If you are cheap (like me) and trying to download satellite telemetry as inexpensively as possible, you may be using the $20 RTL-SDR dongle. It works but you get the performance that you pay for.
If you're willing to part with another $20, you want to consider the Low Noise Amplifier for the RTL-SDR from janieelectronics. I ordered one through eBay and received it yesterday. It ships from Hungary so a little patience is needed with respect to delivery time, but I did get mine a day before the last predicted delivery date.
I used it last night and it works! I definitely downloaded more data packets from AO-85 than I have been getting lately. I also tried it on a pass of AO-73 that was at a lower angle than I would normally attempt. I was able to download data from that pass, which I probably would not have gotten without the preamp.
I wasn't paid and didn't get a discount for the review. I am just happy that an inexpensive item actually works as promised. If you are as cheap as I am and looking for a preamp for your SDR, consider the janieelectronics Wide-Band LNA. It works for me.
Steve AI9IN