Antenna Tuning?

[distortion]

I am currently running a 4 pill fatboy, but a 2x8 x-force is going in Friday along w/ a 200 amp alternator and 2 1200-1300 cca deka batteries, so I'd like to get my antenna right before putting more power into it.

When installing my antenna it tuned in to 1.1 swr with a really short stinger at 40 ohms, 99%, and low reflect on the MFJ 259.
It is a dual coil predator 10k.

Recently, I decided to try the single coil setup, since people had said they preferred it to the dual coil. I removed the top coil, reassembled the 6.5 turns section.. new stinger.. cut it down about 6 inches before it went to 1.1 on the mfj.. but the ohms were still low.. like 44.. Antenna is way taller, so that's probably an advantage.

I have a pre-packaged 18 foot piece of coax, that the connector was cut off of to attach to the lugs of my antenna mount.. Other than that it is 18'.. probably 17'11-11/2".

Anyways, I decided out of curiosity to add 3 feet, and sure enough the analyzer shows alot closer 50 ohms, but slightly higher swr.. so trimming the stinger did that. What am I doing by doing this? I can't imagine this is the correct way of doing things? But maybe it is.. feedback.

Weird part is.. the antenna seems to perform better, but no scientific evidence.. just reports of better signal, and my ears even sound better.. despite losing a coil. I think that might be the single coil working better, however... nothing to do with the 50 ohms.

I am new to this hobby, and claim to know nothing.. just on a quest to learn. Any help given is greatly appreciated. I'd really like to dial this antenna in properly, because adding a second just for testing/fun is currently a consideration.

Thanks,
Josh

 

[FL Native]

hook the MFJ directly to the feedpoint of the antenna. to get an acurate reading. get antenna set right. then add what ever length of coax you need to get from antenna to amp.

you may be getting false readings. unless you use 1/2 wave multiples of coax. wich is different for all types of coax due to the differing velocity factors.

 

[freecell]

"nothing to do with the 50 ohms. "

the additional 3 feet of feedline is responsible for raising the resistance from 44 to 50 ohms as seen at the input end of the line.

the slight increase in swr is the result of additional reactance. what you are unable to determine is whether that reactance is inductive or capacitive. a noise bridge would come in handy right about now.

the increase in performance comes as no surprise. try sweeping the analyzer up and down the band and check to see at what frequency the swr is the lowest with minimal deviation from the 50 ohms resistance. this will be the frequency where reactance is minimum.

swr has nothing to do with resonance. an antenna can be resonant and still exhibit a higher than desired swr and by the same token the swr can be flat without the antenna necessarily being resonant. frequency dependence here cannot be discounted. line length on the other hand can have a definite effect on the resonant frequency of the radiating element.