[amsat-bb] 1. Re: Polarisation Switch
Mark L. Hammond
marklhammond at gmail.com
Sat Dec 27 15:29:07 UTC 2014
At the risk of stating something obvious--another way is to put up an extra set of antennas so you have 2 on 2M and 2 on 70cm :) Then you have dedicated antennas for your SDR receivers. I know the price goes up with preamps, coax, etc. but it's a nice solution that gives me all kinds of options for mixing/matching bands! Also, if there is no xmitter connected, you're not going to xmit into the SDR directly.
>Date: Fri, 26 Dec 2014 08:48:31 -0600
>From: Clayton Coleman <kayakfishtx at gmail.com>
>To: "Stephen E. Belter" <seb at wintek.com>
>Cc: AMSAT-BB <amsat-bb at amsat.org>
>Subject: Re: [amsat-bb] Polarisation Switch
> <CAPovOwc+ZUTkNQ=UF5ygrATCbReQ0nooXfLewsL9tefRo9FBrg at mail.gmail.com>
>Content-Type: text/plain; charset=UTF-8
>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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