I'm using a KJ7U,www.kj7u.com, screwdriver antenna and its "control cable",
for lack of a better term, is around 60 feet long. At this length it
seems to be causing tuneing problems.

It appears that the cable is trying to radiate and thus it causes the SWR
to rise above what it should be. The best way I can validate this is to
tune it the best I can then go unplug the cable from the antenna. When I
do this the SWR drops down to around 1.1 or so. Otherwise on some bands it
is as high as 3 - 4

I put some toriod? cores on the line which helped out the problem on 80m
to some extent. It did help bring the swr back down to a more acceptable
level, but it still isn't as low as it is when the cable is unplugged.

When I had this antenna mounted in a different location and the cable was
considerable shorter, none of this seemed to happen.

Anyone have any ideas or experiences with something like this ?



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Jeremy,
Hmm, sounds 'reasonable' to me. A 60' control cable
is about 1/4 wave on 80 meters, and if you're using the
antenna on 80 meters, well...?
'Doc

PS - Sort'a suprised it hasn't singed your mustache, LOL.

I put some toriod? cores on the line which helped out the problem on 80m
to some extent. It did help bring the swr back down to a more acceptable
level, but it still isn't as low as it is when the cable is unplugged.

Keep adding some more and at different distance too. Also balun at the
feedpoint would help and if possible rerouting the cables.

Yuri, K3BU.us

Yuri Blanarovich wrote:


I put some toriod? cores on the line which helped out the problem on 80m
to some extent. It did help bring the swr back down to a more
acceptable
level, but it still isn't as low as it is when the cable is unplugged.

Keep adding some more and at different distance too. Also balun at the
feedpoint would help and if possible rerouting the cables.

Yuri, K3BU.us

I'll try putting them at different locations along the cable. I have 4 that
are designed to clip onto wire the size of rg-8u so I coiled up the
control cable and cliped the cores over the coil of wire, and i put all 4
on that coil. I'll try making several smaller coils and putting them at
different places along the cable


--
Registered Linux User #346565
http://www.tblx.net
WA5K

Maybe use some capacitors from the control wires to ground to short out the
rf right to ground before it gets to the toroids. The toroids then won't
have so much rf to work with and they may not be as likely to saturate.

Be careful with the capacitors that you get transmitting style that can
handle a good amount of rf current.

Allan Butler wrote:

Maybe use some capacitors from the control wires to ground to short out
the
rf right to ground before it gets to the toroids. The toroids then won't
have so much rf to work with and they may not be as likely to saturate.

Be careful with the capacitors that you get transmitting style that can
handle a good amount of rf current.

I've heard of doing this before, with the capacitors, so would this be the
ceramic type? and how would i distinguish between "transmitting" style and
regular capacitors?



--
Registered Linux User #346565
http://www.tblx.net
WA5K

Jeremy Salch wrote:
I've heard of doing this before, with the capacitors, so would this be the
ceramic type? and how would i distinguish between "transmitting" style and
regular capacitors?

Doorknobs are excellent but expensive.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil Moore wrote:

Jeremy Salch wrote:
I've heard of doing this before, with the capacitors, so would this be
the
ceramic type? and how would i distinguish between "transmitting" style
and
regular capacitors?

Doorknobs are excellent but expensive.
--
73, Cecil http://www.qsl.net/w5dxp



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is that a kind of capacitor, or are you making fun of my not knowing the
different kids of capacitors


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WA5K

Jeremy Salch wrote:

Cecil Moore wrote:

Jeremy Salch wrote:
I've heard of doing this before, with the capacitors, so would this be
the
ceramic type? and how would i distinguish between "transmitting" style
and
regular capacitors?

Doorknobs are excellent but expensive.
--
73, Cecil http://www.qsl.net/w5dxp



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is that a kind of capacitor, or are you making fun of my not knowing the
different kids of capacitors



No he is not making fun of you. There is a style of capacitor that is
called a door knob for the shape that it is made in.

To start out with go ahead and try some good high voltage ceramic capacitors
from the control lines to ground. A fairly high value of 0.47 uF might do
good in parallel with a .01 uF cap.

For the toroids in the line they have to be fairly hefty as there could be
some significant currents running on the lines at the different frequencies.
If the toroids saturate they won't work as intended and can cause some real
interesting things to happen.

Jeremy Salch wrote:
is that a kind of capacitor, or are you making fun of my not knowing the
different kids of capacitors

I only make fun of gurus. :-) The doorknob is my favorite kind of capacitor.
I have a couple of hundred of them. Here are some pictures of capacitors,
including door knobs.

http://www.surplussales.com/CapacitorsAll.html
--
73, Cecil http://www.qsl.net/w5dxp






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