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Full throttle SSB distortion on 15 and 10m

 

I have minimal mods (except for the Axicom I did) on my ver. 3 ubitx (still with the original firmware). The biggest addon is a SL6270C Plessey Vogad compressor between the dynamic mic and the mic input. The Vogad delivers about 100mv and works wonderfully up to the 15m band. To avoid full power distortion I have to lower the output from the Vogad by means of a potentiometer. I have to say that my unit shows an astonishing 15w on 40m (and the output seems clean to my hears) but lowers to 3 on 15m and 2w on 10m. The potentiometer solution works but what is the cause? Is this linked to the low output on the higher bands?

 

Getting 15W on 40 is pushing for excess... should be about 10.

And 2W is about all you get on 15 and 10 with out amp mods.? Likely less.

More audio more power but there is a point of distortion as the power amp cannot do it.

Allison
 

I agree, 10W on 40 should be reference of modulation level.

I have not got my hands on a v5 and when I do I will report.

Raj

At 26-02-19, you wrote:
Getting 15W on 40 is pushing for excess... should be about 10.

And 2W is about all you get on 15 and 10 with out amp mods. Likely less.

More audio more power but there is a point of distortion as the power amp cannot do it.

Allison
 

Actually my unit has always shown more than 10w on low bands, but ironically it develops that full power distortion (total noise) only on the higher bands (15-12-10m) where the power is much lower. Is it just an overdrive issue to the poor 3904s?


Il 26/feb/2019 14:21, "Raj vu2zap" <rajendrakumargg@...> ha scritto:
I agree, 10W on 40 should be reference of modulation level.

I have not got my hands on a v5 and when I do I will report.

Raj

At 26-02-19, you wrote:
>Getting 15W on 40 is pushing for excess... should be about 10.
>
>And 2W is about all you get on 15 and 10 with out amp mods.? Likely less.
>
>More audio more power but there is a point of distortion as the power amp cannot do it.
>
>Allison




 

Oos so ever it is,

I suspect instability caused by your output wires. Shorten them to minimum or wire a coax to the board.

Raj

At 26-02-19, you wrote:

Actually my unit has always shown more than 10w on low bands, but ironically it develops that full power distortion (total noise) only on the higher bands (15-12-10m) where the power is much lower. Is it just an overdrive issue to the poor 3904s?

Il 26/feb/2019 14:21, "Raj vu2zap" < rajendrakumargg@...> ha scritto:
I agree, 10W on 40 should be reference of modulation level.

I have not got my hands on a v5 and when I do I will report.

Raj

At 26-02-19, you wrote:
>Getting 15W on 40 is pushing for excess... should be about 10.
>
>And 2W is about all you get on 15 and 10 with out amp mods.?? Likely less.
>
>More audio more power but there is a point of distortion as the power amp cannot do it.
>
>Allison

 

I will check it during a pit-stop in? the ARRL DX SSB contest this weekend. The output cable to the plastic rear panel is the stock bifilar twisted many times, made a bit shorter. I will replace with a short coax. I will check the PTT cable, which is coax but long a couple of meters long to the pedal. Initially I thought it was a strange ground loop effect.

Il 26/feb/2019 15:29, "Raj vu2zap" <rajendrakumargg@...> ha scritto:
>
> Oos so ever it is,
>
> I suspect instability caused by your output wires. Shorten them to minimum or wire a coax to the board.
>
> Raj
>
> At 26-02-19, you wrote:
>
>> Actually my unit has always shown more than 10w on low bands, but ironically it develops that full power distortion (total noise) only on the higher bands (15-12-10m) where the power is much lower. Is it just an overdrive issue to the poor 3904s?
>>
>> Il 26/feb/2019 14:21, "Raj vu2zap" < rajendrakumargg@...> ha scritto:
>> I agree, 10W on 40 should be reference of modulation level.
>>
>> I have not got my hands on a v5 and when I do I will report.
>>
>> Raj
>>
>> At 26-02-19, you wrote:
>> >Getting 15W on 40 is pushing for excess... should be about 10.
>> >
>> >And 2W is about all you get on 15 and 10 with out amp mods.?? Likely less.
>> >
>> >More audio more power but there is a point of distortion as the power amp cannot do it.
>> >
>> >Allison
>

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