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zaxnet and comtek 216 whine interference


osa

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for quite a while now, I've had this whine interference that has been discussed here in various setups. I manage to work around it but I am also sacrificing full potential of my equipment by doing so. I am using a qrx100 qifb as my zaxnet transmitter. on jobs where i need comteks, I can only transmit at a level of 4 from my qifb, and even then there is still a slight whine - but to me it is satisfactory for general comtek fidelity. ultimately i want to be at 5-7 and using comteks in my bag setup without any interference AND not having to relocate my comtek transmitter. i tried making my own cable with 4.7uh inductors and this did not solve the problem at all for me. Short of making the cables incorrectly (i worked from a diagram posted on a previous discussion that was a bit hard to read) I figure there has got to be a way to filter this interference that i am missing - did a search but cant seem to find, and i swear I posted questions on this subject myself that i cant seem to locate. is there such a filter for comteks (other than filtered cables) that might exist similar to how a mic plexer works that might solve this problem? from my troubleshooting, it seems like it is not interference in cabling. but i could be wrong. I have not tried an actual cable from comtek. unfortunately i dont own one to test. I could try and borrow one in the meantime and see whats doin.

-Ken

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I just ran some tests with this setup and have a few findings. The noise is being induced directly into the body of the M-216 transmitter. Comtek input cabling/filtering makes no difference. An RF filter on the comtek would also make no difference. The only things that made a difference were zaxnet transmission power, physical proximity, and physical obstruction. Short of switching to Lectro IFB, your best option would be to keep them on opposite sides of the bag and try wrapping some RF blocking fabric around the body of the M-216.

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Try wrapping the Comtek transmitter tin foil first before ordering RF fabric. Because you probably already have some. 

If that works then you've solved the problem and can work on making it prettier if you want.

PS, after fighting the good fight with Zaxcom "whine" interference in various places in various bag rigs over the years it ended up being a factor in the move to my current setup which is Lectro and Sennheiser RF only.

I am still using a Maxx but none of their RF. It's good gear though and all of the problem spots can be solved or worked out with enough fiddling. Zaxcom will likely tell you that interference issues are the fault of the other manufacturers designs. Which is probably true but at some point it doesn't matter.

That said, I loved the Zaxcom hops system while I owned it. If they had the CL transmitter and RX200 available when I bought my first hops system I'd probably still be using it.

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thanks everyone for the input. i am gonna put some of these suggestions to work. i am determined to solve this issue somehow without changing my setup. i now have some better ideas based on these suggestions. its diy time. will report back if i have any success

-Ken

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This is currently my solve for the whine. In a small Maxx bag you can't get enough physical separation, so using an ERX to feed the transmitter gets it far enough away.

On a shoot where village doesn't move I put it near there and forget about it, for run and gun I attach them to my waistbelt on the back. So far no problems except needing an extra ERX.

 

tmp_15013-IMG_20160316_150717246633547049.jpg

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And as a side note, the exotic RF fabric DOES have a noticeable effect, but it isn't a huge effect, if only because there are so many ways for RF to get around it.   Re the ancient SD 744T RF spray fight I got some love by using several layers, but this just results in a reduction of the spray, not elimination of it (at the freqs used by the TX in that bag).

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1 hour ago, max said:

This is currently my solve for the whine. In a small Maxx bag you can't get enough physical separation, so using an ERX to feed the transmitter gets it far enough away.

On a shoot where village doesn't move I put it near there and forget about it, for run and gun I attach them to my waistbelt on the back. So far no problems except needing an extra ERX.

 

tmp_15013-IMG_20160316_150717246633547049.jpg

That's an interesting way of doing it. Cool. 

