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

RF coordination simultaneous example using IAS and Workbench

<< < (2/4) > >>

Henry Cohen:

--- Quote from: Jens Palm Bacher on September 04, 2015, 02:43:30 am ---Well you could if the specs showed the intermodulation attenuation  etc. It is clear that a Sennheiser 5212 transitter in "low intermod" mode will have better specs than a cheap Shure unit, but it is not easy to read from the spec sheet.
--- End quote ---

Whereas it would be nice to know the IM suppression number, it's really kind of irrelevant: Whereas one device (the transmitter) may not be producing the IM product, another device might be; the preamp in the antenna, the multi-coupler or the receiver front end. The IM software programs are merely pointing out the math of potentially problematic frequencies and in no way negates the need for a "war game" or other walk test.

Pete Erskine:

--- Quote from: peter dakin on September 05, 2015, 07:08:38 am ---Can I ask what device your using for scans, does this pump out a file format compatible with WW6 or do you need to convert it?

--- End quote ---

Scans are from TTI.  More detail on how I did it can be found at http://www.bestaudio.com/spectrum-analyzer-setups

Normal TTI scans can be used in WB as long as you edit out the Headers using a text file.  All of the scans listed on my website have the headers removed and can be imported into either IAS and WB.

Jason Glass:

--- Quote from: Henry Cohen on September 05, 2015, 08:12:24 pm ---Whereas it would be nice to know the IM suppression number, it's really kind of irrelevant: Whereas one device (the transmitter) may not be producing the IM product, another device might be; the preamp in the antenna, the multi-coupler or the receiver front end. The IM software programs are merely pointing out the math of potentially problematic frequencies and in no way negates the need for a "war game" or other walk test.

--- End quote ---

With this always in mind, I often adjust the intermod bypass window settings in IAS to generate more usable frequencies in large channel-count coordinations, gradually reducing the bypass bandwidths as required.  It's less risky than completely abandoning triple-beat calculations.  The risk can be further mitigated by setting and adhering to a strict band plan, where like-type equipment is assigned to specific areas of spectrum, with large guard bands between the different types.  This technique is also a reason that I try to stay away from broadband RX antenna amplifiers if possible and use passive higher gain antennas on the front end.

Henry Cohen:

--- Quote from: Jason Glass on September 05, 2015, 11:31:18 pm ---This is technique is also a reason that I try to stay away from broadband RX antenna amplifiers if possible and use passive higher gain antennas on the front end.
--- End quote ---

I can't stress enough the validity of this statement. Amplified antennas and other in line preamps cause far more problems than they solve 99% of the time. Their use has limited applications, and not has a band-aid for other inadequate system implementations.

Neil White:

--- Quote from: Henry Cohen on September 06, 2015, 09:15:51 am ---I can't stress enough the validity of this statement. Amplified antennas and other in line preamps cause far more problems than they solve 99% of the time. Their use has limited applications, and not has a band-aid for other inadequate system implementations.

--- End quote ---

It is interesting that some manufacturers seem to market active antenna as their recommended product for radio mic receive antenna. Is the correct application to make up for cable losses, not to compensate for rf path loss?

Are there any rules of thumb for how far to keep transmit and receive frequencies separated by in a spectrum band plan?

Navigation

[0] Message Index

[#] Next page

[*] Previous page

Go to full version