Antenna tuning question

[bradsmith]

I've been looking at tuning my radio antenna, but everything I read is how to tune for one frequency. How do you tune for multiple frequencies?

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[Stepside]

Which frequency you will be using most? and will you be tuning that frequency for
1/4 wave, 1/2 wave, or 5/8 wave?
You'll need an antenna tuner, like MFJ 259B or similar to be more accurate.
You will be able to check SWR (standing wave ratio) with an antenna tuner on multiple frequencies.
Compromise antennas generally do not perform as well.
If you are going to be in . . what's commonly called - One Band,
Then, you'll need to tune for the center of the 'band' in order to get reasonable performance thru-out the band.
If you are going to use multiple 'bands', then you should search for a decent muti-band antenna or buy a 'built-in' antenna tuner.
A tuner incorporated inline between the transceiver & antenna is really just a 'flame-arrestor'
to keep your transceiver from burning up and give you "a good SWR reading"
With a Good antenna tuner . . you could probably tune a door knob.

If you provide the frequencies you are looking at . .
then, there are many guys that may - already have - what you are looking for
or can provide you 'info' . . and tell you where to go . . no pun intended . .

 

[Wilson]

Sub

 

[OrangeAddict]

So what if you are mainly worried about these

151.820SNOW1
151.88SNOW2
151.940SNOW3
152.000TRR1
152.750TRR2

frequencies but later may be interested in othe ham bands like 143.000 MHz

 

[bradsmith]

Which frequency you will be using most? and will you be tuning that frequency for
1/4 wave, 1/2 wave, or 5/8 wave?
You'll need an antenna tuner, like MFJ 259B or similar to be more accurate.
You will be able to check SWR (standing wave ratio) with an antenna tuner on multiple frequencies.
Compromise antennas generally do not perform as well.
If you are going to be in . . what's commonly called - One Band,
Then, you'll need to tune for the center of the 'band' in order to get reasonable performance thru-out the band.
If you are going to use multiple 'bands', then you should search for a decent muti-band antenna or buy a 'built-in' antenna tuner.
A tuner incorporated inline between the transceiver & antenna is really just a 'flame-arrestor'
to keep your transceiver from burning up and give you "a good SWR reading"
With a Good antenna tuner . . you could probably tune a door knob.

If you provide the frequencies you are looking at . .
then, there are many guys that may - already have - what you are looking for
or can provide you 'info' . . and tell you where to go . . no pun intended . .

I have a Larsen NMO150C 5/8 wave. I need at least these frequencies ...

151.820SNOW1
151.88SNOW2
151.940SNOW3
152.000TRR1
152.750TRR2

Stole these from OrangeAddict's post above.

and I'm using an IC-F5021

 

[All The Way]

Antennas can be pretty broad banded. Lets look at the VHF ham band. The voice portion is 144.100 to 148.000. That is 3.900 MHz wide. The spread for the frequencies most runs use is only .930 MHz wide. The antennas I run are all tuned for the amateur portion and cover the run frequencies with a little SWR increase.(well within the safe range) If you buy a pre assembled antenna for the ham band... don't mess with it, just run it. If it needs to be cut, tune it for the center of the ham band. This way if you plan on getting your license down the road you wont need to buy a new antenna because you cut it to short to make it work for frequencies used on runs.

---------- Post added at 03:06 AM ---------- Previous post was at 02:51 AM ----------

Also the MFJ 259B is over kill for a job like this.... Its a nice piece but not necessary. Also antenna tuners, more commonly used with HF bands are rarely needed for UHF/VHF antennas.
A meter similar to MFJ-862 CROSS-NDL with do the job. You may even be able to find a shop or somebody in your area who already has the equipment and is willing to help out.

Also when cutting a antenna start long... its kinda hard to add it back on

 

[treypal]

Use the tuning chart that came with the antenna. Pick a number in the middle of those freqs and you will be fine.

 

[beemerman]

Should the antenna be trimmed to the required length. Or should the mount that it is attached to and the antenna be considered in overall length.


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[All The Way]

Charts are biased on the stainless whip length.

 

[jackrook]

Should the antenna be trimmed to the required length. Or should the mount that it is attached to and the antenna be considered in overall length. Sent from my iPhone using Tapatalk

Only cut the antenna. Don't count the mount. I used the chart that came with my Larsen NMO and cut it myself. I've had no complaints and used it on multiple outings both short range and long distance.