Apache Labs Community Forum

Hello

I upgraded to protocol 2 (V3.9 - 12.1.18) on my Anan 100D and I use version 2.10.3.4 (10/19/23) of Tethis.

I wanted to carry out the calibration using the MW0LGE tutorial:
https://www.youtube.com/watch?v=yuZK9iToNxg

I used an RF generator: https://www.youtube.com/watch?v=gBbCwW__Z6c

I set the generator to 15mhz at -72dbm and started the calibration.

Result: I find the -72dbm (blob measurement spectrum)
and on the meter I find myself reading -72dbm S9.

Once the hf generator is "off", antenna cable unplugged I can read on the VU meter -102dbm (+-) with a signal of 4 (+-), whereas I should normally have a level close to 0

I tested the Anan 100D on SDR Console, I found myself having a signal of 9+2 for -72dbm and when I disconnected the cable from the HF generator, I found myself having a value close to 0

Are we facing a calibration problem on Tethis or is it me who is not doing the right thing?

Thank's,73,

Thierry

Thierry wrote:Hello

I upgraded to protocol 2 (V3.9 - 12.1.18) on my Anan 100D and I use version 2.10.3.4 (10/19/23) of Tethis.

Thetis

I used an RF generator: https://www.youtube.com/watch?v=gBbCwW__Z6c

I saw a nice review of that signal generator on Youtube and it was surprisingly accurate, so the generator looks OK to use.

I set the generator to 15mhz at -72dbm and started the calibration.

Result: I find the -72dbm (blob measurement spectrum)
and on the meter I find myself reading -72dbm S9.

Once the hf generator is "off", antenna cable unplugged I can read on the VU meter

Do you mean S-meter?

-102dbm (+-) with a signal of 4 (+-), whereas I should normally have a level close to 0

We don't need the S units, just the dBm value.

Depending on the bandwidth of your receive passband, -102dBm on the S-meter is just about what you would expect. So that is correct, and there is no problem.

For example, my ANAN-8000 is calibrated properly. Switching to a dummy load at 14.3MHz, in USB with a receive passband of 2.7KHz (100 to 2800Hz), I get an S-meter reading of -106dBm. This is equivalent to a noise power spectral density of -140dBm/Hz, and when I look at the info line below the spectral display it in fact reads NPSD -139.7dBm/Hz (you may have to click on that line to get it to show NPSD. That you are measuring a few dB higher is unsurprising given that you are not terminating the input, that the 100D is just a little noisier than the 8000, and that between the two of us there's probably a 2 or 3 dB margin for error.


In summary, bandwidth matters when making noise measurements. See also viewtopic.php?f=6&t=2463

Hello,

Do you mean S-meter?
> yes

Many thanks Scott for all these explanations.
I took the time to read all your comments and tutorials which are very explanatory and very detailed.

Thanks again,

73,

Thierry

Scott,

This reminds me that I will need to recalibrate for level now that I am using a later version of Thetis, correct?

Juha

If you didn't start a new database the calibration will still be good.