The AM Forum

GM All:

Still messing with the Apache audio set up--I'm not really satisfied that it is as good as it can be. 

I am feeding an externa mixer/eq/filtering line-in to the mod driver.  bypassing all the clipper, filter, and mic amps in the stock configuration.

I am getting good reports but am seeing downward plate current with even moderate mod levels and same on the wattmeter.

I have checked the "phasing" and have somewhat frequency dependant asymmetry in my voice--output from the whole outboard system is positive asymmetry "up" on the scope. (Light goes on here--I am going to double check by looking at the bench scope vs. the Yaesu monitor scope).

When I observe the RF output, it appears that I am getting negative peak overmod quite below the 100% level--looking like I need to change the phase.

Now...the original input to the TX-1 goes thru 4 triode, resistanc ecouple amps before being applied to the driver.  So this is a net zero phase change.  If I put positive peak phase into the same driver input, it should be proper as the original.

So, here is the question:  On some of the SCC mods that remove one of the audio amps and clipper and feed directly to the driver, people have indicated switching the grids at the driver transformer for phasing....others dont mention this.  SHould I be depending on the orignal circuit to be phased correctly from the driver thru to finals?  Or, should I go ahead and change those leads to try it the other way?

I haven't looked at the leads out of the driver transformer to see if they are identified in some way--if they are not, then I guess it could have gotten built either way.

BTW, levels of mod are good and all looks nice right up to 100% with nice sinusoidal input--

Thanks

Curt