berniebeaudry Posted October 27, 2011 Report Share Posted October 27, 2011 Hi All, Just replaced my 211 camera hops with the Lectro D4. The D4 is great but its stepping all over my Comtek 216 and creating a bunch of hiss. I retuned the Cometek and moved it farther away from the D4 transmitter where it is in the bag. I got something that's tolerable but not the nice clear signal I had before going to the D4. When I get a moment I'll go to a different frequency on the D4 transmitter and see if that helps. I scanned for open frequencies on my talent 211s and didn't notice any terrible stuff coming into them from the D4 but it seems like I don't have as much range as I had before and was getting random small hits. I am in a location I've never been before so there may be something around that isn't showing up on the spectrum scan so I will try to rescan soon and see if the range improves. Any D4 users/owners out there that can offer any other insight? Are my talent receivers just in the wrong blocks to go up against the D4? I frankly wasn't thinking about blocks when I bought it because I thought it was operating in a range outside of the analogue units. Maybe I'm wrong. Thanks, Bernie Quote Link to comment Share on other sites More sharing options...
John Blankenship Posted October 28, 2011 Report Share Posted October 28, 2011 Bernie, Are you using a proper Comtek cable to feed into the 216 transmitter? This cable contains an inline filter. Comtek can custom make you one with your preferred connectors. Quote Link to comment Share on other sites More sharing options...
berniebeaudry Posted October 28, 2011 Author Report Share Posted October 28, 2011 Bernie, Are you using a proper Comtek cable to feed into the 216 transmitter? This cable contains an inline filter. Comtek can custom make you one with your preferred connectors. Thanks John, I'm using the cable that came with it an adapter that I made with Comtek's input. I even more concerned about my apparent lack of range on my talent wireless. I'm out with Road Trip and I need the Comtek and the talent mics to work better during game day. Best, Bernie Quote Link to comment Share on other sites More sharing options...
berniebeaudry Posted October 28, 2011 Author Report Share Posted October 28, 2011 Just worked through a combination of changing frequencies on the D-4 and then changing frequencies on the Comtek. Got it to a point that it should be useable if I keep the Comtek further away from the D-4 transmitter in the bag. If I listen to the Comtek without the cable I can hear the noise only when I get very close to the D-4, but when I plug the cable in there's more noise, so I'm guessing the filtering isn't working well enough on the cable perhaps because I'm using an adaptor on it. I also rescanned all four of the talent receivers so hopefully tomorrow/today will be more trouble free. Would a ferrite bead on the Comtek cable help? Bernie Quote Link to comment Share on other sites More sharing options...
Jack Norflus Posted October 28, 2011 Report Share Posted October 28, 2011 Would a ferrite bead on the Comtek cable help? I hate to sound like the Senator - but it depends. But the short answer is it wouldn't make it worse. Quote Link to comment Share on other sites More sharing options...
John Blankenship Posted October 28, 2011 Report Share Posted October 28, 2011 Just worked through a combination of changing frequencies on the D-4 and then changing frequencies on the Comtek. Got it to a point that it should be useable if I keep the Comtek further away from the D-4 transmitter in the bag. If I listen to the Comtek without the cable I can hear the noise only when I get very close to the D-4, but when I plug the cable in there's more noise, so I'm guessing the filtering isn't working well enough on the cable perhaps because I'm using an adaptor on it. I also rescanned all four of the talent receivers so hopefully tomorrow/today will be more trouble free. Would a ferrite bead on the Comtek cable help? Bernie I'd try it. Also, look at grounding as a possible contributor. When dealing with RF, all the voodoo matters. Quote Link to comment Share on other sites More sharing options...
justanross Posted October 28, 2011 Report Share Posted October 28, 2011 Hmmmm...I will have to test this out with my D4. I don't really have any advice I could add. I will let you know if I come up with anything. Quote Link to comment Share on other sites More sharing options...
