Car Ant

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PM08203

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Nov 26, 2004
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Somers Point NJ
I have a 396, live in NJ and for years drove my Explorer with a RS mag mount. With price of gas I switched to a Focus (Explorer now sits in driveway) and I want to put a RS mag on the Focus but the 3 feet stick will look a little out of place. I want to tune a new mag mount ant for my needs. My listening is some 150 VHF, some 400 UHF, some 500 MOT trunked, some 800 MOT trunked and HEAVY on the 800 E trunked. Any suggestions on length?
 

jon_k

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May 7, 2008
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271
Location
Fort Worth, Republic of Texas
With most of your listening appearing on 800mhz then you want to probably make this frequency the primary frequency. It will also result in the shortest antenna. Tuned for 800mhz your reception on 150VHF will only work well if you're inside a strong signal. Forget tuning on 150 for distant stations. If you're close to the transmitter you should be fine though.

Here is how to cut your antenna for 800mhz broke down at wavelength.

1/4Wavelength: Cut down to 3 - 17/32in.
1/2Wavelength: Cut down to 0ft. 7 - 1/32in.
7/8 Wavelength: Cut down to 1ft. 0 - 5/16in.
Full Wavelength: Cut down to 1ft. 2 - 1/16in.

Full wavelength will obviously return best results.

OR tune it to 400mhz which would be an in-the-middle compromise for the full length you want to cover.
1/4 Wave: . 7 - 1/32in.
1/2 WAVE: 1ft. 2 - 1/16in.
7/8 WAVE: 2ft. 0 - 19/32in.
Full WAVE: 2ft. 4 - 3/32in.

If you want the fractions converted to decimal points, I can do that as well. If the whip is removable from the magmount using an allen wrench, I think your measurements start from the very end of that whip. If someone could chime in where the length of antenna truly begins on a magmount.

I'm far from a mathematician but this site has a javascript calculator.
I have a 396, live in NJ and for years drove my Explorer with a RS mag mount. With price of gas I switched to a Focus (Explorer now sits in driveway) and I want to put a RS mag on the Focus but the 3 feet stick will look a little out of place. I want to tune a new mag mount ant for my needs. My listening is some 150 VHF, some 400 UHF, some 500 MOT trunked, some 800 MOT trunked and HEAVY on the 800 E trunked. Any suggestions on length?
 
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N1BHH

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Mar 31, 2007
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1,845
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Jackson Square, East Weymouth, MA.
A good all round antenna to use for scanning from High Band on up is a simple quarter wave on VHF. It will look like 3/4 wave at UHF. I have one which I am presently using on my PRO-2055 at home on top of my air conditioner. It works quite well, and tonight some enhancement is happening and I'm hearing quite a bit more than normal. I didn't think I would hear the Boston citywide trunk as well as I am, since it has a small footprint, but it works, and it works on my van quite well, too.

I normally run with a Larsen NMO-150/450/800 at home and on the road, but I'm doing some experimenting right now at home.
 

stevolene

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Joined
May 5, 2006
Messages
173
Location
chattanooga metro
I have a 396, live in NJ and for years drove my Explorer with a RS mag mount. With price of gas I switched to a Focus (Explorer now sits in driveway) and I want to put a RS mag on the Focus but the 3 feet stick will look a little out of place. I want to tune a new mag mount ant for my needs. My listening is some 150 VHF, some 400 UHF, some 500 MOT trunked, some 800 MOT trunked and HEAVY on the 800 E trunked. Any suggestions on length?
may wanna just try this little antenna, that RS antenna could be used as a base antenna before you chop it up.

http://www.universal-radio.com/catalog/scanants/1190.html
 

prcguy

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Joined
Jun 30, 2006
Messages
10,032
Location
So Cal - Richardson, TX - Tewksbury, MA
A full wavelength will return the worst results and give you a null at the horizon and the 1/2 wave and full wave will not match to 50 ohm coax at all. The actual lengths will probably come out shorter when checked with an antenna analyzer.
prcguy
With most of your listening appearing on 800mhz then you want to probably make this frequency the primary frequency. It will also result in the shortest antenna. Tuned for 800mhz your reception on 150VHF will only work well if you're inside a strong signal. Forget tuning on 150 for distant stations. If you're close to the transmitter you should be fine though.

Here is how to cut your antenna for 800mhz broke down at wavelength.

