DSL noise interferes with secondary dial modem.

[Ric63]

After many attempts to isolate what is believed to be DSL noise coming into my dial up modem I cannot isolate the problem. This problem is definately on two of my three computers. The third has Windows Vista and I have not checked it yet since that computer does not need the dial modem.
The two which definitely have the problem are running Win XP SP-2. I use Hyperterminal 6.2 Private Edition. One Modem is an Agere System PCI Soft Modem. The second modem is a Conexant HCF V90-56K Data Fax PCI Modem. The dial modem is used to control a remote radio site and is NOT USED ON THE INTERNET. The DSL filters seem to have no effect for the dial modem but work fine for telephone line voice. However, occasionally the noise will appear on the voice line but I am able to clear the line. At no time was I able to reduce or eliminate the noise interference to the dial modem. The pulsing noise is more than sufficient to prevent the dial modem from completing its task properly. Although I have not carried either of my computers outside to connect at the service box for a thorough exam of the incoming signal, there is not sign of the problem at the service box using a voice phone.
My internet connection is a Verizon DSL line and I am using a Westel E90-610015-06 modem in bridge mode into a Linksys wired router BEFSR41 ver 4.3. The interference is present with the network disconnected....END
/Ric63

[johnwill]

Remember that the dial-up modems SHOULD have a filter, ONLY the DSL modem should be installed directly to the phone line.

If you're still having issue, here's my recipe for fixing DSL line wiring issues.

Purchase a DSL splitter and install it at the telco service entrance. Run a direct line from the DSL port on the splitter directly to the DSL modem. Connect all of the other phone instruments to the telephone output of the DSL splitter. All of the DSL analog side wiring should be CAT3 or better twisted pair from the telco service entrance to the DSL/ADSL modem. You can use one of the twisted pairs in CAT5 cable if you have that on hand.

This is as good as it gets for DSL installations, and will usually solve in-house wiring issues.

Here's a good detailed description of the process: DSL Wiring Upgrade Tutorial

[Ric63]

DSL Splitter works nicelyand seems to have made an improvement in the telephone voice line. However, it dosen't do much for the original interference problem with dial modem. Pulsing interference still hampers the analog modem on two computers /Ric63

[johnwill]

Hard to say what is going on there, but my guess would be sub-standard wiring on the voice side. If you have DSL, why all the analog modems?

[Ric63]

The dial up modems are used to access a remote radio control point (repeater controller) for Amateur Radio. Necessary by regulation.

[johnwill]

OK, what exactly are the symptoms?

You do realize that EVERYTHING but the DSL modem should be filtered, right? If you followed my previously posted configuration, you should be connecting the analog modems on the POTS side, not the DSL side.

[Ric63]

Yes, the dial modems are on the POTS side. I think that it is a bit more obvious at this point that the problem may be on the telco side of the ledger. The comment about sub-standard wiring may be more acurate than I had hoped. My residence is 600 ft. off the road and my service is supplied by buried cable which may be having a problem after being buried for 25 years etc. Thanks for your assistance.

p.s. The splitter does provide me with a much better DSL service than I had previously with just the vendor supplied line filters.

[johnwill]

The splitter usually resolves in-house wiring issues if installed as I mentioned.

I'm not sure what is going on with the other modems. Have you tried a direct wire to the NID for a single modem to see if that resolves it? You may still have interior wiring issues, the DSL splitter and separate run just solved the issue for the DSL modem, not for the rest of the POTS equipment.