GPSDO Considerations

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  • Updated 2 years ago
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I have the GPSDO in my 6700. I made a couple mistakes with it (mainly because I didn't read the instructions).
I would like to point out a few of my mistakes so that will not happen to others.

Summary (in case you don't feel like reading the whole thing):
  • Pulse GPS antenna is INTERNAL and NOT waterproof. Place indoors.
  • The PULSE engraved on the antenna is NOT the side that should face SATs
  • The crimped SMA connector is delicate, do not pull from the coaxial.

The Pulse GPS antenna included with the GPSDO Module is NOT an external antenna and will get water ingress if it rains on it. I learn this the hard way. My GPSDO stopped tracking Sats and I thought it was a software issue. I reinstalled SmartSDR, performed Factory Resets and GPS will still not work. I then stumble upon the text somewhere that mentioned the lack of waterproofness of the Pulse GPS antenna. I decided to take it inside and open it. There was water inside, not a lot, almost like humidity condensation, but it was enough to make it fail.

I disconnected it from the radio, blew compressed air inside the GPS antenna to remove as much water as possible and let it rest for a few days. I went ahead and ordered a new one on eBay.

After a few days I tested the GPS antenna and it was working and I decided to place it in the highest point of a window I have facing south. From that point I wouldn't get as many sats visible, 7 or 8 max. That is when I figure out my second mistake. The Pulse engraved in the GPS antenna is actually the side that should not face the sats (this is highlighted in the manual). I turned the unit around, losing the double sided tape in the process. 
I used my own double sided tape, a bit on each end of the GPS antenna and I was able to get 9 sats visible and more consistent lock.

My third mistake. I had the antenna on the outside going through a hole in the wall where I feed all the coaxials and rotor cables. I pulled to get the GPS antenna cable out and I ripped the coaxial from the SMA connector. The tip was still there, as it is the only soldered part. I was lucky enough to be able to fish out the SMA connector and I replaced it in and reclamp it.

A couple of days ago I received the first of a couple of antennas I bought on eBay.

The one I received is a GlobalSat AT-65-SMA high gain 28dBi EXTERNAL. I plug it in and what a difference!! 15 Sats visible, 10 tracked, locked almost instantly!

Less than US$10 shipping included and it works great. Much better than the Pulse Antenna when I had it outside.

The other thing I noticed with the new antenna is that the Altitude is spot on at 48m over sea level with no fluctuation and that Speed remains at 0 Knots, as it should be as I am stationary. The Pulse antenna, even before getting water inside, displayed up to 7 to 10 knots from time to time and a wider range of Altitude values.

Here is the eBay link where I bought it.

Not only it is external, it actually has magnets to attach it to a metal plate and 5m of cable.

Maybe FRS should think about including this antenna in their GPSDO package instead of the Pulse.

The other antenna I ordered is this one It has less cable, 3m, but it is also cheaper (a bit over US$5). 
Photo of EA4GLI - 8P9EH - Salvador

EA4GLI - 8P9EH - Salvador

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Posted 2 years ago

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Photo of EA4GLI - 8P9EH - Salvador

EA4GLI - 8P9EH - Salvador

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The sun is out and this is the largest number of SATs both Visible and Tracked I have ever seen with the 6700.

Very happy with the new antenna.
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David Warnberg

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Salvador,  what advantages can you tell with the GPSDO unit verses without?
Photo of EA4GLI - 8P9EH - Salvador

EA4GLI - 8P9EH - Salvador

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Besides knowing that my radio is super stable, not much right now. If we could just get the time out of the GPS to the radio it would be great, and it should be a really easy thing to do.
I also look forward to using the 10Mhz ref out of the 6700 to make all of my other gear super stable. There is a device you can install in some radios instead of the TXCO that will accept a 10Mhz source. You can find more info here
I can add that to my TS-2000 and FT857D and with a Downeast Microwave 10Mhz hub send the ref signal to all the radios. My Flex 1500 will also take a 10Mhz signal.

Eventually I hope FRS can start taking advantage of the GPSDO with new features that will make it the radio for EME, Scatter, Opera, JT, and other interesting radio modes.
I am also hoping we will see progress in the geográfical diversity. GPS Sync will be important then.

As per your question.... not much right now. If stability is the only thing you get (as is the case now), you might as well save the $700, buy a cheaper GPS Clock that will give you a 10Mhz signal and feed that back into the radio.

I wanted my 6700 to have everything, so I bought it... but more like a future investment than a current one.