Topband: dynamic range

[Thomas Kuehl]

This brings up some questions that I have...

When calibrating an S-meter for 50uV equal to S9 the signal generator should
be terminated into a 50 Ohm load, for best accuracy . However, when a
receiver input is driven it would seem that the reflected impedance is
likely something other than simply 50 Ohms resistive. Therefore, the
generator is no longer precisely terminated and the output voltage will be
something other than 50uV. This would create an error.

My thought is you start with a generator with an output much greater than
50uV, then follow it with an attentuator connected between the generator
output and the receiver input. This pads the generator and it sees a load
very close to 50 Ohms. Is this the correct way to go about setting this up?
Also, what frequency should be used to calibrate the receiver? As we all
know the receiver sensitivity changes from band to band.

During CQWW160CW my S-meter was pegged most of the time. I had just obtained
the radio, an Omni VI+, the day before the contest and the S-meter was very,
very active. Ten Tec calibrates it for 50uV equal to S9. My previous radio,
an Omni V, had the same spec and its S-meter seldom pegged.

Thanks, Thomas - AC7A (Tucson)


----- Original Message -----
From: "Sinisa Hristov" <shristov at ptt.yu>
To: <topband at contesting.com>
Sent: Thursday, February 05, 2004 9:22 AM
Subject: Re: Topband: dynamic range


> Jim Jarvis wrote:
>
> > 1)  What's s9? I've got references indicating 50uV or 100uV.
>
>
> It's 50 uV into 50 Ohm load.
> Unloaded generator has 100 uV.
>
> 73,
>
> Sinisa  YT1NT, VA3TTN
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