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Comtek M72 question


leeascher

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Dear Group,

I started my career a few years ago with an ancient Comtek kit comprised of 2 M72 Tx's (channels A & E), and a bunch of PR-72 Rx's.  My Tx antennae are the thin, mini-connector type... not the option 7 BNC.  As you can guess, my Comtek range is terrible, and I've neglected to upgrade this part of my package in order to afford better "essentials" (mixer, recorder, wireless, etc.).

Now that I'm getting booked on bigger projects, I still find myself needing more "toys", and I am wondering if it's possible to improve my Comtek range without investing in a whole new system (for now at least).  Would modding the Tx's to the BNC antenna give me a significant range improvement?  How about a Phase Right Antenna also?  Any insight would be greatly appreciated.  Thanks.

Sincerely,

Lee Ascher

Los Angeles, CA

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Lee,

  You might be able to have your antenna mount modded to a BNC connector, and then get a Phase Right to give you a boost. The next step would be a base station. You can get the ones that use the M72 module, and then you'll have BST power without the cost of a full base station. All your rxs will still work, and you can swap frequencies too. Either way you're looking at a couple hundred bucks, unless you get lucky on ebay.

Tom

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I have followed this same path.  I've been in the biz for a long time and got the micromini-antenna TXs many many years ago.  I finally upgraded them to the BNC and also got them off the lower letter bands (I was on A also) which are terrible around here (SF).  The BNC allowed me to use a much sturdier antenna, which made for better reception.  The PhaseRite helps a lot too, not so much in raw range it seems but in consistency within that range.  I got the Comtek BST75 TX when it came out--same power as the much more expensive BST25/50 but without the fancy display--that and the PhaseRite have really helped with making my TX coverage more consistent.  As with all thing wireless these days, how long all this will keep working is anyone's guess.

Philip Perkins

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Lee,

How long are your antennas?  I have two 72 series transmitters and use what I call "floppy antennas" (mini plug with a single flexible wire antenna) on both,  and also use the same type of antenna on my 216 transmitter.  IIRC, my 72 antennas are 15 inches long.

I mention this because I've had very good results distance-wise with all my Comteks.  Of course, they don't equal a Lectro wireless, but for their purpose, I've found the floppy antennas to be fine.

They've done well this way for for both monitoring and for wireless timecode.

My guess is that you'd need to go with something better than just the whip coming out of the BNC to improve them much.  Of course, I could be wrong.

The phase-right might be what you're looking for.

John Blankenship

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Guest tourtelot

I bought a BST-50 for about $800 and it makes the Comtek PR-72 receivers into a kick-ass, long range director/video village system.  There are other good rigs out there (I have a Lectro T1/R1 myself) but I still love the Commies.  They are fairly inexpensive if lost (unlike the R1s), and pretty near bomb-proof.  I have never, in my memory, had one break that I couldn't fix by bending the headphone jack contact back with a greenie; maybe a couple in 25 years that went to SLC for repair, but not many.  Everyone and his uncle have dropped them, caught them their chairs, left them on the insert car; really tough to beat.  Can't say enough, but the BST-50 made them into a real viable system.  Well worth the money.

D.

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  • 2 years later...

Since my question relates to this older post I figured it would be better to continue with it than start another.  I recently got a hold of a very good condition set of these older non-BNC m72 comteks.  I can't seem to find much information about their details about how the channels work so I thought I'de ask you all.

First off, how do the transmitters work with the receiver crystals?  My receiver has a "1" crystal, does this mean that i have to get that same crystal for more receivers if I add more?  Can I use the same transmitter with receivers with other channel crystals, like E or F types?

Secondly, I can only seem to receive one channel from my mixer's stereo aux out.  Correct me if I'm wrong, but if I'm using balanced outs from my mixer to the transmitter's input, and a pair of stereo headphones, I should hear both channels on the receiver end right?

ty for any help

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Ummm.  I am going to leave the "balanced out to a pair of stereo headphones" question to someone with a more delicate touch.  And I might even go so far as to suggest a call to Comtek when they open in the morning regarding the equipment you own.  But here's what I know...

The M72 is a fixed frequency mono transmitter.  The frequency is stamped at the bottom of the transmitter, typically.  Comtek built these transmitters in several frequency ranges.  For example, the A-M frequencies are closest to the 72mHz range.  They also produced a range "TV 5-6" and various others too, I think.  The receivers must match the transmitter, and not all PR72b receivers are capable of operating in the same frequency range, even if you plug in the "right" crystal.

The PR72 receivers were made with a mono headphone jack until the end of their run, and even with the stereo jack installed near the end of their run, you are only hearing the same thing coming out of each ear of stereo headphones.  The new jack was simply installed to allow the user to use stereo headphones without only hearing from one side.

Comtek is an AMAZING company, and will do whatever they can to fill you with knowledge of their older equipment, as well as helping you to modify it or keep it running.  I have 12xPR72b, many of which have been "modified" with the stereo jack when sent in for service.  They all work perfectly, and are more reliable and idiot proof than the PR75a (which have a tuning button - ugh!).  I originally used a M72 with BNC, but now use the BST-50b base-station.

Please call them.  They will tell you everyting you need to know and will help you become a customer for the long term.

