[SMCARA] 20m Beam Project

[Clarke, Tom AIR4.0P NATOPS]

Congratulations Dan!

Ham Radio at its best.  Playing with antennas is a fun exercise and you
can really see the results immediately, Good or Bad!!

You say you used all PVC.  I take it you did not use wooden dowels for
the elements and I wonder how "floppy" it is?  I tried making an antenna
(homemade Buddipole) a while ago with PVC and wound up putting dowels
inside the PVC to "stiffen" it up.  That sort of defeated the
lightweight aspect of using PVC though.

Measuring front to back ratio pretty much requires an antenna test
range, but you can get a relative idea by tuning in a strong steady
carrier and then peaking with the antenna pointed toward and away from
the signal source with the beam.  The S meter will give you an idea of
the f/b ratio.  If you really wanted to be fancy, you could take a
reading every 15 degrees or so and plot it on a circular chart.  That
would also give you an idea of where the nulls are.  I suppose that you
could also model it with NEC, but getting the real data is more fun!
Relative is the operative word here, but you still will have some
bragging rights!

73 Tom/W4OKW

-----Original Message-----
From: smcara-bounces at mailman.qth.net
[mailto:smcara-bounces at mailman.qth.net] On Behalf Of Daniel Metcalf
Sent: Friday, August 12, 2011 9:01 AM
To: smcara at mailman.qth.net
Subject: [SMCARA] 20m Beam Project

Good Morning All,

I just finished building a two element beam antenna
(http://uts.cc.utexas.edu/~hansongr/Miniyagi.htm but all PVC) last
night and so far the results are looking good. Using my FT-897's SWR
meter and being without a tuner I am showing an SWR of 1.3:1 down at
14.175, SWR of 1.1:1 at 14.250 and SWR of 1.2:1 up at 14.325. Without
having to trim anything once it was up it was up (I am either really
good at this or extremely lucky Hi Hi).

Using only 75 watts I made 2 contacts with it last night W4PSC in
florida but being he was off to the side of the beam (which is
pointing West to North West and pointing it via arm strong method) I
lost him after exchanging call signs. Then came WA0UAY Rick from Iowa
who monitored the signal throughout the conversation about the antenna
periodically reported 58 to 59. I think he is going to build one now.

If I had the patience to wait I would have liked to of answered to the
two gentlemen from Los Angeles on 14.240 and 14.245 last night as I
had them 59++ on the meter but they were busy dealing with their pile
ups. Hope to get more data tonight.

One thing Rick WA0UAY was interested in was the front to back ratio.
How does one go about figuring that out?


73's
Dan -- KB3UUN
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