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Antenna Help Please

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Jan 2, 2011
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Location
Ky
#1
I was given a Motorola PM400 radio and need help with an antenna selection. I am new to radios so be gently. I am using the radio in my home to strictly just listen to local Fire, EMS and Police, basically using it as a scanner. It has all the local Fire, EMS and Police channels already programmed in. I am running it using a A/C to D/C convertor and works great. I have a cheap, half broken antenna on it now and the reception is poor. I was told the Motorola PM400 is a "Trunking Radio" not sure what that means? The channels I listen to are 151.49 to 159.10 . I am looking for a antenna that has a magnet base that I can just sit on the floor inside my home beside the radio. The radio has a antenna connector on the back that is what I think is called a Mini UHF? Can you guys suggest a good antenna with the make and model number so I can order the correct antenna? I really have no clue on what to order and I don't want to order the wrong antenna. Thank you
 
Joined
May 10, 2013
Messages
67
Location
Cass WVa
#2
If you're just using it for listening then a 2m/70cm mag mount antenna would be close enough, with the proper antenna adapter or the correct end to begin with. It would work even better if you could stick it on something metal (but not the radio itself) for a ground plane.
 
Joined
Mar 11, 2003
Messages
1,086
Location
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#3
Its not a trunking radio.Its a conventional 2 way radio..You want a magnet mount with a 1/4 wave whip antenna for VHF and a Magnet mount with a mini uhf.. there are hundreds of sellers out there on the internet that sell them . Best suggestion is to get a sheet of metal like an old cookie sheet to mount it on as a base that will keep it secure and help with reception. Google NMO magnet mount antennna and VHF NMO antenna
 

mmckenna

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#4
At minimum you need this:
http://www.theantennafarm.com/catalog/tram-1233-muhf-3919.html

And this:
http://www.theantennafarm.com/catalog/laird-tech-qw152-720.html (even though it says 152MHz to 162MHz, it will work just fine for receiving on 151MHz)

As was stated above, you need to stick the magnetic mount on something metal to provide a ground plane under the antenna. That could be the cookie sheet, a refrigerator, metal file cabinet, etc. The antenna needs to be vertically oriented for best performance.

Keep in mind that there is no one antenna that will work for every situation. Your exact location in relation to the transmitters, construction of your home, surrounding structures/topology will all dictate how well this works. Depending on your exact situation the above might work fine, or you may need a different set up. The above items will give you an inexpensive place to start. If it works, great, you are done. If not, then come back and someone will help you.
 
Joined
Mar 30, 2005
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So Cali
#5
You have to remember antennas have two parts: The radiator, and the counterpoise. In the case of the mag mount, the counterpoise IS the surface to which the mag mount is placed on.

The counter poise needs to be 1/4 wave, 19 - 20 inches at 150 mhz, in ALL directions.
 
Joined
Aug 30, 2009
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Location
Tunkhannock, PA
#7
I've done this with my Motorola GM300. You will need a mini-uhf to PL259 converter most likely. If you get an antenna, make sure you "tune" it. And by "Tune" I mean cut it too the right length for the frequencies you're going to be monitoring.
 
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Location
Chicago area
#10
I have been installing 2 way radios for 18 years and used only factory NMO antennas other than cutting 5/8 gain. If he is scanning cutting to a frequency will not make really any difference. Like I said lets not make a simple request more complicated
 

SteveC0625

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Northville, NY (Fulton County)
#11
Commercially made NMO whips are cut for a bandwith. If he is just monitoring cutting isnt really a necessity Lets not make it any harder.
Fully agree! Nibbling an eighth or a quarter of an inch off a VHF quarter wave whip will have ZERO affect on reception.

VHF quarter wave antennas come pre-cut for specific band spreads, usually 6 to 8 MHz or so. Fine tuning for reception only is a waste of time and effort.

The KISS principle totally applies here. Buy the right spike, install it correctly and be done with it.
 

mmckenna

Some random guy on the internets.
Joined
Jul 27, 2005
Messages
10,335
Location
Point Nemo.
#12
I've done this with my Motorola GM300. You will need a mini-uhf to PL259 converter most likely. If you get an antenna, make sure you "tune" it. And by "Tune" I mean cut it too the right length for the frequencies you're going to be monitoring.

With all due respect, don't use the adapters. This is the easiest way to break the antenna connector on the back of the radio. The additional leverage put on the connector will snap it off. Replacing the mini-UHF connector on the back of the radio isn't impossible, but for the uninitiated, it isn't recommended. The proper way to do this is to use the proper connector on the end of the coaxial cable. If you -must- use an adapter, you use the ones that are made up of a short length of cable to relieve the stress. The antenna base I linked to has the correct mini-UHF connector on it. No reason to install an adapter if you don't need one and risk damaging the antenna jack.

The antenna I linked to is already cut to the proper length, no need to mess with it. Just install the antenna on the base and thread the mini-UHF onto the radio. No need to make things complicated.
 
Joined
Feb 24, 2001
Messages
65,126
Location
Virginia
#13
Its not a trunking radio.Its a conventional 2 way radio..You want a magnet mount with a 1/4 wave whip antenna for VHF and a Magnet mount with a mini uhf.. there are hundreds of sellers out there on the internet that sell them . Best suggestion is to get a sheet of metal like an old cookie sheet to mount it on as a base that will keep it secure and help with reception. Google NMO magnet mount antennna and VHF NMO antenna
Top of a filing cabinet works great too. Like FFPM says, your mag mount has to be on some metal.
 

spaztic_typer

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Joined
Feb 25, 2011
Messages
47
Location
Acton
#14
I'll just throw my 2 cents worth in too. Go to your local Ham shop and get a mobile magnetic mount with a 5/8 wave commercial whip (vhf) and the adapter, mini uhf to uhf (pl-259). No need to cut it it will work fine. And yes a big metalic surface for the magnetic to stick to (vertically). The bigger the better, a metre in diameter is a good start.The 5/8 might be a bit tall for a frig, so a 1/4 wave will also do. Mounting it outside is better and the higher the better applies also. Have fun!
 
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