GNSS /GPS Perplection

K8JK

Apologies for the length of this post in advance.

I have the following Flex radios:

Aurora 520M

8600 M

6700

The Aurora and 8600 have the supplied GNSS units, the 6700 has the optional GPS-DO module installed and enabled. All 3 radios are cabled to a TAPR GUS unit, designed to share one antenna to up to 4 radios. I am using as the antenna the supplied antenna that came with the Aurora. All 3 radios are being connected to the TAPR GUS unit with brand new shiny SMA to SMA cables, each 3 feet in length. The GPS antenna is connected directly to the GUS unit.

The TAPR device has 5 SMA connectors, one for the antenna, and 4 others for devices desiring to share the antenna. It is configured so that the device connected to port 1 will supply power to the antenna connected to the antenna port.

My initial configuration was the 520M is connected to port 1 (providing power to the antenna), the 8600M to port 2, and the 6700 to port 3. Port 4 has no connection. I have no other clients connected to these radios, and they are all on the same ethernet switch. (of course the 520M and the 8600M have their own front panels connected to them).

When the radios are powered on, the 520M shows a green power led followed shortly (about 5 to 7 minutes) by a lovely blue power led. The 6700 starts with a green power led, within about 1 to 2 minutes begins flashing yellow, then briefly flashes blue, finally ending with a lovely blue power led after about 6 to 7 minutes. The 8600M is not so cooperative.

The 8600M starts out with a lovely green power led, and even after hours still remains green. After 3 days, it was still green, no other colors, flashing or not. A quick look at the GPS setting from the front panel menu showed 12 satellites heard from, but zero tracking.

WITHOUT MAKING ANY CHANGES, the next time I powered up all 3 radios, the behavior of the 520M and 6700 was similar, but after about 3 hours the power led on the 8600M went from green to blue. This is starting to suggest there is an issue with the GNSS in the 8600M, but there are lots of other pieces involved, so I went further into attempting to isolate the culprits(s).

First step, one radio at a time connected directly to the antenna. For these tests I have eliminated the TAPR GUS and the 3 SMA Male to SMA Male cables connecting the radios to the GUS module. The 520M and the 6700 behaved as they have been. Sadly, the 8600M also behaved as it has been - first power up, after 3 days no change in the power LED, second power up, LED blue after 2 to 3 hours, third power up, 2 days with a green power led. Fourth power up, no green LED after 2 days.

Still willing to blame myself, I took the 8600M to a friends house and used their GPS antenna, previously connected to an Aurora. After leaving the radio there, connected and powered up for 3 days, a green led is all we saw. A quick check of the GPS showed us finding 19 satellites, but no tracking.

A little out of order, I returned home and swapped the antenna with 4 other GPS antennas here, and saw the same results.

This is all pointing to an issue with the 8600M, but I’m wondering if there’s something else I should be checking? I did see others with issues on GNSS that appeared to be corrected with a gain antenna? Is the GNSS receiver in the 8600M just not working up to specification?

Comments and sights are welcome.

Al K0VM

My 520 has a similar problem.. The 8600 locks in 2 minute or less. The 520 usually will lock in 5-10 minutes but occasionally never. I have ruled out antenna location. What I have noticed is that when locked, the 8600 GNSS page shows a Freq Error of 63 ppb but the 520 shows an error of 360 ppb.

My theory is that my 520 locking issue is related to the GNSS module internal frequency error. When your 8600 is locked, what does the GPS page show for Frequency Error?

AL, K0VM