I should have re-titled the subject for this. Using a ranger or other AM transmitter with a linear amp requires the amplifier be tuned up with full modulation on the ranger with reduced power out of the ranger watching a scope at the output of the amplifier. It does not have enough carrier at full power to properly drive the SB200 and tune it properly.
The easiest/best way to find out how much drive the amplifier needs is to use your rice box first. If you want to run 125 watts carrier out of the SB200 on AM that means you need to tune the amplifier up for 500 watts or a little more output with the load and plate tune controls on the amp peaked for maximum output with a given amount of drive. That drive will be around 80 to 100 watts. Try 80 watts of carrier from the rice box and peak the output of the amp for maximum output. If you can't quite get the 500 watts out increase the drive slightly and re-peak the amplifier tune and load. NOW reduce the drive until you have 125 watts out of the SB200 and MEASURE the drive power required to produce the 125 watts out of the amplifier and DO NOT TOUCH THE TUNING ON THE AMP! The amount of drive that you measured is the amount of carrier you will need from a ranger or other AM rig to drive the amplifier properly. No more no less! If you want to tune up the amp with the ranger driving the amp it needs to be done with full modulation of the ranger and a scope connected to the output of the amplifier. The first thing you need to do is find out how many peak volts on the scope represents 500 watts out of the amplifier. This is done easier with a rice box used as a driver first to establish the 500 watt level on the scope. Once you have that you can connect the ranger as a driver. Tune the amplifier up for maximum peak output, full modulation on the ranger with a tone or voice, watching the scope. Adjust the carrier output of the ranger so that you do not get much over 500 watts peak out of the amplifier. Readjust the tune and load controls on the amplifier for maximum output after each adjustment of the carrier out of the ranger. Always be sure that you are near 100% modulation and not going over on the negative side. Reducing the modulation to zero should yield a carrier right around 125 watts if you tuned everything right. That will allow the modulation peaks to go to 500 watts peak and the amp will be loaded properly. If you don't get 125 watts or near out you haven't tuned up properly. It is very difficult to tune this combination properly as drive is hard to adjust easily. It is much easier to use the rice box first to establish the parameters. Watching the scope on the output of the amplifier should show the modulation peak voltage double what the carrier voltage is on the scope. If it doesn't you haven't tuned up properly. 73 Gary K4FMX ______________________________________________________________ AMRadio mailing list List Home: http://mailman.qth.net/mailman/listinfo/amradio Partner Website: http://www.amfone.net Help: http://mailman.qth.net/mmfaq.html Post: mailto:[email protected]
