* Received good information
A recent reader comment about using the telephone lines as a radio antenna deserves some additional information. I have been using my telephone lines quite successfully for several years. I can report that this antenna system pulls in all sorts of signals especially when used with a good ground connection. However, there are some cautions to be observed.
1. Never make a direct electrical connection to any of the telephone or power wires, or other communication wiring. Interconnection wires often carry equipment operating voltages. AC line wires may have 125 volts or more of alternating current. Telephone lines have 50 volts of direct current and perhaps 150 volts AC during ringing. Communications circuits often use a steady current to indicate that the remote devices are actively connected. Any radio attached to these wires could route hazardous power through itself (and through its user)!
2. Electric and telephone lines are usually balanced with respect to ground to reduce noise and interference. Connections that are not properly balanced may result in poor or non-performance of the equipment (blown fuses, distorted audio, no telephone ringing, data errors, etc.).
3. Fault conditions occur on public wiring: Storms and vehicle accidents can damage support poles, allowing wires to cross and place unusual voltages on connected devices. Lightning strikes can put spikes of many thousands of volts on a line, damaging equipment and starting fires. Surge protectors limit but do not eliminate voltage spikes.
The only safe way to make use of the public wiring is to use an isolated connection method. The device must pass radio or audio frequencies safely to your receiver without allowing any of the undesired voltages into your circuits. Here is the method that I have used successfully many times.
Materials: Obtain a length of UTP (Unshielded Twisted Pairs) network cable, say 6 to 10 feet (2 to 3 meters). No modular end plugs are needed. Contractors who install communications wiring usually have pieces of cable this size left over after completing a job, and may give them to you at no cost. Home electronics stores often have reels of this cable and will sell it in small lengths. Any grade (Category 4, 5, 6, etc.) cable will do since we are not going to use it for its intended purpose, so get the oldest grade available. Jacket color and conductor size are unimportant.
Preparation: Remove about 1 inch (2.5 cm) of the outer jacket from each end of the cable, exposing 4 twisted pairs of wire. Carefully untwist each pair of wires so that there are now 8 individual wires protruding from each end of the cable. At only one end of the cable, cut each of the white wires with a colored stripe flush with the end of the cable jacket. Be cautious not to damage the insulation on the remaining wires. At the other end of the cable, cut each of the solid color wires flush with the cable jacket. The cable will now have four individual striped white wires at one end, and four solid color wires at the other end. Remove 1/2 inch (1.2 cm) of insulation from each wire. Twist all four of the striped white wires together to form a single wire with four strands. At the opposite end of the cable, separate the four solid color wires so that they do not touch each other.
Installation: Newer telephone wiring uses modular plugs and wall or panel mount equipment jacks. Replacement plugs or cords are available for these jacks. Older telephone wiring used a cord attached to screws on a terminal block. Remove the block or plug cover. Fasten one of the cable's solid color wires to each terminal. Since there is no direct path through the cable wires, color coding is not important. Be certain that none of the bare wire ends touch each other. When the cable wires are all attached, replace the cover.
Operation: Attach the four white striped wires to the receiver antenna terminal or to the whip antenna. Use an additional wire to attach the ground terminal to a cold water pipe. (If no water pipe is available, use the center screw on an AC wall outlet cover.) Route the antenna cable and the ground wire away from power cords and other cables. Do not coil the cable or ground wire.
Note 1: Outside telephone wiring is a grid of many wires, some of them many miles long. Long wire antennas can produce extremely strong signal levels from powerful local radio stations. Too much signal may cause a radio to be unable to tune out the local stations. Add a series resistor between the antenna cable and the receiver to attenuate the voltage. Use a shorter length of UTP cable if receiver overload persists.
Note 2: The antenna cable may not be satisfactory with underground outside telephone wiring or nearby noisy power wires. Telephone wire antennas are not directional or frequency selective, so you may hear two or more stations simultaneously.
* Ferrite Loop Antennas Design and Information
These are descriptions of some very good ferrite loop antennas. It's the top four in the Antennas list.
