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[Jeff Lelko]

Hi All,

I have a kit of Sennheiser EW100 G3 mics that have served me well over the past 2 years.  Lately, the signal strength hasn't been what it usually is.  The system is specifically as follows:

4x Handhelds or Beltpack (EW100 G3) transmits into 2x A 2003-UHF Antennas attached to an ASA1 and into the 4 receivers. 

Usually the signal meters are at full anywhere within 50ft or so of the antennas and slowly starts to decrease the further out you go.  I can almost always get about 200ft line of site transmission without issue (though I don't rely on use at that distance).  Lately the signal is never reading "full" and anything beyond 50ft gets low enough where I worry about having a dropout.  What would cause this sort of problem and how do I fix it?  Doing a bit of troubleshooting, the problem does not appear to me mic or receiver specific.  Unplugging the antennas do show an additional drop on signal strength as expected.  Could the problem be COAX going bad?  I have a Sennheiser BB25 between each antenna and the ASA1.  All Sennheiser parts and no substitutes.  The first time this happened (2 weeks ago) I just thought it was an unusually humid day, but not seeing any improvement over the next week I think something else might be going on.  Any help would be much appreciated!

Thanks,
-Jeff

[Scott Holtzman]

Hi All,

I have a kit of Sennheiser EW100 G3 mics that have served me well over the past 2 years.  Lately, the signal strength hasn't been what it usually is.  The system is specifically as follows:

4x Handhelds or Beltpack (EW100 G3) transmits into 2x A 2003-UHF Antennas attached to an ASA1 and into the 4 receivers. 

Usually the signal meters are at full anywhere within 50ft or so of the antennas and slowly starts to decrease the further out you go.  I can almost always get about 200ft line of site transmission without issue (though I don't rely on use at that distance).  Lately the signal is never reading "full" and anything beyond 50ft gets low enough where I worry about having a dropout.  What would cause this sort of problem and how do I fix it?  Doing a bit of troubleshooting, the problem does not appear to me mic or receiver specific.  Unplugging the antennas do show an additional drop on signal strength as expected.  Could the problem be COAX going bad?  I have a Sennheiser BB25 between each antenna and the ASA1.  All Sennheiser parts and no substitutes.  The first time this happened (2 weeks ago) I just thought it was an unusually humid day, but not seeing any improvement over the next week I think something else might be going on.  Any help would be much appreciated!

Thanks,
-Jeff

Are these installed at one location?  If so I would think a change in the noise floor due to a new emission source.  Do you have the ability to do an RF scan?

[Jeff Lelko]

Are these installed at one location?  If so I would think a change in the noise floor due to a new emission source.  Do you have the ability to do an RF scan?

Thanks Scott.  No, I'm mobile, and this symptom was seen at two different venues about 150 miles apart.  The receivers and ASA1 are all in the same rack if that's what you meant though.  I don't have the ability to do an RF scan but I do always use the built-in feature on the receivers to pick the best channels. 

[Mac Kerr]

Could the problem be COAX going bad?  I have a Sennheiser BB25 between each antenna and the ASA1.  All Sennheiser parts and no substitutes.

Cable would be my first guess, and the thing I changed before attempting any other troubleshooting. While cables can last a long time if cared for properly they are not durable goods, they are expendables.

I don't know what cable is in the BB25, but I would try replacing them, and possibly replacing the jumpers in your rack between the ASA1 and the receivers.

Mac

[Jeff Lelko]

Cable would be my first guess, and the thing I changed before attempting any other troubleshooting. While cables can last a long time if cared for properly they are not durable goods, they are expendables.

I don't know what cable is in the BB25, but I would try replacing them, and possibly replacing the jumpers in your rack between the ASA1 and the receivers.

Mac

Thanks Mac.  Do you have a recommendation on cables that work well?  I'll definitely give that a try!  I should be able to pull the rack from service in another week or so to try some more involved troubleshooting, but just wanted to know where to start!

[Mike Caldwell]

Try bypassing the ASA1 and taking the antennas straight to a receiver to see what you get.
Set the transmitter out a distance from the receivers, note the RF level then bypass the ASA1 and see what the level does.

