Low Power Discovery

In addition to the external grounds, the transmitters are also grounded via their power supplies to the outlets they are plugged into.

Hello The Crow:

Your discovery about using multi-grounding for indoor broadcasting is an important step into the new frontier of improving the outreach from indoor installations.

You have also reminded me of something I read in a book that fits right in with this area of exploration. I will go look it up and tack it onto this thread.

See you in a few minutes.

Note: That title is not mine, but the heading of this item in RADIO HANDBOOK by Wm. I. Orr, W6SAI, 20th Edition, page 27.15

The ground termination for an unbalanced antenna system can be improved by the addition of a radial ground wire which is connected in parallel with the regular ground connection. The radial wire consists simply of a quarter wavelength of insulated wire connected to the ground terminal of the transmitter. The opposite end of the radial wire is left disconnected, or "floating." The radial wire may be run about the baseboard of the operating room or out the window and a foot or two above the ground. A high-impedance point is reached at the end of the wire and a corresponding low impedance (ground) point at the transmitter end which simulates a ground connection. While it may be used by itself as a ground termination, the radial ground wire works best when used in combination with a regular ground connection.

The transmitter I built has a RF output transformer for impedance matching and I left the secondary (antenna side) floating from circuit ground to avoid audio ground loops. In use, one side connects to the antenna and the other to the earth ground.

With no secondary connection there is no detectable signal on my monitor radio. While fooling around with this I disconnected the antenna lead but left the ground connected. I get a usable signal throughout my house with NO ANTENNA! It is down about 20 dB below the signal with the antenna connected but it is usable. It appears my ground is radiating and there is a capacitive coupled return path from the primary to the secondary of the transformer.

RF can be strange sometimes..

Neil

maybe i am misunderstanding but how is this any different from having long wire attached to the transmitter's ground which is radiating rf like in a dipole setup?

Heh-heh. Yep that's just about right. Works well with AM because the freqs are comparatively low and operate on ground wave. This is essentially why KENC's main antenna did so well it brought trouble. I think the tower to which the Hamilton was grounded was doing most of the work, even though it was ground.

Well, dietnews, here's the point of The Crow's discovery and my reference to the Radial Antenna....

We're talking about indoor installations. The KENC setup you are talking about was outdoors. There is a huge difference since being inside a building steeply reduces what gets out.

maybe i am misunderstanding but how is this any different from having long wire attached to the transmitter's ground which is radiating rf like in a dipole setup?

I'm not sure your query was directed at my post but I will assume so and comment. The difference is that there is not connection to the antenna output per se, only to the ground output. I think what was happening was that the capacitive coupling from primary to secondary in the output transformer was feeding RF into my ground circuit (water pipe) and this ground "lead" was radiating. The return path was probably through the tx. circuit ground via the computer audio gnd to the power line ground. This is the same as connecting the antenna output of a transmitter to the ground and having the ground lead act as a radiator working against the power ground.

Neil

... So in this case, the coupling situation turned the ground into the antenna. It would appear that the TX doesn't much care which is which, it just sends signal whichever way it has to go to complete the circuit. Does that seem right?

Ken,

Yes. The output transformer is acting as a series capacitor in this situation and the "ground" connection is acting as an "antenna" connection. Wired this way there is no difference between the antenna and ground connection if only one of these is used at the transformer secondary. This is, as you stated, the same as connecting the antenna output to the antenna system ground.

Neil