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. _______________________________________________ Sent via AMSAT-BB@amsat.org. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb