dxAce wrote:
dxAce Apr 17, 3:11 pm show options
Newsgroups: rec.radio.shortwave
From: dxAce - Find messages by this author
Date: Sun, 17 Apr 2005 18:11:26 -0400
Local: Sun,Apr 17 2005 3:11 pm
Subject: splitter ?
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Yes, the calibration may indeed be off with various manufacturers,
however all things being equal it should be very easy to determine
various antenna changes with a 'particular' receiver.

Damn simple.

dxAce
Michigan
USA
---------------------------
Sadly very few radios have S-meters that behave in a "correct" way.
I have a HP calibrated step attenuator, with .5dB steps. Zin 50Ohm
Zout 50 Ohm. When checked at the electronics lab (at UK) the
error was less then .07dB worst case. I have a simple crystal osc that
is very temp stable. Zout 50 Ohms at .1V. Measured to be 0.10V.

I have had chance to check quite a few receivers. From the famous
R390, to one of the Lowe 150s. I would have to dig out my notes, if
I even still have them, and the R390 was the ony one that tracked
6dB/1S unit.

This url has better data then I can dig out out the moment:
http://www.ac6v.com/sunit.htm

Unless you know, that is have measured, your S-meter, it is only
a rough indication.

You can clearly use your S meter to compare one antenna to another,
but I would be very hesitant to say that "antenna 1 is S2 and antenna
2 is S6, therefore antenna 2 has 24dB more gain then antenna 1."
Based on the assumption that 1 S unit equals 6 dB.
S6-S2=4 S-units, 4 X6dB = 24dB
(Math shown for those new to the hobby)

Now if you have a calibrated step attenuator you could show that:
Ant 1 gives S2
Ant 2 requires 20dB of attenuation to give a reading of S2.
Ant 2 has about 20dB more gain then Ant 1.

I bought my Hp attenuator at a surplus store for $5.
I bought 2 fox industries 50P-077 +12V BCD attenuators
that have a measured error of less then .01dB for $1each!
Coupled with some Pasternak PE7101 coaxial relays I hope
to be able to some "meaningfull" antenna experiments this
summer and next winter.

There is a vacant lot caty corner behind us and I have permission
from the lot owner, and both my rear and next door neigbors to run
an temp antenna to and across that lot. I will be able to get about
300' of wire up in a straight line. I intend to see just how length
effect
signal strength.

Next fall a frined is going to let me spend a few weekends on his
fields to check even longer wires.

Terry