I ended up with a 4 bay antenna that is resonant from 150 - 170.
How much work is it to put this on 2 meters?

Rich L
KB7YEB

wrote:
I ended up with a 4 bay antenna that is resonant from 150 - 170.
How much work is it to put this on 2 meters?

Rich L
KB7YEB


If you would please give a description of the antenna, in as much detail
as possible, the group will be able to help you.

tom
K0TAR

Rich:

Well, as 2m transmit is 144-148, the antenna will be too short for the
2m band, and the spacing of the 4 bays will be too close.

Generally speaking, it's usually easier to cut down element length on a
lower frequency antenna to bring it up to a higher frequency. Depending
upon the design, this may not result in a reasonable gain figure for an
individual antenna...

I'm assuming that when you say 4-bay, you mean an antenna array with 4
separate antennas in a 2x2 (square) configuration, which for the
original design frequency range, would have yielded nearly 6db of gain
over a single antenna of the array.

If you are serious about making the array work on 2m, the first thing
you will need to do is to increase element lengths to bring resonance of
the individual antennas within the 2m range. This may not result in
near the gain the original antenna had at it's design frequency because
the spacing of the elements will no longer be optimal. You might be
able to model it in NEC, ezNEC or one of the other antenna programs to
see what the current antenna gain and bandwidth figures are, and then
change lengths of the elements (leaving the spacing the same) and see
what the new antenna looks like.... Of course, even if it's ok, then
you have to figure out how to "stretch" the elements to fit. Once you
figure all of this out, and get a single antenna with decent gain at
your frequency of interest, then you need to repeat it three more times,
then connect them at the optimum spacing with an appropriate phasing
harness for 2m operation....

If you haven't guessed by now, it may be easier to just sit down and
make (or buy) an antenna with about the same gain figure the existing
4-bay has, and save yourself a lot of time. However, if you're willing
to spend a bunch of time piddling around and aren't looking for optimum
results, it can be a lot of fun to modify something like what you have,
if you enjoy cut and try and have a lot of time on your hands...

Good Luck
--Rick AH7H

wrote:

I ended up with a 4 bay antenna that is resonant from 150 - 170.
How much work is it to put this on 2 meters?

Rich L
KB7YEB

We are assuming you have a 4 bay dipole array, common for commercial
use. Some of these are basic dipoles fed with a gamma match and it would
be fairly easy to lengthen the elements and retune the gamma match.
Other brands use a closed loop dipole and that would be a challenge to
cut and lengthen. The phasing harness would be a specific length for
160mHz center freq and you may need to make a new one for optimum
results on 2m. If the harness if too long or too short it may tend to
pull the pattern up or down slightly from the horizon.
Mike
wrote:
I ended up with a 4 bay antenna that is resonant from 150 - 170.
How much work is it to put this on 2 meters?

Rich L
KB7YEB

wrote in message
...
I ended up with a 4 bay antenna that is resonant from 150 - 170.
How much work is it to put this on 2 meters?

Rich L
KB7YEB
I'd start with putting it on a (low power) radio and meter and seeing what
SWR you come out with in the portion of the 2m band you intend to use it on.
If it's less than 2:1 most would consider that acceptable. (Personally, I'd
shoot for less, but that's me). Depending on how 'wide band' this thing is,
it might cover 2m nicely.

If you want to actually alter it for 2m, it will involve:
Lengthening the antenna elements (2m is lower, so elements are longer)
Lengthening the phasing elements
Increasing the spacing between antenna elements.

I sweep the antenna with a MFJ259B and found out the bandwidth.
The 2 meters match is over 7:1 .
From the advice,it sounds like its a lot of work but good for parts
thanks for all of your help

RichL
KB7YEB


Tyas_MT wrote:
wrote in message
...

I ended up with a 4 bay antenna that is resonant from 150 - 170.
How much work is it to put this on 2 meters?

Rich L
KB7YEB

I'd start with putting it on a (low power) radio and meter and seeing what
SWR you come out with in the portion of the 2m band you intend to use it on.
If it's less than 2:1 most would consider that acceptable. (Personally, I'd
shoot for less, but that's me). Depending on how 'wide band' this thing is,
it might cover 2m nicely.

If you want to actually alter it for 2m, it will involve:
Lengthening the antenna elements (2m is lower, so elements are longer)
Lengthening the phasing elements
Increasing the spacing between antenna elements.