Since asking about transmitter steering, I've been looking into the feasibility of simulcast. The marginal difference between transmitter steering and simulcast (in terms of equipment) is a GPSDO and a transmitter that accepts a 10 MHz reference input. I have some leads on transmitters--Quantars or some Daniels MT-4D. Other transmitter recommendations are welcome, but what I'm really curious about is the GPSDO. It looks like the Trimble Thunderbolt is the gold standard. At less than half the going price of Thunderbolt, you can find these BG7TBL GPSDOs: http://www.ebay.com/itm/121530825744 Some are labeled Trimble and Huawei, so I think it's safe to say they are neither. The question is: are they any good? It looks like KE5FX has done some testing: http://www.ke5fx.com/gpscomp.htm I don't really know what to look for in the graphs, but he says in his conclusion "the BG7TBL unit is actually running at about 9.999 999 999 800 Hz". Is this a deal-breaker for simulcast? If all transmitters have a BG7TBL GPSDO, does it matter that they aren't exactly 10 MHz? Is anyone running these GPSDOs with RTCM simulcast that can comment on their performance? Tom KD7LXL