[amsat-bb] M2 432 polarity switch

[Zach Leffke]

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
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