The AM Forum

 Hello to all.
Well I have a question. The viking Valiant
has audio when I transmit. I can hear my
voice coming from the valiant. I have the
audio set at 3 with 75 watts, so not
to over drive the valiant. It does this
on all the bands. Does anyone have an idea,
why it does this.? I can use some help.

Thanks.

I am not sure I properly understood your question but if you only have the transmitter loaded to 75 watts (is that input or output) it is underloaded throwing off the impedance match between the modulator and final.  Load the final to an indicated 330 mils with 8 mils of grid drive.  Make sure the clipper control is in the full CLOCKWISE position.  Now advance the audio control until the meter (set to read modulator current) reads around 160-170 mils on voice peaks.

It is normal to hear some "talk back" from the modulation transformer in many rigs but in my experience it has not been very loud with a Valiant.  You will notice it if the room is very quiet, otherwise you probably have the audio gain set too high.

Again, make sure you load the Valiant to the rated power on AM.  I have run several Valiant transmitters at the rated AM level with long transmissions and no problems.  The Valiant has some weaker points but the power supply and modulation transformer are well up to the rated power.  If you have the final unloaded it is very easy to over modulate which will cause extremely high voltages to be developed which the mod transformer will not like.

Once you have it loaded properly and the audio gain set, monitor yourself in a receiver and also solicit a report from a fairly close station as to your modulation quality and level.  A scope is a good thing to add to your station as soon as you are able as it is very helpful for setting up an AM transmitter.

 OK WQ9E,
Yes I have had load the valiant to the correct setting.
full power 150watts in 40m and 80m. I do turn it down
a bit just for fun . I'll try your idea thanks for your help.

You will want to get a scope and connect it up to look at the modulation envelope. I cannot consider running a AM rig without that. This will let you see the potential problems before the others start complaining about your signal. This is the most important piece of test equipment you can have for your station. Any cheap 20 MHz scope will do it. The $50 class gear is just fine.
Keith
WA1HZK