Hello, Jack,
VHF interference to wired telephones is not common, but it does happen. The
use of indoor antennas does add to the problem.
In general, you will need an RFI filter at each telephone or affected
device. In addition, you may also need a separate filter for the handset
cord, especially for frequencies about 14 MHz, or a ferrite core (about 10
turns should do) on the power-supply leads going to any of the telephones,
answering machines, standalone modems, etc, especially for frequencies below
14 MHz.
Many telephone filters are not effective at VHF. K-Com makes one
specifically for the VHF range. Contact:
K-Com
PO Box 82
Randolph OH 44265
USA
Phone: 330-325-2110
Fax: 330-325-2525
Products/Services: FILTER-TELEPHONE EMI FILTER, APPEARS IN ARRL HANDBOOK
Notes: Filter models RF-1 (modular), RF-2 (wired) and RF-1 Coiled Cord (for
handsets).
Date of last change: September 4, 1996
The ARRL Web page has a number of interference packages. Check out
http://www.arrl.org.
73 from ARRL HQ,
Ed Hare, W1RFI
ARRL Lab Supervisor
----------
>From: jack.sippel
>To: rfi
>Subject: [RFI] 2 meter interference in my phone system
To: <rfi@contesting.com>
>Date: Friday, January 30, 1998 9:42AM
>
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>From: jack.sippel@nellcorpb.com
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To: <rfi@contesting.com>
>Date: Fri, 30 Jan 98 09:42:13 -0800
>To: <rfi@contesting.com>
>Subject: [RFI] 2 meter interference in my phone system
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>----------------------------------------------------
>
>I recently added a 50 Watt 2 meter rig to my shack and last night my
>wife politely told me that every time I transmitted (SSB) that she could
>hear me while she was using the telephone (a hardwired one, not a
>cordless).
>
>I have a discone in the attic (neighborhood restrictions) which is about
>15 feet from the phone line that runs down into my shack. I suspect
>that the other phone lines for the 2nd story are also in the attic, but
>I think they are buried in the insulation. I have a surge protector on
>the telephone jack in my shack, but I don't know if it has any RFI
>filtering.
>
>I have seen ads for "dohickeys" in QST and other magazines that attach
>to the phone or to the wiring are supposed to cure telephone
>interference for around $25. My question is how many will I need. Just
>one somewhere in the line? One at the junction box? One on every phone
>(costly!)?
>
>I also have occasional problems with my home alarm system (also
>hardwired, also has wires in the attic) when transmitting on 15 meters.
>Will these same devices help here as well?
>
>Any other ideas welcomed.
>
>73 de KU0KU, Jack
>+--------------------------------------------------------------+
>| Jack Sippel, KU0KU <jack.sippel@nellcorpb.com> |
>| former callsigns: KI0JJ, WB0TGZ, KB0YVE FISTS #3933 |
>| near Kansas City, Kansas, USA (38.875N 94.650W) grid=EM28qv |
>+--------------------------------------------------------------+
>| HF: Kenwood TS-850S with 40/20/15/10m dipoles + 75ft longwire|
>| V/UHF: Kenwood TS-790A with an attic discone, Yaesu FT-50R |
>| digital: HAMCOMM |
>+--------------------------------------------------------------+
>
>
>
>
>
>--
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>Administrative requests: rfi-REQUEST@contesting.com
>WWW: http://www.contesting.com/rfi-faq.html
>Questions: owner-rfi@contesting.com
>
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|