In California, we have to use 160 MHz for radio tracking salmonids, and the amount of interference from power lines, even cell phones, is problematic. Even the electric windows of my truck causes interference. Some days are worse than others. I have tried adjusting the gain of the receiver, but then it's harder to get the code from the tag. The funny part is that I used to use 149 MHz, and had few problems, then FCC said we had to use 160 b/c 149 interfers with cell phones, which it didn't! Now at 160, cell phones interfer with our tags, and power lines too. At least in CA, radio telemetry in areas with power lines is most difficult!
I've worked in the 148 Mhz range (aerial telemetry) and experienced a good deal of interference in one of my study areas that was closer to an urban area (~35 miles). When we flew that area, we used a noise reduction unit and that seemed to help. However, don't expect to completely eliminate interference, especially if your study area has a lot of transmission lines, communication towers, etc. ATS and Telonics carry these units if you're interested in giving it a try.
I have worked with 148 - 152 and in the 160s. All can experience interference. Some of the worst interference seemed to be related to the sun. In the 148 - 152, there were mornings that taking a bearing to the east (toward the sun) was impossible. Nothing seemed to help. Electrical transmission lines are also problematic. I am not sure there is a way to reduce interference while retaining decent detection range.
I have used 172-174 which were required on certain Federal projects. They too can have problems with interference. As Mike Conner indicated, there are always potential problems with transmission lines. The only areas I have not had interference problems were western Kansas and northern Maine.
In the UK the situation for me is poor at 143.05 MHz where I monitor radar echoes from meteors.
Thank you all very much for the informaiton based upon your applications! I am using LOTEK, and I will see if they have any noise reduction related products. Luckily, most of the steelhead I am tracking are upstream of rural areas now. I have made a new way to externally attach the radio tags, that doesn't use a harness, and is quite fast (2 minutes tagging time is about max, most is < 1 minute). All of the fish are doing quite well, no mortalities from tagging that we can tell. Thanks again, and happy tracking!
Hello Michael, I have had my handheld GPS interfere with reception when using this range and also the 148-152 range.
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