you should consider adding an AGC bypass switch, redesigning the output stage of your iAM for Class E mode (if possible) and adding a +4dbu professional input to your iAM. maybe a redesign of the external ATU to make it more efficient in terms of power transfer to the antenna with maybe an air coil / cap design like the procaster or toroid / cap design like the rangemaster.
maybe one of the forum posters here who is on good terms with dan (calling MRAM) can point him to this post or otherwise suggest these modifications to him.
it should be easy to add +4dbu to the iAM and redesign the ATU, not sure about modifying it for class E maybe Phil B can chime in on that one and better explain modifications for going from the class "C" of the iAM to Class "E" like the amt5k.
these mods would most certainly make an already great little tx system even better.
the iAM now modulates to +125% but it's ATU and Final output stage is still very inefficient like most certified part 15 am transmitters and there is room for improvement there.
maybe since the ATU when attached is considered the Final RF stage the iAM can be configured to bump up to 100mW TPO input to the ATU (final RF Stage) when ATU mode is selected. and when switched to the internal wire antenna can be 100mW input to the final transistor. since when Selected the ATU is the Final it should be legal to put 100mW input to the Final Stage being the ATU not the final transistor in this case. gotta squeeze every little legal drop of Milliwatts we can get out of these things. Efficiency, Efficiency, Efficiency. that is the nam,e of the game. we are limited to 100mW and a 3m antenna and have to get every last drop of efficiency out of the final RF stage and the antenna tuning design.
this already good little transmitter system has some greater potential if radio systems will consider the input from the part 15 community and make suggested modifications if technically and legally possible.
right now i am torn between the iAM because of it's unique system design and fcc certification and my SSTRAN amt5000 because of it's pro inputs, pos. modulation capabilities, and class E output stage coupled to an efficient ATU design but it's only drawback is it is not FCC certified which means more scrutiny from an inspecting agent and some agents take a dim view of kits while others don't.
not sure how denver FCC which i live only 10 minutes drive from would view a kit transmitter.
presently the iAM with it's Class "C" mode applies 60mW to the External ATU connector and the AM double loopstick tuning design of the External ATU is very inefficient. if the mode was changed to class "E" 90mW would amke it to the RF connector and if a Efficient ATU design were employed then more of that power would make it to the 3m antenna which would garner greater range. my tests showed that under similar circumstances the SSTRAN 5k generated a higher F/S than the rangemaster or TH5/ATU combo when mounted in the same circumstances.
i Used a FIM to tune the SSTRAN to resonance though and didn't follow phils instructions on the antenna tuning portion and then proceded to follow phils table to tune for 100mW input. under those conditions the SSTRAN 5k ran rings around competing transmitters that i tested it against for the same installation location.
these are just some thoughts. i am all for pushing the legal/technical limits of part 15 without breaking them and remaining FCC legal.
that leaves us with improving efficiency of the antenna and RF stage.
just imagine an iAM runnning class E mode at +125% using an efficient ATU unit with it's unique system design. it just might blow away all other part 15 certified transmitters out there in terms of performance.
i know in reality i can wish in one hand and crap in the other but i can certainly dream about it.
in terms of audio quality the amt5k, rangemaster rev. b, and the iAM all has similar audo. raw peak F/S (i own a calibrated FIM) the SSTRAN blew them all away.