Topband: Loop question

Thu Mar 4 11:19:34 EST 2004

Hi Jim, et. al.:

If you cannot shunt feed your tower, then the BC Trapper is a good approach.
I would suggest you can do better on 160 with a shunt feed, assuming the
beams on top of you crank-up tower provide some top loading.  Arbitrarily, I
would put an arm out a couple of feet at the top of the second section and
omega match it at the base and use a piece of flexible braid as the vertical
component of the shunt feed system.

For radials, especially at home, a minimum of 30 radials 65 - 70 feet long
is mandatory.  If this is a permanent installation, look up the radials
table in ON4UN's latest book(s) on Low Band DXing.  If possible go to 40 or
50 radials to reduce near field current losses.  If you can go to 80 or 100
feet radial length, so much the better.

For receive, my best luck with a loop near the transmit antenna has been a
pennant, with the load resistor at the point of the triangle more or less
aimed toward the TX antenna.   I would also use a KD9SV front end saver to
lift the RX feed and ground the auxiliary RX input from your transceiver
when transmitting.  If you can, try a flag from K6SE's original article.
The gain is about 5 db better than a pennant, so the preamp needs are
slightly reduced.  They also work well on 80 with a better gain.  Also, they
are ground independent.  One of the hams near Chicago uses a delta
configuration, about 28 feet wide by 16 feet tall, but I have not had
success with it as the feed line needs to be away from the RX loop, and I
could not do that effectively.  I would think placing the bottom of the loop
just above the height of your metal siding would be OK.

(I have no experience with the K9AY loops)

Good luck,    George    K8GG
(a member of the Battle Creek Special team)

----- Original Message ----- 
From: "KJ0M" <kj0m at mchsi.com>
To: <topband at contesting.com>
Sent: Thursday, March 04, 2004 10:00 AM
Subject: Topband: Loop question

> I'm thinking through the improvement of my antennas here for 80/160
> and would like a little bit of advice.
>
> I'm currently using a quarter wave sloper off the top of my 72 foot
> retractable tower. It works fairly well and has allowed me to attain
> a 5BWAZ and 5BDXCC over the years. I've also managed to garner 34
> countries on 160 meters, although I've never really put a lot of
> effort into that band. The noise is pretty bad with this antenna.
> I've been reading lots of interesting tales on this reflector, so I'd
> like to change my antennas here. In the next few years, 160/80 meters
> is going to be the place to be, I think.
>
> I am in the process of building a BC trapper antenna which I am going
> to suspend from a catenary wire running from my tower to a rooftop
> tripod on my house. I have great hopes for this as a transmitting
> antenna. It gets pretty good reviews and I think in my situation, it
> would work quite well for TX, especially if I lay down 30 or so
> radials.
>
> The problem comes on receive. I know how noisy my sloper can be on
> 160/80 meters and I'm certain the BC trapper will be just as bad.
>
> I am on a small lot and don't have the room for a Beverage so I've
> really given some thought to a 4 way K9AY loop. The problem lies in
> not being able to get more than about 50 feet away from the TX
> antenna. Also, my house is covered in steel siding, which will also
> blow the pattern of the loops. I understand that. The house siding is
> going to cause a big problem with the pattern.
>
> What I'm wondering is this. Would the loops make good listening
> antennas even though they wouldn't have the nice cardioid pattern
> shown by the K9AY loop? What I am looking for is  a nice quiet
> listening antenna to go along with the BC trapper and loops seem to
> be the way to go on a small lot except for the interaction problems
> throwing the pattern off.
>
> With a preamp, will the K9AY loop, or any type of loop for that
> matter, be a good listening antenna in my case or am I better off
> just suffering with the noise on the vertical?
>
> Any comments/suggestions would be greatly appreciated. Thanks.
> -- 
>
> 73,
>
> de KJ0M
> Jim
> ._._.
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