Scanner antenna VHF only vs multiband

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billyfromhill

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I'm going to be installing my BC355N scanner in my vehicle. All but one of the frequencies I will be monitoring are in the 151-162 MHz range. One frequency will be in the 800 MHz range. Would I be better off getting a multiband antenna like the Larsen NMO 150/450/800 or just a VHF whip antenna since I only will be receiving one 800 MHz frequency.
 

N8IAA

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I'm going to be installing my BC355N scanner in my vehicle. All but one of the frequencies I will be monitoring are in the 151-162 MHz range. One frequency will be in the 800 MHz range. Would I be better off getting a multiband antenna like the Larsen NMO 150/450/800 or just a VHF whip antenna since I only will be receiving one 800 MHz frequency.
First, what is the size of the antenna? Is it a quarter wave? Length approximately 18"? Or, is it a 5/8 antenna, approximately 3' in length?
I have the Larsen tri-band antenna and it works maybe a bit better than a Larsen uncut quarter wave on 800MHz.
I'm sure all the antenna purists out there will tell you to have an antenna cut to length to receive. But, the Larsen uncut antenna is resonant at 800MHz.
It's really up to you to make the final decision.
Larry
 

billyfromhill

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The VHF antenna would be 1/4 wave and be around 21". The multiband antenna is around 16.5" long.
 

N8IAA

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Go with the one you think will work. I was using the uncut 1/4 wave mostly for VHF air and VHF hi. 800 was just a lucky by product:)
Larry
 

billyfromhill

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I think I'm going to go with the Larsen NMO 150/450/800. Does anybody know what the bulge is halfway up on the antenna?

 

jackj

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Not sure if it is a coil, a capacitor or a trap. In short, it electrically cuts off the part of the antenna above it on higher frequencies.
 

Halfpint

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I think I'm going to go with the Larsen NMO 150/450/800. Does anybody know what the bulge is halfway up on the antenna?

Well... If it is like the one I had that bulge is a coil that is supposed to be making the upper part resonant at the higher frequencies. I discovered that it was a coil after I managed to break it whilst herding some horses back onto our property. (Apparently I misjudged just how much clearance I had when I chased them through one of the groves of trees along our SW section of fence line. Though, up until then I'd driven through them before and hadn't had any problems. {GRIMACE!}) When we sold that pickup I warned the new owner to be very careful about making clearance calculations. {VB GRIN!}
 

billyfromhill

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Does this antenna also have a spring in the base or is there only the one spring on the whip?
 

mmckenna

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No spring on the base, but you can purchase them separately. You just need to shorten the antenna (from the bottom up) to compensate for the extra length.
Honestly, though, the Larsen antennas I've had with the same base are pretty flexible without the spring. Unless you have frequent meetings with low tree branches and angry parking garages, you might not need it.
 

ronhl

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I've used the Larsen NMO 150/450/800 for yrs with a mag mount and is an excellent choice for the 3 bands specified. There is no spring, its short ab 20" so really no need.
 

billyfromhill

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I was more asking if there was a loading spring/coil in the base in addition to the spring/coil halfway up the antenna. Larsen does rate the antenna up to 100 watts.

I have that exact same spring on my Larsen NMO27C antenna for my CB.

Could I use my NMO27C whip and spring on the NMO150/450/800 base?
 

jhooten

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I use a Motorola 16" SS wire NMO vhf quarter wave for my mobile scanner antenna. It works fine on vhf high, uhf, and 800. vhf low is weak but readable.
 

billyfromhill

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How well does the NMO 150/450/800 work with VHF if it's only 16.5" long? 16" seems rather short for high-VHF
 

mmckenna

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Not really. The coil adds some length. 17.5 inches is right about 160MHz. 16.5 with the center load isn't that much of a stretch for 1/4 wave on VHF.
 

billyfromhill

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I though the coil only helps when transmitting. Does it add length when receiving also?
 

N8IAA

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I though the coil only helps when transmitting. Does it add length when receiving also?
I hope that you don't plan on transmitting on the ham bands with this antenna. It is not tuned there.
The coil is just to make the antenna, as pointed out, "electrically" correct in length.
Just as the spring and coil on the Larsen shorty dual band antenna.
There is no spring on the Tri-band antenna.
Larry
 
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