Trim down a Wilson SS whip for VHF RX?

[Eskimo_Pie]

I've recently rediscovered how much fun scanner monitoring is/was. I've slowly gotten back into scanning and have bought myself a Pro-43 and the rubber duck is worthless in the car and was thinking I could trim down a spare SS whip I have for my Wilson 500. With the loaded coil in the magnetic base, how would I calculate how much to trim the SS whip down to?

Here's my thinking, and I'm rounding numbers for easier math: The 500 is made for 30mhz, my target frequency is 150mhz, so my thinking is the 150mhz wavelength is 5 times shorter than 30 mhz, therefore, the whip needs to be 5 times shorter. Someone jump in tell me if this will work or not. I'm trying not to buy a dedicated magnetic scanner antenna and use what I have here already. Thanks & 73's
Greg

[drdx]

The coil in the bottom of that wilson is the fly in this potato salad, but the general calculation of a quarter wave antenna on any frequency is 234 divided by the frequency, to get the length in feet, then you can multiply that for your inches. So, for 100 mhz, 234 divided by 100 is 2.34, times the 12, and you'd need about a 28 inch antenna. That's for a straight antenna and like I said the coil comes into play and changes it all.

For listening I'd pass on any trimming at all. With a scanner you're typically listening to repeaters, with high antennas and good local signals so often a cb antenna will end up being fine. On some bands it will work better than others but on 2m ham for example, a cb antenna is about a 5/4 wave antenna and will work, esp. for listening.

-drdx

[721HACKSAW]

I use my Imax for my scanner, it works good.

['Doc]

A listening only antenna doesn't hav to be any particular length to work. There are some benefits to having an antenna 'cut' for a particular band, but they aren't going to be super great differences.
For the particular antenna you have, if you don't mind digging into it, just short the coil at the bottom of it. That will ruin it for it's intended purpose, but so would cutting the whip.
Does your car/truck have an antenna on it? It'd work too. Dang near anything will work for just listening...
- 'Doc

[231]

The coil in the bottom of that wilson is the fly in this potato salad, but the general calculation of a quarter wave antenna on any frequency is 234 divided by the frequency, to get the length in feet, then you can multiply that for your inches. So, for 100 mhz, 234 divided by 100 is 2.34, times the 12, and you'd need about a 28 inch antenna. That's for a straight antenna and like I said the coil comes into play and changes it all.

For listening I'd pass on any trimming at all. With a scanner you're typically listening to repeaters, with high antennas and good local signals so often a cb antenna will end up being fine. On some bands it will work better than others but on 2m ham for example, a cb antenna is about a 5/4 wave antenna and will work, esp. for listening.

-drdx

I agree. It's not really going to gain you anything by trimming it...other than the pleasure of hacking up a perfectly good antenna. On second though....

Good luck!

[Eskimo_Pie]

I'll try with a wire coat hanger cut to the length I'm thinking of and see what that does. Right now I'm using an old glass mount 800 mhz cell antenna and seems to work better than the rubber duck. I bought my Wilson 500 with an already shortened whip and bought a replacement for it that is the proper length for 11 meters. Now that I've gotten some feedback, I may save the ss whip for 10 meters when I get my ticket. Thanks for all the input. Greg