I guess some more detailed information may be in order. Our wireless
system is broken up into multiple racks to make it easy for us to accommodate a wide range of events in multiple spaces simultaneously (we're a small high school, so we often have a need for a large
system set up in the
auditorium while simultaneously needing 8-12 additional channels available for use in the gym, outside, or elsewhere). I'm the TD and my primary background is in scenic with lighting a distant second, so audio is very much a
tertiary skill for me. That being said, we hire in very good audio engineers with strong RF backgrounds who have also been mystified by some of the issues we've faced, and have helped me to quickly develop my skills over the last few years. I also have an RF Explorer that I use to
idiot-check what I'm seeing with the RF receivers, and it does show a significant noise floor above 550 MHz (perhaps due to the proximity of Mt. Wilson, as pointed out by FMEng above).
Rack 1- 2x
Sennheiser ASA 1 distros with 8x EM 300-500 G4 receivers in AW+. These are wired in accordance with
Sennheiser's diagrams, so Antenna A feeds into the first
distro and cascades into the second, Antenna B is into the second
distro and cascades into the first, so each receiver is getting 1 antenna without a cascade and 1 antenna with a cascade. This rack has an 8-port
network switch for these receivers to communicate with one another. I've used this rack by itself in the gym with A2003 paddles and seen my scans in the receivers spit back very few open frequencies, then
switch to
whip antennas (outside the rack) or 1031 paddles and seen my available frequencies increase significantly (this is scanning with no transmitters on). As FMEng pointed out above, the difference has significantly increased since the
DTV repack.
Rack 2- 2x RF
Venue Distro4s with 2x
Shure ULXD4Q G50, 2x ULXD4D G50, 1x ULXD4Q H50. These are wired similarly to above, with the primary antenna inputs each going to one
distro and cascading to the other. We are not currently utilizing any of the cascade outputs on the ULXD units. The 3 extra outputs on the distros go to
BNC couplers on the rear of the rack to
daisy chain to other distros when we need to put together a large
system (Example- antennas A and B go into Rack 2, then are cascaded to Rack 1 and 3 to give us a max of 28 channels for our musical production). I just built this rack last week so I haven't had a chance to test it yet with our antennas. It has a 16-port
network switch for these receivers to communicate with one another and to connect to our mixers via Dante.
Rack 3- 1x RF
Venue Distro4 with 4x
Sennheiser EM300 G3 receivers in A band, also an 8-port
network switch for frequency coordination. This rack gets used either on its own for smaller events or hooked up to Rack 2 as in the example above.
Rack 4- 1x RF
Venue Distro4 with 4x
Sennheiser EM100 G3 receivers in A1 band. This rack generally gets used on its own and is my go-to rack for smaller setups in the gym. If it's used in conjunction with Rack 1 above, I use the receivers in rack 1 to coordinate frequencies between the two racks, and use the Distro4 in this rack to cascade into the
Sennheiser ASA 1 to feed the Rack 1 receivers.
I generally use the receivers to scan and coordinate frequencies for smaller events, and WWB (or possibly WSM when we were just using
Sennheiser, can't remember) networked with the receivers to coordinate frequencies for our musical production each year, and 1 or two secondary events per year if we're doing something special. Generally coordinating in the receivers is fine if I'm sticking with one range (or an overlapping range, like AW+ with A1 or A in the
Sennheiser world), but we'll likely use WWB a lot more often now that we're mixing manufacturers as well as ranges with the larger events. When coordinating in the rack, I try to keep the
squelch set as low as possible (under 15 db usually works ok) and still get enough channels for whatever event we're doing.
It's interesting to hear about the differences between the
Sennheiser and
Shure gear when it comes to the way they treat antennas. Given that we've observed this behavior while solely using
Sennheiser receivers and antennas up to this
point, I doubt that the behavior is due to that difference. Similarly, I doubt it's anything the RF
Venue distros are doing with the
Sennheiser receivers as we're seeing the same behavior with the
Sennheiser ASA 1s.
When we were setting up the musical production in 2020, we did some simple tests.
Test 1- Hook up the
system (rack organization was different as we did not yet have the
Shure units, but the connections were essentially the same) and scan in WWB/WSM with the A2003
paddle antennas in position on either side of the
stage just in front of the
proscenium (we had a pretty sizable
thrust, so this position should have given us good coverage).
Result: very few open frequencies and tons of RF interference across the bands, with no available channels in the G band.
Test 2- swap out the paddles for 1/2 wave whips and
BNC couplers (we didn't have the 1031s at this
point, I bought those partially because of this experience) and scan in WWB/WSM.
Result: significantly more open frequencies and noticeably lower RF noise across the useful range
Test 3- unplug the long cable runs from the
system, use a shorter 50
ohm BNC cable directly connected to one A2003
paddle antenna, and walk around the space pointing the antenna in different directions.
Result: Noticed a massive difference in RF signal at the receivers between the antenna being pointed at the
ground vs. pointed towards the
stage, especially from
stage left (antenna pointing north from our location, which is West Hills zip code 91307. Looking on a map, this is not directly pointed toward Mt. Wilson, though now that I'm aware of that location in our vicinity I'll be more attuned to how it may affect us when it comes to antenna placement). Again, all of this testing was with none of our transmitters turned on. After seeing this we decided to just use the 1/2 wave whips, which for the most part worked fine for the production, except for the limited RF dropouts we experienced.
Hopefully that helps answer some of the questions above. I can take some photos of the racks while I'm at work tomorrow if that could be useful, and I'm waiting to hear back on getting the scans from the last production and from a month ago. My next step is probably to hook the new rack into the
system and run the same tests we ran last year and see if we get the same kind of results.
