Hi Wouter,

Many thanks and also thanks to Ken. I’m currently sorting out the station on the FO-29 passes, mainly debugging the software.

FWIW I am using a NetSDR + Down-converter (from RFspace) on RX and a TS-2000 on TX. Using the SDR on RX is so much better than flying blind IMO J . I need to get some cables ordered to I can easily switch between 2m and 70cms, when I do this I’ll start with AO-73.

Simon Brown G4ELI http://v2.sdr-radio.com

From: Wouter Weggelaar [mailto:[email protected]] Sent: 25 December 2014 11:11 To: Simon Brown Cc: AMSAT BB Subject: Re: [amsat-bb] Polarisation Switch

Hi Simon,

This depends on the satellite and its attitude.

For instance, Delfi-C3 carries circular antennas (canted turnstile) and is free tumbling. So you would need to switch polarisation as the satellite spins. FUNcube has linear antennas and also is free tumbling, so if you listen to it with a circular antenna there is no need to switch.

Note the following:

Circular in the wrong sense gives 20dB of loss (listening to LHCP signals with an RHCP antenna and vice versa)

Circular to linear gives 3dB loss (listening with a horizontal / vertical / diagonal antenna to a circular spacecraft or vice versa)

Now if the satellite is oriented or spin stabalised towards the earth, the polarisation will be known, and matching the apporopriate polarisation on the ground gives you the best signals.

Wouter PA3WEG

On Thu, Dec 25, 2014 at 8:17 AM, Simon Brown [email protected] wrote:

Hi All,

Is there a logical way to know which is the optimal polarization (left, right) for a LEO?

Simon Brown G4ELI http://v2.sdr-radio.com

_______________________________________________ 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 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 http://v2.sdr-radio.com

-----Original Message----- From: Clayton Coleman [mailto:[email protected]]

Simon,

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.

73 Clayton W5PFG

Hmmm,

Nice recommendation - not cheap but the right way to go.

Simon Brown G4ELI http://v2.sdr-radio.com

-----Original Message----- From: Stephen E. Belter [mailto:[email protected]]

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.

Clayton,

FWIW I'm using a Diplexer on the 145 MHz before the pre-amp, this knocks out the 3rd harmonics. My WIMO crossed Yagis are 2m apart on a fiberglass boom, the SDR is not being overloaded at all.

TX: 100W LSB, TS-2000 RX: NetSDR + RFspace's own down-converter.

When it stops raining & 1 remember I'll take a photo.

The system is working very nicely on FO-29. Total North Americans worked in the last few days - just the one! There's a pass in 150 minutes which would be nice for working into New England and the frozen North :) .

Simon Brown G4ELI http://v2.sdr-radio.com

-----Original Message----- From: Clayton Coleman [mailto:[email protected]]

Steve, I have been looking at those same relays. My biggest concern has been protecting the SDR's & FUNcube Dongle from any RF transmissions.

Clayton,

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, [email protected]

On Dec 26, 2014, at 8:48 AM, Clayton Coleman [email protected] wrote:

Steve, I have been looking at those same relays. My biggest concern has been protecting the SDR's & FUNcube Dongle from any RF transmissions.

73, Clayton W5PFG

On Thu, Dec 25, 2014 at 6:47 PM, Stephen E. Belter [email protected] wrote:

...

Simon,

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, [email protected]

...

On Dec 25, 2014, at 3:57 PM, Simon Brown [email protected] 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 http://v2.sdr-radio.com

-----Original Message----- From: Clayton Coleman [mailto:[email protected]]

Simon,

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.

73 Clayton W5PFG

---

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