"Lancer" wrote in message
news:h0dnv09thrmmfbmtln9llck6p044ufscfl@2355323778 ...
On Sat, 29 Jan 2005 03:23:53 GMT, SideBand wrote:

Vinnie S. wrote:
On Thu, 27 Jan 2005 05:00:04 GMT, SideBand wrote:


Vinnie S. wrote:

On Thu, 27 Jan 2005 02:56:39 GMT, SideBand wrote:


That I can do. I got 16" between the joists, and stick the coil
directly under
the antenna. So if you are looking from an overhead view, the antenna
is
directly in the middle of the open part of the coil. The GP wires will
be over
it. Is this correct? It sounds like a plan.

Thanks for your help !






Vinnie S.

Yep.. you got it this time. Looking down the antenna, you're looking at
an "O" (the choke) with the antenna being the center point of the
circle. Wires physically above the coil.

Good luck.

That's what us HAMs are supposed to be here for.

-SSB



The PVC condiut is up. I ran a conduit so I can run the coax right to
the
basement, from the attic. I will make a run tomorrow to get coax and
supplies.
The Firestik arrived.

Also, I roughly measured the distance to the tree where I want to put a
permanent antenna. The distance is huge, about 275 feet of total coax. I
figured
I can use LMR-400DB (direct burial). I estimate about 2 dB loss at that
distance. How much power loss is that on a HR-2510, using a Imax-2000
with a GP
kit, assuming a good SWR? I am not running power. Will that antenna
offset that
loss by itself?I really don't have a choice. It's not going on the
house.
Besides, the damn house is too low anyway. I can get way higher on the
tree.

Vinnie S.

Vin:

Your loss will actually fall somewhere between 1.89 and 2dB.

2 db equates to roughly 23% power loss, assuming 1:1 SWR at the antenna.
Since 1:1 isn't easily attained (you can't get it with a resonant dipole
or a 1/4 wave whip without some sort of feed point matching, and then
you lose some radiation efficiency), you can assume you're going to get
some additional feed line (coax) losses (heating, mostly) because of
the mismatch at the antenna. For that run I would highly suggest
staying away from coax and see if you can find some 200 ohm twinlead.
Output coax from the radio to the outside to a 4:1 balun to the twinlead
to a 4:1 balun (in reverse), to about 20 feet of coax to the antenna.
Losses will be MUCH lower than with coax.

The other option would be 450 ohm twinlead (ladderline) and a 9:1 balun
at both ends. Ladderline is running about $0.19 +/- a foot, depending on
where you're getting it. The cost for the baluns and the ladderline WILL
be less than the run of LMR400.

Great idea, trash one of baluns and use a MFJ-949E at the transmitter
end..


The caveat here will be that you will need to keep the ladderline well
away from ALL metal.. within about a foot of the ladderline.

For that long of a run, I would personally run a pair of 9:1 baluns and
the 450 ohm ladderline. The cost and the losses will be lowest there.

The reason for the 25' of coax at the antenna end is to keep the
ladderline from being unbalanced by the antenna.

Isn't that why you put a balun on the antenna end?

Why use 25 feet?


Estimated losses for the 9:1's and 450 ohm... .6 db (and that's at the
highest), depending on the quality of the baluns. Less than 5% power
loss, and not quite so much effect due to poor SWR at the end.

Your dipole should see about a 1.3:1 - 1.5:1 SWR across the CB band. If
it's possible to make a "V" antenna in the branches (inverted or not)
the SWR could be lower, and you could definitely see some improvements
over a vertical dipole.

HTH

-SSB

If he is going to build an inverted V , or dipole there is no reason
to use a balun at all.. ladder line to the antenna, and tuner at the
transmit end..

Maybe the output of the radio is a reason? I have yet to see a CB with
balanced output.