Adjustable Gamma match for mobile antennas

If x equals 0 on channel 17 and does not equal 0 on Channel 19 the coil will be useless on Channel 19.
You need a little bit of capacitive reactance for the coil to function.
You need a little bit of inductive reactance for a variable capacitor to do the same thing.
A simple solution could also be an automatic antenna tuner which takes all your guesswork out of it, although that would force you to use an extra cable and have an extra couple connections which would introduce more loss into your system and make it more difficult to hear someone way out in the distance.
Personally if it was me I'd rather use a 50 cent piece of copper wire than go out and spend a couple hundred bucks on a tuner.

 

Ya got me confused on this now..You told me to detune off 19(as a example)and install the shunt..But if 19 =0 whats the point of the shunt..I want r to be closer to 50...My resonance is pretty good on 19..Slightly on the cap side -3.0 and ch 1 is about 5...

 

There are several ways to match a short antenna. You can increase the antenna length a bit (making it inductive), and add shunt capacitive base matching. Or decrease antenna length a bit (making it capacitive) and add shunt inductive base matching.

 

Depending upon where the inductance and/or capacitance are located (each series, parallel, one of each, where on the radiator they are), they can help at least keep the transmitter putting out full power over a wider freq spread. The antenna will still be just as inefficient a radiator and receiver because of its radiating element's length. But you can at least present a closer impedance over a wider freq range. The shorter the radiator, the closer the entire thing gets to being a dummy load.
73
diddly dahdidah
dit dit

 

Well im not adding physical length cause ots a 7ft skip shooter...I can add a longer tuneable tip but that changes nothing really,still gotta lengthen or shorten to get swr down and resonance where it needs to be..

 

I'm assuming resonance occurs in the middle of adjustment allowing you to go either capacitive or inductive

 

I can get #### near resonante on 19 ut usually seems to be high on the inductive side,not knowing what # is considered high..

 

You are in error about trying to get your antenna impedance to 50 ohms. Most quarter wave vertical antennas are between 25 and 36 ohms of impedance at the input of the antenna. A dipole antenna is around 72 ohms. So 50/36 = 1:38:1 for Swr and 72 ohms is 72/50 = 1:44:1, so as you can see both antennas SWR is around 1.4 for Swr. Your antenna system is doing what is designed to do. If you try and force that 50 Ohm impedance on the antenna to get that magical 1:1:1 Swr, it will be the same as a dummy load. Or at least not very efficient for the 27 MHz frequency band. The only antenna that I know thats 50 ohms is a ground plane, with the three lower elements bent at a 45° angle to bring the impedance closer to 50 ohms. Now that I think about it maybe that’s why that Stardust base antenna I had back in the 70s at such a low SWR. I’m sure it was due to the design of the three elements facing down a 45° angle, now that I think about it.

 

Only runninning 1 ant and im up around 58ish ohms on 26965 and mid 60's on 27185 and high 60's on 27405...

Something has changed but i dont know where..Cleaned and changed most all everything for same results..Dont wanna use more braded straps cause all i can find are 13" ones..Been told 8" or less if possible..

I know my swr is around 1.3-1.5 across the board and my resonance on 1 is about 5 and 19 is -.3 and 40 is about 12(dont remember if thats cap or ind side)
Dont seem to have the range as i did,radio is a lil toooo quiet(white noise wise)and it came on quick..Both a analyzers say pert near same thing..Dont wanna think its my radio,tried another (same radio type but slight dofferent tune)and do get more white noise..Still the range is not there...Im gonna take a 10k and another skip shooter on the road and switch them out to see.....Running lmr 240 and compared analyzer results with some other coax and again about the same...

I know my impedence ohms have to come down so thats my starting issue..

 

reactance lags SWR.

Resondance should be aimed at the reactance X=0.

You should start with checking your antenna with a very short feed to remove the influence of the feed line and work yourself backward.