Drive to Amplifier

[Recon]

:cough: :cough:
...I have radios older than you.

FYI: I purchased the radio in 2002 and it has been in storage since six months after I purchased it. My DOB is 1948 and I started using CB since 1966.

 

[Recon]

"Tuned to 7 watts"? I wonder if the radio still has a clean signal. It must have been tuned to "Ghost Watts" that are up in the 50MHz range.

When I used the radio in 2002 as a base unit, I never received any complaints about spill-over. I recently unpacked it and I am currently using it again as a base unit with a I-MAX 2000 antenna and it is working fine. I did not trust the onboard meter and I now have a MFJ-870 meter which indicates 7 watts on dead key on AM. This is the first time I have seen the RF output power level.

 

[kopcicle]

 

[Shadetree Mechanic]

They can be turned up to produce a 7 Watts carrier, I wouldn't expect the radio to be able to reach 100% modulation from there.

That's a good point. Because the amplifier is not linear, the radio will need a low dead key because the max peak output is what it is. The radio will need more "swing" to get 100% modulation out of the amp. I did not completely understand this until I got a scope and played around with the dead key adjustment. With the radio dead keying 7w, the amplifier output will be lucky to get 30% modulation because the dead key is taking up the headroom.

 

[LeapFrog]

That's a good point. Because the amplifier is not linear, the radio will need a low dead key because the max peak output is what it is. The radio will need more "swing" to get 100% modulation out of the amp. I did not completely understand this until I got a scope and played around with the dead key adjustment. With the radio dead keying 7w, the amplifier output will be lucky to get 30% modulation because the dead key is taking up the headroom.

The audio amp in the radio can only do so much without creating excessive THD %, the radio itself will struggle to produce anything near 100% modulation with sinusoidal output at such high carrier power.

Watch the 'scope while sampling only the radio and play with the carrier level.