antenna tuning

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mattchew1296

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Not sure if this is the right category. I am getting an icom 2300h vhf radio and a larsen nmo150 antenna. What I am wanting to know is about the antenna tuning. I know that I can only get TX 144-148mhz and RX 136-172 mhz. I would like to be able to listen to any frequency between 136-172. What should I be tuning my antenna to?

Thanks
 

SCPD

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Tune your antenna for the middle of the 2 meter band. Transmitting is more critical than receiving when tuning. Your antenna, and radio, probably won't notice a difference on receive but will definitely know the difference when transmitting.
 

prcguy

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I can tell you from experience that a 5/8 wave Larsen tuned to 2m is around 10dB down on 162MHz weather frequencies compared to the same antenna tuned to weather. The Larsen 5/8 is good for a few MHz either side of your center freq, then it starts to degrade.

A 1/4 wave VHF whip seems to have a lot more band width and will give you more consistent results across 136 to 172MHz but it too will drop some performance at the edges. There are wide band VHF antennas in both 1/4 wave and `1/2 wave made by Larsen and other that will work better across your needed wide range.
prcguy


Tune your antenna for the middle of the 2 meter band. Transmitting is more critical than receiving when tuning. Your antenna, and radio, probably won't notice a difference on receive but will definitely know the difference when transmitting.
 

mattchew1296

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Thanks for your info, I already have it and it is installed. What I would like to know is what to tune the antenna to?

Also should I pay 25 to get it tuned and cut or just follow the cutting guide.
 

N8IAA

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Thanks for your info, I already have it and it is installed. What I would like to know is what to tune the antenna to?

Also should I pay 25 to get it tuned and cut or just follow the cutting guide.
Since you will be operating in the 2m band, cut the antenna to transmit in the middle-146MHz.
Follow the cutting guide. It is better to cut small amounts off, 1/8", at a time. Follow the directions!! Checking the SWR after each cut. You can always cut shorter, but can't add back on:)
Larry
 

SCPD

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My advice is to either get an SWR meter, of have some ham tune it for you. Just going off the cutting chart may not give you a good match. And like others have said, tune it to the middle of the two meter band.
 

mattchew1296

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There is a guy by my house that will do it for $25 but he won't be back till mid October. I don't have any other access to a meter and the instructions and the company I bought the stuff from said to just cut it.

At this point, I think I am just going to do that, and can bu a new whip from him for $8 for future tuning needs.
 

mm

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http://www.repeater-builder.com/antenna/pdf/larsencuttingcharts.pdf

Save your money and buy a file, use the above PDF and find your exact model and cut it yourself.

Use the file to score around the circumference of the whip and cut to your desired frequency then use the file to clean the sharp edges around the scored/cut area of the whip.

I have used similar cutting charts to this one for 25 plus years and found them to be spot on.
 

mattchew1296

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Same stuff my antenna came with. Thanks though. I have been told to cut to 146 and that is 48" without spring (which I don't have) and the antenna is currently at 48".
 
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