Derek H Posted October 28, 2011 Report Share Posted October 28, 2011 Hey Bernie, I feel your pain man! I'm using a 72MHz Comtek system and I have the same problem with audible RF noise coming from my Zaxcom transmitter. On my system it sounds like a high pitched whine a buy above the nose floor. Noticeable to me and annoying but I don't get complaints about it from producers. I've tried many things to alleviate the problem including the ferrite chokes and cable routing. Nothing makes it completely vanish except for turning the Zaxcom off... Good luck. Quote Link to comment Share on other sites More sharing options...
berniebeaudry Posted October 28, 2011 Author Report Share Posted October 28, 2011 Hey Bernie, I feel your pain man! I'm using a 72MHz Comtek system and I have the same problem with audible RF noise coming from my Zaxcom transmitter. On my system it sounds like a high pitched whine a buy above the nose floor. Noticeable to me and annoying but I don't get complaints about it from producers. I've tried many things to alleviate the problem including the ferrite chokes and cable routing. Nothing makes it completely vanish except for turning the Zaxcom off... Good luck. Thanks Derek, This noise is a loud hiss, that is more than annoying and noticeable. From my tests it getting in via the cable more than anything once I found a frequency combination that helped. I've got a message into Comtek to see if they have any ideas. Thanks, Bernie Quote Link to comment Share on other sites More sharing options...
Derek H Posted October 28, 2011 Report Share Posted October 28, 2011 I also contacted Comtek about it. Unfortunately they couldn't help much. They just suggested getting add much physical space between the digital transmitter and the Comtek transmitter as possible. Not really feasible in a bag rig. I asked a few times about a filtered cable with a capacitor but they didn't seem to think this would help. Quote Link to comment Share on other sites More sharing options...
carbonhobbit Posted October 28, 2011 Report Share Posted October 28, 2011 Here's a shot in the dark. What would happen if you put the transmitter with the camera and get a return feed to boot. This gets the Comtek away from the other transmitter and both the producer and the mixer get to hear the return off the camera. Might work if you can get the camera op to hang one more thing off his rig. Say hi to JJNR in Kansas. Scott....... Quote Link to comment Share on other sites More sharing options...
LarryF Posted October 28, 2011 Report Share Posted October 28, 2011 Hi Bernie, We did tests of the D4T over and above what is required for FCC approval and concluded that the D4T emmissions were much lower than required and would not interfere with receivers in the 470 to 800 MHz band even in a bag. We didn't check for the Comtek's 216 MHz area. However, here's what the designer of the D4T had to say in an email to me: <<Hey Larry. Just been looking at the D4T. It does not radiate around 216MHz at all. Even with the analyzer set to max sensitivity I don’t see any emissions. I found the original thread on the JWsound forum and my guess is that it seems to be RF getting into the audio of the Comtek since he talks about unplugging the cable going into the Comtek and having the problem diminish and only manifest when the D4 is really close to the Comtek. Also he mentioned using a homebrew adaptor on the input of the Comtek. He does mention thinking that the range of the Comtek units are impaired by the D4T but if this is true it is hard to know if this is because of the ingress of RF into the audio circuits of the Contek causing less than stellar audio. It’s hard to know without having the Comtek here to play with. But someone else mentioned a similar problem they had with a Comtec and a different brand. So first thought is that it is RF ingress from the D4 into the audio section of the Comtek and not spurious emissions from the D4T. Derek.>> I'm not so sure about Derek's thoughts about the digital RF getting into the audio circuits because the D4T spread spectrum modulation scheme has the AM components almost completely outside the audio frequencies. We tested against unshielded mic preamps, etc., to show very low AM to audio conversion. Still, it is possible. If you want us to look into further this, we can play with your Comtek near a D4T here. We'd only need it for a day or so. Let me know. larryf@lectrosonics.com Best Regards, Larry Fisher Lectrosonics Hi All, Just replaced my 211 camera hops with the Lectro D4. The D4 is great but its stepping all over my Comtek 216 and creating a bunch of hiss. I retuned the Cometek and moved it farther away from the D4 transmitter where it is in the bag. I got something that's tolerable but not the nice clear signal I had before going to the D4. When I get a moment I'll go to a different frequency on the D4 transmitter and see if that helps. I scanned for open frequencies on my talent 211s and didn't notice any terrible stuff coming into them from the D4 but it seems like I don't have as much range as I had before and was getting random small hits. I am in a location I've never been before so there may be something around that isn't showing up on the spectrum scan so I will try to rescan soon and see if the range improves. Any D4 users/owners out there that can offer any other insight? Are my talent receivers just in the wrong blocks to go up against the D4? I frankly wasn't thinking about blocks when I bought it because I thought it was operating in a range outside of the analogue units. Maybe I'm wrong. Thanks, Bernie Quote Link to comment Share on other sites More sharing options...
studiomprd Posted October 28, 2011 Report Share Posted October 28, 2011 " I hate to sound like the Senator - " Why ?? Quote Link to comment Share on other sites More sharing options...
