M2 sells a driven element assembly that allows polarity switching for there 435 antennas. Has any one used this product and can comment? Is there a cheaper way to do this? Thanks Mike
We use the M2 polarity switches in the VTGS for both our 70cm and 2m antennas.
In my experience they work very well. I have not conducted any critical analysis of their performance (Axial ratio measurements and the like), but I can say they are sturdy and solid and in the few years we've had them 'on the tower' I have had no problems with defects or failures (no water ingress or anything like that). Anecdotally, I will say that being able to switch polarizations mid-pass has been of huge benefit, and you can definitely see a difference in signal strength (depending on the satellite, its antennas, geometry, etc.).
So generally, I highly recommend the M2 products for this, if you can afford it. I also use the M2 antennas personally, but can't afford the polarization switches for myself for my home setup.
If you are looking for DIY / cheaper alternatives, The ARRL Antenna Handbook has some good 'schemes' for polarization switching. Depending on how you tackle the problem you may need access to either 75 or 100 Ohm coax for the phasing (I recommend www.therfc.com for this, he has all kinds of cable and may even fabricate some phase aligned ones for you if you ask nicely). Most of those schemes require some type of coax relay, but you might be able to find something relatively cheap on ebay. Also, you can find a good article on using Omron PCB relays for RF work here, if you would like to attempt to 'build' a coax relay: https://www.w6pql.com/using_inexpensive_relays.htm.
Hope this helps! Goodluck!
-Zach, KJ4QLP
Research Associate Aerospace Systems Lab Ted & Karyn Hume Center for National Security & Technology Virginia Polytechnic Institute & State University Work Phone: 540-231-4174 Cell Phone: 540-808-6305
On 3/25/2018 9:58 AM, WB8PFZ via AMSAT-BB wrote:
M2 sells a driven element assembly that allows polarity switching for there 435 antennas. Has any one used this product and can comment? Is there a cheaper way to do this? Thanks Mike _______________________________________________ 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://www.amsat.org/mailman/listinfo/amsat-bb
Hello Mike
there is a much cheaper way!! M² is good but VERY pricy. just put a tohtsu cx-120A or CX-140 coaxrelay in a box, a folded dipole and a 1/2 coax balun. The relay has 2 connections at 1 side and 1 connection at the other side. the one side with the 2 connections: connect each side of the folded dipole to either relay contact, the side with the 1 relay-conection is for the feeder to trx. i made this for 2m and 70cm crossyagis, and works FB for switching from RHCP to LHCP. the price for the relay cx-120: 37.50€ , a small plastic box: a few €'s....the price for the M²'s: multiply by 7 or 8
best 73's
Jerry,ON4CJQ
----- Oorspronkelijk bericht ----- Van: "amsat-bb" [email protected] Aan: "amsat-bb" [email protected] Verzonden: Zondag 25 maart 2018 15:58:45 Onderwerp: [amsat-bb] M2 432 polarity switch
M2 sells a driven element assembly that allows polarity switching for there 435 antennas. Has any one used this product and can comment? Is there a cheaper way to do this? Thanks Mike _______________________________________________ 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://www.amsat.org/mailman/listinfo/amsat-bb
Good Evening,
I again believe that I need to provide some feedback on the polarization issue.
In one using polarized antenna RHCP or LHCP it is quite obvious that one should be able to change the polarization when working the birds. The most evident example is AO-92, whereby you have to change same every minute or so to keep a constant Rx signal strength, this both on the uplink and downlink. It may be due to the spinning of the satellite which may have a higher rate than usual, AO-91 is much more stable on this aspect.
Whatever system you may be using to change the polarization is your own choice, what I wanted to stress is that for 100% reliability you need to be able to do so on both the uplink and downlink.
