This rotor is less than a year old. It works perfectly and is in very good condition. Works with any of the ST series interfaces (ST-1 and ST-3). Selling the rotor, control box, Satellite serial port interfaces ST-3 and SAT668. It really is Plug and Play
$450 plus shipping
Thanks
-----Original Message----- From: Phil Karn Sent: Sunday, July 27, 2014 1:12 AM To: [email protected] Subject: Re: [amsat-bb] going digital
On 07/22/2014 07:27 AM, JoAnne Maenpaa wrote:
When thinking of projects to enter into the digital communication world plan on building or buying that digital interface to connect your radio to the soundcard.
Soundcard interfaces to existing voice radios were a good start, but it's time to move past them. I've designed several modulation and coding schemes to fit existing radios, and their inherently limited bandwidth is a major pain. For ARISSat-1 I agreed to cram everything through a SSB filter, and I'm not doing that again.
Not only does the narrow bandwidth often limit the data rate to much less than what the link budget could actually support, but it enormously aggravates the Doppler problem. It doesn't help that there are no industry-wide standards for SSB phase response or computer tuning, or that every time you retune one (which is often) there is a poorly characterized phase jump.
Doppler is much easier to handle at high data rates because it's the ratio of the symbol rate to the Doppler that matters, not the absolute amount of Doppler.
Now that we have a variety of "pure digital" radio front ends to choose from, it's time to set aside the voice radio + soundcard model. Not only do the SDRs support wider bandwidths but they tend to be considerably smaller, lighter and easier to work with in software. Some, like the Funcube dongle, are even considerably cheaper than conventional radios.
--Phil
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