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[Andrew Henderson]

Hi all. Are there any negative repercussions to putting a 2.4GHz cardioid paddle (for wireless mic receivers) and a 5GHz omni antenna (for console remote control) on the same mic stand for a live sound event? They could be separated by a few inches horizontally by using a "stereo bar", or by a foot or so vertically by using a clamp-on arm for one of them.

I'm an RF novice, but eager to learn more. When making a decision like this, is possible intermodulation the deciding factor? I read up on IM in a couple of different articles. This one is from a Shure white paper:

The strongest IM products are the two so-called 3rd order products produced by two adjacent transmitters operating at frequency f1 and frequency f2, where f1 is lower than f2. The resulting IM products may be calculated as:
          IM1 = (2 x f1) – f2
          IM2 = (2 x f2) – f1

It seems that with my 2 antennas, depending on the exact frequency, IM1 would be near zero and IM2 would be near 7.5GHz, which are both nowhere near the frequencies I'm operating at. Am I on the right track here?

Antennas in use:
Line 6 P180: http://store.line6.com/p180-antenna-pair.html
L-Com HGV-4958-12U: http://www.l-com.com/tabbeditem_mobi.aspx?id=43208

[Pete Erskine]

Hi all. Are there any negative repercussions to putting a 2.4GHz cardioid paddle (for wireless mic receivers) and a 5GHz omni antenna (for console remote control) on the same mic stand for a live sound event? They could be separated by a few inches horizontally by using a "stereo bar", or by a foot or so vertically by using a clamp-on arm for one of them.

I'm an RF novice, but eager to learn more. When making a decision like this, is possible intermodulation the deciding factor? I read up on IM in a couple of different articles. This one is from a Shure white paper:

It seems that with my 2 antennas, depending on the exact frequency, IM1 would be near zero and IM2 would be near 7.5GHz, which are both nowhere near the frequencies I'm operating at. Am I on the right track here?

Antennas in use:
Line 6 P180: http://store.line6.com/p180-antenna-pair.html
L-Com HGV-4958-12U: http://www.l-com.com/tabbeditem_mobi.aspx?id=43208

One is only for RX.  Therefore there are no IM issues.  Even if they were both TX the IM issues probably would not extend more then a few feet from the antennas.

More importantly will your RX antenna pick up enough of the TX RF to desensitize the reciever and make your mic not work very well?

Try it and see, if there are issues, If possible, separate the RX by at least 2 feet from the TX.

[Andrew Henderson]

Okay, so IM is only a factor with transmitters. I should have picked up on that.

Having TX nearby, even on a different frequency spectrum, can desensitize the RX? So I guess RX don't "ignore" data outside of their own receiving range?

Thanks for the knowledge, Pete.


Sent from my iPhone using Tapatalk

[Tim McCulloch]

Okay, so IM is only a factor with transmitters. I should have picked up on that.

Having TX nearby, even on a different frequency spectrum, can desensitize the RX? So I guess RX don't "ignore" data outside of their own receiving range?

Thanks for the knowledge, Pete.


Sent from my iPhone using Tapatalk

It's not "data", it's RF. 

[Henry Cohen]

Intermodulation products (and the resulting distortion to analog RF systems) is not really a factor in digital systems. The only concern here is receiver desensitization form a spatially or frequency close transmitter (the two are inversely proportional), in this case when the 5GHz WAP is transmitting while the 2.4GHz mic is receiving. Given the frequency separation of more than an octave, a few feet vertical (omni on top), or several feet horizontal, spatial separation will be fine.

One caveat; if the WAP also has a second 2.4GHz radio, make sure it is turned off.

Hi all. Are there any negative repercussions to putting a 2.4GHz cardioid paddle (for wireless mic receivers) and a 5GHz omni antenna (for console remote control) on the same mic stand for a live sound event? They could be separated by a few inches horizontally by using a "stereo bar", or by a foot or so vertically by using a clamp-on arm for one of them.

I'm an RF novice, but eager to learn more. When making a decision like this, is possible intermodulation the deciding factor? I read up on IM in a couple of different articles. This one is from a Shure white paper:

It seems that with my 2 antennas, depending on the exact frequency, IM1 would be near zero and IM2 would be near 7.5GHz, which are both nowhere near the frequencies I'm operating at. Am I on the right track here?

Antennas in use:
Line 6 P180: http://store.line6.com/p180-antenna-pair.html
L-Com HGV-4958-12U: http://www.l-com.com/tabbeditem_mobi.aspx?id=43208

[Andrew Henderson]

It's not "data", it's RF.

I should've said that. I was thinking in terms of someone talking right in my face while I'm trying to listen to someone across the room, and ignoring the information, or "data" coming out of their head.

[Andrew Henderson]

Intermodulation products (and the resulting distortion to analog RF systems) is not really a factor in digital systems. The only concern here is receiver desensitization form a spatially or frequency close transmitter (the two are inversely proportional), in this case when the 5GHz WAP is transmitting while the 2.4GHz mic is receiving. Given the frequency separation of more than an octave, a few feet vertical (omni on top), or several feet horizontal, spatial separation will be fine.

Okay, that sounds reasonable. Would it be best to put the 5GHz omni in the null of (behind) the 2.4GHz cardioid wireless mic antenna?

One caveat; if the WAP also has a second 2.4GHz radio, make sure it is turned off.

Thanks for checking, Henry; I've done exactly that.


Sent from my iPhone using Tapatalk

[Henry Cohen]

Okay, that sounds reasonable. Would it be best to put the 5GHz omni in the null of (behind) the 2.4GHz cardioid wireless mic antenna?

Directly above the panel antenna is also a null. Height will be to your advantage as you move about the venue.

[Tim Weaver]

Not to disrespect some of the most knowledgable rf guys in the biz, but I think you'll be fine.

I did exactly this for a few years and noticed no performance impact on my rx or my wap.  I had a sennheiser passive paddle on top of a straight mic stand. Right underneath that I had a ubiquiti nanostation m5 which is a directional 5ghz wap. It was just clamped to the mic stand within a foot or so of the paddle.

Worked great. Maybe there were measureable problems with the setup, I don't know. In practice it worked fine.

I also had another senn paddle placed upstage a good distance from the downstage paddle. They were a diversity pair for ulxd mics.

[Henry Cohen]

Not to disrespect some of the most knowledgable rf guys in the biz, but I think you'll be fine.

I did exactly this for a few years and noticed no performance impact on my rx or my wap.  I had a sennheiser passive paddle on top of a straight mic stand. Right underneath that I had a ubiquiti nanostation m5 which is a directional 5ghz wap. It was just clamped to the mic stand within a foot or so of the paddle.

Worked great. Maybe there were measureable problems with the setup, I don't know. In practice it worked fine.

Because the spatial separation versus frequency separation (3 octaves) is/was sufficient.

[ProSoundWeb Community]