Tuuk wrote:
Thanks for the info
Yes, that is the Hy-Gain 14AVQ antenna I have. I found the owners manual
online.
http://www.hy-gain.com/man/pdf/AV-14AVQ.pdf
I will have to find someone locally to test each trap, its an old
antenna and I want to make sure they are operational before I put it up.
It will go on a tower about 50ft. No way I can put the gnd planes up
there as the manual recommends.
The manual says its a dead short over the input termenals so I can
measure that but I don't have a resonance tester.
Thanks
I rebuilt some trap antennas many years ago and the main issues were
simply minor mechanical things. Corrosion or loose sheet metal screws.
I'd suggest giving it a good mechanically-minded workover and you'll
probably be good to go. I recall on my KLM beam that some of the
plastic 'end' boots had deteriorated within just a few years so be wary
of those plastic parts.
The bigger issue here would seem to be the ability to adjust the
antenna. The dimensions are not necessarily "plug-n-play" and even in
the best of situations with tuned radials may require some adjustment.
It can work on top of a tower without the tuned radials but WILL require
some adjusting of the lengths unless you just want to accept it as it
happens to fall. Managing a vertical like that the top of a tower is an
exercise in physics leverage-wise and its no fun to do it multiple times
-Bill
"Dr. Barry L. Ornitz" wrote in message
...
"sorry-spammers" ""w9wi\"@(sorry-spammers)" wrote in message
m...
Tuuk wrote:
I have a 50ft self supporting tower, my goal is to put 2 antennas
up. One dipole and one omni.
I have an old omni direction antenna that I wish to put at the top,
it has 3 traps in it with no writing on it so I am not sure what
bands it will be suitable for however I have a pretty good tuner so
I can use it on most bands. I also have one of those brackets that
allows me to use ground planes with it, 4 ground planes aluminum and
longest possible is what I try because the wind brings them down fast.
Second is a simple dipole, I think it is 60 foot each side or little
more however it hangs over the trees on each side so it isn't
perfectly straight. It is connected to a ladder line then connected
to my tuner then my Drake TR7.
These two seem to work OK for me in the past, I hope for some advice
on these and please answer the following questions.
1- Any idea what the omni direction antenna with the three traps is
for which bands? It is about 22ft long with the three traps on the
bottom half, old aluminum antenna.
*probably* 20, 15, and 10 meters but "mikea" has the right idea,
suggesting you try a SWR analyzer on it.
With three traps, and with the size, they are likely traps for 10, 15,
and 20 meters. This would make the antenna a 4-band antenna. The
traps act like open circuits at their resonant frequency. At
frequencies below the trap's resonant frequency, the trap acts like a
loading coil. So this vertical would work on 10, 15, 20 and 40
meters. The antenna sounds like a Hy-Gain 14AVQ or its clone.
2- What about those ground planes? Are they necessary?
Yes, probably. (there were some vertical antennas designed that
don't need them but this doesn't sound like one of them) Usually
with a vertical antenna, the ground plane is half the antenna - to
put it differently, if you don't put up the ground plane, half the
antenna is missing.
You will need a ground plane for 40 meters (about 33 feet), 20 meters
(16.5 feet), and 10 meters (8 feet 4 inches). The wires for 40 meters
would be resonant on 15 meters, the third harmonic. Allowing the
radial wires to slope down at an angle will raise the feed impedance
slightly. With the proper end insulators, they can assist in guying
the antenna. The shorter radials can be hung below the longer radials
using some CPVC pipe to separate the two a few inches.
3- On the dipole, I have a 1:1 balun in the garage, should I use
this with the dipole? The antenna tuner already has some device to
balance so is it necessary for the other balun? Someone told me it
is so I must ask.
If you're center-feeding an antenna with ladder line then I don't
think there's any need for a balun at the antenna. And if your tuner
has a balanced output for connecting the ladder line, then you don't
need a balun at the shack either.
It {the balun} would be more useful if you were using coaxial cable
to feed the dipole.
Do not worry about the dipole being absolutely straight. Since you
fed the dipole with ladder line, a balun at the antenna is not
needed. The vertical should be fed with coaxial cable.
Using the dipole and the tuner alone will let you operate from 80
through 10 meters. There will likely be some interaction between the
dipole and the vertical so tune the vertical with the dipole in
place. Even if the dipole is in reality an inverted-V, its radiation
will be predominantly horizontal, while the vertical will be, you
guessed it, vertical. Having both a horizontally and vertically
polarized antenna will allow you to switch to the one giving the best
signals.
The TR-7 is a nice rig. You should enjoy using it on the HF bands.
Have fun...
--
73, Dr. Barry L. Ornitz WA4VZQ