When I drive my LK-500ZA on 160, I get only 100 mA of grid current, while on 40, I get 200 mA grid current. The VSWR and the drive is the same on both bands...so where is the power going? Could I be driving some lossy ferrites inside the amp on 160??
thanks, Don W4JVE
WHERE IS THE POWER GOING?
I am not familiar with your amplifier, so I would have to have some more information. What configuration is the amplifier? Grounded Grid, Grounded Cathode, Class B, C ? What tube(s) does it use? What type of matching is used between exciter ( rig ) and amp? How much power are you driving the amp with, and how much power is the amp feeding to the load?
You should hook the system up to a dummy load to do all this testing. The different impedances of your antennas would be one very important variable. You really don't want to be throwing carriers out on the air when trying to do all this measureing. Also, the output power of the exciter itself would be another variable. You say the VSWR and the drive are the same on both bands, but how are you verifying this? What is the output power of the exciter on each band, into a 50 ohm dummy load?
I suspect that the difference in grid current ( which is only a rough indication of efficency ) is certainly related to the amplifier tube's characteristic frequency response as well as the configuration of the amplifier itself ( especially the input circuitry )
Can't be much further help unless you give us more info!
73 from Jim AG3Y
You should hook the system up to a dummy load to do all this testing. The different impedances of your antennas would be one very important variable. You really don't want to be throwing carriers out on the air when trying to do all this measureing. Also, the output power of the exciter itself would be another variable. You say the VSWR and the drive are the same on both bands, but how are you verifying this? What is the output power of the exciter on each band, into a 50 ohm dummy load?
I suspect that the difference in grid current ( which is only a rough indication of efficency ) is certainly related to the amplifier tube's characteristic frequency response as well as the configuration of the amplifier itself ( especially the input circuitry )
Can't be much further help unless you give us more info!
73 from Jim AG3Y