[AMRadio] Valiant and Loop progress


Bill w2dgb at ptd.net
Tue Dec 6 10:33:49 EST 2005


For what it's worth, allow me to offer my own experiences here.
I am presently using a horizontal loop, fed with open wire line, in turn
matched with a home-brew low-pass balanced antenna tuner, with two controls.
The loop and the tuner have both been described in QST, and the loop is in
the ARRL antenna manual. The tuner here consists of a home-brew coax choke
balun, two ganged rotary inductors, and one tuning capacitor. I use a simple
reflectometer circuit for matching...I don't bother with SWR, just the
lowest reflected current. Average height is about 30 ft.

In my case the loop is 520 ft, but I have talked to a number of hams who use
an 80 meter loop with good results. I am able to tune from 160 through 10,
and changing bands is a snap with but two controls in the tuner.  I use it
primarily on 75 and 40, although I have made contacts on 20 also. I have not
tried other bands as yet.

What this approach boils down to is run wire in the space you have, feed
with open wire, get a good tuner, and see what you can do.  The MFJ 259 or
269 SWR analyzer is a great help here. I will be happy to supply details.

Bill  W2DGB
----- Original Message ----- 
From: "Brett gazdzinski" <Brett.gazdzinski at mci.com>
To: "'Discussion of AM Radio'" <amradio at mailman.qth.net>
Sent: Tuesday, December 06, 2005 9:41 AM
Subject: RE: [AMRadio] Valiant and Loop progress


> Yes, I know I want something impossible, given the space and supports I
have
> to work with.
> The best solution would be a higher support in the center, but a tower
> is out, due to cost, looks, and maybe zoning.
> I would be able to get away with some sort of 60 foot mast, its only
> going to hold the center of the antennas up, but I have not seen anything
> like a 60 foot mast. Radio shack does not even sell the
> 36 foot telescoping mast anymore.
>
> I have looked in many books for antenna ideas, but given what space
> and supports I have to work with, I have not seen anything that would do
> what I want at the power levels I can get to.
>
> The 40 meter antenna works great, and I suppose I don't need to do
anything
> with it, but fitting an 80 meter antenna in the space, without it being
> right
> over the house is the problem.
>
> The bigger trees in the front of the house are close to the house, not out
> by the street, which limits the length.
>
> I have the 2kw heathkit antenna tuner (I built it) with the meters built
in.
> On coax, it always worked ok as long as the high voltage point was away
from
> it.
> Peak power on the 813 rig can get well over 2500 watts, past what the
> heathkit
> was designed for.
>
> The built in balun was very small, and I never had it work well, but that
> may
> not be its fault, maybe it was always at a high voltage point....
>
> Maybe the best solution is to try to put up some sort of 80 meter antenna
> parallel to the 40 meter dipole, using another tree out front.
> I could run some open wire line to it, or coax, or some mixture of both,
> and put it into the tuner, or make a balanced tuner.
> That would put it at right angles to the house, and maybe cut the rf into
> everything.
>
> I will have to look at the trees, and think about it...
>
> Thanks for all the tips, I will look at each and see if there is any way
> to try them.
>
> Brett
>
............................................................................
> ..
>
> Keep on with thie list of things you don't want, or won't put up with,
> and you'll force yourself to you only solution ;-)
>
> Move the pole on the side of the house, to the middle of the back of the
> house.  Use whatever methods to extend the top of this mast to 60'.
> Twist the pole until it's in the ground a good foot or so, secure this
> pole to the eave of the house, then from about another 10' up from the
> eave, secure the pole with UV resistant rope, to both sides of the house
> and Secure the ropes the eave of the house,  Use the pole to support the
> apex of a pair of dipoles.  the 75m dipole should run from the Cedar
> Tree, across the top of the house, out towards the street.  Put the 40m
> dipole on the same pole, fed with a different run of coax, but run the
> 40m dipole at 90 degree angles to the existing 75m dipole.  Use some
> more of the UV resistant rope and tie one end to the center insulators,
> and run it through a pulley, so you can work on the dipole with having
> to climb up the pole.
>
> That's one way.
>
> In my case, I had the same concerns about RF in the shack... I put
> thetuner on a shelf near the wall where the coax comes in - there's
> *maybe* 6 ~ 8" of ladderline in the shack.  The Heathkit tuner is
> grounded. I don't know which Heathkit tuner you've had, but I've pumped
> 1,500 watts of CARRIER into this one (after it was tuned for minimum
> SWR) into a dumy load and Modulated it.  I'm still using the tuner.  If
> you ddin't build it, then I'd say that the balun wasn't crappy, rather
> that the builder's technique might have been nothing to be desired.
>
> 73
> -Geoff/W5OMR
>
>
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