an antenna tuner provides a more efficient transfer of energy from the low Z output of a ham transceiver to whatever complex Z the antenna (and its associated feed line) offers. Ideally, there should be very little loss on a feed line when employing a tuner. THis is true for balanced line feeds. However, coax cable has some properties that make the use of a tuner a little problematic. Also, unbalanced feed lines can suffer induced noise issues (like common mode noise). Also, if there is sufficient mismatch between the antenna and the coax, energy transfer will suffer. THere may also be voltage nodes in the coax that may (if running sufficiently high power levels) break down the dielectric in the cable and cause other problems.

now, an antenna that is mostly just an end fed wire will benefit from the use of a tuner. The tuner will provide the efficient transfer and proper match such that said wire will perform almost as well as a resonant antenna of any other type. I can see this on receive when using a 35 foot long wire for a receive antenna. When tuned with a tuner, signals become far stronger and there is less broadband noise.

The ARRL has a lot of publications on antennas and antenna theory. If they have accessible formats, it would make for an enlightening read.

-eric
N7ZZT

On Jun 30, 2014, at 9:11 AM, David Pearson wrote:

> Hello List:
> 
> A previous post suggested that an antenna tuner "fooled"an antenna into 
> thinking that the antenna was resonant on a particular band/frequency(I 
> think that he was referring to verticals).
> 
> My question concerns multi-band wire horizonntals(a 10-40 half-size g5rv for 
> example).
> 
> In this situation, is an antenna tuner performing the same function as it 
> did with the vertical("fooling" the feed system into believing it's matched, 
> or does it perform some other positives(better power transfer, etc.)?
> 
> Sincerely yours,
> 
> 
> 
> David S. Pearson-wa4dsp 
> 
> 
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