10-Meter Amp - FM Mode?

[W8HDU]

Has anyone worked with a "Baojie BJ-300 Power Amplifier"? (Attached PDF). I purchased it for my mobile, which on 29.6000 FM is only 3.87 watts. I would like to get the TPO up to a point where I can make some contacts when the band opens up. Using a 2 dB gain roof mount.

The docs are somewhat cryptic in that Switch 2 is not documented which position is for "FM". I've not found any clarity in a Google search. The question being: Switch 2, is it "Up" or "Down" for FM?


73 de Fred - W8HDU

 

[K5MPH]

The second switch goes to the bottom its for AM and FM

 

[K5MPH]

 

[W8HDU]

The second switch goes to the bottom its for AM and FM

Up would be which modes? SSB? (Trying to rationalize what it would be used for).

 

[AB5ID]

Up would be which modes? SSB? (Trying to rationalize what it would be used for).

Yes, It will add a delay to the rf sensing relay inside the amplifier so it will not "chatter" during voice pauses when using SSB.

 

[RFI-EMI-GUY]

The switch position does not matter in AM or FM, but it will result in a slight delay of RX on dekey.

The amp is a linear mode, there is no Class C biasing for FM.

 

[merlin]

Looks like the amp works in class C or AB via the center switch.
AM, FM, or DSB with carrier class C is an OK mode.
SSB supressed carrier adds a delay to the keying to prevent chatter
and should also set a bias for the devices for linearity.
This mode is also acceptable for AM and FM.
The schematic shows this is a class C only amplifier so it is not linear and will distort
SSB RF.
Add a diode and selected resistor and put it in class AB. About 120 Ma, no drive.
A typical cheap CB amp. Lucky if you get 150W PEP out of this and it will run hotter.
You might consider a cooling fan and low pass filter.

 

[RFI-EMI-GUY]

I dont see any bias circuitry being switched.

 

[W8HDU]

Thanks for the help on the switch position. Hopefully this helps out with some of the contacts where I was near the noise floor. And I'm praying for another stellar opening on 29.600 MHz like a couple weeks ago.

 

[merlin]

I dont see any bias circuitry being switched.

Note the center tap on the input transformer tied to ground. that makes for zero volt DC bias on the bases of the output devices so this is class C only without modification.