[amsat-bb] Lindenblads

[Jerry Buxton]

Hi Robin,

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.
http://n0jy.org/Symposium/lindy.jpg

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
> Lindy.
>
> 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
> antennas.
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