Noisy site

Bruce Dawson

Active Member
I had a lot of trouble today on an urban site trying to get RTK solutions. I was fine within about 1000 feet of my base, but after that - no go. I did a scan of the frequencies and every single one showed up as being noisy. I recall having trouble similar to this with other systems throughout my career in the same type of areas.

Is there a solution other than working prior to or after normal working hours, or even on weekends?

Bruce
 

Matt Johnson

Well-Known Member
5PLS
I assume you saw the link quality drop below 100%? This is the indication of the radio corrections not being received by the rover. What modulation were you using for the radio? If you are only using 1 Hz corrections, DBPSK modulation would be least subject to interference.

Another option would be to transmit corrections the internet (TCP base). Base/Rover Setup will support TCP corrections in the next release of J-Field.
 

Bruce Dawson

Active Member
Yes Matt, I saw various reductions in the quality, typically 83% (I think) but mostly just a red box with no quality percent (large countdown numbers trying to connect, I guess). Modulation was DQPSK, 1hz corrections.

I am not familiar with the TCP base option.
 

Shawn Billings

Shawn Billings
5PLS
Be sure that when you run those scans that your own base is not broadcasting. When you are standing next to the base and running the scan, you'll get a bleed over from the broadcast frequency to neighboring frequencies. It might not have been as bad as you think with the other frequencies.
 

Bruce Dawson

Active Member
Shawn, I was away from the base (about 1/2 mile or so) when I had first had trouble and ran the scan that found all the frequencies noisy. I returned to the base, stopped it, then checked again and still found everything noisy. I am going out tomorrow to a different site that is a mile or so nearby, just not as "urban", so I will look again. The site I was at today was near a hospital, police station, fire station, all sorts of possible problems. Tomorrow not so much. Most of my work is in suburban or decidedly rural areas, so this is kind of new with the LS for me.
 

Shawn Billings

Shawn Billings
5PLS
Sounds like you may have had a truly noisy site, Bruce. Also, being a 1/2 mile away should be enough to avoid the bleed over I was describing. The TCP that Matt was referring to is using the internet to broadcast your corrections. Typically you use a cellular modem at the base and a cellular modem at the rover and send the corrections over the internet. It works great in urban places with good cellular coverage.
 

Bruce Dawson

Active Member
Yeah, I think it was just noisy. I will see how tomorrow goes at the other site, but I was there before and had no problems. It's a small site, however, no farther than a few hundred feet from the base. I was breaking down a partial section today, so long vectors. Probably just have to try doing my work very early, or on the weekend.

Thanks for the ideas guys!

Bruce
 

Nate The Surveyor

Well-Known Member
Ok, I'm going to lead you off into the world of radio crime.
A long time ago, I had trouble finding a frequency that was not busy. I went to the internet, and went looking for licenses, that others had. I found a channel, that was assigned to another surveyor, that was big on staying current, with all things. He had a slew of radios, and wanted his own private frequency, with a HIGH POWER communication, between crews, and office. Well, he has changed his methods, and now runs semi solo, and is no longer using this radio stuff. So, I borrowed his frequency. It is channel 11 in my old Legacy E RTK system. When I get into a noisy environment, almost ALWAYS this channel is clear.
Another comment. If ALL the available channels in the LS (the pre assigned channels) are busy, you probably are getting "Bleed Over" from other nearby channels. I did once set up on a hill, near a huge multi antenna cell tower. It was a big tall fenced tower, with loads of antennas. MISTAKE!
NO CHANNELS would work well. I finally made a long shot to a place in a cul de sac, (out in the middle of the cul de sac) and got a shot there. Moved my base. Ran with a deliberately LOWER antenna, (it was near my project) and it ran fine, with very little interference.
Sometimes UP ON THE HILL is counterproductive. Get low, where you are not going to pick up other signals, and near your site, and run less output power, and well, we can go back into the HAPPY HAPPY HAPPY zone!

I'm not telling you that these solutions are the BEST. I am telling you to "Get out of the box" and get productive.

Sometimes you have to make a trip through trouble, to discover it is not your equipment that is not working. It is your environment that is interfering. And, you will have to find creative solutions.

And, NEVER break the law.

N
 

Adam

Well-Known Member
5PLS
When I got my license back there was statement on it about no other licensed users were within 50 miles of me. None of the construction company's around here even know what an FCC license is, but still they have there machine plowing along.
 

Matt Johnson

Well-Known Member
5PLS
It is channel 11 in my old Legacy E RTK system.

This sounds like you were using a spread spectrum radio. I believe Bruce has a UHF radio. Anyone can operate a SS radio without a licence so there is more possibility to have interference with a SS radio. UHF frequencies must be licenced so the chances of them all being in use should be unlikely. I still suggest using DBPSK modulation if you are having problems with interference. It is 8 dBm less sensitive to noise than D8PSK modulation:

upload_2016-3-24_9-47-58.png


It is also desirable to increase the radio power output to increase the carrier-to-noise ratio (CNR).
 

