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.
You can't switch polarity on a single Lindenblad.
The polarity is determined by the mechanical "slant" of the elements, hence the need for one each of RHCP and LHCP.
You'd then switch feedlines to the radio for the polarity desired.
73, Jim KQ6EA
On 09/15/2014 01:38 AM, 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 [email protected]. 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
Hi Robin.
If you want to monitor satellite telemetry, e.g. AO-73, or listen to the strong signals from the ISS, then the Lindenblad is a great choice.
However, if you want to make QSOs via the satellites I believe you will need an antenna with some gain.
Of the satellites that are available, SO-50 has quite a weak downlink. Meanwhile, the available linear transponders by their nature divide the available power between the users. It's always an advantage to have a good receiving system and an omnidirectional antenna is unlikely to be an optimal solution. Circular polarisation however is a definite advantage.
Let us know how what choices you make and how you get on.
Good luck
David G0MRF
-----Original Message----- From: Robin Midgett [email protected] To: AMSAT-BB [email protected] Sent: Mon, 15 Sep 2014 6:23 Subject: [amsat-bb] Lindenblads
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 [email protected]. 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
-----Original Message----- From: Robin Midgett [email protected] To: AMSAT-BB [email protected] Sent: Mon, 15 Sep 2014 6:23 Subject: [amsat-bb] Lindenblads
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 have used for some time a small satellite station composed of two lindenblads, one for 145 MHz and the other for 435 MHz. The UHF one was a parasitic lindenblad from a well known project of some years ago that I think is still available on the web (I don't remember the details now). I have commented on my experience with lindenblads on this mailing list a few times in the past, so there might be my messages in the archives (if they exist at all). What I can say is: signals are nowhere near the ones you can have with even small yagis with azimuth and elevation controls, also adding two preamplfiers under the antennas greatly improved the chances to make QSOs. I was able to work many contacts with that setup (FT-847 as rtx), mostly CW on the linear sats, but also some FM contacts on all satellites available some years ago (2008-2010), and of course some SSB contacts on the linear sats. I assume that having switchable polarity can only make things better.
HTH Frank IZ8DWF
Gentlemen, Perhaps I didn't phrase my question plainly enough. Doug is correct; my question centers around the perceived benefit of having both LHCP & RHCP Lindenblads with a switch to select between the two...is there a real benefit?
Having recently been part of an ARRISS event, I witnessed the benefit of being able to reverse the sense of the cross-polarized Yagi we were using for the QSO, so it seems to carry forward that having that agility would be beneficial for Lindenblad antennas, which is why I asked for input from experienced Lindenblad users.
And yes, the sense of a single Lindy can be changed if the elements are mechanically rotated in phase with one another about the Z axis. Saying that it can't be done is akin to saying a Yagi can only be used in one direction, and none of us accept that as truth.
Again, I appreciate the input from experienced users of this antenna array.
On Wed, Sep 17, 2014 at 4:39 AM, Francesco Messineo < [email protected]> wrote:
-----Original Message----- From: Robin Midgett [email protected] To: AMSAT-BB [email protected] Sent: Mon, 15 Sep 2014 6:23 Subject: [amsat-bb] Lindenblads
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 have used for some time a small satellite station composed of two lindenblads, one for 145 MHz and the other for 435 MHz. The UHF one was a parasitic lindenblad from a well known project of some years ago that I think is still available on the web (I don't remember the details now). I have commented on my experience with lindenblads on this mailing list a few times in the past, so there might be my messages in the archives (if they exist at all). What I can say is: signals are nowhere near the ones you can have with even small yagis with azimuth and elevation controls, also adding two preamplfiers under the antennas greatly improved the chances to make QSOs. I was able to work many contacts with that setup (FT-847 as rtx), mostly CW on the linear sats, but also some FM contacts on all satellites available some years ago (2008-2010), and of course some SSB contacts on the linear sats. I assume that having switchable polarity can only make things better.
HTH Frank IZ8DWF _______________________________________________ Sent via [email protected]. 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
On 09/17/2014 11:51 AM, Robin Midgett wrote:
And yes, the sense of a single Lindy can be changed if the elements are mechanically rotated in phase with one another about the Z axis.
Similarly, the sense of an axial-mode helix can be changed by simply unwinding the helix and winding it back in the other direction. Some would call this "rebuilding the antenna", rather than "switching the polarity", but I am not one of those.
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 [email protected]. 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
participants (6)
-
David G0MRF -
Francesco Messineo -
Gus -
Jerry Buxton -
Jim Jerzycke -
Robin Midgett