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Author Topic: Need (paid) RF diagnostic help in No VA  (Read 369 times)

Kirby Yarbrough

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Need (paid) RF diagnostic help in No VA
« on: December 09, 2013, 10:58:01 am »

I'm in the northern Virginia area and looking for some help in resolving an RF problem.  I'm happy to pay a reasonable hourly or day rate for competent help.  The gear at issue is all Audio Technica, all in the 600MHz band.

I did a show this past weekend with six RF channels, four in one rack, two in another.  The problems occurred with the two channel set-up, which has ATW-R310b and ATW-R3100b receivers, with an ATW-49SP antenna splitter and a pair of the A3D half wave antennas.  I was using them each with an ATW-T310b bodypack and ATM75 headset mic. 

Venue was a high school auditorium, both RF racks on a table in monitor world, side stage.  Performers with the two bodypacks were at most 60 feet from the receivers, bodypacks in coat pockets or clipped to pants with a dress coat over them.  At one point there was a theatre curtain between the performers and receivers, but for most of the show the curtain was open.

I got intermittent low level but audible static, and occasional loud pops and dropouts on both systems in the two-channel rack.

In case it's germane, the four channel rack was on the same table, underneath the two channel rack.  It has four ATW-R3100b receivers, an AEW-660D antenna distribution unit and a pair of ATW-A49 LPDA antennas.  Those four channels presented no problems.

I checked with the AT website and I set all six RF systems to their recommended frequencies for that zip code (staying away from DTV in that area) ahead of time.  I was also running RF Explorer with a laptop during the show and saw no other activity near the two channels in question.  Here's where all six systems were set:

Headset   662.500*
Headset   656.975*
Handheld   656.225
Handheld   658.025
Handheld   661.000
Handheld   658.775

Contact me at kirby -at- kirbysound -dot- com.
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Mac Kerr

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Re: Need (paid) RF diagnostic help in No VA
« Reply #1 on: December 09, 2013, 11:40:13 am »

I got intermittent low level but audible static, and occasional loud pops and dropouts on both systems in the two-channel rack.

I would check the microphones and cables going into the pack. RF level should have no impact on audio levels, this is not AM transmission. The low level and pops are probably before the input to the transmitter, or they are within the transmitter itself.

Try swapping the mics between transmitters and see if the problem moves.

Mac
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Jason Glass

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Re: Need (paid) RF diagnostic help in No VA
« Reply #2 on: December 09, 2013, 11:49:01 am »

I'm in the northern Virginia area and looking for some help in resolving an RF problem.  I'm happy to pay a reasonable hourly or day rate for competent help.  The gear at issue is all Audio Technica, all in the 600MHz band.

I did a show this past weekend with six RF channels, four in one rack, two in another.  The problems occurred with the two channel set-up, which has ATW-R310b and ATW-R3100b receivers, with an ATW-49SP antenna splitter and a pair of the A3D half wave antennas.  I was using them each with an ATW-T310b bodypack and ATM75 headset mic. 

Venue was a high school auditorium, both RF racks on a table in monitor world, side stage.  Performers with the two bodypacks were at most 60 feet from the receivers, bodypacks in coat pockets or clipped to pants with a dress coat over them.  At one point there was a theatre curtain between the performers and receivers, but for most of the show the curtain was open.

I got intermittent low level but audible static, and occasional loud pops and dropouts on both systems in the two-channel rack.

In case it's germane, the four channel rack was on the same table, underneath the two channel rack.  It has four ATW-R3100b receivers, an AEW-660D antenna distribution unit and a pair of ATW-A49 LPDA antennas.  Those four channels presented no problems.

I checked with the AT website and I set all six RF systems to their recommended frequencies for that zip code (staying away from DTV in that area) ahead of time.  I was also running RF Explorer with a laptop during the show and saw no other activity near the two channels in question.  Here's where all six systems were set:

Headset   662.500*
Headset   656.975*
Handheld   656.225
Handheld   658.025
Handheld   661.000
Handheld   658.775

Contact me at kirby -at- kirbysound -dot- com.

Hi Kirby,

If you haven't already, check that the coax DC bias is present and the power indicators on the ATW-49SP's are lighting up.

I would use the cascade outputs of your AEW-660D out to the two ATW-49SP units and not use the A3D's at all.  This would take advantage of the extra gain and directional rejection of your ATW-A49's for the whole system.

