I have had different experience, Jerry.
Living in Europe, I often found myself with the ham shack on the 2nd or 3rd
floor and occasionally even higher.
Obtaining a good ground is a challenge under these conditions.
Running my Omni V, VI, and VI+ into a linear, I sometimes found I would have
certain bands where I couldn't run more than about 300w before the circuit
breaker on the 961 blew. Usually it was 15m but sometimes even 40m.
I found by inserting a line isolator (mine was from Radio Works) between the
transceiver and the linear, it always cured this problem.
A few times I had my shack at ground level or in the basement and had a
short lead to a good ground.
I never encountered this problem under these good conditions.
My take out of that was always have one of these line isolators with me on
my portable operations because you never know what kind of ground you will
get at the portable QTH.
73
Rick
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of Dr. Gerald N. Johnson
Sent: Friday, August 06, 2010 11:48 AM
To: tentec@contesting.com
Subject: Re: [TenTec] [Fwd: Line Isolator Balun (sorta) question.]
The purpose of these "baluns" is to attenuate any RF current on the
outside of the shield. That helps cut feed line radiation when the coax
is hooked to an antenna. Sometimes that helps cut TVI and received
interference from local sources. Sometimes that hurts working stations
that need the vertically polarized component from feedline radiation.
Unless the radio and amplifier and such are not shielded, beads on those
jumper cables will have no detectable effect. If the coax connectors
don't make good braid contact they will have some effect, but not much
benefit over having tight and well crimped or soldered coax connectors.
UHF connectors have a history of poor ground connections if not kept
really tight.
73, Jerry, K0CQ
On 8/6/2010 11:38 AM, Jim Lowman wrote:
> Background -
>
> QST Magazine, and various commercial entities, tout the benefits of a
> 1:1 line-isolation balun - sometimes simply made by slipping a number of
> ferrite beads over the coax feed lime. and securing them with heat
> shrink tubing. (e.g., Palomar Engineers, BuxCom, and other vendors
> sell these as an inexpensive kit.)
>
> Several articles and commercial vendors suggest using line isolation
> baluns ( which are often made of ferrite beads) on feed lines in the
> shack - including the short jumper cables running between rig and amp,
> and between amp and tuner, and so forth.
>
> Questions -
>
> 1) What if I put those ferrite beads on ALL my coax jumper cables as
> they run between rig and amp and tuner ? Any downside to this ?
>
> 2) What if I installed those beads on outside coax cables, at the feed
> point, as suggested in the many articles I have read. Any downside to
> this ?
>
> 3) What if I do both 1) and 2)... and install them all over the
> place ?
>
> THANKS in advance for your insight.
>
> ====================== James - K8JHR ========================
>
>
>
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>
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