73
Jean Marc (3B8DU)
On Mar 26, 2018, at 8:39 PM, [email protected] wrote:
Hello Mike
there is a much cheaper way!! M² is good but VERY pricy. just put a tohtsu cx-120A or CX-140 coaxrelay in a box, a folded dipole and a 1/2 coax balun. The relay has 2 connections at 1 side and 1 connection at the other side. the one side with the 2 connections: connect each side of the folded dipole to either relay contact, the side with the 1 relay-conection is for the feeder to trx. i made this for 2m and 70cm crossyagis, and works FB for switching from RHCP to LHCP. the price for the relay cx-120: 37.50€ , a small plastic box: a few €'s....the price for the M²'s: multiply by 7 or 8
best 73's
Jerry,ON4CJQ
----- Oorspronkelijk bericht ----- Van: "amsat-bb" [email protected] Aan: "amsat-bb" [email protected] Verzonden: Zondag 25 maart 2018 15:58:45 Onderwerp: [amsat-bb] M2 432 polarity switch
M2 sells a driven element assembly that allows polarity switching for there 435 antennas. Has any one used this product and can comment? Is there a cheaper way to do this? Thanks Mike _______________________________________________ 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://www.amsat.org/mailman/listinfo/amsat-bb _______________________________________________ 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://www.amsat.org/mailman/listinfo/amsat-bb
Hoi Jean Marc
I'm active on sats for 20y i think, and did it the first years with simple yagis, which worked ok. Then made myself some crossed yagis with fixed RHCP, but with a ot of reading and understanding some things i made it all switchable. All crossed yagis have now exactly 1/4 spacings at the boom between the 2 planes, and all delay lines and phasing lines are well cut to the needed lengths with max difference of about 0.5°. The fun of switching now between R an L or R/L/V/H polarisations makes a big difference in both uplink and downlink, would never miss it again. I also have the MASPRO sat system with only R to L switch, but that relay is a simple print relay. The switch i made on some folded dipole is a coax relay to get more power on the yagi. I agree that switching is best on up- and dwnlink; i do this on all passes though.
Best 73's
Jerry,ON4CJQ
----- Oorspronkelijk bericht ----- Van: "Jean Marc Momple" [email protected] Aan: "on4cjq" [email protected] Cc: "mikflathead" [email protected], "amsat-bb" [email protected] Verzonden: Maandag 26 maart 2018 20:14:38 Onderwerp: Re: [amsat-bb] M2 432 polarity switch
Good Evening,
I again believe that I need to provide some feedback on the polarization issue.
In one using polarized antenna RHCP or LHCP it is quite obvious that one should be able to change the polarization when working the birds. The most evident example is AO-92, whereby you have to change same every minute or so to keep a constant Rx signal strength, this both on the uplink and downlink. It may be due to the spinning of the satellite which may have a higher rate than usual, AO-91 is much more stable on this aspect.
Whatever system you may be using to change the polarization is your own choice, what I wanted to stress is that for 100% reliability you need to be able to do so on both the uplink and downlink.
73
Jean Marc (3B8DU)
On Mar 26, 2018, at 8:39 PM, [email protected] wrote:
Hello Mike
there is a much cheaper way!! M² is good but VERY pricy. just put a tohtsu cx-120A or CX-140 coaxrelay in a box, a folded dipole and a 1/2 coax balun. The relay has 2 connections at 1 side and 1 connection at the other side. the one side with the 2 connections: connect each side of the folded dipole to either relay contact, the side with the 1 relay-conection is for the feeder to trx. i made this for 2m and 70cm crossyagis, and works FB for switching from RHCP to LHCP. the price for the relay cx-120: 37.50€ , a small plastic box: a few €'s....the price for the M²'s: multiply by 7 or 8
best 73's
Jerry,ON4CJQ
----- Oorspronkelijk bericht ----- Van: "amsat-bb" [email protected] Aan: "amsat-bb" [email protected] Verzonden: Zondag 25 maart 2018 15:58:45 Onderwerp: [amsat-bb] M2 432 polarity switch
M2 sells a driven element assembly that allows polarity switching for there 435 antennas. Has any one used this product and can comment? Is there a cheaper way to do this? Thanks Mike _______________________________________________ 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://www.amsat.org/mailman/listinfo/amsat-bb _______________________________________________ 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://www.amsat.org/mailman/listinfo/amsat-bb
participants (4)
-
Jean Marc Momple -
mikflathead＠aol.com -
on4cjq＠telenet.be -
Zach Leffke