[amsat-bb] SDRplay RSP as downlink receiver

Patrick STODDARD (WD9EWK/VA7EWK) amsat-bb at wd9ewk.net
Sun Aug 30 22:05:20 UTC 2015


In July, I ordered an SDRplay RSP SDR receiver from the SDRplay web site:


This is an SDR receiver that covers from 100 kHz to 2 GHz without gaps,
at bandwidths from 200 kHz up to 8 MHz. There is front-end filtering
across the entire range this radio covers - something that caught my eye
for use as a satellite downlink receiver with an FT-817ND. At US$ 149 plus
shipping from the UK, it is a good value. It is a small box, larger than
the FUNcube Dongle Pro+ I have been using for some time. After some issues
getting this device working on Windows 8.1 and 10 tablets, resolved with a
new API installer, I have been testing my SDRplay on my 8- and 10-inch
tablets - now running Windows 10, after being upgraded earlier this month.

Over this weekend, after installing the new API and ExtIO drivers needed
for HDSDR to see the SDRplay receiver, I wanted to try it to work satellites.
I made an attempt on Friday evening, during an AO-73 pass. Although I could
hear the satellite, I could not hear myself with the SDRplay and HDSDR. I
went back to the documentation and the different interfaces in HDSDR that
control the SDRplay, and I figured out the issue. SDRplay's ExtIO driver
assumes the user will want to reduce the amount of gain in the receiver,
where I want as much as I can get for working satellites. After making some
changes, I successfully worked another AO-73 pass this morning. I made two
QSOs, with Leo W7JPI in southern Arizona and Brad KG7NXH a few miles/km
southeast of me in the Phoenix area. Other than the normal delay I hear
from the SDR receiver and software (I hear the same sort of delay when I use
my FUNcube Dongle Pro+), the SDRplay receiver did a good job.

As I have done when using my FUNcube dongle, I made an RF recording of this
pass in HDSDR. That WAV file is big - for an 8:35 recording, it was about
450 MB in size. I also made an audio recording, in the same way I would if
I used my second FT-817ND as the downlink receiver - audio splitter plugged
into the tablet, feeding audio to both my headset/mic and Sony digital audio
recorder. With these tablets, I find that the performance of HDSDR is very
poor when it is trying to write both AF and RF recordings. Since I can make
an AF recording away from the tablet, I let HDSDR do the RF recording.

The default bandwidth used by the SDRplay receiver is 1.536 MHz. It can go
up to 8 MHz, but my tablets have issues when the bandwidth is more than the
1.536 MHz default value. When I work our satellites, whether using my
tablets or a laptop, I'll probably go with the 200 kHz bandwidth. This is
all I really need, and this will help keep the RF recordings from taking
over the drives in the tablets and laptop. :-)

I have been posting more details about how I have been using the SDRplay to
work satellites in a QRZ.com satellite forum thread. That thread is at:


My HDSDR RF recording, along with screenshots and photos of my station, I
have put them in my Dropbox space, accessible at:


I am not planning on selling my FUNcube Dongle Pro+. It is still a good SDR
receiver for working our satellites. It is smaller than the SDRplay, it works
with the FUNcube Dashboard software, and sales of the dongle support the
FUNcube project. It is nice that there is another SDR device that is showing
promise as a downlink receiver for our satellites, and at a reasonable price.


Twitter: @WD9EWK

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