Part 15 operation on frequencies 1710KHz and above requires field strength measurements.
From 1705KHz to 30MHz a measurement at a distance of 30 meters is required;
Part 15 operation on frequencies 1710KHz and above requires field strength measurements.
From 1705KHz to 30MHz a measurement at a distance of 30 meters is required;
FM band must be measured at a distance of 3 meters.
What is the brand name and description of the device needed for making such low power field strength measurements?
Some say that's one of the reasons the "3 meter/100mW" rule was adopted for the AM band (pre-expanded band of 550 KHz - 1610 KHz)
Certified, around $3,000
http://www.emctd.com
Not certified, around $300
http://www.detectortechnologies.com/store/detail.aspx?ID=28
And it is said that the certified meter should be operated by an engineer for best results. Bigger cities might have service firms that could be hired for this, otherwise, I don't know.
That's far more than I knew before. Appreciate it.
Neither of the field strength meters mentioned have enough sensitivity to be useful for Part 15. To get a certified instrument with enough sensitivity, you have to spend a lot more bucks.
Hello Ermi Roos
Then what are those more expensive devices by brand name and description? If I'm ever rich I'd tinker with that kind of dis-proportional measurement.
The FCC does not have that either. Don't let the trolls out here scare you. Most of the time the FCC won't even pick up the gas for the guys and gals that work for them. The FCC uses for AM, that same FSM that's been used for years. If you need references, I can supply them 🙂
Here's something newer: http://www.ztechnology.com/pdf/AMTesting.pdf
These guys are lookin at 30,000uV/M on AM rather than your piss weak AM Part 15 signal.
This instrument may be the one that was neant when referring to the "old" equipment used by the FCC. It is still available, and has a sensitivity of 10 uV/m, which is nominally enough for measuring Section 15.209 signal levels. Unfortunately, the 15.209 (or 15.223) limits are usually lower than the AM BCB background noise in urban areas.
The price is more than twice that of the $3000 instrument mentioned previously. This instrument will not work at FM frequencies.
Added Note:
By the way, you may be wondering what good a field strength meter is if it is not capable of measuring field strength, not because of a lack of sensitivity, but because of excessive background noise. The real question is: what good are transmitters that comply with 15.209, 15.221, or 15.223 (for 1710 kHz)? Through my own experiments with such devices, I found that the range in an urban area is 15-20 feet. If the FCC were to increase these field strength limits by a factor of 10 (something that is not likely to happen), the range would be increased to about 100 feet, which is approximately the distance at which the field strength measurements are supposed to be made.