Date: Thu, 21 Apr 2016 03:28:00 -0400
From: "Roger (K8RI) on TT" <K8RI-on-TowerTalk@tm.net>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] CMC-230-5K
I don't have any antennas that cover 3-30 MHz so why would I need a
choke that covers that range? A quickly wound choke for the specific
antenna is more than sufficient. Only if you want a choke for all the
HF antennas you "might" put up would that bandwidth be justified. I do
have two chokes in series on 75/80.
### I only have ONE feedline going up the tower. The remote switch box is at
the
top of the tower. For this application, for experimental purposes, I want to
be able
to quickly move the CMC from one ant to another to another, so it has to
cover at least from
160-15m. I also want to evaluate the effects of cascading both boxes in
series, on each of the
160-15m ants. For this series of tests, it will only see a max of 1200w pep
out on ssb..and flat
swr across each band. So Im not concerned about heating. I also want to try
one then both of em
on the output of the 1200 w amps. I string all 4 x 1200 watt amps in series,
since they will all handle
2 kw on bypass, and flat swr.they can be tune dup on different bands, or
several on one band etc.
A simple rotary switch between xcvr and the 4 amps, ensures that only one amp
can ever be keyed at
one time. That simplifies switching between amps, IE: no myriad of switch
boxes required.
## I want to try using one cmc, then both in series, on the output of linear
#4, which is the last in the chain.
I also want to try one or both, at base of tower, and also at the entrance to
basement. So for this application,
I need something that covers the entire spectrum, is in a box, uses connectors,
and can be swapped out quickly.
Normally you only need the cores. Just run the feed line through the
required number of cores, the required number of turns and add the coax
connector. That's it. I stocked up on cores and that's normally all I need
Normally there is no need for a box, Teflon coax with double silver
braid, and those special connectors. Actually, they are just SO239s
with a tapered shield added.
Rarely is there a need for anything other than a chassis mount SO239 at
HF, if you must use a box. The impedance bump is so slight on HF that
the power to the antenna will likely never notice, so you really don't
need the fancy connectors. It's like the power loss we see for UHF
connectors. Even when you add a bunch the loss on HF is still small.
## I use water proof boxes as they are easy to mount to a boom or mast.
The turns of the coax on the cores cant be near metal, or the stray C will
kill the choke. At least dead center in a box, the stray C is minimized.
If no box used, the turns have to be spaced away a bit from any metal
boom, tower, or mast.
## So for this particular series of experiments, the CMC-230-5K fits the bill.
I spend $60 every 4-5 days on 94 octane gas for my 500 hp Roush mustang,
so in the bigger scheme of expenditures, a couple of CMC devices is a moot
point.
At least with the cmcs, I have something to show for it..... unlike car
gas..and stuff
like hundreds of rounds of ammo every month.
Jim VE7RF
73
Roger (K8RI)
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|