14 June 2013
* AM Radio Noise Interference May Be Lowered?
Over the past decades, electrical noise on the AM Band has made DXing and even AM reception more
difficult. The FCC may enforce their rules to lower noise. They may even add more practical
laws to help the AM Band. Here is a Radio World
02 March 2013
* Antenna Z-Match design
J. Bruce McCreath, VE3EAR has built a MW antenna tuner.
View the information and pictures here.
20 September 2012
* MLA Antenna design
Arthur Hernandez has made a new type receive antenna. It's quite a bit smaller than the flag or other loop
type antennas that are common today. There is a descriptive PDF file that can be viewed here.
19 December 2010
* A new SDR Radio
The September 2010 ARRL QST magazine has a review of a new Software Defined Radio. The QS1R is in some ways similar to the others,
yet has some interesting possibilities. It can display a very wide bandwidth and has synchronous AM detection. There are several software choices including WinradHD that can record up to 2MHz of bandwidth. View it here.
17 August 2010
* BOG Antenna work
Jim Glover, WB5UDE has done some work with BOG (Beverage On Ground) antennas. A link to the overview is here.
He's also worked on two occasions with portable setups. One here and the second here. It's some interesting work on how these wire antennas can be used.
04 October 2009
* Loop Antenna Article
Gary DeBock has been doing some excellent work on building loop antennas. They are various sizes, and can be portable types as well as more permanent varieties. The PDF article is here.
01 September 2009
* Simple Phasing System
I put together a very simple and effective antenna phasing system. It's simple enough that somebody, somewhere must have built this before but I don't remember seeing it.
The article is here.
13 December 2008
* Vertical Antenna
Here is a variant on the vertical or whip antenna often used for AM DXing. Link is here.
28 November 2008
* Passive Loop Antenna article
Kevin Schanilec has written an article on the use of passive loop antennas. It includes nulling techniques and how to connect their signal reception to a radio. Some great graphics included. Nice work! The PDF is here.
24 October 2008
* National RF LW/MW Ferrite Loop Antenna
National RF has introduced a ferrite loop antenna for the LW and MW bands. A link to the product description is here. It includes a port for an external sense antenna that can make a cardioid pattern, and output gain control. One ferrite loop covers longwave and the other covers mediumwave. Price is about $370US for the unit and one loop, and $90US for the second loop.
21 October 2008
* Palstar R30 Updated
The Palstar R30CC receiver has been updated. A parts supply problem triggered this, but there were some improvements made while redesigning for the new components. A link to the radio is here. One of the better radios for the MW bands.
06 September 2008
* Receiver reviews added
Three receiver reviews from Brian Beezley, K6STI have been added. They are the Sangean HDT-1, Sangean HDT-1X and the Sony XDR-F1HD. They are in the Receivers section.
05 July 2008
* Antenna Overview
An overview of the various antennas used for AM DXing is here. If you have additions, corrections or comments, send them along.
04 July 2008
* Sony SRF-59 audio phasing
Sony has a nice small Walkman radio that works very well for DXing. Kevin Shanilec has found that connecting the audio outputs out of phase and setting
the radios about 90 degrees to each other works for audio phasing. This is a new approach that hasn't been seen before. He has made a .PDF file to
explain the process here.
28 January 2008
* Antenna cable work and notes
I have been doing some work on cables for outdoor antennas, and the results have been a bit surprising. The article is here.
24 August 2007
* Loop antenna work
I'm working on a series of single-turn copper tube loops. So far, results have been very good. Nulling is as good as
a common wire multi-turn loop, but this doesn't need to be tuned. It's broadband from longwave up through the shortwave bands.
A pair of two foot versions have been mounted in the back of my truck at 90 degrees to each other for mobile work. It has been very effective, and picks up much less noise than a whip.
I have an article posted here including construction photos.
A recent modification was the addition of a second pickup on the top of the loop. When run into a phaser, it provides a virtual tilt and much deeper nulls.
The loop was inspired by a version used for VLF weather noise reception on the Stormwise site.
18 February 2006