If that doesn't work, replace your jumper coax's on the two-channel setup.  Continuity testing on coax is not a reliable indicator of a cable's RF performance, so replacement of the less expensive shorty's is usually the easy fix.

All of the hardware stuff aside, audible static and pops are usually symptoms of channel interference while quiet dropouts are more indicative of an antenna system problem.  RF Explorer rocks for the money, but isn't infallible.  The FCC database that the A-T site uses to predict clear channels is not quite reliable enough for perfect results every time.  It would be a good idea to query their site again for as many compatible channel assignments as possible, and try different combinations until you nail it.

Another option is to export CSV trace data files from the RF Explorer PC software, import it into WWB6, and use WWB6 to do your channel assignment calculations.  This is WAY more reliable than the A-T website and you already own the gear to do it.

You can make your RF Explorer a much more robust tool by adapting the SMA input to BNC, and using it with a cable and a good dipole antenna like the Sennheiser A1031-U mounted high on a mic stand.  The factory antenna is moderately OK but not ideal for our application.

Kevin Maxwell

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Re: Need (paid) RF diagnostic help in No VA
« Reply #3 on: December 09, 2013, 01:59:01 pm »



I checked with the AT website and I set all six RF systems to their recommended frequencies for that zip code (staying away from DTV in that area) ahead of time.  I was also running RF Explorer with a laptop during the show and saw no other activity near the two channels in question.  Here's where all six systems were set:

Headset   662.500*
Headset   656.975*
Handheld   656.225
Handheld   658.025
Handheld   661.000
Handheld   658.775

Contact me at kirby -at- kirbysound -dot- com.

I agree with Mac most of your problems sounds like the mics or cables themselves.

I always test each mic and pack before they are rigged up to be put on the actors. I talk into each one and with the mic hanging loosely I run my fingers down the cable and check the connector. All while wearing headphones with the channel under test soloed. If there is a problem it will usually show itself in these tests. When running this mic tests before a theatrical/musical show recently I noticed some static and it turned out the be the nut that holds the antenna jack on the body pack was slightly loose. I tightened it up and it cleaned up. I have also had times that I have tracked noise down to the nut on the mic jack in the body pack being loose.

For curiosity I ran the frequencies you are using thru Shures Wireless Work Bench version 5.4 and looked for frequency compatibility with each other. Without entering any zip code info since it was unknown to me. And I set them as generic wireless units.

Summary of Results
Channel to Channel Spacing Conflicts
(Generic Generic - 656.975) with (Generic Generic - 656.225)
(Generic Generic - 658.775) with (Generic Generic - 658.025)
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Jason Glass

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Re: Need (paid) RF diagnostic help in No VA
« Reply #4 on: December 09, 2013, 02:04:57 pm »

I agree with Mac most of your problems sounds like the mics or cables themselves.

I always test each mic and pack before they are rigged up to be put on the actors. I talk into each one and with the mic hanging loosely I run my fingers down the cable and check the connector. All while wearing headphones with the channel under test soloed. If there is a problem it will usually show itself in these tests. When running this mic tests before a theatrical/musical show recently I noticed some static and it turned out the be the nut that holds the antenna jack on the body pack was slightly loose. I tightened it up and it cleaned up. I have also had times that I have tracked noise down to the nut on the mic jack in the body pack being loose.

For curiosity I ran the frequencies you are using thru Shures Wireless Work Bench version 5.4 and looked for frequency compatibility with each other. Without entering any zip code info since it was unknown to me. And I set them as generic wireless units.

Summary of Results
Channel to Channel Spacing Conflicts
(Generic Generic - 656.975) with (Generic Generic - 656.225)
(Generic Generic - 658.775) with (Generic Generic - 658.025)

656.975MHz-656.225MHz=750KHz spacing.  658.775MHz-658.025MHz=750KHz spacing.  That's plenty for 3000 series.

Kevin Maxwell

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Re: Need (paid) RF diagnostic help in No VA
« Reply #5 on: December 09, 2013, 02:17:52 pm »

656.975MHz-656.225MHz=750KHz spacing.  658.775MHz-658.025MHz=750KHz spacing.  That's plenty for 3000 series.

Just telling you the results of WWB using the generic settings since 5.4 doesn’t have the AT system in it. I use its recommendations (using a combination of Sennheiser and Shure UHF-R) all the time and never have problems with the RF.
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