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4 hours ago, Glen Deakin said:

That's an interesting way of doing it. Cool. 

this is great as the point of me trying to clean this up is to use my erx's more (another diy project in the works) in combo with the comtek kit. this is a surefire way when i am in studio/video village setups. thx!

i cant believe this but - according to my bench tests early this afternoon - tinfoil actually worked!!! thanks derek h. i tested it with tinfoil wrapped around the 216 transmitter several layers and balled at the bottom to make a sealed surround. top was left open. i made an open top project box around the tinfoil out of scrap lexan plexiglass type material and black gaffers. so basically the transmitter slips in and out of the tinfoil casing real easy for batt switching. i have zaxnet up to 7 and i cannot hear the whine at all. when i grab the transmitter and pull it out of the diy tinfoil case and listening with a pr216, full whine. slide back in, whine is gone. unbelievable. i was all set to buy some of that fabric, some rfi spray in a can, an rfi shielded project box, etc but looks like i might not have to. i have a job the next 4 days where i will be using the comtek kit so i will be full up to 7 on zaxnet transmission and periodically testing all throughout. thanks again Derek and to everyone for your input! time will tell but fingers crossed, tinfoil might be the solution

-Ken

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You can also get aluminum foil tape that has a very sticky adhesive backing.  I got some when I was repairing an iMac.  Its silver, two inches wide and has a very aggressive adhesive.  I don't remember where I got it though.  I was looking on line for a source and I found this: http://www.ebay.com/bhp/adhesive-copper-tape  The adhesive backed would be nice to keep everything in place.  You could line a nice project box with several layers of this stuff.

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17 hours ago, berniebeaudry said:

You can also get aluminum foil tape that has a very sticky adhesive backing.  I got some when I was repairing an iMac.  Its silver, two inches wide and has a very aggressive adhesive.  I don't remember where I got it though.  I was looking on line for a source and I found this: http://www.ebay.com/bhp/adhesive-copper-tape  The adhesive backed would be nice to keep everything in place.  You could line a nice project box with several layers of this stuff.

I used some of this on this project, furnace tape for air ducts and dryer vents. I used to tape foil at top opening to allow tx to slide in n out without foil sleeve losing its shape

-Ken

image.jpg

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Field test was not as good as bench test - of couse it works perfect stationary on a bench. But up runing around, the whine would come in and out to varying degrees. BUT still at a reduced level which still works. I am able to stay at 5 and even up to 6 at times for zaxnet transmission which is definitely an improvement.  Still workin on it

-Ken

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54 minutes ago, osa said:

I used some of this on this project, furnace tape for air ducts and dryer vents. I used to tape foil at top opening to allow tx to slide in n out without foil sleeve losing its shape

-Ken

image.jpg

That might be the same stuff I have.  I wonder if the copper tape I linked to would be more effective since you're still getting some whine.  What if you also made the enclosure taller so the connections have more shielding?

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1 hour ago, berniebeaudry said:

That might be the same stuff I have.  I wonder if the copper tape I linked to would be more effective since you're still getting some whine.  What if you also made the enclosure taller so the connections have more shielding?

Hard to tell from pic but it does come up about 1/2" above top of transmitter. Before i built i experimented with the foil wrapping up higher. My tests showed the rf appears to be invading the body of the transmitter. I am gonna try the black wrap as well when i can break into the light kit here. 

-Ken

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1 hour ago, osa said:

Hard to tell from pic but it does come up about 1/2" above top of transmitter. Before i built i experimented with the foil wrapping up higher. My tests showed the rf appears to be invading the body of the transmitter. I am gonna try the black wrap as well when i can break into the light kit here. 

-Ken

Don't break. Just ask!!

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Have you considered makign a "lid" for your Comtek TX box with the same treatment, with a hole for the ant?  I guess the changes in the interference due the proximity of everything (including the antenna) changing while wearing the bag are to be expected.  So adding chokes or ferrite beads to the input cable didn't help?

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23 hours ago, Glen Deakin said:

Don't break. Just ask!!

Ha - "dig" is maybe the better term. Small crew  this job, arri kit in the van burried a little too deep but hopefully will be needing some of those lights one of these days here. They will be more than happy to support my research

22 hours ago, Philip Perkins said:

Have you considered makign a "lid" for your Comtek TX box with the same treatment, with a hole for the ant?  I guess the changes in the interference due the proximity of everything (including the antenna) changing while wearing the bag are to be expected.  So adding chokes or ferrite beads to the input cable didn't help?

Good idea - will try with the black wrap too like a mini foil hat for it! A lid prob wouldnt hurt

-Ken

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