Adjustable Gamma match for mobile antennas

That's the reason for all the questions. Surely, my first impression was of that of an impedance matching" coil. Ordinarily matching 11 Meter antennas don't require much. Generally the higher you go, the higher the natural *feedpoint* impedance will be. Gamma match is usually associated with beams, quads, and the like. If a coil like shown here matches at 75 & 40 Meters, it will usually match anywhere, 80-10. I actually LIKE the type of impedance coil shown in the photo because it is simple, effective, and inexpensive, AND can be hidden away at the back of a ball mount like the photo for a neat install. They are pretty flexible and forgiving. I DO wonder why a coil is needed at the feedpoint of an 11 Meter antenna. Gotta be something else out of whack if his impedance is off!

 

X=0 and R=50 rarely occur simultaneously if ever in every mobile application I've seen

 

But again that's not a gamma match. Without looking at it up close and personal it could be a simple coil link (open air) circuit, but it isn't a gamma match.

What it looks like is a simple balun which will if done right give a close match impedence, minding the fact that it is at the end of the feed line and many antennas don't come close to 50 ohms just sitting there. Much of the impedence matching seems to be happening in the feed line, not the antenna itself.

For it to be a gamma match circuit, it has to induce capacitance into the circuit, which in the case of beams, is done with two tubes (metal) with one inside of the other.

 

True, but not so much an issue up at 10-11M. That's the beauty of that little coil in th pic. It is forgiving, works across most ALL bands. As an aside, I got curious and removed my screwdriver as it needed some service anyway. I installed a 102" whip. Now I didn't get down to the real nitty gritty of it, and I didn't put the analyzer on it, but the whip works best (predictably) at 11M, "fair" on 10, ah....................sorta "OK" on 10 (with higher than normal SWR, but acceptable for general work), and still FLAT on 12M. I removed the shunt clip from the coil and checked it again. Makes little difference either way....predictably, in my book. It just tells me that *usually*, worrying with Reactance and Impedance isn't worth the trouble...............mostly. Its also why most CBers have never heard of "impedance matching, and coils & the like! Not always. Just gotta take into account what's causing any troubles, etc.

If I added an extension, I could go down to about 17M! IMHO, so long as the impedance and reactance is within the ball park, I don't worry about having everything purrrr-fect. I have watched people worry themselves sick trying to get their SWR down nothing which FLASH! A few points of SWR won't make a hill of beans to a signal.

Now I've been messin' with the whip a bit, I'll prob'ly fool with it some and see how low I can go. A 20 Meter whip would be a sight, wouldn't it!!! And also illegal!

 

Been looking into a shunt for my rig....Dont know why but seems my.impedence has climbed a lil..Im up in the 59-65 ohm range...Cleaned everything,changed most everything and no diff..
Gotta research materials needed for best results and how to keep it clean with all the salt n crap on the winter roads..

 

Saw that online earlier today..

 

You could make one

 

What is it and what does it do? Tune the antenna?

 

Brings your ohm(resistance closer to 50 ohms)