Zip Cord for Ant/Gnd Wires - theoretical questions

8/28/2007 9:56:09 AMDoug Criner

For a 1920s TRF set, the antenna is typically connected to one end of the antenna coil and the ground to the other end.

Two questions:

1. Does it make any difference if the ground and antenna are reversed? I think not.

2. Let's say I use (unseparated) 2-conductor lamp cord for the ant/gnd. I connect the lamp cord to a 3-prong 120-V plug. One wire I connect to the ground prong. The other wire is left unconnected to the plug, and that is used as the antenna. Since the ground and antenna are running alongside each other, will the RF cancel out between the ant and gnd?
Doug

8/28/2007 10:08:17 AMLewis Linson

:For a 1920s TRF set, the antenna is typically connected to one end of the antenna coil and the ground to the other end.
:
:Two questions:
:
:1. Does it make any difference if the ground and antenna are reversed? I think not.
:
:2. Let's say I use (unseparated) 2-conductor lamp cord for the ant/gnd. I connect the lamp cord to a 3-prong 120-V plug. One wire I connect to the ground prong. The other wire is left unconnected to the plug, and that is used as the antenna. Since the ground and antenna are running alongside each other, will the RF cancel out between the ant and gnd?
:Doug

Doug :
1. I agree.
2. I think they should be separated. Ideally, 50-100 feet of wire, strung as far from modern AC devices in the house, such as dimmers, microwaves, vacuum cleaners, etc.

Lewis

8/28/2007 10:18:28 AMBill J.

As far as using a zip cord, I would think this is essentially adding capacitance between the antenna and ground with the insulation acting as a dielectric. Likely this will reduce signal strength - but probably not enough to notice. Your idea of using a wall plug is, however, potentially dangerous and ill-advised. Even with a polarized plug, you can't be sure that some shade tree electrician hasn't wired the socket incorrectly in the past. Using the ground lug on a grounded plug is probably safer but still not recommended. There were some devices sold years ago that claimed to "turn your home wiring into an antenna" - esentially this isolated the voltage with a capacitor but resulted in lousy, noisy reception.

8/28/2007 12:11:10 PMLewis Linson

:As far as using a zip cord, I would think this is essentially adding capacitance between the antenna and ground with the insulation acting as a dielectric. Likely this will reduce signal strength - but probably not enough to notice. Your idea of using a wall plug is, however, potentially dangerous and ill-advised. Even with a polarized plug, you can't be sure that some shade tree electrician hasn't wired the socket incorrectly in the past. Using the ground lug on a grounded plug is probably safer but still not recommended. There were some devices sold years ago that claimed to "turn your home wiring into an antenna" - esentially this isolated the voltage with a capacitor but resulted in lousy, noisy reception.

Oh I disagree! If you wanted to get great reception of every light turned on, every mixer, vacuum, or any other motor with brushes, everything else that made interference, it picked up great! If, however, watching television was your intent, you are correct. Lewis ((;>)

8/28/2007 12:25:15 PMMarv Nuce

Doug,
You've essentially created "twin lead", much like the old 300 ohm TV antenna wire, except a much lower impedance. In general twin lead at a much higher impedance would match many antenna configurations ie 300-600 ohms. I wouldn't suggest using any part of your house wiring as an antenna, even though capacitor coupling can be used to avoid the shock hazzard. As for cancellation, the ground and RF path should be derived from the same source (house wiring) creating somewhat of a balanced pair, in which common mode signals would cancel, whereas RF might get through.

marv

8/28/2007 1:30:05 PMbob p

:Doug,
:You've essentially created "twin lead", much like the old 300 ohm TV antenna wire, except a much lower impedance. In general twin lead at a much higher impedance would match many antenna configurations ie 300-600 ohms. I wouldn't suggest using any part of your house wiring as an antenna, even though capacitor coupling can be used to avoid the shock hazzard. As for cancellation, the ground and RF path should be derived from the same source (house wiring) creating somewhat of a balanced pair, in which common mode signals would cancel, whereas RF might get through.
:
:marv
:
::For a 1920s TRF set, the antenna is typically connected to one end of the antenna coil and the ground to the other end.
::
::Two questions:
::
::1. Does it make any difference if the ground and antenna are reversed? I think not.
::
::2. Let's say I use (unseparated) 2-conductor lamp cord for the ant/gnd. I connect the lamp cord to a 3-prong 120-V plug. One wire I connect to the ground prong. The other wire is left unconnected to the plug, and that is used as the antenna. Since the ground and antenna are running alongside each other, will the RF cancel out between the ant and gnd?
::Doug

A 10' lenght of Zip cord ahs enough capacitance between the leads to look like a dead short at MW frequencies. In facr, if you wish to use your home lighting circuit as an antenna just connect one conductor th tha antenna lead on your set, and the other to the "Hot" lead of your lighting circuit. Of course this sort of antenna is rather noisy, and not too effective, unless your home is wired knob and tube. A much more effective "Cheater" aerial utilises a disused conductor (Black in a standard single line system) in one's home's telephone wiring to couple capacitatively to the aerial drop wire. This is much more satisfactory than a light socket aerial, although a rotary dial telephone instrument cna baly the very deuce with your reception.