Maybe you're at a higher elevation. I think I read you live in the foothills. I think both Tucson and Phoenix have highly directional antennas that only transmit their best strength signal at the glidepath. I've tried Yaesu VX-6R's, radioshack scanners, old radioshack realistic scanners. I can't get tower or approach.
I am DEFINITELY NOT in the glide slope or pattern of either airfields and I have a large hill totally shadowing me from DM. Using 2 Uniden BC-780's plain jane with plain BNC mounted antennas, Yaesu FT-60 stock antenna. Uniden's out perform the HT.
TIA UNICOM............122.950
GROUND..........124.400 MIL...348.600
TOWER............118.300 MIL... 257.800
APPROACH......119.400..125.100..128.500
DM TOWER.....121.800 MIL..253.500
GROUND...118.250 MIL..275.800
Again you are the only person I know who is complaining of "issues" with such difficulty in monitoring aviation traffic in Tucson AND Phoenix. Whatever your problem may be, you'll have to figure that one out. I notice on these forums ( Aircraft monitoring OR Arizona) HAVING not seen anyone from EITHER city complaining of the problems you are experiencing ..I figure if there is a problem someone else would be complaining or asking for help. I don't see it, I don't know.....No one I have talked to the past 2 days have EVER even heard of any " ancient volcano" causing RF interference of any type in Tucson Valley and a Avionics Tech said all FAA voice system communications have NO reported issues.. No aircraft / aircrew complaints. No NOTAM's issued about comm issues at TIA...
Oh well..I explained it in a previous posting AM is quieter and NOT as loud as FM that most people are used listening to and that confuses one when trying to monitor. I am at a loss.
I tried.. sorry I can't be of any assistance.....Good Luck... over and out...