[Scott Holtzman]

Thanks Scott.  No, I'm mobile, and this symptom was seen at two different venues about 150 miles apart.  The receivers and ASA1 are all in the same rack if that's what you meant though.  I don't have the ability to do an RF scan but I do always use the built-in feature on the receivers to pick the best channels.

No I was just trying to determine if this was an installed system.  Since the problem is at multiple venues it is more than likely in the rig.  The multicoupler itself could be generating noise or a cable could be oxidized or mechanically damaged.

Taking the multicoupler out is the first step.  Actually try just turning it off (if it powers the units like the Shure does you will have to connect the power brick back to the unit(s).

[Xiang Cao]

I had similar issue with just one single receiver in a 8xew100 rack, it seems to be cable.

[Jeff Lelko]

Thanks guys.  I'll try bypassing the ASA1 and seeing what happens.  I might be able to sneak in a quick test this week, otherwise it'll have to wait until next.  Is there a preferred coax product to use for such applications?  I just used the 1ft cables that come with the ASA1 for the internal hookup, the super-expensive for what they are AM2 to get out of the rack, and the aforementioned Sennheiser 25ft coax to get to my paddle antennas.  I admitted don't know what's "good" in the world of coax!  Also, thinking of possible oxidation on the connectors, is there a way to clean them?  I don't mind replacing cables, but knowing they only account for half the connections I really don't want to replace the antennas or receivers just because a connector went bad.  Thanks!

[Jeff Lelko]

So I had the chance to pull my wireless mic rack from service today and do a bit of quick testing.  It definitely seems that the 25ft coax cables are the problem.  I first played around with reception using no antennas just to see what kind of signal strength I could get.  I then added the paddle antennas - signal increased a bit but it was weak just like when I noticed the original problem.  Covering the mic's antenna and putting myself then between the mic and the antenna 10ft away was enough to cause a drop-out.  I then swapped the paddles out for the rubber duck antennas that come with each receiver kit and the signal popped right back up to full strength.  Covering the mic's antenna and putting both myself and the rack in the signal path barely even caused a blip on the meter.  So it looks like I'll be swapping those cables out right away, and while I'm at it I'll replace the internal cables too.

After searching around, is LMR400 Ultraflex still the best choice?  Is there a safe way to clean the BNC connectors on the receivers and splitter too while I'm in there?

Thanks!

[Mac Kerr]

After searching around, is LMR400 Ultraflex still the best choice?  Is there a safe way to clean the BNC connectors on the receivers and splitter too while I'm in there?

Thanks!

For your longer runs LMR400 is still a top choice, although at 25' runs is probably overkill. Inside your rack good quality RG58 is good. For a 25' good quality RG58 may also be fine, although I always try to use low loss cable to external antennas. RG8 or RG213 are also good low loss cables.

I assume your ASA1 i getting powered properly, there have been several times I have solved an RF problem by turning on the antenna distribution that somehow got turned off.

Mac

[Mike Caldwell]

When you tried the "rubber duck antennas" did you connect then directly to the ASA1 input connectors or at the end of the 25' coax with a barrel adapter.

[Jeff Lelko]

For your longer runs LMR400 is still a top choice, although at 25' runs is probably overkill. Inside your rack good quality RG58 is good. For a 25' good quality RG58 may also be fine, although I always try to use low loss cable to external antennas. RG8 or RG213 are also good low loss cables.

I assume your ASA1 i getting powered properly, there have been several times I have solved an RF problem by turning on the antenna distribution that somehow got turned off.

Mac

Thank again Mac.  Forgive the junior question, but what constitutes as "good quality" RG58?  Is there something in particular that I should be looking for?  Like I've said, this is one area of the industry I know very little about.  Also, is there a way to test the performance of a cable?  My thought would be to just use my ohmmeter and see how close I am to 50, but I could be way off with that...

Yes, everything is getting adequate power as far as I can tell.  I utilize the ASA1's ability to power the 4 receivers through the coax, so it's just the one plug on the ASA1 and everything comes to life.  No issues whatsoever, and the power going into that is coming from my Eaton UPS.

