The cable I used was armored with a spiral copper shield over 5 twisted pair lines. I did try grounding the shield at one end, and at both ends with no results. Putting caps across the twisted pair and to ground also did not eliminate the problem, but did reduce it. I used 600:600 isolation transformers in the audio input and output lines at the repeater.
It all became a mute point when the cable got mowed in two during a grass cutting this last summer, and then we lost the public IP address and EchoLink was no longer usable. So any more trouble shooting exercises will await the return (if ever) of the public IP address. Thanks for the suggestions folks - 73 - Jim W5ZIT --- Frank or Barbara Rossi <[EMAIL PROTECTED]> wrote: > Depends on what kind of cable on your 500' run. > Shielded cable, try Earth ground on the shield on > both ends. > > I have got away using Cat-5 cable for audio with a > 100' run. > Use 2 cables 1 for Tx and 1 for RX to prevent cross > talk. > Cat -5 has 4 pairs of wire, solid colors all + and > stripes all - > connected together to minimize resistance. > Twisted Pair does a great job of inducing RF voltage > equally on each > wire so there is no difference potential on each > wire. > Ran speaker level audio through the wire then > reduced the audio level to > mic level with 2 resistors at the radio mic and > sound card mic, 100 ohm > in series with the *+* and 10 ohm to audio* *minus* > *as a voltage divider. > + and - audio come from across the 10 ohm resistor. > That reduced the audio level to 1/10 its original > level, and at the same > time reduced any interference > on the audio line by the same factor of 10. > Depending your audio levels you may be able to go as > high as a 1K in > series with the 10 ohm. > That will reduce the audio and interference by a > factor of 100. > > Another thing to try may be as simple as a ferrite > toroid on both ends > of the wire. > They will act like an RF Sponge. > > Another thing to try, .001 or .01 cap across the mic > inputs, depending > on the impedance of your audio circuit. > Wrong cap will affect your high audio frequencies. > May take some playing around but you can beat the > interference. > N3FLR - Frank > > On 11/21/2007 12:21 PM, Mike Morris WA6ILQ wrote: > > At 05:58 AM 11/21/07, you wrote: > >> (big chunk cut out) > >> > >> Al published my EchoLink interface on his web > site > >> (the PSE508 web site) that used the PSE-508. I > had a > >> 500 ft cable between the computer and the > repeater > >> using this interface which worked OK until a > >> high-power AM broadcast station came on line > about 5 > >> miles from my location. I had audio from the BC > >> station on the input of my repeater and also on > the > >> EchoLink audio to the internet. I will have to > go to > >> an RF in-band link to eliminate the problem as I > was > >> not able to get rid of it on the long cable. > >> > >> 73 - Jim W5ZIT > > > > Rather than go to all the trouble of setting up > the RF link, maybe we > > can help you get the broadcast interference out of > the cable. After > > all, the telecom industry has been getting RF out > of long cable runs > > for over a century. > > > > The info in this writeup may help... > > Mike Sandman has a wholesale telephone equipment > distribution company > > in the Chicago area.plus he > > has a telecom service company... and he has done a > number of > > interesting things... look at > > www.sandman.com <http://www.sandman.com/>... > > but his RF elimination page is good. See < > > http://www.sandman.com/pdf/Page43.pdf> > > > > Unfortunately his company is up for sale, I hope > the web site does not > > go away... > > > > Mike WA6ILQ > > > > > ------------------------------------------------------------------------ > > > > No virus found in this incoming message. > > Checked by AVG Free Edition. > > Version: 7.5.503 / Virus Database: 269.16.3/1144 - > Release Date: 11/21/2007 4:28 PM > > > ____________________________________________________________________________________ Never miss a thing. Make Yahoo your home page. http://www.yahoo.com/r/hs
