Here's a question on a base antenna

[Bobcat]

This antenna is an old, early 80's Radio Shack 5/8 wave vertical, 3 ground plane radials flat, all aluminum, no coating or anything like that and back then, it did it's job reasonable well. Now it is over 20 years later and I have re-connected it to a radio. The first thing that I saw was that the SWR was over 3:1 so something is wrong somewhere. BTW.... the coax is new ( about 8 months ) Radio Shack Mini-8 stuff. I just unscrewed the old cable, screwed on the new cable, and tried it.

Here is my question.... if one were to take the connector off at the base of the antenna and ohm between the antenna's center pin and the ground on the connector.... would one expect to see a low reading in the "couple of ohms" range or not?

I have no idea what kind of things they did to tune these antennas, there is no kind of adjustable ring that I can see, nothing adjustable at all. Did they use any coils as part of a tuning network?

Bob

 

[Hamin' X]

More than likely, there is a center tapped coil in the base section, below the radials. This was used to shunt load the antenna. If you can find a way to disassemble the coil, you may find that little critters have mad a home in there ans it will be full of all kinds of s**t. Happened to an old CLR II of mine.

Rich

 

[Master Chief]

Actually, this antenna has a small circuit board at the base. You should see a direct short at DC. It wasn't unheard of for these small circuit boards to get smoked.

Remove the main radiator by removing the screw at the end and drill out the 3 rivets that hold the black plastic cap to the base of the antenna (closest to the coax connector).

Check the circuit board for damage from weather or mis-use. If it is bad, you are done.

You can use stainless steel hardware and Permatex "Ultra Black" to re-seal the base.