The Collector wrote: ↑11 Jan 2019, 17:46
Are you saying that a copper whip would be shorter than an stainless whip needs to be to get the same swr? Never heard of that before...although I reckon copper's a better conductor.
It's true! Page 22 of Lou Franklin's Screwdriver Expert's Guide:
(Discussing 102" whips)
. . . have you ever noticed that fiberglass whips are shorter than steel whips? They're 96", to be exact. Reason: The fiberglass whip is essentially a copper wire embedded in fiberglass; in other words, a "copper whip." Your CB radio is generating radio waves at the rate of 27 million times per second. But even at this incredible speed, it still takes a definite amount of time for the radio wave to travel from one end of the whip to the other end. Since copper is a much better conductor of electricity than steel, the same wave shoots through the copper much faster. So in other words, the fiberglass-copper whip doesn't have to be as long for ¼ wave of the CB signal to "fit" on the whip. Technically, this is called "propagation delay." But both types perform equally well.
Lou Franklin = childhood hero!
The Collector wrote:
If I make a copper Sigma 4, would it be much shorter than the aluminium version then???
The idea that you're going to make a copper Sigma 4 the size of your Antron is pushing it a bit!
The Collector wrote:
I've got a 5ft stainless whip to use, so I'll chop off just an inch at a time from that until it swr's decently. Or I could just use Dave's measurement and add an inch to be safe if he reckons it doesn't swr in very well.
An inch at a time is a lot to chop off! I'd be chopping off a quarter of an inch at a time. How about taking SWR readings over six blocks of 40 as you prune, to get more of an idea of how much the SWR is changing with each pollarding event?
We're all trying to save you from that "oh crumbs!" moment, when you realise you've chopped too much off!
