[amsat-bb] RTL-SDR downlink
jbarbre at xmission.com
Thu Jun 16 21:27:29 UTC 2016
The Airspy Mini sells for $114. Worth looking into.
On 6/16/2016 1:22 PM, Patrick STODDARD (WD9EWK/VA7EWK) wrote:
> 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
> Twitter: @WD9EWK
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