Vinnie S. wrote:
On Sat, 29 Jan 2005 03:23:53 GMT, SideBand wrote:



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.


If I have the HR-2510 at 10 Watts DK, I am still putting out about 7.5 watts. If
I turn up the DK to about 20 watts, I can still transmit about 15.5 watts. I
guess that is not bad.

I guess the point is I can still get at least the power of a standard CB with an
antenna directly overhead.


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.



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.


This will be a major problem. I have all my plumbing well within a foot, across
the entire length of the house. All where I would bring the ladder line into the
house. I cannot move the entry point without some serious digging and entering
from the front of the house. There are numerous obstacles like the driveway and
sidewalk. I will have to look into the 200 ohm twin lead.


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.

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.



In the attic, I am using a 6 foot Firestik. It is the highest I can go up there.
It is an electrical 5/8 wave, though physical 6 feet. I am using 8 pieces of 9
foot wires as a ground plane. Luckily, I have electricians in the family. This
should work OK for now?

Vinnie S.

No, no...

You'd use coax to get out of the house, use the balun to switch to the
ladderline OUTSIDE the house, then switch back to coax thru the other
balun 20'-25' from the antenna.

-SSB