amsat at n0jy.org
Wed Sep 17 14:49:15 UTC 2014
I built two Lindenblad antennas some 18 years ago using information from
the ARRL Antenna Book, if I recall. One for 2m, one for 70cm.
I built them with yardsticks, household wiring, PVC, and twin lead.
The worked quite well for MIR and as recently as about 3 years ago I
took one out to use at a public service event we did, and also used it
to copy the HO-68 beacon during event downtime.
I used the set at Field Day that same year, although with no preamp the
linear birds were a bit rough unless they were pretty high up. But we
were in a noisy location, too.
They worked very well for FM AO-51 and ISS packet, pretty good on SO-50.
On these I can switch polarity by simply changing the angle of the
yardstick-elements, with them being mounted to the PVC with a bolt you
just rotate them around the bolt to the opposite polarity and put it
back up on the pole.
To your question then, when using these if I'm working a linear
polarization bird I usually just leave it alone. If it's a CP bird then
I match that and leave it alone. Of course, I don't get too excited if
it fades because it's not like a terrestrial band opening where you
don't know if it will happen again and to where. With satellites it
will either fade back the other way or worst case, I work the same bird
on the next pass in 1 1/2 or 12 hours.
And they are very picky about their configuration for circularity. At
one Field Day, I forgot what the angle was supposed to be. It was
marked on the PVC but in transit when I fold the "arms" all horizontal,
the PVC marking/end caps got turned as well. I set it (guessed) wrong,
it didn't work worth a hoot. Go home, look it up (this was B.S., Before
Smart-phone) go back and set it right made a big difference for the rest
of the event!
You can just see the 2 meter in this picture from Field Day. If you
look closely, you'll see the folded dipole of house wiring on the
element to the right.
Good luck, 73!
Jerry Buxton, NØJY
On 9/14/2014 8:38 PM, Robin Midgett wrote:
> Hello to the group,
> I'd like to hear from any users of the Lindenblad antennas regarding
> switching polarity & circularity.
> Based on the article on the AMSAT web page by W6SHP at
> http://www.amsat.org/amsat/articles/w6shp/lindy.html, I'm led to believe
> that the maximum effect comes from having one Lindy for each of RHCP & LHCP
> per band in addition to being able to invert the polarity of each.
> I'd like to hear from users concerning how often switching between RH & LH
> circularity yields benefits as compared to switching polarity on a single
> I've long had an interest in satellite operation. Due to being involved
> with a recent ARISS event, the interest level has been elevated..it's time
> for me to get on the birds. I welcome your input regarding the Lindenblad
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