Sean Joyce

Well-Known Member
Another option would be to transmit corrections the internet (TCP base). Base/Rover Setup will support TCP corrections in the next release of J-Field.[/QUOTE]
Matt;
I have a home office on top of a hill, nearest neighbor 1/2 mile away. Broadcasting my base corrections by internet is looking more and more like a winner for me. I am thinking of building a mount on my roof for the T-2. It would be well within my wireless router range. Is it possible to link the T2 to my network and broadcast the corrections to the rover?
I would either use phone hotspot or sim card at rover.
 

Nate The Surveyor

Well-Known Member
I don't think so. It is a Pac Crest 35 Watt, with a PDL 3500 on Rover. I got some software, went into the radios, and shall we say, modified it a bit.
N
 

Shawn Billings

Shawn Billings
5PLS
Is it possible to link the T2 to my network and broadcast the corrections to the rover?
I would either use phone hotspot or sim card at rover.

Yes absolutely. I do this at my office. Some days I use the modem and some days I use the TCP. If I'm working close to the office (within 6 or 7 miles) I use the TCP from the office.
 

Matt Johnson

Well-Known Member
5PLS
Matt;
I have a home office on top of a hill, nearest neighbor 1/2 mile away. Broadcasting my base corrections by internet is looking more and more like a winner for me. I am thinking of building a mount on my roof for the T-2. It would be well within my wireless router range. Is it possible to link the T2 to my network and broadcast the corrections to the rover?
I would either use phone hotspot or sim card at rover.

Yes this is possible. I attached instructions on how to do this with the current released version of J-Field. In the next version Base/Rover Setup will support it. If you mostly work near your office, this is a good solution. RTK performance decreases with baseline length.
 

Attachments

  • TriumpLS TCP Base Setup.pdf
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Shawn Billings

Shawn Billings
5PLS
I don't think so. It is a Pac Crest 35 Watt, with a PDL 3500 on Rover. I got some software, went into the radios, and shall we say, modified it a bit.
N

"Channel 11" isn't an official designation. The software in the radio has a table, something like 0-99. Each element (0-99) is a channel and can have a frequency programmed into it. 0 = 461.125, 1 = 464.75, etc. So your Channel 11 may not be the same as the next guy's Channel 11. He may not even have a Channel 11.
 

Shawn Billings

Shawn Billings
5PLS
Yes this is possible. I attached instructions on how to do this with the current released version of J-Field. In the next version Base/Rover Setup will support it. If you mostly work near your office, this is a good solution. RTK performance decreases with baseline length.

To me, the trickiest part was going into my router and programming the port forwarding for the first time. I'm not an IT specialist, so this was a very new experience. It took me most of a day to figure out how to configure everything. There wasn't any documentation then, but Michael Glutting walked me through it (very patiently). Now I can do this pretty quickly. But I know my system. If I were to try to set up port forwarding in another router, it would probably take me a while because the router software is different (at least slightly) from one make to another.

Even at that, the full day tinkering around was well worth the effort. Anywhere in my town, I get to the job, step out of the truck and go straight to work. It's a beautiful.
 

Sean Joyce

Well-Known Member
Yes understood.
I am fortunate to have a CORS very close by but I am hooked on the 5hz corrections.
Most projects I set my own base or base(s) I have the SS radio.
BTW is there a possibility of getting even more than 5hz in the future?
 

Bruce Dawson

Active Member
My tale of woes continues...

After having no problem yesterday at a small site (200' square) about a mile away from my problem site, I had the same problems at a decidedly rural site 30 miles away. This site is a resort community, with no cell towers, fire stations, etc. About 10am I setup my base on one of my control points, checked the noise levels with a scan (very clean, no issues), and began working. I have done work here before with my system and had no issues whatsoever. Not so today.

After about 2 hours, I began to have dropouts in my reception. It would just go yellow (67%) for a moment and I would be floating. Then it would come back. I was working at the edge of the magical 1000' distance (or so) from my base. I still had some more corners to search for further away and so decided to move the base closer to that work. I setup on another control point closer, checked fine to a previously stored corner, and began work again. As soon as I dropped over a small bank, it began to fail again. I tried checking into another control point nearby using stakeout, and it said I was out of position by like 8 feet! I collected data (100 epochs worth) on it and after importing I found it was a good check. I tried to check into another pair of corners and got similar errors, only now more like 20 feet. I also saw that when I tried to stakeout to them, the distance to them did not change even as I moved around. By now, however, it was dropping out of reception and I was floating, then just as quickly would have 6 solutions. I scanned the frequencies and found everyone green, and the one I was using red.

I am desperate. I don't know what has happened. When I first got the unit, I was getting solutions on 2 mile vectors not far from the urban area I am now having trouble with.

Bruce
 
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