On Sat, 12 May 2007 20:48:44 -0700, Roy Lewallen
wrote:


It would be really neat if we had a tuner that would selectively tune
the signal and noise. But alas, we don't. At HF, the signal and noise
are both coming from outside the antenna, so anything we do at the tuner
-- or anywhere between the antenna and receiver -- affects both equally.
The tuner won't affect the received s/n ratio unless you get it so badly
mistuned that you start hearing receiver noise, which isn't likely at
HF. So tune it any way you want.

For transmitting, you're always best off getting as much power to the
antenna as you can. (I mean actual power, not "forward power".) What
you're trying to do is make the best s/n ratio at the other guy's
receiver. You can't do anything about his noise, but for every dB you
increase your signal, you get a one dB improvement in the s/n ratio at
his end. This means having an SWR low enough that your rig doesn't shut
down. Unless you have an extraordinarily lossy transmission line, any
SWR below the shutdown point will get the same amount of power to the
antenna for practical purposes.

At VHF and above, receiver noise is usually greater than atmospheric
noise, so the rules change for receiving antennas. There, you do want to
get as much signal from your antenna as you can in order to get the best
s/n ratio. The rule for transmitting is still the same, though.

Roy Lewallen, W7EL

Thanks, Roy,

A friend of mine suggests I setup a field strength meter and tune for
maximum fs. I don't usually use baluns so I would wonder how accurate
that would be.

Currently, I am tuning my gutters up for HF. I checked it with an
analyzer the other day and found it is an excellent 160 meter and 20
meter antenna without the tuner (swr-wise). In the meantime I am
building a vertical for 20 and up.

Thanks again,
73 for now,
BUck
N4PGW

--
73 for now
Buck, N4PGW

www.lumpuckeroo.com

"Small - broadband - efficient: pick any two."