Odd spectrum noise from Sennheiser ew100 at DVinfo.net

Oren Arieli · July 14th, 2009, 05:48 PM

This started happening recently (see attached image), from my Sennheiser ew100 lav system. Haven't had this issue before, and its quite annoying. The multiple horizontal lines can be removed, but it's time consuming, and results in some loss of frequencies. This appears to be harmonic interference, as it's always along the same frequencies. Time to send the units to Sennheiser? Anyone experience this before?

Brooks Harrington · July 14th, 2009, 10:37 PM

What frequencies? Which block?
Rescan and change frequency.. and try manual tuning.

Oren Arieli · July 14th, 2009, 11:09 PM

Yeah, tried that. I rescan before my shoots and have had clear channels on 530.000. I get the same issue regardless of frequency setting. The strangest thing is that it just came up suddenly a few weeks ago. Now it won't go away.

Chris Soucy · July 15th, 2009, 12:28 AM

Not entirely sure what that picture is supposed to tell me, but will press on regardless....

This sounds like something I was getting with a Sony receiver a decade ago (nothing to do with wireless mikes, but relevant nevertheless) where "pirate" radio stations in London were using such crap transmitters the harmonics spread all over the FM wave band.

The Sony receiver in question had a totally "synthesised" front end and had no, zero, nada defense against these damn harmonics of their transmit frequency and they would break through on channels miles away from where it was tuned to (from memory, in multiples of the receivers first IF frequency).

Despite roaring complaints to the powers that be, they were never shut down (the frequency police got "privatised" and thus disbanded, or at least castrated).

As the Sennies are using a similar "synthesised" front end, as do most receivers nowadays, it is quite possible you have a new transmitter working in the neighbourhood with less than, how shall I say it, "perfect" harmonic spuriants being produced.

This would indeed cause the Sennies to go bonkers, even tho' they would detect no activity on a particular channel (this is very dependant on the circuitry of the input stage and way too technical for even me to fully understand).

Don't know where you've tested these units but if they still show the symptoms either buried in underground tunnels or 50 miles from your current location, it's probably them.

If it dissapers under the above circumstances it's most probably a brand new (legal but wonky) transmitter, due to the recent frequency re - allocations.

Test 'em and fix 'em, else complain loud and long to the FCC.

CS

Greg Bellotte · July 15th, 2009, 12:55 AM

http://74.205.3.123/ff/ <---is your friend

There is a 500 kilowatt DTV station on 530-536MHz only 50 miles from your location, could very well be DTV interference. Even though the sennys say a freq is clear in the scan, they have ZERO ability to see DTV signals. Keep trying channels until you find a better one...518-524 looks the best on paper...

Oren Arieli · July 15th, 2009, 09:31 AM

Thanks Greg and Chris. I did go to the site you mentioned well before this issue cropped up...and haven't had any trouble with 530 frequency until just last month. So it could be the DTV interference, or a problem with my mic. I'm running a full-scale test today on multiple frequencies, various distances, and using the plug-in and body-pack transmitter. I'd love to use the Lectrosonics I still own, but their sheer size and weight makes them a poor fit for the A1. Still, I'll run a test with the Lectros (no surprise, I'm sure they'll outperform their cheaper cousin).
Anyone using the new Sony diversity mics with great results?

July 14th, 2009, 05:48 PM	#1
Oren Arieli Major Player Join Date: May 2007 Location: San Jose, California Posts: 919	Odd spectrum noise from Sennheiser ew100 This started happening recently (see attached image), from my Sennheiser ew100 lav system. Haven't had this issue before, and its quite annoying. The multiple horizontal lines can be removed, but it's time consuming, and results in some loss of frequencies. This appears to be harmonic interference, as it's always along the same frequencies. Time to send the units to Sennheiser? Anyone experience this before? Attached Thumbnails

July 15th, 2009, 12:28 AM	#4
Chris Soucy Inner Circle Join Date: Feb 2007 Location: Fairfield, Dunedin, New Zealand Posts: 3,691 Images: 18	Hi Oren........... Not entirely sure what that picture is supposed to tell me, but will press on regardless.... This sounds like something I was getting with a Sony receiver a decade ago (nothing to do with wireless mikes, but relevant nevertheless) where "pirate" radio stations in London were using such crap transmitters the harmonics spread all over the FM wave band. The Sony receiver in question had a totally "synthesised" front end and had no, zero, nada defense against these damn harmonics of their transmit frequency and they would break through on channels miles away from where it was tuned to (from memory, in multiples of the receivers first IF frequency). Despite roaring complaints to the powers that be, they were never shut down (the frequency police got "privatised" and thus disbanded, or at least castrated). As the Sennies are using a similar "synthesised" front end, as do most receivers nowadays, it is quite possible you have a new transmitter working in the neighbourhood with less than, how shall I say it, "perfect" harmonic spuriants being produced. This would indeed cause the Sennies to go bonkers, even tho' they would detect no activity on a particular channel (this is very dependant on the circuitry of the input stage and way too technical for even me to fully understand). Don't know where you've tested these units but if they still show the symptoms either buried in underground tunnels or 50 miles from your current location, it's probably them. If it dissapers under the above circumstances it's most probably a brand new (legal but wonky) transmitter, due to the recent frequency re - allocations. Test 'em and fix 'em, else complain loud and long to the FCC. CS

July 14th, 2009, 10:37 PM	#2
Brooks Harrington Regular Crew Join Date: May 2007 Location: Pasadena, CA Posts: 152	What frequencies? Which block? Rescan and change frequency.. and try manual tuning.

July 14th, 2009, 11:09 PM	#3
Oren Arieli Major Player Join Date: May 2007 Location: San Jose, California Posts: 919	Yeah, tried that. I rescan before my shoots and have had clear channels on 530.000. I get the same issue regardless of frequency setting. The strangest thing is that it just came up suddenly a few weeks ago. Now it won't go away.

July 15th, 2009, 12:55 AM	#5
Greg Bellotte Major Player Join Date: Sep 2005 Location: SLC, UT Posts: 291	http://74.205.3.123/ff/ <---is your friend There is a 500 kilowatt DTV station on 530-536MHz only 50 miles from your location, could very well be DTV interference. Even though the sennys say a freq is clear in the scan, they have ZERO ability to see DTV signals. Keep trying channels until you find a better one...518-524 looks the best on paper...

July 15th, 2009, 09:31 AM	#6
Oren Arieli Major Player Join Date: May 2007 Location: San Jose, California Posts: 919	Thanks Greg and Chris. I did go to the site you mentioned well before this issue cropped up...and haven't had any trouble with 530 frequency until just last month. So it could be the DTV interference, or a problem with my mic. I'm running a full-scale test today on multiple frequencies, various distances, and using the plug-in and body-pack transmitter. I'd love to use the Lectrosonics I still own, but their sheer size and weight makes them a poor fit for the A1. Still, I'll run a test with the Lectros (no surprise, I'm sure they'll outperform their cheaper cousin). Anyone using the new Sony diversity mics with great results?