I originally did the mod for the GPS location benefit and the oscillator discipline was secondary. I noticed the GPS referenced setting can be a lot different than the factory setting in the radio. I wouldn't run without it now, especially when it can be done for $100. You don't necessarily need the internal module. The standalone units work just fine, but you'll have wires running everywhere. Not a big deal if your just using it at home.
So , catch me up to speed , I’m about 4 minutes in What does this GPS thing do for this particular radio ? Is there modes of operation that require your location via GPS ?
The GPSDO injects a GPS referenced 10mhz signal into the radio for increased frequency stability. It's just one option. There are more accurate and expensive alternatives. It's all based on use case and how far down the rabbit hole you want to go. For me, an occasional GPSDO based calibration is more than enough. The board also has a serial output for the GPS NMEA sentences. This is fed into the data port on the back of the radio for setting the time, DAPRS location, etc.
The site where I bought the board from stated it had a +10db output. I have no way of measuring the output, so I just went with what they stated. I ran the board and the other unit I showed with no ATT at all for several days. I'm not sure you even need one. I didn't notice any difference with or without.
UPDATE: I took the radio apart once more to "thread-lock" the mounting standoffs. I switched out the -20db pad for a -10db pad to test the difference. Let the GPSDO warm up for a couple hours and then ran a calibration. Absolutely no difference between the two ATTs.
@@n5yiz By the way, I like your project, I was just wondering how you came up with the 20dB pad to begin with. After doing some 9700 research I see it the 10mhz input expects approximately -10dBm. you're probably ok with the 10dB pad but without full knowledge of the GPSDO output level I'd likely keep the 20db pad in the circuit. Thanks for the responses
