I am going to install a antenna on my truck. I want to use it for 2 meters mostly. 144-148 but also like to monitor other frequencies higher up the band. I have 2 different coils here that I could use but I do not know which one is the best. The NMO-150 I know is pretty standard a lot of folks run those. However what is the Wide band VHF all about? Does anyone have any experience with these or what their intended purpose was?
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What is the difference between larsen NMO-150 and larsen wideband VHF coil
- Thread starter pyro424
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mmckenna
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The NMO-150 is the 5/8th's wave coil. It'll give you about 3dB of gain compared to a quarter wave antenna.
That extra gain effectively doubles your transmit power, it does this by narrowing the radiation pattern by focusing more of the RF energy out at the horizon.
This can be helpful in most cases. Drawbacks would be that they tend to have a narrower useable bandwidth when it comes to transmitting.
It would be fine to use for transmitting on the 2 meter amateur bands. You'll need to trim the whip using the included cutting chart for lowest SWR.
Good overall antenna if you don't mind the extra length and the slightly narrow bandwidth.
For receiving it'll work just fine. The narrower TX bandwidth won't impact the reception. Shouldn't have any issue covering the 144-174 VHF band, as well as down to the VHF Air band if your radio covers that.
The "wide band" coil really depends on the exact model number. Larsen sells a number of "WB" coils that cover the VHF band. Some are for half wave antennas, some are for quarter wave antennas.
If it says: NMOWB150, then it's the half wave antenna coil.
If it says: NMOWBQ, then it's the quarter wave antenna coil.
You'll also need the appropriate whip for those, either the quarter wave (20 inches when new) or the half wave (51.75 inches when new).
Half wave antennas have a benefit of not requiring a ground plane underneath them to work. I use a half wave antenna on a UTV roll cage and it works well. Difficult to get a proper ground plane in an installation like that. Works well. They do work better if yo supply a ground plane under a half wave antenna.
They are pretty broad banded, and would be tunable to cover almost the entire VHF 135-174MHz band with acceptable SWR.
Quarter waves are 0 gain, but have really wide bandwidth. They're also about 18 inches long (roughly) on the 2 meter amateur radio band. Nice fat radiation patter that works well out in the hills. Quarter wave antennas are really wide banded. I use them on my own vehicles and on all installations at work. I have the quarter wave mounted on the center of the cab of an F-150 pickup and it works very well. I've hooked it up to a spectrum analyzer with a tracking generator to do a return loss sweep, and it's got 2.5:1 SWR across the VHF band, from 140 to 174.
The wide band antennas are great for public safety users where you might need to transmit on 151MHz and all the way up in the 170MHz range.
Either coil would work for you, if you have the correct whip for it.
That extra gain effectively doubles your transmit power, it does this by narrowing the radiation pattern by focusing more of the RF energy out at the horizon.
This can be helpful in most cases. Drawbacks would be that they tend to have a narrower useable bandwidth when it comes to transmitting.
It would be fine to use for transmitting on the 2 meter amateur bands. You'll need to trim the whip using the included cutting chart for lowest SWR.
Good overall antenna if you don't mind the extra length and the slightly narrow bandwidth.
For receiving it'll work just fine. The narrower TX bandwidth won't impact the reception. Shouldn't have any issue covering the 144-174 VHF band, as well as down to the VHF Air band if your radio covers that.
The "wide band" coil really depends on the exact model number. Larsen sells a number of "WB" coils that cover the VHF band. Some are for half wave antennas, some are for quarter wave antennas.
If it says: NMOWB150, then it's the half wave antenna coil.
If it says: NMOWBQ, then it's the quarter wave antenna coil.
You'll also need the appropriate whip for those, either the quarter wave (20 inches when new) or the half wave (51.75 inches when new).
Half wave antennas have a benefit of not requiring a ground plane underneath them to work. I use a half wave antenna on a UTV roll cage and it works well. Difficult to get a proper ground plane in an installation like that. Works well. They do work better if yo supply a ground plane under a half wave antenna.
They are pretty broad banded, and would be tunable to cover almost the entire VHF 135-174MHz band with acceptable SWR.
Quarter waves are 0 gain, but have really wide bandwidth. They're also about 18 inches long (roughly) on the 2 meter amateur radio band. Nice fat radiation patter that works well out in the hills. Quarter wave antennas are really wide banded. I use them on my own vehicles and on all installations at work. I have the quarter wave mounted on the center of the cab of an F-150 pickup and it works very well. I've hooked it up to a spectrum analyzer with a tracking generator to do a return loss sweep, and it's got 2.5:1 SWR across the VHF band, from 140 to 174.
The wide band antennas are great for public safety users where you might need to transmit on 151MHz and all the way up in the 170MHz range.
Either coil would work for you, if you have the correct whip for it.
kayn1n32008
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The WB VHF marked coil is a 1/2wave coil. I have 2 of them on my work truck. They really do work well for wide band transmit situations. Myself, I work in the Alberta oilpatch, I can be on a radio controlled road using a 150.xxxMHz frequency, turn off onto another radio controlled road and end up using a 17x.xxxMHz frequency. All our companies radios use Larsen, Sinclab or Maxrad antennas. I chose Larsen antennas to match my Larsen NMO 2/70 ham dual band antenna.
mmckenna
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To center it at 146MHz:
Without spring = 48 inches.
With spring = 45 1/4 inches.
http://www.repeater-builder.com/antenna/pdf/larsencuttingcharts.pdf
That should get you close, but since each install is different (different ground plane, different surroundings, etc.) you should follow up with an SWR meter.
To add, always cut it a little long and them trim for lowest reflected power. It's a little difficult to add back to the rod once it's been snipped!
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