I've written often enough about the audio system I'm using to drive the 991a. The object of the thing is the same as any processor... to raise the average power levels, and make maximum use of the available power in the transmitter. I'm fairly close to what I want. I'm finding it much easier to bust pileups and make contacts.
Thing is, I'm not really satisfied with the sound of the thing. After working with the external audio proc stack I'm using and experimenting with various settings over the last couple months, and combos of hardware, and the comments I sometimes get, I'm becoming more convinced of something I've suspected since I got this 991a: That being, that the audio you get back through the monitor circuits (and into in my case, my headphones) is not what's on the air, but rather, is tapped from the audio circuits before it goes to the transmitter.
I guess I should have expected this.
Look, for average use that setup is fine, but this isn't what most would consider average use. I'm aiming at a much higher average power level, on the order of 80 watts average for my 100 watt PEP signal, as oppose to the 25w average power we all get without any processing. I'm actually getting that kind of increase,(and the respots I get suggest that the signal on their end s more more powerful) but the amount of on air distortion is rather more than I'd like, and I think more than the average power levels I'm after should require.
It sounds good.... and I mean REALLY good, in my cans, but on air, there's more of a distortion component than I'd like, and since I'm not getting the actual transmitted audio in my headset, it's impossible to find that "crest of the wave" if you will.... that sweet spot where the system is giving what it can with what I consider to be acceptable distortion levels.
Given the density of the audio I'm feeding the 991a, the on board processor and the ALC are both driven somewhat harder than they would be without the outboard proc, and so it makes it even trickier to set up, and even more imperative that you get what's actually on the air. (As an aside, I've even tried running a clipper in mine after the agc/limiter, and then running with the 991 processor disabled. Still cant find the sweet spot because I can't hear what the transmitter is actually doing.)
I'm starting to think I should be using an SDR to monitor the actual on-air signal.. Trouble is, I'm unclear how to do that, since in most setups, the SDR is cut off while the rig is in transmit mode to protect the SDR from overload and burnout. I suppose that some resistance in the SDR's antenna line is called for... but that makes using the thing as a diversity receiver, as well as the transmit monitor a problem.
Obviously, this is going to require a custom solution.
