1750Hz Tone not exact? FM-Repeater problem

DG3GSP
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Location: Southern Germany

1750Hz Tone not exact? FM-Repeater problem

Post by DG3GSP » Sun Jul 12, 2020 10:09 am

A friend reported to me, that he can't open one of our local FM-repeater with his GD-77.
I did a quick test on a FM-repeater near, also have a problem to trigger the repeater with the 1750Hz Tone.

The 1750Hz tone on my GD-77 sounds slight differently than on my FT-65 (and the repeater respond correct to the tonecall on the FT-65).

Had someone else tested the 1750Hz Tone?

P.S. I tested this with the newest dev. release and also with a older version - same problem.
73, Peter DG3GSP

DO4CZ
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Location: near Rostock, Germany

Re: 1750Hz Tone not exact? FM-Repeater problem

Post by DO4CZ » Sun Jul 12, 2020 11:02 am

Hello Peter

The same here.
The 1750Hz tone seems to fit here (by ear), but the tone on the GD-77 is far too quiet. I tested/compared with another device.
I not have a repeater in the immediate vicinity, only further away. I arrive safely with noise and then to yet with the very quiet 1750Hz tone...
In the middle of May the opening with 1750Hz tone, worked without any problems.
I was on the way and the GD-77 opened various repeaters.
73, Joerg DO4CZ - 2x GD-77 ( 1x as a hotspot and 1x for normal operation )

DG3GSP
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Location: Southern Germany

Re: 1750Hz Tone not exact? FM-Repeater problem

Post by DG3GSP » Mon Jul 13, 2020 7:23 pm

I did some measurements: the frequency of the 1750Hz tonecall seems to be correct.
Maybe the problem is caused by a too low FM deviation (only at the tonecall, voice seems to be ok).

Unfortunately i can`t measure the deviation at the moment..
Attachments
1750Hz.jpg
1750Hz.jpg (27.06 KiB) Viewed 539 times
73, Peter DG3GSP

LY1RF
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Re: 1750Hz Tone not exact? FM-Repeater problem

Post by LY1RF » Mon Jul 13, 2020 8:11 pm

Dont know if thats 1750 tone problem, but I can't open repeater with 1750 tone 40 miles away with opengd77 radio, but that works first time with 878uv HT. And btw both radios can hit another repeater 60 miles away that doesnt requare 1750 tone ...

KI5GZK
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Re: 1750Hz Tone not exact? FM-Repeater problem

Post by KI5GZK » Mon Jul 13, 2020 10:46 pm

In the radio calibration settings under Analog Tx deviation there is a tone burst adjustment. You might want to try kicking it up a few notches to see if it helps. Make sure to back up your calibration settings first just in case you need to restore them.

VK3KYY
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Re: 1750Hz Tone not exact? FM-Repeater problem

Post by VK3KYY » Tue Jul 14, 2020 12:34 am

Also check your channel bandwidth setting, as if the bandwidth is set to 12.5kHz it will half the deviation.

KI5GZK
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Re: 1750Hz Tone not exact? FM-Repeater problem

Post by KI5GZK » Tue Jul 14, 2020 6:33 am

That's a very good point Roger. They should probably check the bandwidth setting first.

DG3GSP
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Location: Southern Germany

Re: 1750Hz Tone not exact? FM-Repeater problem

Post by DG3GSP » Tue Jul 14, 2020 2:46 pm

The channel bandwidth setting is 12.5kHz, because it´s normaly used here in germany @2m ..
(At bandwidth 12.5kHz the FM deviation should be 2.5kHz)

I had today a litte free time in the lab, so i measured the deviation of my GD-77:

At voice the measured deviation is proper (about the 2.5kHz I expected), but at the tonecall the deviation is only 0,63kHz - this is a very little value and should be about 2.5kHz too.

Because not only my radio has this problem, this issue should be not solved via individual tone burst adjustment in the CPS..
Attachments
deviation_calltone.jpg
deviation_calltone.jpg (22.17 KiB) Viewed 473 times
73, Peter DG3GSP

LY1RF
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Re: 1750Hz Tone not exact? FM-Repeater problem

Post by LY1RF » Tue Jul 14, 2020 5:29 pm

I"m using 25Khz bandwidth but thats doesnt help...

VK3KYY
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Re: 1750Hz Tone not exact? FM-Repeater problem

Post by VK3KYY » Wed Jul 15, 2020 1:46 am

I had a look in the code

https://github.com/rogerclarkmelbourne/ ... 1127-L1137

It seems to use a value from the calibration table to set this deviation

Possibly the wrong memory address in the calibration data is being read, for the tone bust.

There seem to be 6 separate deviation values for the different types of tone, and in this case its using the deviation setting for something called "Tone" (I think). This differs from the value for DTMF, so perhaps thats the problems.

Or possibly the value in the calibration data need to be multipled before using them to control the RF chip, but that seems unlikely, as the numbers used for these are relatively small, and the storage space in the calibration table can easily store the value without a multipler being needed.

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