Ah, but the S meter should indicate a reference signal strength at the
antenna input to the receiver. Gain or no gain antennas simply means more
or less signal. A 50 uV signal should indicate S-9 regardless of antenna
gain or loss.
With all the discussion of recent, I've looked at a couple of my radios
using a HP 8656B generator of known accuracy with a precision 10 dB
attenuator on the generator output to assure correct isolation and a true
source Z of 50 ohms. In all cases, all bands, 50 uV produces S-9 except for
the Collins S-Line to which they use 100 uV for S-9. As to levels below
S-9, generally a 6 dB reduction in signal shows a reduction of 1 S unit.
And a 10, 20 or 30 dB increase above 50 uV shows a reasonably accurate dB
indication accordingly above S-9.
One point here is that the output of the generator must be maintained at 50
ohms regardless of load. Failure to achieve this, the generator output
calibration may not be accurate as one is lead to believe. Don't assume
that the receiver input is actually 50 ohms. It most likely is not.
73
Bob, K4TAX
----- Original Message -----
From: "Ken Brown" <ken.d.brown@verizon.net>
To: <gsm@mendelson.com>; "Discussion of Ten-Tec Equipment"
<tentec@contesting.com>
Sent: Wednesday, December 28, 2005 1:24 PM
Subject: Re: [TenTec] Orion II - Initial Reactions and Impressions
Geoffrey S. Mendelson wrote:
On Wed, Dec 28, 2005 at 08:21:03AM -1000, Ken Brown wrote:
S-meter readings are already virtually meaningless.
Yes, but what worries me is that almost all the time using the same
antenna. my Argo 509, Triton-IV digital, Drake TR-5, Kenwood TS-430s
and R5000 all read within one S unit of each other.
I should have clarified. S meters are virtually meaningless as signal
strength indicators, because they are hooked up to antenna systems that
vary over such a wide range of gains/efficiencies and in such a wide
range of environments. S meters are however NOT useless. There are
useful to compare from day to day, or antenna to antenna AT ONE QTH.
They are not useful to compare readings from one QTH with differnt
antenna systems and local conditions to another.
DE N6KB
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