[amsat-bb] Polarisation Switch
Stephen E. Belter
seb at wintek.com
Fri Dec 26 16:22:29 UTC 2014
I haven’t had any problems damaging my FCD Pro+ dongle operating full duplex. The relay setup prevents me from running the transmitter output into the dongle.
The waterfall display makes it painfully obvious when I’m experiencing desense from the transmitter. Changing the circular polarization of one of the antennas frequently solves that problem.
After using the manual coax switches and failing miserably, my second attempt used the Tohtsu CX-120P relays. They worked fine, but it is challenging work to solder and clamp the coax without introducing a short. Keep all of the coax braid and the likelihood of a short increases. Remove the excess braid and the current carrying capability of the connection decreases. :-(
The CX-120 setup is what I used for Field Day and subsequent occasional operation.
For reliability, my next iteration will use the CX-800N relays. I’ve not had any problems (yet) installing N connectors.
73, Steve N9IP
Steve Belter, seb at wintek.com
> On Dec 26, 2014, at 8:48 AM, Clayton Coleman <kayakfishtx at gmail.com> wrote:
> Steve, I have been looking at those same relays. My biggest concern
> has been protecting the SDR's & FUNcube Dongle from any RF
> On Thu, Dec 25, 2014 at 6:47 PM, Stephen E. Belter <seb at wintek.com> wrote:
>> One word of caution using manual coax switches for an SDR/TX application: Most of them *short* the unused ports. This means you can’t parallel two or three switches. It also fouls up feeding preamp power up the coax to the antennas. Unfortunately, this is the voice of experience. :-(
>> In my next implementation, I’m planning to use the Tohtsu CX-800N coaxial relays. They are expensive, but are non-shorting, come with N connectors, and are DPDT.
>> If you use a radio with a single VHF/UHF connector, you might consider using a diplexer (or duplexer) instead of a switch. The Comet CF-416 series work well.
>> Thank you for your on SDR-Radio! Merry Christmas and Happy Boxing Day.
>> 73, Steve N9IP
>> Steve Belter, seb at wintek.com
>>> On Dec 25, 2014, at 3:57 PM, Simon Brown <simon at sdr-radio.com> wrote:
>>> Hi Clayton,
>>> My solution for switching will be three N-Type switches in the shack, one on each antenna cable and one on the SDR. The switches could be relays but good N-Typ3e relays seem to cost a small fortune, so it looks like I'll use switches.
>>> If I use a VHF / UHF TX with only one connected such as the FT-819 or FT-991 then I'll need four switches.
>>> I'm slowly getting the hang of things, just had my first two QSO's on SO-50 so next item to be 'attacked' is AO-73.
>>> Simon Brown G4ELI
>>> -----Original Message-----
>>> From: Clayton Coleman [mailto:kayakfishtx at gmail.com]
>>> I agree with your assessment. Using SDR on satellites is a wonderful thing. I have been assessing the value of SDR on satellites for several months and my personal conclusion is that it's benefits far outweigh the negatives. I'll be writing up my notes for a short column soon.
>>> I'm quite spoiled using my FUNcube Dongle Pro+ to receive. It does a great job, allowing me to see the entire passband of all our current satellite fleet. Not only can I visually see the passband, I am recording it in both AF+RF so that I can go back and look for things I might have missed during a previous satellite pass.
>>> My biggest complaint about using the SDR setup is having to switch cables depending on by transmit band. I'm looking for clean solutions to switch between U/V and V/U configurations, giving me the best isolation and protection for my SDR devices from the transmitter.
>>> Some folks don't like the short delay effect using SDR. I find it is manageable and can be "tweaked" for optimum performance.
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