Could these pops possibly be dropouts? If so you would see all green LEDs go off and switch to Red on the RF ladder on the receiver.
I suspect the pops are not caused by RF interference. Do they occur randomly across all five systems or just in a single system? Just double checking that you are using the factory mic capsules and power supplies, correct? What firmware version are you running (both TX & Rx)?
If it is just in one system there may be a hardware failure in that system. If in all systems that probably rule that out as it would be highly unlikely to have 5 defective units. You should also check for mechanical issues. Possible you have a transmitter where the mic capsule is not making solid contact with the transmitter body. Check the pogo pins. You also need to rule out that the pop is being induced into the output cables. When the pops occur can you see them in the LED meters on the receivers?
As far as scanning ... the scanner only indicates RF2 channel availability and can't tell you anything relevant about RF1 channel availability. In RF1 it doesn't really matter in a practical sense as long as you are not very near any wi-fi access points or transmitters.
Adding P180 antennas would probably be a big advantage in your situation. The first thing is that if you use the whip antennas in the middle of your rack they will only be a few feet off the ground. That's usually a bad thing for line of sight. Using paddles will allow you to get them 6-8 feet up in the air where they should have an unobstructed path. also they have a "dead side" and you can use that to your advantage by pointing the dead side at known interferers (WAPS). Also the diversity aspect of any wireless receivers works much better when the distance between antennas is 6 wavelengths apart (or more). The way your's are using the half rack spacing is only one wavelength.
Hello Don, thanks for the quick response.
All factory capsules, all factory power plugs, as you can see in the attached images. 2 whip antennas were separated by 19" at top of the rack 4' above ground. It is at the side of the stage, so line-of-sight is not the best. I thought by putting receivers by the stage would favorably improve the distance for Line 6 systems vs. WiFi APs. Apparently not good enough.
The pops happen random from multiple systems, I am not sure all 5, but sometimes the pops happen when only 1 is on, and sometimes it happens when that one is off and others are on. Sometimes it doesn't happen for 10 minutes; sometimes the same mic pops more than once a minute. The randomness makes it really hard to replicate the error to diagnose. I wasn't at a spot where I can see receiver LEDs, since I was either on stage playing, or at FOH 100 ft back. Unfortunately I am not near that venue to troubleshoot. This only happens at large hotels.
I can assure it is not the mic capsules loose. When it is sitting on a stand in front of podium with keynote speaking to it, no touching at all. The capsules are all fairly tight.
Power was very stable, supplied by the Middle Atlantic power distribution unit, which also powered the Shure UR system operating in 590 MHz, which was rock solid through the convention, even though its antenna did not have as good line-of-sight as the Line 6 antenna.
I used smartphone scanning app Wifi Analyzer on Android. It picked up all published WiFi sources. Most of the WiFi space was occupied with fairly strong signals in most channels by the stage. Just curious, does WiFi "frame bursting" have anything to do with the pop I'm hearing on Line 6 systems?
I thought in RF1 mode, the systems are supposed to "lock in", so will still operate flawlessly through interference. Is this a feature available with newer firmware? Or when the WiFi environment is so bad that all 3 or 4 carrier frequencies of a RF1 system go out simultaneously?
Sounds like I am not in a game of finding enough clear channels, but forcing my way through crowded bands. If I were to add P180s, would I need the AD8 to boost the antenna, or does the XD-V70 receiver provide enough power for 2 P180s?