K40 used as a scanner antenna

[ve3zo]

Has anyone used a K40 CB antenna for a scanner? A friend of mine has one laying around and thought maybe he could use it......The whip would be cut of course.

Any suggestions?

Chris
VE3CTP

 

[rcvmo]

Becuase of the coil at the bottom, it's probably going to be best tuned for the low-bands, 25-50 MHz. Anything above that will have degraded performance.
RCVMO

 

[bwhite]

I use an old RS cb antenna, works well for VHF-Lo, not too bad for VHF-Hi or 800. Certainly better than the duckie (even the high-priced ducks). You may need an adapter to plug into your scanner, about $5 from RS. The price is right, try it before spending real money.

 

[RevGary]

Just did some quick math using the coil turns to diameter ratio of the K 40 - Since the K40 has a set screw which holds the whip in place, loosen the set screw and remove the original CB whip. Pick up a USED 800 MHZ curly center coil 16 inch whip and install that in the K 40 whip adaptor and secure the set screw. Taking the K 40 loading coil into consideration, this will give you very close to 1/4 wave multiple on low band, 5/8 wave multiple on VHF high band, 1/2 wave multiple on UHF and a full wave multiple on 800.

For the price of an 800 curly center whip, you might be surprised at the operation of this configuration. Just using the K40 as-is is better than nothing, but you can tweak it a bit for better performance by replacing the original whip and relying on the loading coil to extend the operation of the replacement 800 whip.

 

[bwhite]

We're assuming he's trying for 800.....perhaps not.
At least now he has options and info no matter what direction he's going in.