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2000GTL Low AM peaks-SSB OK
- Thread starter Seven01
- Start date
As I said before, this unit has been put back into stock configuration...bias set...all TX cans tuned, etc.
With a 5w dead key it should show, with AMC/ALC open, about 10w peaks on AM. This one does 7-8w peaks on AM, with 20w peaks on SSB.
That's the prob...low output on AM..full output on SSB.
I usually get, from a 148 to a Grant to a Madison (same circuit board), 5w carrier with 18-20w peaks on AM with the swing mod/voltage mod.
(By the way, the final AM voltage mod puts the same voltage to the final as it would using SSB... does not do damage...been doing this for years).
Everything looks normal on a scope.
This one has got be puzzled...LOL
TNX for all your responses...
With a 5w dead key it should show, with AMC/ALC open, about 10w peaks on AM. This one does 7-8w peaks on AM, with 20w peaks on SSB.
That's the prob...low output on AM..full output on SSB.
I usually get, from a 148 to a Grant to a Madison (same circuit board), 5w carrier with 18-20w peaks on AM with the swing mod/voltage mod.
(By the way, the final AM voltage mod puts the same voltage to the final as it would using SSB... does not do damage...been doing this for years).
Everything looks normal on a scope.
This one has got be puzzled...LOL
TNX for all your responses...
Remember that the carrier and both side bands spread the power available, with SSB the power is only with one of the side bands and no carrier. This will give almost three times the power of AM.
Reducing the carrier and increasing the modulation for swing will not equal SSB in Watts, the math does not add up.
There are ways to overcome this limitation, Increasing voltage but would shorten the life of components or change out the finals to MOSFETs.
Sometimes the electrolytic capacitors age to a point where they bleed off voltage, especially in the AM power section and less common is the ceramic capacitors in the output tank can lose their dielectric and partially short internally, another voltage loss. Older units used Tantalum capacitors and these can age to a near shorted state.
If I am not mistaken, the 2000GTL is about 20 plus years old now....
73 mechanic
Reducing the carrier and increasing the modulation for swing will not equal SSB in Watts, the math does not add up.
There are ways to overcome this limitation, Increasing voltage but would shorten the life of components or change out the finals to MOSFETs.
Sometimes the electrolytic capacitors age to a point where they bleed off voltage, especially in the AM power section and less common is the ceramic capacitors in the output tank can lose their dielectric and partially short internally, another voltage loss. Older units used Tantalum capacitors and these can age to a near shorted state.
If I am not mistaken, the 2000GTL is about 20 plus years old now....
73 mechanic
