This is my updated config, all bundled together using industrial strength velcro/wiring wraps, located in the kitchen next to patio door, facing due west. Any thoughts?

You will get better readings when right up against the filter. I cut my grill so the geiger counter touches the filter. If you do not want to damage the grill, just remove it.

Ok, thx!

On your geiger counter the GM tube is on the bottom of the geiger counter so you want it near most of the uncovered filter.

Now it is right up against the filter. Trimmed a hole to fit the GMC as suggested thx!

I own that same model of purifier as you know.

I took the black mesh out.

Try turning you unit upside down. It will put the GM tube near more of the open filter which is where the radiation will be trapped. Also if you considered moving it outside you want it upside down anyway so water does not get in the data/power hole.

I turned it upside down late last night, cut a hole in the black mesh as well so it is right up against hepa filter. I also placed my other GMC300 right next to the filter/GMC/PI and notice the differential in readings.

See what I mean, it makes a difference

From the picture it looks like you have the ion switch on.

While I have not done any tests with it on vs. off, I decided to leave it off to rule out any possible false readings caused by having it on.

If you own a basement, you will notice with that setup your basement readings will likely be high mostly due to radon. If you have it connected to NETC while in your basement please delete you location so your station will not appear on the public map and cause alarm with the higher readings.

A quick comparison test(s), without versus with a new air filter installed, with the ion switch on or off should eliminate whether the ion switch itself is putting out enough EMI to affect the Geiger Counter measurement, no? If such testing indicates it does not, then it probably makes sense to leave it on if it accentuates particulate collection in the filter.

The ion feature is said to attract more dust particles. Radiation is naturally attracted to dust particles. I only want that natural buildup. My reasoning has nothing to do with EMF. The GMC models detect ionizing radiation, not EMF electromagnetic radiation.

This is a really good collection of radiation information:

https://www.netc.com/bb/viewtopic.php?f=7&t=364