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)
