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Listening to interference on UHF 461-465

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WQRR992

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I am a land surveyor. During the course of GPS work, I use a pair of Topcon Hiper Pro GNSS receivers. There are several communication capabilities involved in these units (receive satellite signals, bluetooth to external computer, etc.) but one of these capabilities is that each receiver is capable of transmitting and receiving a UHF signal in the 461-465 MHz range. l have an FCC license to transmit at powers up to 35 watts.

If I am working in a busy developed area, others (both licensed and unlicensed) may be using the frequencies that I am permitted to use. At the moment, it is guesswork for me to understand whether someone is using a particular frequency, and this is the reason for my post.

I am looking for advice as to what would be the options to determine the status of a particular frequency in the field. In other words, I'd like to be able to "listen in" on the frequency by using some sort of radio capable device (scanner? handheld?). I'm not sure if communications in this range can be literally "heard" or whether they need to be "seen" on some sort of graphic device, but the bottom line is that I'd like to be able to accurately and quickly tell whether a particular frequency is occupied. A sub-goal, I suppose, would be to be able to determine whether the chosen frequency is "clean" from miscellaneous noise/interference.

Could someone point me in the right direction?

Al
 

WA0CBW

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For the most part all frequencies are in use. It just depends on the coordinators how far away from you they will assign other users. If your frequency is an itinerant then you most likely will have other users on that frequency as there is no protection (distance) that other users will be assigned. It could even be unlicensed users who failed to read the FCC requirement for needing a license for their blister packed radios. As far as noise and interference goes it would depend on the environment where you are using the equipment. Industrial equipment, computers, electrical distribution plants, and even weather can cause external interference to the frequency you are using. A scanner covering the UHF band could also be a help in "hearing" if there is something on your frequency.
You can also search the FCC ULS database for any licensed users on your frequency and their location of operation. PM me with your call sign and I can help you identifying other users.
BB
 

WQRR992

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So I want a scanner?

Thanks, WA0CBW. I'm sorry, but I do not know how to send you a personal message. My call sign is my userID. Not sure whether my license is "itinerant", although I see that it is good for "Nationwide" operation. I am licensed for use of 461.025, 461.050, 461.075, 461.100, 461.125, 462.375, 462.400, 464.600, 464.625, 464.650, 464.725, 464.750, 464.500, and 464.550. I don't need a perfectly clean frequency, just clean enough that my communications between base and rover can succeed. As far as I can tell, the cleaner the better in that respect. So, a scanner would be the device used to determine how clean a frequency is?
 
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WA0CBW

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Looks like you have 2 Fixed Base Itinerant and the rest are Fixed Base Temporary frequencies. The area of operation is Nationwide. Because they are itinerant and nationwide you can expect to have interference on some of those frequencies. With that many frequencies you should be able to find one that has little or no other users. You should be able to use a simple analog UHF scanner to scan those frequencies to see if you hear anything. That would be a simple quick and easy way to determine if they are in use. Depending on how often someone transmits you might miss hearing them but it should give you some idea of who else is using the frequency along with an indication if there is some kind of interference. A spectrum analyzer (high $$$$ device) would also let you analyze a portion of the spectrum that you are interested in.
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WQRR992

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WA0CBW

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I'm not familiar with how that radio works as a scanner but I remember others here indicating that it doesn't make a very good scanner in the sense of how regular scanners work. It does cover the frequencies but it is also a transceiver. Compared to other scanners it is cheaper but then you also get what you pay for. Maybe others here can suggest a better choice of radios.
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WX5JCH

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I use my baofeng as a scanner works fine with 16 channels I keep the rest blank so it scans as fast as my motorola ht1250 I put a better antenna and large capacity battery on it and it works great


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popnokick

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Uniden BCT125XLT. Program all of your licensed channels into one of the scan banks, turn it on in SCAN mode, and turn up the volume. You should be able to find a clear channel. Would help to start listening as soon as you get to the area of operations... Night or day before, etc. you probably know your license does not give you an exclusive use of those channels. So searching for the most unused channel in a given area is the right thing to do.
A purpose-built scanner like the BCT125 is going to scan faster than any of the rice-box radios. And you may find the Uniden CloseCall feature useful, too.
 
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