[RFI] Why we badly need "party line" materials for all hams

Tom Rauch w8ji at contesting.com
Tue Jul 20 19:43:15 EDT 2004

> S-meter readings for levels of S-1, S-5, S-9, and S-9+20).
When it became
> obvious that I could grow a very long beard by the time
the cals got done
> because each radio varies by band in its S-meter
characteristics, I
> reconsidered and agreed with Ed that anything is better
than nothing.

Most radios I have seen are very repeatable band-by-band for
dB change per S unit change. For example my IC751A's are all
identical from band to band so far as dB change per S unit.
They are about 1dB per S unit near S-1, and 4.5dB per unit
near S-9.

Even my old Drake receivers track, since the IF AGC loop
doesn't change gain with band change.

If the radio failed to maintain the same dB change per S
unit, we could always use a cheap MFJ attenuator pad and an
external preamp and simply normalize to one S meter point.
The pad would give an accurate dB change indication.

Perhaps you were trying to get to an absolute reading in uV
or dBm. That would not be useful anyway, since no one knows
the antenna sensitivity.

> found.  I also had e-mail communication with Greg Lapin,
N9GL, who heads up
> the League's ARIA project, over the subject.  In the end,
we all agreed
> that while calibrated S-meters would be nice, they are not
required to make
> a point.  (ARIA formal reporting does rely upon calibrated
receivers, but
> that is another issue.)

I strongly disagree with that. When I read reports saying
"the BPL was S5 on my Hamstick" I think "what the hell does
that mean?". S5 might be meaningless, or it might be severe.
I think that, and I want us to win this fight.

Giving useless information like "S" units makes us look very
unprofessional, and probably gets the data tossed right in
the trash. I know if I was working for a BPL company and
some said "the BPL is S-9" I'd just say "What a waste of
time" and pitch the data in the trash can.

Now if the same fellow with the same basic equipment said:

 "The BPL increased the background level 13dB from a typical
suburban environment that was absent any BPL system." I'd
say, "Woah, that's nasty! We need to knock it down 13dB."

No one needs to know dBuV or dBm since the antennas are
unknowns, but dB change in background noise would be simple,
fast, effective and prove what needs to be proven.

73 Tom

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