I quit reading unread posts for a while because EEVblog was eating too much time. I've only skimmed this thread, so please forgive me if I restate something already said.
I have 2 LED lamps in a 4 ft fluorescent fixture. This produced a tremendous amount if EMI until I added a large Corcom filter and 1/8th" hardware cloth screen.
I have also put HW cloth over the openings of my Z400 workstations. But still more to do.
Because of the staggering amount of EMI produced by my Instek MSO2024EA SMPS, I made a custom power cable for all my instruments which is fully shielded with MX and EMT all the way to the back of the instruments. I posted about the project some time ago with photos. I also bought, but have not installed a 2.5 KVA isolation transformer.
The Instek GDS-2000E line can be hacked to enable the spectrum analyzer app for the MDO-2000E variant. This is a very useful tool and far more sensitive than my 8560A. Above the 200 MHz maximum BW of the GDS-2000E, an SDR is the cheapest solution. A SDRplay RSP2 will give a lot more dynamic range than and RTL-SDR, but also at 8x the price.
Most of the noise of concern is below 1 MHz. There is a lot of it, from a variety of sources.
Even without a good FFT on a scope, a small wire loop from tip to ground on a scope probe is very useful for locating nearby EMI sources. A proper H field probe of large dimension is needed to locate more distant sources, but easy to make from solid shield RG402.
I went on a rather extreme TEA binge and now have three 5ft stacks of T&M kit on mover's dollies in my dining room for lack of space to set it up. My current space is part of a 7' x 10' closet. In order to have the displays for SA, VNA, scopes, etc at a comfortable level I need 16' of bench, so I am building a 12' x 16' room in my shop which will be lined on all faces with 28-30 gauge galvanized steel sheet soldered at the seams. I am told by a retired Tempest engineer that should provide about 120 dB of shielding. The room will have its own HVAC zone on a 3 zone mini-split system. Counting the cost of the extra HVAC zone, I expect that will run about $3K. The steel sheet alone is about $800 for a 16' x 12' x 8' room.
A less costly approach and more easily moved solution would be to build desktop size steel box to hold equipment and DUT and extract the data via an optoisolated link. Galvanized wire screen soldered to the steel sheet will allow airflow while blocking EMI.
To get from the 60 Mhz limit of an F***Tech to 120 MHz try one of these:
https://www.ebay.com/itm/NEW-1-200MHz-radio-frequency-multiplier-module/112082979199I just saw them a couple of days ago and bought a couple. Above that an ADF4351 module from ebay will serve to 4.4 GHz with harmonics much higher.
This book:
https://www.amazon.com/Electromagnetic-Compatibility-Engineering-Henry-Ott/dp/0470189304has a great deal of useful information. however, the author writes poorly in passive voice, so it is difficult reading.
Finally, if you live near a high power broadcast tower, move. I lived about a mile from a 250 KW FM tower and it drove me nuts. Even a few inches of wire picked up strong EMI. I built a 120 dB DC audio amplifier. With a speaker hooked to the output I could listen to the FM station merely by holding my finger 1/2" from the input. Driving a 3" speaker it was loud enough to hear in the next room.
That experience left me with a very strong desire for a quiet room in which to work.
Have Fun!
Reg