"Roy Lewallen" wrote in message
...
I'm glad to see that my chiding has had a positive result.

Be sure you calibrate your S-meter on each band you'll be using it on,
and that the RF gain control and any preamplifier and input attenuator
settings are the same as they are when making measurements.

Especially when comparing horizontal and vertical antennas, you'll
likely have to make several measurements over a period of time. I've
seen many cases where one antenna is a good 20 dB stronger than the
other, then over the next minute or so their relative strengths reverse.
This is due to polarization rotation of the received signal. On 40 and
80 meters at least, this is common and often has a period of around a
minute or more. Really makes me chuckle when I hear "Ok, this is antenna
1. Now this is antenna 2. Which is stronger?"

If neither antenna is consistently stronger than the other, you can put
a fixed attenuator is line with one of the antennas and the step
attenuator in line with the other to make comparison easier.

People who blindly assume the marks on their S-meters are 6 dB apart
should take a good look at your calibration results.

Roy Lewallen, W7EL

Mike Coslo wrote:
Based on another thread a few weeks back in which Horizontal dipoles
were being compared to Vertical antennas, and from a little chiding from
Roy, W7EL, I decided to do some testing on my own personal versions of
the two.


My setup is:

Icom IC-761
Antenna 1 - Homebrew OCF dipole at ~ 50 feet.
Antenna 2 - Butternut HF6V -ground mounted and 18 radials on the ground.


Part one of this experiment is to calibrate the S-meter. I found that
trying to calibrate the thing with on-air signals was a nuisance, and
probably wouldn't be as accurate, so I used a signal generator.

I started out with a +20 signal, then worked my way down.

+20 start
S9 -18 db
S8 -23 db
S7 -26 db
S6 -29 db
S5 -32 db
S4 -35 db
S3 -37 db
S2 -39 db
S1 -41 db

All in all, I would have to say that the meter tracks very well from S8
to S4, and the only place that wasn't that great was from S9 to S8. But
considering the transient nature of the signals we are receiving, I
would have to day that the S-meter is of reasonably close accuracy.

With my newly calibrated S-meter I am ready to start looking at what the
two different antennas are doing for me. I have a coaxial switch to jump
back and forth between the two. My initial impressions are that there
are some surprises. The difference in noise levels varies by antenna by
band. On some bands the vertical is noisier, and on others it is the OCF
dipole. Especially intriguing is that on PSK mode, where I can see
several signals at one time, switching between antennas will attenuate
some signals, while other signals increase in strength. I think that my
vertical works better than I gave it credit for, but If I definitely
want *both* antennas.

Next installment will be the band to band comparison of the two antennas
with some numbers.

Installment three will be an investigation of that PSK signal strength
business.

- 73 de Mike KB3EIA -


Man, this is Ham Radio at its best!

west
AF4GC