Comtek M216 Noise

[Sam Kashefi]

Hi

Finally today my remote audio miracle whip MW216 antenna has arrived.

With the hope of helping boosting my M216 transmitter to get some decent interference free

signal for the range of 10-20 meter. but nothing changed at all.

here it's my big issue with my M216 transmitter :

when i connect the Tx into my laptop , or i phone or whatever with Headphone out ..

it just work great as advertised and as all of you guys have been talked about this product.

but when i connect it to any output from my SD442 , or 744T , or even Lectro 411a mic out

im getting very strong interference even or the range of 2-3 meters ,with or without Whip antenna or MW216 remote audio.

is there any special cable for these type of transmitter ? or a normal 3.5 mm jack to 3.5 mm jack is

enough for the standard line input?

also I've read the manual and it said the RF output is just 10mw , which is even less than sennheiser EW series.

is this interference something normal for a 10mw tx or i am doing something wrong , with cable or with type of

output from my gear.

Sam

[David Waelder]

Sam, I don't use the M-216 myself so my comments are general in nature. However, Comtek transmitters are customarily used with an audio cable incorporating a filter trap to avoid unwanted RF feed into your mixer or recorder. Without that filter trap, noise bleeds into your audio gear. Typically a filtered input cable was available directly from Comtek and, I must admit, I don't see such an animal on their site. It may be that more recent iterations of the Comtek transmitters now incorporate the filter in the transmitter itself. Still, I would check to see if your configuration has an in-line filter. It should be easy to spot - the XLR connector is usually a bit longer than normal. On opening the connector, you would expect to see components soldered onto the pins. If you don't have a filtered connection, contact Comtek (technical@comtek.com) and ask if your application would benefit from a filtered connection.

David

[aristotle_kumpis]

I own the M-216 and use it primarily in a bag system. I use the XLR to 1/8" cable that came with it. You should have received the cable upon purchase. If not, maybe Comtek can send you one. I don't get interference, even with using the small whip antenna. But I'm not sure if the Comtek cable is designed differently than other cables. Have you tried changing channels? Make sure you are using the companded channels, since they work the best.

[Sam Kashefi]

Thank you david for the very useful notes.

You are talking about CB-36 XLR cable from Comtek which comes with it when

you buy the transmitter.i have that , but unfortunately the connection inside the

cable is not right and its loose somehow,i don't remember if that helped me

much when it was working.but i will get one of those to see if that

helps me avoiding RF interference which is so strong even for a distance of

3-4 meters.

sam

[pvanstry]

I fear something is not right with your comtek.  I have a M216 opt7 with the small antenna and use it with my 302, 552 and 788T kit.  ALl have no filtered custom cables i made and i get a lot more range than you.  Usually around 50 meters at least.  One of the thing i do is simply go to my location and use a Spare comtek receiver and with the transmitter off, i go form freq 01 and listen for 3 seconds on each channel ( like a manual rf scan basically ).  i select a channel that is centered to at least 5-6 free channel. 

My 2 cents

Pascal

[Chris R]

The M-216 "aux" input is looking for a line level signal.

The laptop or iPhone is putting out a line level signal.

You mention you tried a "mic level output" from your 411.

If you are sending a mic level signal into the 216 I could see you having an issue.If you didn't adjust your output you are putting out a very weak signal into the air.

[RPSharman]

I hate to say "contact the manufacturer" but Comtek will let you speak to their techs. You may need to send it in. Service is swift and reasonable.

[Rob Lewis]

As Chris Said, Line Level signal in.  The XLR Cable that is supplied has filters in the XLR connector and a Ferrite Bead at the 1/8" end.  The only time I have had induced noise is when using it in conjunction with the Zaxcom transmitter.  I use it as an IFB for live shots and as a producer feed from the bag, and I get better range than most UHF systems.  I would have your transmitter checked, but make sure all receivers are tuned properly first, and check that you are sending line level to the transmitter.

[studiomprd]

" I hate to say "contact the manufacturer" "

Why??

[Sam Kashefi]

Thank you guys for all of the great input on this issue.

Well , i did contact the manufacture few weeks back , and they asked me to do a walk test.

my main concern is about the fact that , M216 Tx has just 10mw output compare to BST or the

new compact version of 216 which has 100Mw or more .

what i like to understand is should i expect a transmission range like a Sennheiser EW tx? or better?

this is something that can be clear for me from the people who actually put it on the test and using

it in the field.

when the client comes to me and saying that they're getting lots of hiss and noise , i want to figure it out

that should i upgrade to BST or other ifb with more RF out or stick with this and try to improve the cables

or the antennas.

sam

[Derek H]

Sounds like more experimentation is needed..

I use M72 transmitters and the range is so so.  I couldn't put a number on it but its pretty short range. 

I also have slight issues with digital rf noise from my zaxcom transmitters in the bag..  Sounds like a high pitched wine, its less of a problem with the newer trx900 than the older stereo line though.  I talked to the tech at comtek and his only advice was to separate the transmitters more, possibly remote mounting the m72 out of the bag..  Unfortunately not very feasible for me.  As much as I suggested filtered cables and rf traps he didn't seem to think that would help..

I'm tempted to try it anyway, does anyone have any recommendations for a small (to fit in TA connector) rf trap circuit with cap values and so on?  I notice the comtek made cable has two inductors as well as a small cap... Not sure what the inductors accomplish,, I assumed it was more so for preventing the signal looping back into a mixing console somehow rather than rf noise.

[John Blankenship]

Sam,

You know what, I've never even given a thought to the output power of the Comteks.  They do their job and that's what I care about.

I've gotten good range out of both the 72s and the 216s and have both on my cart -- the 216s for crew and the 72s for video village.  On a feature I worked on last summer, a production coordinator wanted to be able to listen in a separate building located several hundred feet away, so instead of the floppy antenna I normally have on the cart, on my 216 transmitter I installed a stiff, 15" vertical antenna that I carry for just that purpose.  There's nothing special about the antenna -- just a piece of wire that sticks straight up in the air.  She said reception was great -- even that far away and in a different building.

Contact Comtek and have them make you up a filtered cable with whatever connector you specify.  They're nice people and their prices are reasonable.

Derek,

Contact Comtek and talk to tech support.  They'll give you the values of the components, can send you a schematic if you like, and even sell you the parts at a reasonable price.

If for some reason the Comtek gang has turned nasty (I seriously doubt it), contact me and I can dig the info out of my archives.