I use both Geomax Zenith40's in my solo practice and Leica GS18's for a firm I do quite a bit of contract work for. Both run GPS/GLO/GAL/BEI.
Typically I use an elevation mask of 10° at RTK base (in case logging static at same time) and 15° at rover. Both are satel 1w radio's using 8-FSK with Geomax on rtcm3.2 msm protocol and Leica on their Lecia 4g protocol.
In last few months started to have problems with Zenith40's dropping a constellation and then reacquiring it quickly enough that I don't lose RTK fix but CQs jump up slightly and is disconcerting. Dealer suggested turning off GPS L2C which didn't help but more recently they also suggested dropping BEI which when I disabled at the base seemed to fix issue straight away (but didn't do a full day after testing). I had wondered if I was getting interference on my radio channel but when dropping BEI out seemed to fix it, I figured must be a data transfer problem.
Restarted the base/rover using 15° mask at both base/rover and working ok with ~35 satellites max. being used in solution. Again restarted base/rover with 10° masks and 16-FSK on radio and working ok with ~40 satellites max. in solution. So appears either need to use 15° mask and keep 8-FSK for slightly better range or if base is to use 10° mask then use 16-FSK and accept radio not punching as far. Cell latency around here more problematic than radio too so that's not my solution.
Seems RTCM3.2 MSM with 8-FSK can't transfer much more the 35 satellites worth to rover, not a problem all day but at peak times it is. Probably the best option would be to drop out all the geostationary BEI satellites only not the whole constellation but Zenith 40's not that fine grained.
Questions:
1) Haven't had same issue with GS18's (yet) so Lecia 4G must be more compact than rtcm3.2 msm?
2) How many satellites are being used in your RTK base/rover solution and can your internal base radio/radio protocol get the message though in time?
3) My problems started back in April so I'm thinking that must have coincided with more satellites coming onstream; where would I confirm this?
Talk about timing. I rarely utilize my base/rover setup with radios these days. Recently I've been working on a larger project without cellular connectivity requiring the use of my radio system. I have noticed that utilizing the three G constellations causes a lot of radio headaches.
I'm using GS16s as base and rover. The base broadcasts to my Satel 4Pro repeater via the built in UHF. I'm transmitting RTCM 3.2 msm with a compact message over 8-FSK w/FEC. When using the 3 constellations, I get no radio love unless I have the repeater transmit on a different frequency. It just stomps all over itself causing the rover to randomly loose whole constellations.
As for Leica's Leica 4G message, I was unaware that it sent more that GPS/Glonass.
@mark-silver has provided much very useful information on YouTube and his website.
Using a handheld UHF transceiver to debug radio problems:
Choosing a protocol when using many constellations. Targeted at UHF repeater users but lots of good information about protocols, bandwidth, timing, etc.
There are links to Mark's blog articles in the YouTube video descriptions.
Thank you @mark-silver!
Tony.
Yep will aware of both of those but neither apply here as not interference and not using repeaters + my equipment uses different radio protocols (no CMRx). May help others though.
Looks like it might be 16-FSK for you and slight drop in range. Maybe cancel out the losses by using 1m whip antenna on 5m pole if not already??
Fully understood your post now about the losing the whole constellation, that is exactly what I am seeing.
Any other 4 constellation users able to advise the maximum number satellites their receiver is tracking/using in the solution with their given elevation mask?
Any Trimble etc. users finding too many satellites and associated signals for RTK radio to keep up?
Cheers
Any Trimble etc. users finding too many satellites and associated signals for RTK radio to keep up?
Nope, not with CMRx broadcast format at 9600bps on UHF. It's pretty typical to see around 20-25 SVs for short occupations (5 epochs or less), and get up around 30 or more for 1-3 minute occupations. With RTCM3.2 over cellular (what our RTN provides) we see moderate to high latency often, and it's pretty common to see a constellation drop out of the solution.
CMRx takes up a lot less bandwidth than RTCM if I remember correctly - as much as one-third to one-half less.
What bitrate are you transmitting at? We had some older receivers that could only transmit/receive 4800bps, which is just not enough to get the entire message, especially using RTCM. 9600 will suffice, but it seems like that runs right up against the limit with a repeater in the mix.
Using 8fsk/rtcm 3.2 msm, not narrow banded either 25 kHz. Not sure on baud, not a setting I can adjust.
Down here in New Zealand I'm seeing more like 40 satellites being used in the solution at peak with more being tracked. Maybe those extra 10 to what your seeing are the problem. Less than ~35-36 doesn't seem to cause me problems either. Think it must be all the new Beidou says that are pushing me over the edge, can be up to 14 of those alone, it's a pity I can't turn off all the geostationary ones as figure they are not as helpful as not changing their geometry doesn't provide such an independent check for second fix.
The cellular system here seems built to put data transfer at lowest priority. Fine if you are downloading a PDF etc. as gaps in data transfer don't matter as it all gets their in the end but with NRTK those small gaps are the difference between working and standing frustrated hence only use it at start of the day to get the RTK base in the ballpark to find local control.
