Dave,
this is exactly what I'm after. The RF in the shack it is causing all
kinds of problems. My TS50 is turning itself off, sprinklers turning
on etc.
Thanks
Fred
wb6iiq

On 21 Nov 2004 12:07:28 -0800, (Fred) wrote:
this is exactly what I'm after. The RF in the shack it is causing all
kinds of problems. My TS50 is turning itself off, sprinklers turning
on etc.

Hi Fred,

This is, really, a very common topic here. The praises heaped upon
expensive "BalUns" comes at the cost for simple ferrite plus rather
stiff prices added for advertising and the illusion of worth.

Simply take common garden variety ferrite cores and stack them up on a
12" length of RG-58. Very simple: one gozinta and one comesoutta.
This alone will quiet noisy receivers, remove RF potentials on the
case, cure rigs of instability; and make sprinklers and touch lamps
settle down.

Consult the archives for 1:1 BalUns, ferrite chokes, et. al. to
research the nuances of which ferrite you should use (or simply build
the conventional coiled coax choke).

73's
Richard Clark, KB7QHC

This is, really, a very common topic here. The praises heaped upon
expensive "BalUns" comes at the cost for simple ferrite plus rather
stiff prices added for advertising and the illusion of worth.

Simply take common garden variety ferrite cores and stack them up on a
12" length of RG-58. Very simple: one gozinta and one comesoutta.
This alone will quiet noisy receivers, remove RF potentials on the
case, cure rigs of instability; and make sprinklers and touch lamps
settle down.

Consult the archives for 1:1 BalUns, ferrite chokes, et. al. to
research the nuances of which ferrite you should use (or simply build
the conventional coiled coax choke).

73's
Richard Clark, KB7QHC

=============================

- - - - and if your antenna or feedline is balanced, just get a ferrite
ring, about 2" in diameter, and wind on it a dozen or so turns of 18 or 20
gauge, twin, stranded, flexible, Radio-Shack speaker cable.

Transmission loss is sensibly zero. Just keep length of cable on the ring
less than 1/10 th of free-space wavelength at the highest frequency of
interest to avoid sprurious responses.

It's about time great, heavy, hanks of coax were removed from the handbooks.
Ferrites have been around for at least 50 years. But I suppose authors must
have SOMETHING to write about. ;o)
---
Reg.

Thank you all for your help. I used Richards approach and Bingo all my
problems went away.
73
Fred
wb6iiq

A balun isn't primarily for this job, but it works here.
A balanced antenna plus a balun would be best.

There are those who say they can't tell any improvement with this, but that
says to me that they have other and larger problems.

Let me try to summarise.

A simple thing like a balun does only two simultaneous things.

It changes the impedance presented to the receiver (or transmitter).

And, because it disconnects the usually slightly radiating feedline from the
antenna, it changes to some uncertain extent the antenna's directional
properties both locally and at a distance.

On receive, the change in impedance matters very little. It doesn't matter
very much whether the impedances involved are 600 or 300 or 50 ohms. They
are quite arbitrarily decided by the mechanical construction of the
transformer and are arithmetically derived by (often wildly incorrect)
assumptions of values for line and receiver impedances.

The change in the antenna's directional properties sometimes, but not always
matters. It depends on the local environment and can affect such things as
signal to noise and signal to interference ratios. But you never know until
you've tried it.

The very general moral is - if there's an improvement in performance in any
respect due to fitting a balun then keep it. If there's no improvement then
you could leave it where it is or try to sell it back to the manufacturer.
It will seldom degrade performance.

On rare occasions, fitting a balun can make matters worse. But once again
you'll never know until you've tried it. And the "made worse" circumstances
are never reported in magazines. This causes bias in the statistics.

It can hardly be called "engineering". But there's nothing else one can do
in the presence of inevitable large uncertainties in the local environment.
It's this piquancy which adds to the pleasure of both amateur and
professional radio.

Professionals who have to earn a living play safe by predicting radio paths
to be typically within plus or minus 15 or 20 dB. Amateurs have the time to
spare to quibble about minute fractions of S-units.

And balun and antenna salesmen have no alternative but to hover around and
attempt to make a living out of the suckers. Everyone has a right to make a
living.
----
Reg, G4FGQ