As a matter of curiosity:
You have a (CMC) Common Mode Choke in a feed line. You add another, identical,
choke in line.
If the first choke attenuates the common mode current by 20 dB, the what is the
total attenuation after you add the second Choke?
Tod, K0TO
Sent from my iPhone 6
> On Apr 21, 2016, at 7:42 AM, Jim Thomson <jim.thom@telus.net> wrote:
>
> 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
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|