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GM 300 - surveying radio

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cordgrass

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I recently purchased a Trimble Trimmark IIe radio (GM300). I am planning to use it for running RTK survey equipment. I do not have a scanner to determine what frequency the radio is running. anyone have a clue what the default UHF frequency is?
 

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cmdrwill

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Radio probably is NOT Narrowband capable.

There is no "default frequency" but most were in the 464-465 range.

An FCC License IS Required.
 

902

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I echo the concern for your RTK system. That GM300 is not narrowbandable, so, that's a problem. You also need to be coordinated and get a license. Most public sector RTK operations license several frequencies as they travel around their jurisdictions. That way they set up where they are not interfering with anyone. It would be the licensee's responsibility to monitor before transmitting.

You might be able to gut the GM300 out of it and replace it with an M1225. That might even be a direct plug-and-play replacement, but do get yourself a license.
 
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I echo the concern for your RTK system. That GM300 is not narrowbandable, so, that's a problem. You also need to be coordinated and get a license. Most public sector RTK operations license several frequencies as they travel around their jurisdictions. That way they set up where they are not interfering with anyone. It would be the licensee's responsibility to monitor before transmitting.



You might be able to gut the GM300 out of it and replace it with an M1225. That might even be a direct plug-and-play replacement, but do get yourself a license.


I'm unfamiliar with the operation of RKT radios but there are wideband licenses available for some data only applications. However, the number of people who will willingly support the GM300 (or even the M1225 now) is becoming a smaller list everyday.


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I echo the concern for your RTK system. That GM300 is not narrowbandable, so, that's a problem. You also need to be coordinated and get a license. Most public sector RTK operations license several frequencies as they travel around their jurisdictions. That way they set up where they are not interfering with anyone. It would be the licensee's responsibility to monitor before transmitting.



You might be able to gut the GM300 out of it and replace it with an M1225. That might even be a direct plug-and-play replacement, but do get yourself a license.


I'm unfamiliar with the operation of RKT radios but there are wideband licenses available for some data only applications. However, the number of people who will willingly support the GM300 (or even the M1225 now) is becoming a smaller list everyday.


Sent from my iPhone using Tapatalk
 

nd5y

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Most of the license for RTK units have the same common channels (in the US).
461.025
461.05
461.075
461.1
461.125
461.15
462.125
462.375
462.4
464.5
464.55
464.6
464.625
464.65
464.7
464.725
464.75
 

clbsquared

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RTK is a differential correction for using GPS and/or GLONASS. The base station will receive it's location data from several satellites. The receiver on your equipment will receive that same data from the same satellites. Since the base station is a fixed location that never moves, it sends a correction differential via UHF or 800, 900 MHz every second. This increases your accuracy to within 1 inch. If you're moving the "base station" around, then you will need to set it up to do "quick survey" instead of "base station". You will also need to know what correction frequency is being used. RTK is incredibly accurate. I've never had it be off more than an inch in either direction. Whereas SF2 can be off by 3 to 5 feet and SF1 could be off by as much as 10. The following images show my set up and the frequencies used for the RTK base station and the correction frequency.



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clbsquared

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RTK is a differential correction for using GPS and/or GLONASS. The base station will receive it's location data from several satellites. The receiver on your equipment will receive that same data from the same satellites. Since the base station is a fixed location that never moves, it sends a correction differential via UHF or 800, 900 MHz every second. This increases your accuracy to within 1 inch. If you're moving the "base station" around, then you will need to set it up to do "quick survey" instead of "base station". You will also need to know what correction frequency is being used. RTK is incredibly accurate. I've never had it be off more than an inch in either direction. Whereas SF2 can be off by 3 to 5 feet and SF1 could be off by as much as 10. The following images show my set up and the frequencies used for the RTK base station and the correction frequency.



To answer your question, RTK can use UHF, 800 and 900 MHz. You will definitely need a license. And you may be better off finding the RSS and a programming cable for that radio in order to read it to find out how it's set up.

Sent from my HTC One A9 using Tapatalk


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Joined
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3,580
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Texas
RTK is a differential correction for using GPS and/or GLONASS. The base station will receive it's location data from several satellites. The receiver on your equipment will receive that same data from the same satellites. Since the base station is a fixed location that never moves, it sends a correction differential via UHF or 800, 900 MHz every second. This increases your accuracy to within 1 inch. If you're moving the "base station" around, then you will need to set it up to do "quick survey" instead of "base station". You will also need to know what correction frequency is being used. RTK is incredibly accurate. I've never had it be off more than an inch in either direction. Whereas SF2 can be off by 3 to 5 feet and SF1 could be off by as much as 10. The following images show my set up and the frequencies used for the RTK base station and the correction frequency.



Sent from my HTC One A9 using Tapatalk


Okay, I'm with you now. A couple of the local Deere shops have setups on 900 MHz in the region. Your pictures were very helpful.


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902

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I'm unfamiliar with the operation of RKT radios but there are wideband licenses available for some data only applications. However, the number of people who will willingly support the GM300 (or even the M1225 now) is becoming a smaller list everyday.
The data is packetized and sent as bursts, not a continuous stream. It's also not fast enough to qualify for a wideband emission and there are no exemptions in Part 90 for RTK operations, so I'm pretty confident in recommending the replacement of the GM300.
 

petnrdx

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Feb 5, 2004
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Sparks, NV
There were narrowband GM300's.
So check the actual model number just to be sure before you just change it.
They were not all that common, but they are out there.
M44GMC00D1A for example would be narrow.
M44GMC20D1A would be wide.
I am pretty sure in all cases of NB GM300's that seventh digit is a 0 for NB and a 2 for WB.
Worth checking.
 
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