Derek H Posted October 28, 2011 Report Share Posted October 28, 2011 Thanks for the info Larry. Just to clarify, the issues I've been having with the 72mhz Comtek are in conjunction with a Zaxcom transmitter, not the D4t. Quote Link to comment Share on other sites More sharing options...
berniebeaudry Posted October 29, 2011 Author Report Share Posted October 29, 2011 Larry, I think your designer is correct. I'm thinking its the cable sending audio to the comtek. The adaptor is an 1/8 inch to xlr to allow me to plug into the tape out of the 442. The cable monos the signal as well. I got the transmitter out of the bag, and with the change in frequencies I was able to get a cleaner signal. Interesingly when I was systematically changing frequencies on the D-4 the noise level was worse on some of the lower frequencies. I tried all four blocks of the Comtek as well till I got something that was decent. Even then I had to move the Comtek as far from the D-4 as possible. The range issue I spoke about was my talent receivers, not the Comtek. I rescanned those and seemed to have better range. Again after changing the frequency on the D-4. Might just be coincidental but the receiver closest to the D-4 in the bag had more low level stuff showing on the analyzer. New issue, now that I have the Comtek working I find that the producer's ear buds don't work in the receiver. My 7506s and the camera guys earbuds work but not his. Argggh! Bernie Quote Link to comment Share on other sites More sharing options...
John Blankenship Posted October 29, 2011 Report Share Posted October 29, 2011 New issue, now that I have the Comtek working I find that the producer's ear buds don't work in the receiver. My 7506s and the camera guys earbuds work but not his. It appears that the plug on the producer's ear buds may be somehow wired differently or is shorting out the signal. The jack on the pr216 receivers is wired in a unique way. In order to make the receivers compatible with both stereo and mono plugs, it has the same signal on both legs of the stereo jack, but wired out of phase with each other. This method is used by Comtek so that if someone inserts a mono plug it doesn't short out the signal as it would if both sides were connected directly to the same signal. Therefore, the 216 is compatible with both mono and stereo plugs. I dislike the way that the out of phase signal sounds, so, when someone wants to plug stereo headphone in to a PR216, I normally use a short mono to stereo adapter cable that is then taking the signal off of one leg of the jack only. Typically, no matter what earphones someone uses with the pr216, if it's stereo, I'll use a stereo to mono adapter. Quote Link to comment Share on other sites More sharing options...
berniebeaudry Posted October 29, 2011 Author Report Share Posted October 29, 2011 It appears that the plug on the producer's ear buds may be somehow wired differently or is shorting out the signal. The jack on the pr216 receivers is wired in a unique way. In order to make the receivers compatible with both stereo and mono plugs, it has the same signal on both legs of the stereo jack, but wired out of phase with each other. This method is used by Comtek so that if someone inserts a mono plug it doesn't short out the signal as it would if both sides were connected directly to the same signal. Therefore, the 216 is compatible with both mono and stereo plugs. I dislike the way that the out of phase signal sounds, so, when someone wants to plug stereo headphone in to a PR216, I normally use a short mono to stereo adapter cable that is then taking the signal off of one leg of the jack only. Typically, no matter what earphones someone uses with the pr216, if it's stereo, I'll use a stereo to mono adapter. Must be the case. Ironically my Comtek is the first one he's had this issue with in five shows. It had to be the one I was on. Bernie Quote Link to comment Share on other sites More sharing options...
Matt McGowin Posted October 29, 2011 Report Share Posted October 29, 2011 I use stereo to mono adptrs for use with my pr72's mono headphone jack so that it can be used with stereo hp's. Some headphones (iphone earbuds and others) have trrs and that isnt compatible. but ya probably already know that. Quote Link to comment Share on other sites More sharing options...