When you tried the "rubber duck antennas" did you connect then directly to the ASA1 input connectors or at the end of the 25' coax with a barrel adapter.

They were connected to the output end of the AM2 product.  I use that to get from the back of the ASA1 to the GA3 rack mount panel for easy plug-in.  Correct me if I'm wrong, but an antenna such as these little rubber ones need a metal grounding plate behind them to work properly, and thus I wouldn't want to use one at the end of any length of coax unlike a paddle antenna, right? 

[Mike Caldwell]

They were connected to the output end of the AM2 product.  I use that to get from the back of the ASA1 to the GA3 rack mount panel for easy plug-in.  Correct me if I'm wrong, but an antenna such as these little rubber ones need a metal grounding plate behind them to work properly, and thus I wouldn't want to use one at the end of any length of coax unlike a paddle antenna, right?

From my understanding the shorter 1/4 wave antennas need a ground plane, when connected directly to the connectors on a receiver the metal case of the receiver provides the ground plane.

Do your test with the small antennas using the 25' coax jumpers and see what you get.

Also check the BNC connectors on the paddle antennas for a solid connection to the antenna. That type of antenna is basically just a circuit board with the BNC connector solder to the copper traces used for the antenna elements, maybe there is a cracked solder connection at the BNC connector.

[Jeff Lelko]

From my understanding the shorter 1/4 wave antennas need a ground plane, when connected directly to the connectors on a receiver the metal case of the receiver provides the ground plane.

Do your test with the small antennas using the 25' coax jumpers and see what you get.

Also check the BNC connectors on the paddle antennas for a solid connection to the antenna. That type of antenna is basically just a circuit board with the BNC connector solder to the copper traces used for the antenna elements, maybe there is a cracked solder connection at the BNC connector.

Yes, grounding plane (iPad autocorrect).  I'll give that test a try to see what happens, but it'll be another few days until I can pull the rack again.  It works well enough still to keep in service but I want to correct the issue before the problem becomes audible!  I did test with both my omnidirectional paddles and the unidirectional paddles with no difference in result, even when out of alignment with the directional paddles.  This, coupled with the huge improvement with the lower gain rubber ducks led me to believe the 25ft coax is the problem.  I'll swap out the cables and hope it works, but I'll also check the solder joints as well.  Thanks Mike!

[Ike Zimbel]

Yes, grounding plane (iPad autocorrect).  I'll give that test a try to see what happens, but it'll be another few days until I can pull the rack again.  It works well enough still to keep in service but I want to correct the issue before the problem becomes audible!  I did test with both my omnidirectional paddles and the unidirectional paddles with no difference in result, even when out of alignment with the directional paddles.  This, coupled with the huge improvement with the lower gain rubber ducks led me to believe the 25ft coax is the problem.  I'll swap out the cables and hope it works, but I'll also check the solder joints as well.  Thanks Mike!

Some BNC cables, especially molded end ones can have a problem with the center pin getting pushed in. You can usually eyeball this. If you see that, the cable is toast. From what trouble shooting you've done so far, I think it's a pretty good bet that your 25' cables are the issue. RG58 cables from the big wireless manufacturers (Shure, Sennheiser, Lectrosonics etc.) are all fine for what you need.

[Jeff Lelko]

So as a follow-up, I Amazon Primed a pair of cheap RG58 cables to see if I would notice a difference with them before spending more money on higher quality cables, just in case this wasn't the problem after all.  For $6.99 it's hard to go wrong, even if just for testing purposes.  I tried them out last night at one of my regular larger outdoor venues and sure enough, the signal strength is right back where it should be.  I'll still go ahead and buy some higher quality RG58 or LMR400 and keep these cheapo cables as spares, but it looks like the cables were in fact the problem and I'm glad this is something that can be fixed quickly and easily.  Thanks for the help! 

[Keith Broughton]

At this point, just buy the LMR 240 or 400 instead of buying "better" RG58.

[ProSoundWeb Community]