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tjjamguitar

XD-V75 signal drop outs

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I have seven  XD-V75 mics setup.  They are all  connected to the line6 antenna distribution unit and it is connected to two unidirectional line6 paddle antennas.  They are all on RF2 mode, but I have tried RF1 before.  I recently updated to firmware using line6 monkey.  I've tried scanning for channels and switching from Hi power to Lo.  I still get signal drop outs on at least two of the mics most of the time.  Even when I turn all of the receivers off and try scanning one at a time, when I scan, usually half of the channels are busy(bars above the channel numbers).  I've tried everything I could think of.  I use these mics in a church.  We have wifi, there are laptops there and everyone has a cell phone.  Plus we're located not far from an Airport.  What else can I do? 

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Did these problems start when you upgraded the firmware or was the upgrade an attempt to solve them?

 

In a busy RF environment, you really should be using RF1. It may slow down nearby wifi a little but (in my opinion), that's preferable to mics dropping out.

 

With all the transmitters off, how many red RF LEDs are lit up on each receiver?

 

What's the distance between the receiver antennae and the transmitters?

 

How long are your antennae cables, what type of cable are they and what's the gain on the paddles set to?

 

From what I've seen of other peoples' problems on here over the years, more often than not, the cause is related to physical locations of things e.g. leaving a spare transmitter switched on right next to the receivers or having an IEM transmitter antennae near to the mic receivers' antennae. Make sure that your receiver paddles are up high with clear line of sight and well away from anything else that transmits on any frequency.

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The firmware update was an attempt to solve the drop out problem.  We've had these mics for about 4 years and have never been updated.  

 

With all the transmitters off, some of the receivers have 4 or 5 red bars and some just have 1 or 2 red bars.

 

The singers line up across the stage but move around dancing a lot.  There are 6 or 7 singers at most,  the closest to the antenna is about 3 feet and the one in center stage are about 15 feet from either antenna. 

 

One cable is 50' long but the antenna is about 10 feet away from the receivers which are in a rack.  The other cable is 100' and the antenna is about 20' from the receivers rack.  I think it's 50 ohm cable, I remember making sure we got the right ohms cable because we had to send one cable back, because it was wrong.  I've tried the all gain settings on the paddles.  

 

How high should I place the paddles?  Also, on both sides of the stage, there are laptops near the paddles and there are other mic receivers (Shure and Senhieser) on top of and below the receiver rack.  

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Perfect - I was just about to ask if you had a picture of the layout!

 

Several issues to tackle here... Dropouts can be caused either by lack of the wanted signal or excess of an unwanted signal. I suspect you may be facing both here along with a couple of other points.

 

Five red bars is worrying and will definitely be a problem. I routinely see three which I've found to be acceptable. Occasionally four which would make me worry a bit but never five.

 

Antennae location

There's an RF phenomenon called "near far" whereby a nearby RF signal (i.e. a very close transmitter pack) can swamp the receiver's input stage and prevent it from picking up a source that's further away. If in your current layout you get singers very close to both antennae, it's possible that those centre stage may suffer. To use a backwards sound analogy, if your speakers are at head height right in front of the front row, they'll get blasted whilst those at the back won't hear as much. You solve that by getting the speakers up higher so that the difference in distance (and hence volume) between speaker & front row and speaker & back row is minimised. Same with the antennae. If they have to be "floor mounted", a standard boom mic stand at full extension will get them just above head height which is usually OK. I use K&M's rather useful 240/5 clamp if there's a lighting boom or an edge of something I can clamp on to at a good height. Those paddles' polar pattern is a bit like a cardioid mic so you can use the null behind them to point towards an unavoidable RF source if necessary.

 

The proximity of those laptops may also be problematic if the antennae aren't currently very high up. I'd aim to keep them at least 5' away from anything that transmits. Keep an eye out for wifi access points too - steer well clear of them!

 

Antennae cable

It would be worth checking exactly what type of cable you're using. If it's something like RG58, that won't work well, especially at those lengths. There's more to speccing the right cable than just the impedance. The recommended cable is LMR195 - it's not particularly cheap but it does work. However I'd say your cables are far too long. You're dropping around 25dB of signal over that length which really won't be helping. I've also been wondering whether using two very different lengths of cable may be problematic. I've not come to any conclusions on that front though.

 

Suggestions

As per normal troubleshooting procedures, this is a case of divide & conquer. Let's tackle the interference first.

  1. If your antennae aren't already high up, get them mounted as high as you can, away from the laptops and any other sources of interference. If you're not then seeing fewer red bars, try...
  2. ...testing with the stubby antennae that come bundled with the receivers plugged straight in to the front of the AD8. That will hopefully show much lower levels of interference from sources like the laptops. It also eliminates the long cable runs from the equation. Try this with any nearby equipment switched off though - you mentioned other radio mic receivers which shouldn't really be a problem but let's play it safe for the purposes of testing. If you see fewer red bars, that's progress.
  3. Switch everything else back on. If you're now seeing more interference (red bars), I'd actually be tempted to relocate your antennae to the rear of the stage near the rack and use much shorter (<20') LMR195 cables. You're on such a small stage, distance really shouldn't be a problem.

Hopefully by this point, you're seeing fewer red bars. Let's have a look at the transmitters.

  1. Switch to RF1. Triple check that they're all on RF1 - just one transmitter left on RF2 will cause trouble.
  2. Shorter cables as mentioned above will help with wanted signal strength & quality.

Without actually being there to see the full set up, I can't think of much else to suggest.

 

In summary, your broad approach is twofold:

  • Keep unwanted signals out of the receiver - locate antennae away from sources of interference and maximise cable quality
  • Get as much wanted signal as possible - minimise cable length, minimise differences in transmission path length

Let me know how you get on!

 

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Thanks for your help.  On stage we also have tresses with lights which are directly behind the receiver rack and horizontal banners which have metal tubes, directly in front of the receiver rack.  Does all this metal affect the signal.  Last night I raised the paddles up to about 6 feet.  I turned on all the receivers with all the mic transmitters off.  Still had one red bar on all of them and at least 5 bars on one receiver.  

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Lots of metal will only possibly be an issue near the antennae themselves if it's blocking line of sight to the transmitters. If the antennae are remote away from the rack, then metal near the rack shouldn't make any difference.

 

20 hours ago, tjjamguitar said:

Still had one red bar on all of them and at least 5 bars on one receiver.  

 

One or two red bars is normal in my experience and shouldn't cause any issues. Can you change the channel of the one that's showing five to get a better result? There may be a powerful wifi (or other) transmitter nearby that's on one of the frequencies used by that mic channel. You've got five other channels to try so one of them is bound to work better. Bluetooth devices and microwaves are also sources of interference - is anyone streaming audio over Bluetooth nearby? Any RF transmitter on any frequency near to the antennae can cause problems so it's worth really carefully looking out for anything that transmits anything.

 

Do you have a wifi analyser app on your phone? It's always useful to see if there are any really strong signals nearby that might cause problems. If you have the option to move any wifi up to the 5GHz band, that will help no end. A proper RF spectrum analyser is more useful as that will show non-wifi transmissions as well but I guess you may not have one of those.

 

Note that the channel scan function in the receivers is pretty useless in my opinion - it only scans for the frequency scheme used by the RF2 mode so is no help when using RF1. It also confuses many users as it shows 14 channels but they bear no relation whatsoever to the 14 wifi channels!

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