Robert

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Are you sure your RX isn't an "I" instead of a "1"?  If it is an "I" then you are in the "letter band" for Comtek, and can use the BST75 TX and can also swap out the crystals to change freqs on the RXs.  I have bought up small batches of PR72bs over he years in various letter band freqs, bought new Xtals for them in the freqs I wanted to use but kept the others as a backup, since the BST75 can transmit to any letter band freq. 

Philip Perkins

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Awesome Robert.. thanks a bunch, and I'll give them a call tomorrow.  I tried looking for the freq # on the bottom, but it looks more like a serial number... there's no decimal anywhere lol.

Under the serial number on the bottom there should be a letter or number designation. My 72's have the letter M embossed under the serial number.

Eric

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Yep, that's a one (and a two and a... -- to reprise verbiage from a recent thread...).

Not too long ago someone had a list of Comtek (and other) frequencies.  It was either here or on RAMPS.  If no one has it at hand, later I can dig for it since I know I saved it somewhere.

John B. 

Here you go.

-----------------------------------------------------------

                                                                184.600  Comtek M72 FM Ch.8-20

                                                                185.000  Location Reporting

                                                                  185.150  Nady Ch. Orange

                                                                186.800  Comtek M72 FM Ch.9-2

                                                                187.600  Comtek M72 FM Ch.9-6

                                                                  188.400  Comtek M72 FM Ch.9-10

                                                                  190.200  Comtek M72 FM Ch.9-18

                                                                  192.800  Comtek M72 FM Ch.10-2

                                                                  193.200  Comtek M72 FM Ch.10-4

                                                                  193.600  Comtek M72 FM Ch.10-6

                                                                  194.400  Comtek M72 FM Ch.10-10

                                                                  195.200  Comtek M72 FM Ch.10-13

                                                                  195.400  Comtek M72 FM Ch.10-14

                                                                  196.200  Comtek M72 FM Ch.10-18

  72.100  Comtek M72 FM Ch.A                        196.600  Comtek M72 FM Ch.10-20

  72.300  Comtek M72 FM Ch.B            197.400  Comtek M72 FM Ch.10-24

  72.500  Comtek M72 FM Ch.C            198.750  Comtek M72 FM Ch.11-2

  72.700  Comtek M72 FM Ch.D            199.600  Comtek M72 FM Ch.11-6

  72.900  Comtek M72 FM Ch.E            200.400  Comtek M72 FM Ch.11-10

  73.100  Comtek M72 FM Ch.N            202.200  Comtek M72 FM Ch.11-18

  73.300  Comtek M72 FM Ch.M            202.650  Comtek M72 FM Ch.11-20

  73.600  Comtek M72 FM Ch.K            204.800  Comtek M72 FM Ch.12-2

  75.100  Comtek M72 FM Ch.L            205.600  Comtek M72 FM Ch.12-6

  75.500  Comtek M72 FM Ch.F            206.400  Comtek M72 FM Ch.12-10

  75.700  Comtek M72 FM Ch.G            208.200  Comtek M72 FM Ch.12-18

  75.900  Comtek M72 FM Ch.H            208.650  Comtek M72 FM Ch.12-20

  82.500  Comtek M72 FM Ch.6-1          209.150  Nady Ch. Green

  82.800  Comtek M72 FM Ch.6-3          210.800  Comtek M72 FM Ch.13-2

  83.800  Comtek M72 FM Ch.6-2          211.600  Comtek M72 FM Ch.13-6

  86.800  Comtek M72 FM Ch.6-5          212.400  Comtek M72 FM Ch.13-10

 

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Nice!

So if I were a betting man, you probably have Comtek M72 FM Ch.6 - 1 (82.500) and its corresponding receiver.

If I were you, I would consider getting into the lettered frequencies while you are still not heavily invested.  The M72 with BNC are all over the place, as are PR72b with crystals.  They are inexpensive and reliable, and will allow you to upgrade to a base-station later.  You will likely keep the portable for those situations that require it.

Robert

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Thanks a bunch all, I have another set I found cheap off Ebay coming, that includes a base station, but user has not been able to give me any freq or model id #'s yet.  Tried calling Comtek today and see what they can tell me, but they're on vacation at the moment :P.

Cheers all,

Zack

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Under the serial number on the bottom there should be a letter or number designation. My 72's have the letter M embossed under the serial number.

Eric

Eric.. my transmitter has a "1" under it's serial # (120315), and receiver has a "NB" under it's serial (120321).

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That's not a band I've heard used much for movie work--you might have trouble finding used receivers in that range, and you should ask Comtek if receivers designed for the letter bands will work with crystals in that higher range.  If they do then you can find lots of cheap used Rxs around and buy new xtals for them to match your TX.  If you can get a base station TX that would be great too, esp if it is in a range that you can re-crystal your RXs to.  It is good to have more than one channel of Comtek available.

Philip Perkins

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Philip, I'm waiting on comtek to get back from vacation to see what options I have with this set I got.  I've been trying to find some more sets out there, but keep finding miss-matched freq's so far :P.  Any of you guys looking to sell some off? lol (had to try).

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Philip, I'm waiting on comtek to get back from vacation to see what options I have with this set I got.  I've been trying to find some more sets out there, but keep finding miss-matched freq's so far :P.  Any of you guys looking to sell some off? lol (had to try).

Watch ebay and TrewCoffAtion Sound consignment, they come up pretty often.

Philip Perkins

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