Hi, (name or call?)!
The inexpensive RTL-SDR dongles are a great way to get started with SDR receivers. For amateur satellite work, other than the ISS and maybe AO-85, they have a couple of significant drawbacks...
1. These dongles were designed to be TV receivers, working with signals much stronger than we have from our satellites or even the ISS ham station.
2. These dongles lack front-end filtering. This means that there could be a strong signal near you that swamps the receiver that wipes out what you're trying to hear. If you are trying to work satellites full-duplex, it is possible that your transmitter will shut down the dongle until you end your transmission. This was a problem I experienced early on when I tried using one of these dongles as my downlink receiver, and quickly moved on to something else.
Unfortunately there isn't anything in the middle ground between these dongles and devices like the SDRplay (sold by HRO in the US for $149) or the FUNcube Dongle Pro+ (sold by its UK manufacturer for around $200 depending on exchange rates, which includes FedEx next-day shipping from England to most addresses in the continental USA). Both of these devices do well as the downlink receiver for working satellites. Both come with front-end filtering that the RTL-SDR dongles lack, and still have sensitive receivers. The SDRplay has a low-noise amplifier that is engaged when receiving at VHF or higher, but you can reduce the amount of gain from the built-in LNA. For my work, I keep that gain reduction value set to 0, so I have maximum gain to hear the downlinks.
Good luck, and 73!
Patrick WD9EWK/VA7EWK http://www.wd9ewk.net/ Twitter: @WD9EWK
On Thu, Jun 16, 2016 at 2:30 PM, [email protected] [email protected] wrote:
Hello all! Been lurking a while here and just wanted to say hi and thanks to everyone. Just started working the birds. VERY limited success so far on the linear transponders. Limited budget leads me to either have to run in half duplex (obviously not preferred) or come up with another low cost receiving option. I bought an RTL-SDR to see if it could be any help. I have to say I really like this little receiver. It’s a little buggy figuring things out but it receives really pretty well…UNTIL I try to receive CW and SSB on the transponders. I have no problem receiving FM repeaters and simplex and have monitored a few SO50 passes with it no problem, but for some reason I’m not hearing the same signals I can hear on the receiver of my FT100 with the EXACT same antenna. I A/B them and have nothing on the SDR. Is anyone using one of these? I am probably missing something simple. When I started receiving HF I couldn’t make it work until I figured out I had to change the sampeling in the setup to direct from quadrature…only learned that through a forum and I assume something like that will make the thing come to life. Lack of documentation on some of these things is kind of a pain. Thanks in advance for any help you can offer and my apologies to anyone I have frustrated working half duplex! I will figure out what I’m doing! ____________________________________________________________