> > _______________________________________________
> >
> >
> >
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