1/4Wavelength: Cut down to 3 - 17/32in.
1/2Wavelength: Cut down to 0ft. 7 - 1/32in.
7/8 Wavelength: Cut down to 1ft. 0 - 5/16in.
Full Wavelength: Cut down to 1ft. 2 - 1/16in.

Full wavelength will obviously return best results.

OR tune it to 400mhz which would be an in-the-middle compromise for the full length you want to cover.
1/4 Wave: . 7 - 1/32in.
1/2 WAVE: 1ft. 2 - 1/16in.
7/8 WAVE: 2ft. 0 - 19/32in.
Full WAVE: 2ft. 4 - 3/32in.

If you want the fractions converted to decimal points, I can do that as well. If the whip is removable from the magmount using an allen wrench, I think your measurements start from the very end of that whip. If someone could chime in where the length of antenna truly begins on a magmount.

I'm far from a mathematician but this site has a javascript calculator.

 

bee

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Premium Subscriber
Joined
Jan 5, 2003
Messages
1,056
Location
Belmont, Ms.
I have three of the "pmm3b" antennas from "Universal"(gonna order another one). I consider them to be really good all around antennas, they are all I have on my vehicals. They are only 13 inches tall, low profile, and will not "blow off"!
 

hntsgt

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Joined
Aug 2, 2006
Messages
184
Location
Pawleys Island, SC
I have three of the "pmm3b" antennas from "Universal"(gonna order another one). I consider them to be really good all around antennas, they are all I have on my vehicals. They are only 13 inches tall, low profile, and will not "blow off"!
Beware the the PMM3B's are on back order. I have been waiting almost three weeks for mine.
 

rankin39

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Sep 12, 2004
Messages
367
Location
Western Leavenworth Co., KS
I normally run with a Larsen NMO-150/450/800 at home and on the road, but I'm doing some experimenting right now at home.
I use one of these and have compared it to several other antennas. The 150/450/800 is hard to beat.

One other possibility is to get an 800 MHz. "cellular" antenna that is a half-wave feeding a 5/8 wave with a coil in the middle. (There should be a lot of these surplus since modern cellular has mostly moved to 1.9 GHz.) This will give about 3.5 db gain on 800 and be very close to a quarterwave on 150. They work fairly well on 450.

Bob, WoNXN
 

andrewccm

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Joined
Mar 25, 2008
Messages
286
Location
Dallas/Fort Worth
Beware the the PMM3B's are on back order. I have been waiting almost three weeks for mine.
Yeah.. I know what you mean. I ordered a few items to make an adapter to my Eton E1. All came in but one small adapter. Said on backorder and would ship around the 12th.. OF JUNE.

Month later.. NADA.

I have been fairly unimpressed with UR.
 

hntsgt

Member
Joined
Aug 2, 2006
Messages
184
Location
Pawleys Island, SC
Are there any other dealers that sell the Valor PMM3B? If I like this one I may purchase another one but don't want to wait that long.
 

w8hey

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Joined
Aug 20, 2007
Messages
0
Location
Tipp City, Ohio
Even when I bought it I was told it was backordered (last year). I think it took about a week longer than the other items I ordered from Universal Radio.
 

Rochound2003

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Joined
Jan 8, 2003
Messages
9
Location
Rochester NY
I spent a year in Jersey in the Hudson/Bergen county area and found that the surplus RadioShack mag mount cellular antenna did best. The state 800 was the weakest reception. VHF and UHF were fine I could get them at good distance. I would get NYC SOD all the way to the Delaware Gap on Rt.80 when I would drive home. MY wife (girlfriend @ time) lived in Jersey City right above Hoboken and with the RS800 on my Pro93 and my B780XLT in her apartment, I would get police and fire from East Orange to Hackensack to all of NYC. I also had a RH77 but didnt find that it helped at all, would overload on pagers where the 800mhz antennas would just let the good stuff through. Even now I still use the RS mag mount Cell on my car even though I live where mostly rural UHF and VHF. It does good enough, From Just north of Batavia NY on a good day I can get most everything between Buffalo and Rochester all the way west to Hamilton Ontario. This includes RR freqs as well. If I leave the antenna inside the back window(more stealth) I get about 2/3 the distance. Petty good for a $3.00 antenna (clearance).

I vote for just a good old cell antenna, not too tall and nobody pays attention to them. I don't know if they would be best towards the sothern end of the state since I only got down there a couple of times.
 
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