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Comtek interference caused by Kinoflo?


Blas Kisic

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I had an interesting issue crop up a few days ago.

I have two Comtek feeds: one for my crew and one for Production (which includes Director & Scripty, as well as agency types in VV.) Transmitters are two BST-25 216.

So I was working on a commercial shoot in a home. My cart ended up in a corner in the kitchen, and I installed my two Mini-Mite antennas upside down so as not to hit the ceiling. Everything was tested, no problems found.

At some point, a four-foot Kino fixture with four bulbs was put next to the car, vertically. It was connected to a Variac dimmer, at what I would call minimal intensity. After all adjustments were made, the light ended up about one foot from the Mini-Mite, directly in the path to where Director and Scripty were seated, some 25' away.

Eventually (don't know the timeframe, it was a pretty busy and tense set) we heard that the signal is "cutting out". My boom op checked and, indeed, it was cutting in and out intermittently. We moved the cart to get a clear line of sight to them and it mostly was resolved.

Unfortunately, we were short on time and dealing with a difficult shoot, so there wasn't much time to test and troubleshoot properly, so I can't share any more information - but I'd love to hear comments or experiences from my colleagues, in case the issue crops up again.

TIA,

BK

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Just a thought-

You said that the Kinoflo light was controlled by a Variac. Some use the name casually to refer to any rheostat. Was the dimmer used a genuine Variac or another type of rheostat?

Typically, a Variac is about the size of a coffee can with a large Bakelite knob for adjustment. The examples I've seen have been painted a light industrial blue. (No doubt there are other sizes and styles.)

Generic dimmers are notorious for introducing interference; Variacs are usually clean. 

David

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It might not have had anything to do with that light--your TX ant (or the receivers) might have ended up in an RF null point caused by several interacting factors.  Moving the antenna usually fixes this unless you are being stepped on by another transmission (all too common nowadays).   You prob didn't have time to shut down the TX and see what was still coming thru the RX, but that can be helpful in understanding what's going on (when possible).

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Thanks, David. This one was actually a Variac

I thought that was most likely the case. Your proper capitalization of the name "Variac" was a tipoff that you probably knew what you were about. But I thought it worth inquiring. I hope you find the cause or, better, just go through the rest of your career being lucky.

David

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After trying a couple of things to keep Zaxnet out of my 216s and failing, I switched to Lectro IFBs and have been very happy.  I don't use a ton of them so the expense wasn't mind-blowing.  The decrease in general RF issues, compared to Comteks, is huge (at least for me, in NYC).

There was a thread where some people had more success than I did keeping stray Zaxnet etc. out.  I think you're ahead of where I was in regards to using base stations vs. the M216, but maybe there's a tip in there that would help.

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I have both Lectro IFBs and 216s, and while I prefer the sound and performance of the Lectros they are harder procure extras of if you need to scale up for a big job--ie rentals, from other soundies or from rental houses (esp re getting RX in the correct block).   A 216 is a 216, at least among location sound folks, so they can all work off the same TX.

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