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Re: [Amps] Line Isolators for RF feedback

To: Joe Isabella <n3ji@yahoo.com>
Subject: Re: [Amps] Line Isolators for RF feedback
From: R.Measures <r@somis.org>
Date: Wed, 4 Aug 2004 05:59:21 -0700
List-post: <mailto:amps@contesting.com>

On Aug 3, 2004, at 9:40 AM, Joe Isabella wrote:


Good point, Rich!! I guess I should say "DUUHHH!!!".

Rube Goldberg showed up that high-tech solutions are not always mo' bettah.

I would imagine that the coax and/or PL-259 would be the weak link in this case though, wouldn't
it??

PL-259 connectors are always the weak link because they allow water and water vapor to enter the coax.


Even say RG-400 or RG-303 would give up before they get saturated, right?

Hello, Joe -- Coax doesn't saturate, it melts and/or ignites. Cores saturate.


Just curious --
even if I ran my 3K-A at full bore, it wouldn't kill 'em (given that the dipole is at it's
resonant point).

A 3K-A will do about 2-out. This should not be a problem for small coax using SSB, especially because the choke balun is at the center of the dipole - so it gets cooled by the breeze. I make the choke balun for a dipole out of the same coax used in the feedline because there are no coax splices or connectors out in the weather and because the balun would definitely be as capable as the feedline. Sure, an ugly-balun won't win any beauty contests, but it Will do the job. // The main weakness of an outdoor coax choke balun is that UV from the sun deteriorates the nylon cable ties that are used to hold the coax to the ABS sewer pipe. A solution is to cover the nylon cable ties with black electrical tape.
end

Joe


--- "R.Measures" <r@somis.org> wrote:


On Jul 31, 2004, at 10:21 AM, Joe Isabella wrote:


The one I use has ferrite beads stacked on top of each other (about 50
of the little buggers!!) on
about a 12 inch piece of teflon coax. Since it isn't a torroid, it
can't be saturated.

One wire through the center of a ferrite bead is a one-turn toroid. And yes, given enough current and freq., they can be saturated. The only coax choke device that can not be saturated has an air-core or powdered-iron core.

 It'
supposed to handle 5kW, but I haven't quite hit it with that much
power yet ( :-)  ).  It totally
fixed all my RF woes, and I had plenty!!

Joe,
N3JI

--- Alek Petkovic <vk6apk@eon.net.au> wrote:

Ditto for me downunder.

The Radioworks line isolators do the trick nicely.

You can make your own as they are just coax wound around a ferrite
rod. You
can also use the coil of coax like Rich suggests.

They all work well  but the RadioWorks product is very neat and
convenient
to use. It is nicely encapsulated with the female connectors on each
end.
Makes it real easy.

73, Alek
VK6APK

ps: Their wire antennas are well made and work quite ok as well.

At 12:19 PM 30/07/2004, Harold B. Mandel wrote:
Seconding the message below I add my personal endorsement
to Radio Works.com.

When moving my shack from the 12 month "dxpedition" in
Secaucus, New Jersey to my home in Kentucky, a severe case
of RF feedback plagued the station when activating a linear
amplifier.

Even though I was ready to plunk down cash for goodies, Jim, W4THU,
took time to speak with me at length, and suggested several tests
to further diagnose the culprit and refused to sell me anything until
reporting back to him.


I found out about Radio Works when up in new Jersey, and purchased
line
isolators to cure RF feedback going into the hotel telephone system.


Score for Radio Works: AAAAA+

Hal Mandel
KA1XO
On Tue, 27 Jul 2004 07:34:28 -0500 "Gene Bigham" <jbigham2@kc.rr.com>
writes:
I followed Radio Works recommendations for RF feedback problems.
Their line isolators and grounding ideas worked to cure a bad case
here.
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http://www.qrz.com/vk6apk http://profiles.yahoo.com/vk6apk

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Richard L. Measures, AG6K, 805.386.3734. www.somis.org

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