Hi everyone:

I am about to compare the performance of two HF antennas and have an idea for doing this, that I would appreciate comments on.

The objective is to determine which antenna yields a stronger signal to DX locations, and even get a measure of the difference in dB. I am assuming that the antennas are reciprocal, so if antenna A receives an X-dB stronger signal than antenna B, antenna A will also yield an X-dB stronger signal from my transmitter to that location. So, I would like to measure the signal strengths received through these antennas and compare them. For this I would listen for CW or digital mode signals, switch back and forth between antennas, turn off the AGC and record the audio into a file (or monitor it directly), where I could accurately estimate the signal strengths and compare. I realize that different noise levels, fading, intermittent signal transmission, etc. will affect the absolute signal levels, so the software should be able to handle this. For example, by measuring the signal carrier alone and/or SNR. And it would be nice if the software could give me an "envelope reading" of the signal, for example, to estimate the CW signal.

Do any of you have comments on this methodology to compare antenna performance? And do you know of any DSP / sound card software that could be used for this?

73 - Kristinn, TF3KX

On Thu, 16 Aug 2012 09:25:12 -0700, TF3KX wrote:

Hi everyone:

I am about to compare the performance of two HF antennas and have an
idea for doing this, that I would appreciate comments on.

The objective is to determine which antenna yields a stronger signal to
DX locations, and even get a measure of the difference in dB. I am
assuming that the antennas are reciprocal, so if antenna A receives an
X-dB stronger signal than antenna B, antenna A will also yield an X-dB
stronger signal from my transmitter to that location. So, I would like
to measure the signal strengths received through these antennas and
compare them. For this I would listen for CW or digital mode signals,
switch back and forth between antennas, turn off the AGC and record the
audio into a file (or monitor it directly), where I could accurately
estimate the signal strengths and compare. I realize that different
noise levels, fading, intermittent signal transmission, etc. will affect
the absolute signal levels, so the software should be able to handle
this. For example, by measuring the signal carrier alone and/or SNR. And
it would be nice if the software could give me an "envelope reading" of
the signal, for example, to estimate the CW signal.

Do any of you have comments on this methodology to compare antenna
performance? And do you know of any DSP / sound card software that
could be used for this?

73 - Kristinn, TF3KX

http://w5big.com/spectrogram.htm

On Fri, 17 Aug 2012 12:56:55 +0000 (UTC), David
wrote:

http://w5big.com/spectrogram.htm

Free, made for ham radio, and possibly better:
http://www.qsl.net/dl4yhf/spectra1.html
http://www.weaksignals.com

When using detected audio to compare antennas, make sure you're
comparing signals, not comparing noise levels. Picking up more
atmospheric noise is not the mark of a better antenna.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558