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[darren mcmahon]

Hi (again) guys

Just courting opinion from some RF gurus here if possible.

I have a fairly remote site with 60 or so rf channels on both shure and sennheiser units. I have spent some time coordinating of the site in RF  terms, but not in advance unfortunately as I found out what I was doing when I got there. Hence I have limited tools available to me.

As I said I am courting opinion here really but my problem here is trying to eliminate one or two things which are affecting RF signal when we go live. The installation has two paddles for shure and an additional 2 for Sennheiser (routed via a few DA's, all correct ranges) on 20 & 30m 50 ohm low loss cable. I would say that for at least 2-3 meters of the runs back to the receivers the cables run parallel to some lighting (at about 10cm) there isn't a lot of dimmed power but it is there (2 or 3 soca's). It is difficult to re route but at some point I will try and bypass. In the meantime I would welcome any expertise on just how badly the signal would be affected by this when the lighting kicks in (mainly source 4's and DMX'd LED's)..

I only lose RF level from one paddle at a time as they are place at opposite sides of the stage, occasionally this presents a problem I would obviously like to eliminate.

I have shure workbench 6 running but only currently on 6 of the 15 shure units in the system. I have scanned what I can using WW6 and am working mainly by manufacturers frequency charts. I don't have access to windows so I am unable (at this point) to use a theoretical intermod calc as I can't seem to find one that works on a mac.

Other than that we are doing well

[Keith Broughton]

Hi (again) guys

Just courting opinion from some RF gurus here if possible.

I have a fairly remote site with 60 or so rf channels on both shure and sennheiser units. I have spent some time coordinating of the site in RF  terms, but not in advance unfortunately as I found out what I was doing when I got there. Hence I have limited tools available to me.

As I said I am courting opinion here really but my problem here is trying to eliminate one or two things which are affecting RF signal when we go live. The installation has two paddles for shure and an additional 2 for Sennheiser (routed via a few DA's, all correct ranges) on 20 & 30m 50 ohm low loss cable. I would say that for at least 2-3 meters of the runs back to the receivers the cables run parallel to some lighting (at about 10cm) there isn't a lot of dimmed power but it is there (2 or 3 soca's). It is difficult to re route but at some point I will try and bypass. In the meantime I would welcome any expertise on just how badly the signal would be affected by this when the lighting kicks in (mainly source 4's and DMX'd LED's)..

I only lose RF level from one paddle at a time as they are place at opposite sides of the stage, occasionally this presents a problem I would obviously like to eliminate.

I have shure workbench 6 running but only currently on 6 of the 15 shure units in the system. I have scanned what I can using WW6 and am working mainly by manufacturers frequency charts. I don't have access to windows so I am unable (at this point) to use a theoretical intermod calc as I can't seem to find one that works on a mac.

Other than that we are doing well

A pair of paddles , for a diversity system, should be treated as one "receiver" zone.
If they are too far apart, they act as single antennas and not as a diversity pair.
The result is much as you describe.
Try having both antennas on the same side of the stage and get them well up in the air and pointing down to the surface.
Also, try to use shorter antenna cables and keep them close to the same length.

[darren mcmahon]

Hi Keith,

Thanks for the reply. The 'Stage' here is a somewhat loose term but I take your point. Now you mention it I am more used to having paddles either side of a pros arch pointing the same way. The result of my re routing one of the paddles cable has been that I now have paddles about 13m apart pointing roughly the same direction. They are more at the rear on stage left but there is an improvement as you will have no doubt expected. The Radio room is situated in a terribly inconvenient place so this rather limits what I can do in terms of keeping cable runs short but I understand what you are saying and will endeavour to improve things a little further. We are still testing well unfortunately so it is frustrating to get the odd issue when we go live. We are in the Middle east and there is something of a cultural education on both sides when it comes to schedules and rehearsing however, as I said, things are improving.

Thanks again for your time.

[Mac Kerr]

If they are too far apart, they act as single antennas and not as a diversity pair.

In what way does this matter? Two antennas covering the same area are a diversity pair. It does not matter how far apart they are if the coverage is the same. Two antennas covering completely different areas are not. Two antennas covering largely the same area, but spread for complete coverage of the performance area are still largely diversity, but with better coverage, that might be better than removing coverage from the larger area to make sure they covered exactly the same area.

Mac

[Jason Glass]

I what way does this matter? Two antennas covering the same area are a diversity pair. It does not matter how far apart they are if the coverage is the same. Two antennas covering completely different areas are not. Two antennas covering largely the same area, but spread for complete coverage of the performance area are still largely diversity, but with better coverage, that might be better than removing coverage from the larger area to make sure they covered exactly the same area.

Mac

+1

The attached graphics show two different but equally effective diversity coverage schemes.  The antenna polar patterns shown represent PWS helicals, but illustrate the point for using just about any commonly available directional antennas.

[darren mcmahon]

Thanks guys,

That's pretty much what I understood the situation to be, initially I had them in config a and now we have config b, my situation remains (we still get the occasional RF level bounce) but that element of doubt (as well as others earlier mentioned) has now been removed.

Much appreciated..

[Keith Broughton]

In what way does this matter?
Mac

For example, if you are too far away from the A antenna and only the B is receiving , you have lost the diversity capability at that side of the stage.
You can have RF issues that should cause the diversity to switch but as the A antenna is too far away, the receiver won't see a "better" signal so the diversity benefit is lost.

Now this depends on the size of the "stage" but I have seen people try to cover much too large a space with just 2 antennas and loose diversity altogether.

[Mac Kerr]

For example, if you are too far away from the A antenna and only the B is receiving , you have lost the diversity capability at that side of the stage.
You can have RF issues that should cause the diversity to switch but as the A antenna is too far away, the receiver won't see a "better" signal so the diversity benefit is lost.

Now this depends on the size of the "stage" but I have seen people try to cover much too large a space with just 2 antennas and loose diversity altogether.

See Jason's and my explanation above.

Mac

[Keith Broughton]

See Jason's and my explanation above.

Mac

Understood. Very clear graphic explanation.

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