On 22 May 2005 23:47:27 -0700, "
wrote:

I don't have a tuner yet. It's directly connected to an antenna.

resolves:

What could be the possibl;e reasons for the high SWR I am seeing?

Hi Ramakrishnan,

The why of your question is simple: the antenna is not tuned to the
frequency you are applying. An alternative is that the set's built-in
SWR meter is hardly a precision instrument - another reason for an
external tuner (with a larger readable SWR meter).

But back to the antenna not being tuned. Again, this is the thrill of
"the last frontier." There are MANY variables that contribute to
tuning and it takes only one variable to be off, and so is the tune.
You should count it as great luck to have been so close to tune with
your first try.

Tune through all frequencies that are available to you, and build a
chart of SWR vs. Frequency. Then make a change in the antenna. This
can include
* changing the angle of the V
* changing the length of either leg of the V
* raising or lowering either/both leg(s) of the V
* raising or lowering the feedpoint of the V
and for each variation taking readings for new charts of SWR vs.
Frequency. Note the trends as they will reveal where your design
focus should be heading.

I would point out, however, that antennas intended for even harmonics
(40M/20M) usually portend disaster. I suggest you research the net
for "fan dipole." That you do not report any such disaster suggests
that due to what you DO report (unequal length dipole legs) suggests
that you have is what is called an OCF (off-center feed) dipole. This
makes yet another variable that tends to throw a spanner in the gears
of tuning. In this regard, you need to research the net for the topic
of "feedpoint choke" or "W2DU style BalUns."

Well, as you can see the discussion has barely warmed up and you have
the prospects of starting a journal dedicated to all the variations of
a simple design. One maxim to observe:
"No one ever builds ONE antenna."
You may as well get used to the idea that nothing is permanent, even
if you get it right. Plan on being flexible so that doing things
repeatedly does not become a chore. If you note all the variations
listed above, it should suggest that at a minimum you should invest in
pulleys. ;-)

73's
Richard Clark, KB7QHC