[amsat-bb] SDR Front End Protection and Spin Modulation Fading

[Patrick STODDARD (WD9EWK/VA7EWK)]

Hi Mike!

The SDRplay receivers (all models) have front-end filtering across
the range they are capable of receiving. As long as you aren't
transmitting in the same band as you are receiving with an SDRplay,
you should be fine. If you want additional protection for the SDRplay
when working satellites, a 2m/70cm diplexer can be put in front of
the SDRplay as another layer of protection. Again, the SDRplay is not
protected if you transmit on the same band it is being used to
receive. You won't need to run full power from your IC-7000 for
satellite work. As many use Yaesu's FT-817s and FT-818s to work
satellites, you will be able to scale back on the transmit power
from your IC-7000. Once you get your station set up, you will be
able to test and see how much power is sufficient.

I normally use an Elk 2m/70cm log periodic for my satellite work.
For the SSB satellites, I must use a diplexer so the antenna is
connected to both radios. I have used SDRplay receivers, a FUNcube
Dongle Pro+ SDR receiver, and other radios (FT-817s, the all-mode
receivers in Kenwood TH-F6A and TH-D74 HTs, and all-mode receivers
like an AOR AR8200 and Icom's IC-R20 and IC-R30) in this manner.
The diplexer is another layer of protection for whatever radio I
use as a receiver, along with ensuring I never transmit on the
same band I am receiving with the second radio or SDR receiver.

As for the Alaskan Arrow compared to the standard Arrow, you will
have more gain with the Alaskan Arrow. You will have to be more
accurate in pointing the antenna at the satellites, as the increased
gain reduces the beamwidth from the larger antenna. With any antenna
used at a fixed orientation, you will occasionally have fading that
you'll have to deal with. Signals will fade out, then fade back in.

Good luck, and 73!





Patrick WD9EWK/VA7EWK
http://www.wd9ewk.net/
Twitter: @WD9EWK or http://twitter.com/WD9EWK





On Thu, May 23, 2019 at 3:35 PM Mike N8MR via AMSAT-BB <amsat-bb at amsat.org>
wrote:

> I have an SDRplay RSP1 that I’d like to use as a downlink receiver, along
> with an Arrow 146/437-10 antenna and Yaesu G-5400 az/el rotators. Uplink
> will be an Icom IC-7000. Using this setup, will the SDRplay need a Front
> End Protector to keep it from overloading? If so, which ones are
> recommended?
>
> Also, I am considering upgrading the antenna to an Alaskan Arrow. Is there
> a noticeable improvement in antenna performance and gain between the
> standard Arrow and the Alaskan? Would the improvement in gain also result
> in deeper fading during spin modulation?
>
> 73,
> Mike, N8MR
>
>