Radio corrections, and possible multi-path.

#1
Just out of curiosity, has anyone experienced radio issues near bodies of water?

I was surveying the other day. The base was on one side of a reservoir, I was on the other.
I was a little over one mile from the base. Base was transmitting at 35 watts. About one mile of water between us. Line of sight to the base.
When I got closer to the water, I would lose radio corrections. This was with both the internal, and external antenna.
When I went higher in elevation, or when a building would block my view of the water, I would receive corrections without issue.
It was a shallow angle from the base to the water, to the rover.
The only thing I could think of was multi-path, not much else happening in that area that could cause the loss of corrections.
 

Adam

Well-Known Member
5PLS
#2
I don't know the answer. I wonder if the water acts a huge ground plane shooting the signals up. I have never worked around any bodies of water more than several hundred feet or so across.
 
#5
Thank you for your replies, and thoughts about this issue.
I have possibly seen this before with other equipment while working on a seismic gun boat, but I cannot say for certain.
Circumstances were very similar, shallow angle between the base, surface of the water, and the rover, radio transmitting at 35 watts.
 
#7
Thanks for the suggestion Matt!

I will remember that the next time.

I was too busy using profanities, and other magic words to do so at the time.
 

Matt Johnson

Well-Known Member
5PLS
#8
Also I will mention that the link quality value displayed in the green box of the action screen has been broken for a long time but has recently been fixed in the version of J-Field that will be released with Linux. Currently it incorrectly always displays 100%.
 
#9
Ideas:
I got into a spot, with no radio. Move 40', and it's got full strength. I believe it was a cell tower signal, sympathetic crossover.
Try 1/2 wave andenna.
Try removing the ground plane.
Try leaning the base tx pole.
Try a taller tx pole. I run around 16 to 20 foot base transmit mast. Elevate the transmit antenna. It's the number one "cure".

Nate
 

Matt Johnson

Well-Known Member
5PLS
#10
The ground plane should not be removed with the 5 dB antenna. Removing it causes a big antenna impedance mismatch that reduces the radio range and overheats the radio because of returned power.
 
#11
Thanks Matt, and Nate!

Nate,
All of those things work, but this was a very strange thing.
No cell phone service in the area where this happened. A little over one mile away from the base, line of sight, I could see the base with my naked eye(s).
No ground plane on the antenna, do not use one. I had the antenna up about 12 feet using a Hixon 25' pole supported by a tripod. I didn't feel I needed any real elevation for the antenna given the distance to the base, line of sight, and transmitting at 35 watts. (Maybe a bit of overkill with the wattage, and that could possibly be part of the problem.)

Have worked in and around that area a lot lately without these issues, then only real difference is the amount of water between the base and the rover.

I am just going to chalk it up to the plate in my head creating the interference until I can determine the real cause.