I have had reports of bad audio quality since I have been using the IMAX2000. I suspect some kind of common mode issue that is not present (or at a relative level that causes issue at least) at low power but rears itself to some degree when I use 100W. People have said the audio is fluffy and there is a crackling when I de-key.
I changed a patch lead and magically it cleared up. I tested the old patch lead that was in line for continuity at home and it checks out fine. Even when I was testing and waggling the lead vigorously. So I don't think it was that. Though it does not account for why it cleared up., Maybe PL259 tolerances ? (I solder my own and do them properly). Seems odd that a tested lead should cause such a problem especially when your SWR is reading 1.4:1 throughout.
People keep saying I am over driving the amp. I am putting about 5 watts in. I have my RF output on the radio at 10 'o' clock and my audio meter peaks a S5 that is hardly over driving, if anything it is under driving. I have operated like that for ages so nothing has changed. Unless something is getting screwy in the radio itself it is only a £99.00 radio and it has done a lot of mobile service in and out of my radio box for the last 15 months. I opened the mic and the switch looks clean and dust free.
Odd thing is the same time people saying the audio is rough I am working stations on line of sight 100 miles + away so I don't understand it.
So I suspect there may be a common mode issue with the IMAX2000 but just enough to cause some minor audio problems. There is no question the RX is a bit noisier on my Alinco DR-135 radio I suspect it would be the case on any radio.
I will see what happens when I go out next time. I will try the Gain Master and see if anyone says the audio is rough.
Fact is there will be some common mode on the pole and line using a 5/8 wave without radials. The question is how much and how is it interacting with every other part of your radio system including the obvious one the radio itself or the linear.
I operate different setups (poles, heights, antennas, grounded or not) and QTH's so there are many more variables than base stations which can set and forget, to a degree anyway.
Being static mobile can have its challenges, if you get bored of running the same set up over and over again. I am in this hobby to be the best I can as an operator and a station and that does not mean using 1 set up and resting on your laurels.
I will try and get to the bottom of it.