NATO 2000 Low SSB talk power

[andymuza]

Yeah checked bias and FM deviation. Bias needed a slight adjustment. The FM deviation was also adjust as it was way to loud.

Cheers

[Retrodog]

Don't for get to set the SSB ALC also.
I found that the bias in mine needed to be almost full up to be linear.

I will try the resistor mod also, thanks for the info guys.

[cjay]

Don't for get to set the SSB ALC also.
I found that the bias in mine needed to be almost full up to be linear.

I will try the resistor mod also, thanks for the info guys.

Good way to smoke the outputs, the problem with the Nato and other similar rigs is I believe that the source impedance of the bias circuit is too highv so the bias voltage droops under load, there's a video on youtube 'perfectioning audio' I think, shows you how to mod the bias circuit so it can supply more current under load.

[Retrodog]

Thanks for that,
I won’t be modifying much as it won’t get a lot of use. Given the operating range of the bias potentiometer at first I thought someone had replaced it with the wrong value as it was almost on full before the signal became what I’d call class AB “linear”.
I must admit though I have never heard one sounding rough in terms of linearity, the complaint has always been thin audio and slight clipping.
Appreciate you putting me wise to this as I don’t want to fry the 2SC1969.
Talking of which the IMD performance anything over 10w is poor by the looks of things anyway as it rapidly drops below -35dbc.

[Retrodog]

Well now back at home its all immaterial really as RV2 only gives 0.6v full up anyway!

[cjay]

Well now back at home its all immaterial really as RV2 only gives 0.6v full up anyway!

Might be worth the small effort https://www.youtube.com/watch?v=uDDWhr6 ... Cy8lgmalJQ

[Retrodog]

Well now back at home its all immaterial really as RV2 only gives 0.6v full up anyway!

Might be worth the small effort https://www.youtube.com/watch?v=uDDWhr6 ... Cy8lgmalJQ

Excellent! thank you for the link, I thought when I was setting up the bias initially by "ear" it only just reach linear output when the potentiometer was at maximum. At 0.6v it's not quite there.

I must sort this next week when I'm on holiday.
Thanks again!