Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums > Wireless and Communications
IEM FFT scan
Don Boomer:
When you are measuring is only one radio turned on or multiple radios active?
Cliff Fuller:
--- Quote from: Don Boomer on February 01, 2023, 04:51:29 PM ---When you are measuring is only one radio turned on or multiple radios active?
--- End quote ---
Only one. I don't believe IM is a factor, although there are numerous video displays and other assorted devices in the environment - a gambling casino.
I don't notice any audio issues but thought it looked strange especially with one system (504 MHz) displaying what I think I should be seeing. There have been a couple of receivers that will not pass audio, nothing heard nor does the blue light indicator come up on the receiver (if you are familiar with the PSM 900 systems). I've checked the receivers against different transmitters and vice-versa, they just don't function. They are on the way to the "doctor".
Thanks for reading and offering assistance! :-)
Russell Ault:
--- Quote from: Cliff Fuller on February 01, 2023, 05:16:45 PM ---Only one. I don't believe IM is a factor, although there are numerous video displays and other assorted devices in the environment - a gambling casino. {...}
--- End quote ---
Given the possibility for non-IEM RF noise, have you tried running a scan with none of the transmitters on, just to see what your baseline noise levels look like?
-Russ
Henry Cohen:
--- Quote from: Cliff Fuller on January 31, 2023, 10:03:29 PM ---Good evening, Henry.
I'll do my best to answer your questions. Prefacing those answers, I'm using an RTL-SDR USB dongle to do the scans and using an application called "GQRX" as the tuner. I will apologize that I'm not an RF engineer so I'm having a bit of a challenge translating your questions.
Both images were grabbed under the same circumstances. No other transmitters were powered on at the time of measurement. I think the answers are as follows:
span: 2.5 MHz
RBW: 293.0 Hz
VBW: 2.5 Mhz
Window type: hamming
Detector: ?
Averaging: 85%
Thanks for the look and any insight given.
--- End quote ---
Detector is usually peak or average. Whereas I might quibble with some of the parameters, the fact that both measurements used identical parameters makes that issue almost inconsequential. With that said:
- Are you measuring over the air, or direct out of the transmitters?
- Have you done a baseline scan to see the environmental RF noise floor (or at least the two TV channels 16 & 19)?
- If you swap frequencies on the two transmitters, do the resultant spectral displays on the SA stay with the transmitter or the frequencies?
Cliff Fuller:
--- Quote from: Henry Cohen on February 01, 2023, 05:56:24 PM ---Detector is usually peak or average. Whereas I might quibble with some of the parameters, the fact that both measurements used identical parameters makes that issue almost inconsequential. With that said:
- Are you measuring over the air, or direct out of the transmitters?
- Have you done a baseline scan to see the environmental RF noise floor (or at least the two TV channels 16 & 19)?
- If you swap frequencies on the two transmitters, do the resultant spectral displays on the SA stay with the transmitter or the frequencies?
--- End quote ---
I am measuring over the air, I have measured using the antennas separated from the transmitters and I see no anomalies. I have not measured the outputs directly.
I have done a baseline, in this locality neither 16 nor 19 are of concern (channel 18 is however).
I have not measured a swap of the transmitters, however, 4 of the 6 transmitters show similar "noise". Any one transmitter (except 504 MHz) throws similar noise throughout the spectrum.
Attached are images of pre-transmitter and post. I have imported the scans into WWB to give us something a little more familiar to look at. :-)
Thanks, Henry...
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version