External digital S-Meter

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andrew30
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External digital S-Meter

Post by andrew30 » 18 Sep 2018, 14:35

Hi,
is there a S-Meter with standard 0-3.3V input which would show not just S-units but also equivalent dBm with possibly 1dBm precision?

HFDX
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Re: External digital S-Meter

Post by HFDX » 22 Sep 2018, 19:47

No

andrew30
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Re: External digital S-Meter

Post by andrew30 » 23 Sep 2018, 08:33

What makes it impossible to exist?
I suppose project based on Arduino Nano + 16x2 LCD should be possible.
All that's required is to measure input voltage and convert it to corresponding dBm value.
2-3 calibration points and it should be set to go...

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Tigersaw
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Re: External digital S-Meter

Post by Tigersaw » 23 Sep 2018, 09:56

I did a similar thing some moons ago with an Arduino but used the 4 bit digital S meter output of the FT857 to drive a display.
https://www.youtube.com/watch?v=3LNirO7Wi58

andrew30
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Re: External digital S-Meter

Post by andrew30 » 23 Sep 2018, 10:06

Wow, this looks interesting!
Can you get dBm values out of FT817/857 through CAT ?

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Tigersaw
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Re: External digital S-Meter

Post by Tigersaw » 23 Sep 2018, 11:12

andrew30 wrote:
23 Sep 2018, 10:06
Wow, this looks interesting!
Can you get dBm values out of FT817/857 through CAT ?
No, its just a 4 bit number corresponding to the bargraph S meter on the front, I think it corresponds to
0,1,2,3,4,5,6,7,8,9,+10,+20,+30,+40,+50 or something like that, the FT857 has a very inaccurate meter.
It does have a 0-10ma (or could be 0-1ma, 0-100ma) analogue output as well for an external meter.

S meter levels are relative anyway, no two radios seem to read the same, and if you use RF gain to get the best SNR then you cant really use them to give signal reports. Thats why a report of 5/9 or 5/9+10 is meaningless, it should be a quantitative assessment based on:
1 Faint—signals barely perceptible
2 Very weak signals
3 Weak signals
4 Fair signals
5 Fairly good signals
6 Good signals
7 Moderately strong signals
8 Strong signals
9 Extremely strong signals

Your best bet of getting dBm values that can be compared day to day I would think would be with a SDR setup, I know SDRconsole can be set to show received dBm

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