Solid Goldberger Posted January 12, 2012 Report Share Posted January 12, 2012 Sorry to revive this old topic, but it seemed the best place for this discussion. I just got done with a 3 month gig using a bag rig consisting of a Zaxcom Fusion 10, a Lectro Octopack with 3 SRa receivers on block 26, 2 lectro SMQv transmitters for hops (@250mW on block 21) and a Comtek 216 transmitter (the 9v battery powered one with the bendy helical antenna, which was modified by Professional Sound Services in NYC to power off a BDS with a lectrosonics battery eliminator). Id used everything in the rig on prior gigs, except the Comtek, which was purchased specifically for the job). Anyways, on the first day of shooting the producers were noting that the Comtek was cutting out intermittently. Initially I thought the cable was busted and replaced it, but it didnt help at all. Later on I realized that proximity to the hops transmitters was causing the transmission of the Comtek to completely cut out. I assumed based on my experience with my prior IFB system, which was built around a Lectro T1, that proximity between different transmitters would be no problem, but apparently the Comtek is a little touchier? After moving the Comtek tx to the other side of my bag (about a foot from the nearest hops transmitter on block 21) everything worked fine, though the bag became significantly less tidy. Have any of you experienced your Comtek signal completely cutting out due to proximity to another transmitter of a totally different frequency? If so, do you know of any workarounds? I'd love to keep everything a little tighter together in the bag. As a side note, Ive always been crazy impressed that Lectrosonics Wireless receivers can work so flawlessly within close proximity to their 250mW transmitters--given proper frequency coordination of course. E. Quote Link to comment Share on other sites More sharing options...
studiomprd Posted January 12, 2012 Report Share Posted January 12, 2012 " thought the cable was busted and replaced it, but it didnt help at all. " how did you determine that ?? problem solving usually begins with isolating the problem often through "trial and error"... " that proximity between different transmitters would be no problem, " not necessarily... " the Comtek is a little touchier? " different animal, different circuitry... " the bag became significantly less tidy. " life sucks! " signal completely cutting out due to proximity to another transmitter of a totally different frequency? If so, do you know of any workarounds? " happens all the time, with all sorts of devices... (all sorts of devices radiate!).. and the "workarounds" include physical separation, shielding, and math. Quote Link to comment Share on other sites More sharing options...
RPSharman Posted January 12, 2012 Report Share Posted January 12, 2012 The M-216 is only 10mW and can easily be overpowered by ***harmonics?*** of more powerful transmitters on completely different frequencies. Separation might not be pretty, but helps with range, interference, and other such issues. Quote Link to comment Share on other sites More sharing options...
studiomprd Posted January 12, 2012 Report Share Posted January 12, 2012 " ***harmonics?*** " to include intermod products and other spurious emmissions. Quote Link to comment Share on other sites More sharing options...
Solid Goldberger Posted January 12, 2012 Report Share Posted January 12, 2012 Ok Mike, on shielding, could you be more specific? I have never experienced analog wireless simply cutting out completely. Theres typically SOME signal present even if it's mostly being overpowered by the interfering RF. In my case te audio would instantaneously cut off, similar in effect to a busted cable jiggling (the reason for my assumption). Am I alone in thinking that's wierd? E. Quote Link to comment Share on other sites More sharing options...
studiomprd Posted January 12, 2012 Report Share Posted January 12, 2012 (edited) " on shielding, could you be more specific? " preferably metal -though all metals are not equal-, on, in, around, and/or between all units involved, and properly grounded. additionally proper vshielding includes a lot of electronic issues (bypassing, coupling/decoupling, filtering, etc.) " simply cutting out completely. " 'capture effect' aka 'FM capture effect' Edited January 14, 2012 by studiomprd Quote Link to comment Share on other sites More sharing options...
John Blankenship Posted January 12, 2012 Report Share Posted January 12, 2012 I have no problem with my M216s near transmitters or receivers. At least, not after I started using the proper cables. The Comtek transmitters need a filtered cable feeding them to keep spurious radiation from entering and causing the types of havoc you've described. Contact Comtek support and tell them what type of termination you need at either end of the cable and they'll fix you up. Either that, or they'll send you the filter components with instructions so you can make the cable yourself. With each of my Comtek transmitters (a 216 in the bag and several 216s & 72s on the cart), I use a filtered line level cable. I'm using cables made by Comtek and also some I made using the specified filter components. I'm using only the small transmitters and have been quite happy with the range and dependability. There have been a couple of hospital locations where there has been interference that caused a problem (one killed both the 216s and the 72s, the other killed only the 72s), but other than that, things have been fine. Quote Link to comment Share on other sites More sharing options...
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