Re: [Repeater-Builder] LOOONG audio runs
On 2/27/2010 4:53 PM, Joe wrote: Oz, in DFW wrote: Make sure you use twisted pair. Station wire like that use to wire houses is often not twisted. Ethernet cable is good and has a high twist pitch - better for this application. I wonder if CAT 6 would be better than CAT5 due to the difference in twist? Joe I'm not sure it will matter much. Mostly I think a tight twist will provide better isolation at the higher frequencies. Cross connect and some multipair telephone cable can have as little as two twists per foot. This is an appreciable portion of a wavelength at UHF and is likely to offer lower common mode value. The twist rates of CAT5 and CAT6 are high enough that I suspect they are substantially similar in this application. Oz, in DFW -- mailto:o...@ozindfw.net Oz POB 93167 Southlake, TX 76092 (Near DFW Airport)
Re: [Repeater-Builder] LOOONG audio runs
I have to stick my nose into this one. Use balanced audio ESPECIALLY if there is any other strong RF at or near your site. 140 feet is a good AM broadcast antenna! Shield grounds for your cable should be at one end (best bet is at the controller for everything!) It also might be wise to snap on an RF choke at each end of the cable, after all ... you don't need any strong RF on your analog signaling lines to get rectified somewheres and present you with a locked up or in-operable repeater. my 0.02 James WJ1D JOHN MACKEY wrote: I have a odd situation where I need to run long audio cables between my repeater controller and two repeaters. In this case, the repeater controller will be connected to 2 repeaters in the same cabinette. The other two repeaters will connected thru about 140 feet of wiring to the other side of a building. I am thinking of using balanced audio wires for the long runs and using Henry Engineeering boxes to convert between balanced/un-balanced at each end. Anyone ever done long audio runs like this? Am I over engineering it and unbalanced will be good enough? I use the Henry Engineering boxes for several audio conversions in broadcasting, here is a link for what they are:
RE: [Repeater-Builder] LOOONG audio runs
John, The professional sound and recording industry addressed this problem long ago, when wired microphones and other pickups needed to be run several hundred feet from the performer on stage to the mixing board. We used balanced twisted pair shielded cable with XLR connectors on each end. A device called a Direct Box is used to convert unbalanced to balanced, and also avoid ground-loop issues. Since it is important to have a high-quality transformer in a direct box, I made my own with units from Jensen Transformer- a company that is still in business today. http://www.jensen-transformers.com/ 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of JOHN MACKEY Sent: Friday, February 26, 2010 10:49 PM To: Repeater-Builder@yahoogroups.com Subject: [Repeater-Builder] LOOONG audio runs I have a odd situation where I need to run long audio cables between my repeater controller and two repeaters. In this case, the repeater controller will be connected to 2 repeaters in the same cabinette. The other two repeaters will connected thru about 140 feet of wiring to the other side of a building. I am thinking of using balanced audio wires for the long runs and using Henry Engineeering boxes to convert between balanced/un-balanced at each end. Anyone ever done long audio runs like this? Am I over engineering it and unbalanced will be good enough? I use the Henry Engineering boxes for several audio conversions in broadcasting, here is a link for what they are: http://www.henryeng.com/matchbox.html http://www.henryeng.com/matchbox.html
RE: [Repeater-Builder] LOOONG audio runs
I have a odd situation where I need to run long audio cables between my repeater controller and two repeaters. In this case, the repeater controller will be connected to 2 repeaters in the same cabinette. The other two repeaters will connected thru about 140 feet of wiring to the other side of a building. I am thinking of using balanced audio wires for the long runs and using Henry Engineeering boxes to convert between balanced/un-balanced at each end. I'd definately go balanced, but I'd use transformers rather than active balanced devices. Decent transformers (even audiofile-grade Jensens) would still cost less than Henry matchboxes (or anyone else's active converters most likely), and be more reliable. Back in the old days, Western Electric 111C repeating coils were supplied by the telco for program audio lines. Look around broadcast transmitter sites and old studios, you'll probably find a few nailed up to the telco backboard that the LEC no longer has an interest in maintaining ownership of... The common mode rejection of Henry matchboxes isn't all that great, I've tested them. If you can, keep the audio level high on the sending side (I think 111C's were good up to close to a watt at 600 ohms!), and pad it down on the far side's secondary as necessary to maximize S/N. --- Jeff WN3A
Re: [Repeater-Builder] LOOONG audio runs
