On Fri, 26 Nov 2004 07:05:46 -0600, "William E. Sabin"
wrote:


"William E. Sabin" wrote in message
...

"Avery Fineman" wrote in message
...
Is there a standard RF input level per "S" Unit?

If so, please post the location. Thanks.


My homebrew solid state receiver (see QRZ.COM) uses 5 dB per S-unit. S9
corresponds to -73 dBm available power, which is 100 microvolts
open-circuit from a 50 ohm sig gen, or 50 microvolts into a 50 ohm load.
Available power and open-circuit voltage are used because the input
inpedance of the receiver is not guaranteed to be 50 ohms. I use 5 dB per
S unit because it compresses the scale a little and it also agrees more
closely with the intuitive listening test measure that I have used for
many years. The upper end of the scale is 30 dB above S9, which is -43
dBm, a very strong signal. Signals stronger than S9+30 dB I don't bother
to measure. At S1 the signal level is -73 - 40 = -113 dBm. Signals weaker
than that S1 I don't try to quantify.

My receiver has a low noise RF preamp with 8 dB of gain that I use on the
12 and 10 meter bands, when those bands are quiet. This makes the S meter
less accurate but I don't worry about that. To get an S meter reading I
turn off the preamp briefly.

My receiver has a custom made, computer printed scale using a calibrated
sig gen, and there are two trimpot adjustments, one for the low end and
one for the high end. This circuit uses voltage regulated opamps. The S
meter dynamics are adjusted using RC time constants.

My S meter is accurate within +/- 2 dB from 160 M to 10 M, because the
receiver is designed for this accuracy. Because of the IF and RF circuit
design, the scale calibration is fairly correct and reliable, as I
mentioned.

Bill W0IYH


My receiver also has a 20 dB antenna input attenuator that can be switched
in from the front panel. This extends the upper signal range to S9 + 50 dB.
I use it very rarely.

Bill W0IYH


defining the proper time-constant for ssb is another problem. My
activity has mainly been VHF/UHF cw and ssb, and working a few HF
contests on cw. Found that reporting and operational style is somewhat
different on HF and VHF. While the normal report on HF is 59 or 599,
it varies much more on VHF, and 519 report is not rare on VHF -
particularly if the OP has no experience from HF.
My favourite report is 559, because it is easy to send using elbug,
and it makes some fun, particularly when everybody expects to receive
a 599 report, so the opposite OP must make a note in his log that the
report wasn't the usual type, and somebody most likely may loose score

73
Jan-Martin, LA8AK
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm