LMR-400 problem

[dmonty83]

Hi...I have a friend that has 100ft of LMR-400 connected to a discone antenna with a type N connector and to a BCT-15. He cannot receive anything on the antenna. What are the possibilities of the cable being bad or even the antenna? The antenna is brand new. What can I do to test the consistency of the cable?

 

[iMONITOR]

Hi...I have a friend that has 100ft of LMR-400 connected to a discone antenna with a type N connector and to a BCT-15. He cannot receive anything on the antenna. What are the possibilities of the cable being bad or even the antenna? The antenna is brand new. What can I do to test the consistency of the cable?

A discone is not a high gain antenna. LMR-400 is excellent cable, but at 100', even LMR-400 will have some loss. You didn't say what band, or frequencies he's trying to receive? If it's in the 800MHz area, the discone is not your best choice. Could also be that someone didn't attach the cable connectors properly, etc, etc, etc. More info needed.

 

[dmonty83]

...

From what I have been told he cannot hear any comms on any band. I am leaning more on the fact that there might be something wrong with the cable, and not the antenna. The cable was purchased locally and the receipt indicates 'Test'.

He is running RG-56 from a Scantenna that is just laying on his roof and he can atleast hear what is going on in his community. The limited loss of LMR-400 and the fact that the discone isn't a high gain shouldn't deny him the capability of listening to services in his town...

 

[W4KRR]

From what I have been told he cannot hear any comms on any band. I am leaning more on the fact that there might be something wrong with the cable, and not the antenna. The cable was purchased locally and the receipt indicates 'Test'.

He is running RG-56 from a Scantenna that is just laying on his roof and he can atleast hear what is going on in his community. The limited loss of LMR-400 and the fact that the discone isn't a high gain shouldn't deny him the capability of listening to services in his town...

Attach the cable that is currently feeding the Scantenna to the discone. If things improve you know the problem is with the LMR-400 cable, or the connectors attached the cable. If nothing improves, it might be the antenna. If things improve with the other cable, then try removing the connectors from the LMR-400 and replacing them with new ones.

 

[iMONITOR]

From what I have been told he cannot hear any comms on any band. I am leaning more on the fact that there might be something wrong with the cable, and not the antenna. The cable was purchased locally and the receipt indicates 'Test'.

He is running RG-56 from a Scantenna that is just laying on his roof and he can atleast hear what is going on in his community. The limited loss of LMR-400 and the fact that the discone isn't a high gain shouldn't deny him the capability of listening to services in his town...

Can he hear anything with any other antenna? How far is he from what he's trying to monitor? Also check the BNC connector on the back of the scanner. Sometimes they get worn, and loose.

 

[dmonty83]

...

The scantenna is connected and he says that he can hear everything in town. That cable is only RG-56, so it is not an ideal run for 100ft. The local FD is only 3 miles from his antenna.

 

[DPD1]

It's almost always something simple... Sounds like a connector is attached poorly. There might be a piece of braid that's shorting or something. I would take those apart and see what's up. Not all connectors are perfectly matched... Sometimes two brands will have pins that don't mate right, or they were put on too short. Make sure the receiver pin on the female isn't spread apart from somebody trying to shove a UHF on it.

Dave
http://www.dpdproductions.com
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