I vigorously second Jeff's recommendation. This is an application where iron is still the right answer. Make sure you use twisted pair. Station wire like that use to wire houses is often not twisted. Ethernet cable is good and has a high twist pitch - better for this application. Repeat coils are the classic answer. Here's a hint about what you are looking for if you don't already know: http://users.snip.net/~mrbibbs/gearpix/Western_Electric_Repeat_Coils_4040.jpg http://users.snip.net/~mrbibbs/gearpix/Western_Electric_Repeat_Coils_4042.jpg http://oldphoneguy.net/Coils1.jpg Jensen's stuff is really nice, but you'd be paying a premium price for performance you can't use. If you can't find an old set of repeat coils, most small audio transformers with reasonable turns ratios will do the job fine. Reasonable in this case is probably less than 4 or 5:1, though 1:1 would be best. I'm not sure where you are, but if you can't find anything easily, the coupling transformers out of **OLD** modems (1200 Baud or less) are likely suspects. On 2/27/2010 10:32 AM, Jeff DePolo wrote: I'd definately go balanced, but I'd use transformers rather than active balanced devices. Decent transformers (even audiofile-grade Jensens) would still cost less than Henry matchboxes (or anyone else's active converters most likely), and be more reliable. Back in the old days, Western Electric 111C repeating coils were supplied by the telco for program audio lines. Look around broadcast transmitter sites and old studios, you'll probably find a few nailed up to the telco backboard that the LEC no longer has an interest in maintaining ownership of... The common mode rejection of Henry matchboxes isn't all that great, I've tested them. If you can, keep the audio level high on the sending side (I think 111C's were good up to close to a watt at 600 ohms!), and pad it down on the far side's secondary as necessary to maximize S/N. --- Jeff WN3A -- mailto:o...@ozindfw.net Rich Osman N1OZ POB 93167 Southlake, TX 76092 (Near DFW Airport)
Re: [Repeater-Builder] LOOONG audio runs
Oz, in DFW wrote: Make sure you use twisted pair. Station wire like that use to wire houses is often not twisted. Ethernet cable is good and has a high twist pitch - better for this application. I wonder if CAT 6 would be better than CAT5 due to the difference in twist? Joe
Re: [Repeater-Builder] LOOONG audio runs
I think when I made the original post it was late I was tired!! I work in broadcasting and use the 111C coils often in long analog audio runs for remote broadcasts. I do agree that transformers would be better than active balanced devices. The active devices are easier to deal with for short audio runs in a production room or control room when you have to interface with something that is consumer grade un-balanced. But for the long runs I definately agree that 111C coils are the best option. -- Original Message -- Received: Sat, 27 Feb 2010 01:24:49 PM PST From: Oz, in DFW li...@ozindfw.net To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] LOOONG audio runs I vigorously second Jeff's recommendation. This is an application where iron is still the right answer. Make sure you use twisted pair. Station wire like that use to wire houses is often not twisted. Ethernet cable is good and has a high twist pitch - better for this application. Repeat coils are the classic answer. Here's a hint about what you are looking for if you don't already know: http://users.snip.net/~mrbibbs/gearpix/Western_Electric_Repeat_Coils_4040.jpg http://users.snip.net/~mrbibbs/gearpix/Western_Electric_Repeat_Coils_4042.jpg http://oldphoneguy.net/Coils1.jpg Jensen's stuff is really nice, but you'd be paying a premium price for performance you can't use. If you can't find an old set of repeat coils, most small audio transformers with reasonable turns ratios will do the job fine. Reasonable in this case is probably less than 4 or 5:1, though 1:1 would be best. I'm not sure where you are, but if you can't find anything easily, the coupling transformers out of **OLD** modems (1200 Baud or less) are likely suspects. On 2/27/2010 10:32 AM, Jeff DePolo wrote: I'd definately go balanced, but I'd use transformers rather than active balanced devices. Decent transformers (even audiofile-grade Jensens) would still cost less than Henry matchboxes (or anyone else's active converters most likely), and be more reliable. Back in the old days, Western Electric 111C repeating coils were supplied by the telco for program audio lines. Look around broadcast transmitter sites and old studios, you'll probably find a few nailed up to the telco backboard that the LEC no longer has an interest in maintaining ownership of... The common mode rejection of Henry matchboxes isn't all that great, I've tested them. If you can, keep the audio level high on the sending side (I think 111C's were good up to close to a watt at 600 ohms!), and pad it down on the far side's secondary as necessary to maximize S/N. --- Jeff WN3A -- mailto:o...@ozindfw.net Rich Osman N1OZ POB 93167 Southlake, TX 76092 (Near DFW Airport)
Re: [Repeater-Builder] LOOONG audio runs
On Fri, 26 Feb 2010, JOHN MACKEY wrote: I have a odd situation where I need to run long audio cables between my repeater controller and two repeaters. In this case, the repeater controller will be connected to 2 repeaters in the same cabinette. The other two repeaters will connected thru about 140 feet of wiring to the other side of a building. I am thinking of using balanced audio wires for the long runs and using Henry Engineeering boxes to convert between balanced/un-balanced at each end. Anyone ever done long audio runs like this? Am I over engineering it and unbalanced will be good enough? unbal to bal is a good idea. It isn't over engineering as Motorola did this for years with radio accessories. And they only had to go 17 feet. Getting rid of common-mode interference (ground loops) is worth it. -- Kris Kirby, KE4AHR Disinformation Analyst
