Topband: Broadbanding An Antenna and Impedance Matching

[Jim Brown]

On Sat,12/5/2015 2:43 PM, Mark Lunday wrote:
>   I have learned from the wise
> old-timers on this message board that a vertical antenna with broad-banded
> behavior is a lossy antenna.  Same with a vertical antenna that shows 1:1
> match.

Horse-pucky on both counts. I've been reading this message board for ten 
years, and most guys here are a LOT smarter than that.

There are several ways to broadband an antenna. One is to increase the 
conductor diameter. A vertical made from Rohn 25 will have greater SWR 
bandwidth than one made from a single #14 copper wire (or even a single 
#10 wire). It is well known that the SWR bandwidth of a wire vertical 
can increased by building it from two widely spaced conductors that are 
tied together top and bottom. Both ways of doing it will yield an 
antenna that is physically shorter to achieve resonance.

Likewise, there are multiple ways to achieve a 1:1 match. Yes, a 
vertical with a poor radial or counterpoise will show a match closer to 
1:1 because of ground losses. BUT -- a vertical with a very good radial 
or counterpoise system, which has a feedpoint Z near 30 ohms, can be 
matched to 50 ohms in several ways that do not increase loss. One is 
with an autoformer. Another is with a simple matching network. Another 
is to tune the antenna long by adding top-loading, which increases the 
feedpoint Z to 50 + jX ohms, then add series C at the feedpoint to tune 
out jX. ALL of these methods yield 1:1 SWR with high efficiency.

73, Jim K9YC