Need short mobile scanner antenna with good low band performance

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bernie530

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My title pretty much says it all. I have to magnet mount an "all band" antenna to my roof. My criteria are:
-Low band (46 MHZ area) prime concern
-High band (145 MHZ area) secondary concern
-Other frequencies will be listened to as well, but not as critical
-Fairly short (ideally under 20 inches)
-Magnet mount (or NMO / Thread that I an get a magnet mount base for)
-Ideally one I can unscrew from the magnet mount base for parking garages when needed
-Good quality / long lasting / won't corrode (live in north east, winter is hard on equipment)

Suggestions?
 

Rt169Radio

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Well the only short NMO antenna that I can think of would be the Larsen tri-band antenna with the coverage of 150/450/800 MHz.The antenna is 17 inches tall and is built quite sturdy.
 

ka3jjz

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A better choice would be the Austin Spectra. Expensive but well worth it. You can cut the top whip with a hacksaw to improve the low-band performance (there's a chart in the wiki for this).

I have it on a heavy duty NMO trunk mount and it works very well. I can hear Baltimore county's 46 mhz fire dispatch on the DC beltway - a distance of about 30 miles. Pretty darn good for a 2 foot whip with coils. It's scratchy, to be sure, but perfectly audible. Just make sure your mount is well grounded - the antenna needs it. A quick check with a cheap VOM will do the job.

HTH...Mike
 

bernie530

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Well the only short NMO antenna that I can think of would be the Larsen tri-band antenna with the coverage of 150/450/800 MHz.The antenna is 17 inches tall and is built quite sturdy.
That is the antenna I was looking at. My concern is there are no low bands (46 MHZ area) listed for this. Does anybody have any experience with the Larson tri-band and those frequencies?

I do need some even lower frequencies (in the 34 MHZ area) but I have a two way Motorola Radius for most of those that I need.
 

N5TWB

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For $24 plus shipping, you could get a Hustler VHF 1/4-wave (~19") that will meet your needs very well. I have one that receives lowband (44MHZ) very well and will also do VHF-hi and UHF.

Link: AES Price list
 

prcguy

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Several people responding are not reading that the OP needs VHF low band and the Austin Spectra is the only antenna currently made that will suit your needs.

The low band performance is somewhat compromised but about as good as it gets for something that size. It comes from the factory tuned to about 33MHz and you need to trim it for higher freqs or the efficiency will fall into the toilet.

I have several Larsen tri-band antennas and they do not cover VHF lo band.
prcguy
 

N5TWB

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Several people responding are not reading that the OP needs VHF low band and the Austin Spectra is the only antenna currently made that will suit your needs.
Then we're all equal since you didn't read his ideal length of 20" or less. Anything is going to be a compromise, given the electrical realities of how frequency and length interact. My suggestion was something that met his ideal length requirement that I knew was capable of performing because I had experienced it personally.
 

prcguy

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I missed the part about 20" or less, sorry.

OK, I'm really not sorry, so getting back to his VHF lo band needs a Larsen tri-band or a 19" whip is going to be a good 20-30dB down in reception compared to an Austin Spectra within its lo band sweet spot.

I did a series of measurements with the Austin Spectra and other antennas across the 27-512MHz range and have seen how bad VHF lo band reception can be without an antenna that's tuned for that band.
prcguy

Then we're all equal since you didn't read his ideal length of 20" or less. Anything is going to be a compromise, given the electrical realities of how frequency and length interact. My suggestion was something that met his ideal length requirement that I knew was capable of performing because I had experienced it personally.
 

gewecke

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My title pretty much says it all. I have to magnet mount an "all band" antenna to my roof. My criteria are:
-Low band (46 MHZ area) prime concern
-High band (145 MHZ area) secondary concern
-Other frequencies will be listened to as well, but not as critical
-Fairly short (ideally under 20 inches)
-Magnet mount (or NMO / Thread that I an get a magnet mount base for)
-Ideally one I can unscrew from the magnet mount base for parking garages when needed
-Good quality / long lasting / won't corrode (live in north east, winter is hard on equipment)

Suggestions?
Bernie, please keep in mind that almost no magnetic antenna under 20" tall is going to give you satisfactory performance on the vhf low band simply because it's not going to be resonant at that length. Vhf hi band is doable however. Some may give you suggestions, but generally speaking, you'll need a longer antenna for the vhf low band.
The lower in frequency,the longer the antenna needs to be. The vice versa is true for UHF; a short 6" for a quarter wave.


73,
n9zas
 

bernie530

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Mar 27, 2012
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Ellicottville, NY
Mon 52?

There is an Antenna Specialist Mon 52 for sale on eBay. I am wondering if anyone has the original directions for that antenna? Specifically, do I cut it down to perform best at the 46 MHZ range. If so, how much? I am looking for overall height when cut down to the 46 MHZ range. Thanks.
 
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