View Single Post
  #3   Report Post  
Old May 23rd 04, 07:52 AM
Leland C. Scott
 
Posts: n/a
Default

Jim;

What are your goals for the antenna? There are several things you need to
realize about using an inverted vee antenna.

First the antenna is highly directional. The main direction of maximum
signal is perpendicular to the plane of the triangle formed by the Vee. If
you want omni directional coverage this is not the antenna you want to use.

Second the impedance, thus the SWR, varies with the angle between the two
wires. An angle of around 90 degrees or more should be used. Smaller angles
will result in a lowering of the feed-point impedance possibility making the
match to a 50 ohm coax line poor. Also as the angle varies the required
length will change for resonance. Also as the angle decreases the frequency
range over which you will get an acceptable match will also tend to decrease
too.

Third you may have problems with RF energy getting back in to the radio. The
general fix for this is to install some ferrite toroids at the feed-point on
the coax cable, or coiling up a number of turns of coax at the same
location. You can try 6 to 12 turns in a coil about 6 inches in diameter and
taped to hold the loop in shape.

Finally the point of maximum signal radiation from the antenna is at the
feed-point. Getting the feed-point as high up as you can will improve the
signal.

--
Leland C. Scott
KC8LDO

Wireless Network
Mobile computing
on the go brought
to you by Micro$oft


"Jim noname" wrote in message
news:6_Wrc.8907$af3.502893@attbi_s51...
I was thinking about trying a inverted v in the backyard attached to a
tree. I was going to make some kind of wooden insulator for the middle and
screw that into a tree as high up as I can get on a ladder.

I have a 4 foot drop or so on the back of the house compared to the front.
All my trees are in the back yard. Its sort of like a mini forest. Would

a
inverted V still perform well if the top wasnt above my house? I have

vinyl
siding so maybe I would be better off just keeping the antenna indoors?

thanks