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Commercial Radio Antennas - Please keep discussion related to professional, commercially used antennas and antenna systems for the two-way radio industry. Topics for the use of these antennas on amateur bands are accepted here.

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  #1 (permalink)  
Old 12-04-2011, 10:44 PM
Join Date: Oct 2005
Location: Northern Kentucky
Posts: 97
Default Mobile Antenna for a Portable Radio?

Question for the experts here. I am trying to mostly listen, minimal Tx, on a portable radio (Motorola HT1250) to a VHF analog ( system that's about 25 miles from me while mobile in my vehicle. I can pick up some transmissions while out of my vehicle on the portable, nada once I get in the truck, obviously until I get closer. I was recently told to just put up a NMO quarter wave on the roof and adapt it down to the portable and that should be an easy and inexpensive fix.

I know this has been done in the past. Do you guys think this would be sufficient and worth it? Also, is there anything to worry about with the portable upon Tx? Or should I just bite it and purchase/install a mobile.

Thanks in advance.
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  #2 (permalink)  
Old 12-05-2011, 7:41 AM
Join Date: Dec 2006
Location: Oklahoma
Posts: 2,145

An antenna inside a vehicle is never going to work as well as the same antenna outside of that vehicle, that's easy to understand, right? So, using a mobile antenna while in that mobile is a pretty good idea. It does mean that you have to make a connection between radio and mobile antenna, don't forget that part of it, and sometimes that's not very convenient.
If you have the choice, and can afford it, a typical 5/8 wave antenna will give you more range than a typical 1/4 wave antenna. I'd recommend that if possible.
I'm not a big fan of mag-mount antennas, but they do work and are a possible option for you.
Good luck.
- 'Doc
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Old 12-05-2011, 9:24 AM
  Amateur Radio Operator
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Join Date: Oct 2011
Location: Fayetteville NC
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Another thing to consider is that where you're getting no signal inside the truck, the increase that an external antenna will give you probably won't be enough for you to be able to transmit back to the base. (That's why Motorola made "docking stations" with amplifiers in them.)
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Old 03-31-2012, 2:59 PM
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Join Date: Aug 2005
Location: Mifflintown, PA
Posts: 420

I have done what you are asking. I used an NMO mount into my vehicle's roof with the proper antenna attached to the mount (mine was a dual-band VHF/UHF Ham antenna connected to my dual-band ham portable with BNC antenna connector) but I also have an HT1250 UHF that was connected to another NMO UHF mount external antenna on my vehicle and it worked perfect!

The part you'll need for your HT1250 will be this little piece here: ( 2X BNC Antenna adapter for Motorola GP300 HT1250 EX600 | eBay ) and then an RG58 run of coax with BNC connector terminated on the end (whether you do the mag mount or through-the-roof method is up to you)
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Old 04-01-2012, 2:27 AM
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Join Date: Jul 2005
Location: WTVLCA01DS0
Posts: 8,547

Yep, this will certainly work.

Flexible antennas on a portable radio are a weak solution at best. On an 800MHz or similar radio, they work pretty well because the ground plane presented by the radio is sufficient. As you drop down to UHF, it's still pretty good. Getting down to VHF, and the size of the radio makes it difficult to provide a proper ground plane under the antenna. Low band, forget about it. Low band HT's work, but not always well.

Getting a "real" antenna outside the vehicle will eliminate the weakness inherent in the flexible antenna, and it will also fix the big issue you are having. The truck cab is acting as a faraday cage, all the metal around you , metallic tinted windows, etc block the signal. A good external antenna will greatly improve your reception, and it will help your transmitted signal, even without an amp.

I've done this with VHF and UHF radios, and it works very well.

The big issue is the hassle of constantly connecting and disconnecting your radio, and potential damage to the connector. Most adapters that fit the top of the radios are intended for in shop testing, not long term every day use. You will risk flexing the antenna mount and causing issues with the connection between the mount and the circuit board. It's not uncommon for the solder joint to fail at this point on some radios. Also, RF connectors are usually rated for a certain number of mating cycles. After a while, they just wear out. Depending on the type and quality of the connector, this could range from a few hundred to a few thousand cycles before you'd likely see enough wear to cause problems.

Unfortunately Motorola doesn't make a vehicle adapter for the Waris (HT-1250 etc) line of radios that I'm aware of. They do for the Jedi and XTS line. They make switching back and forth as easy as sticking the radio in a docking station and locking the lever to hold the radio in. Nice solution, but not going to work with your current radio.

Likely it might be cheaper and easier to just get the proper mobile radio. A decent mobile VHF radio can be found used for anywhere from $100 on up. You can get new Icom VHF mobiles in the mid $200 range. I think if you are going to need a long term solution, getting a mobile radio is going to save you a lot of headache later.

You didn
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Old 04-16-2012, 9:44 PM
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Join Date: Sep 2007
Location: Albany, NY
Posts: 389

Just get a mobile. IMO
GE Orion, 2 HT1250s, BCD396T, BCD436HP
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