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The author mentions that he used "A 2 metre bit of wire jammed in the screwhole at the base of the tiny antenna" to try and get better reception. While the sig
by olympus 11y ago
The author mentions that he used "A 2 metre bit of wire jammed in the screwhole at the base of the tiny antenna" to try and get better reception. While the signal he is receiving is in the 2-meter band, a monopole antenna works better if it is 1/4 the wavelength, so he might actually get better reception with a 0.5 meter length of wire. What he created is usually called a "random wire" antenna, and may deliver acceptable performance with a strong signal.
But the NOAA satellites (and quite a few other satellites) use a circularly polarized signal, and for just a tiny bit more money (perhaps the cost of the dongle) you can make a MUCH better antenna for circularly polarized signals. Some designs are just helixes made with coax cable, some are just a couple of wires in an x-shape.
Google is your friend, and building an antenna is a fun cheap weekend project and will greatly enhance your results when hunting for satellite signals.
P.S. if you make a circularly polarized antenna and you discover that you made a LH polarization instead of the RH that you wanted (or vice versa), just turn the antenna upside down. It may behoove you if you are planning on listening to signals with both polarities to construct one that is easily flipped over.
- weinzierl 11y agoWhile the signal he is receiving is in the 2-meter band, a monopole antenna works better if it is 1/4 the wavelength, so he might actually get better reception with a 0.5 meter length of wire. I always thought a lambda/4 antenna is used because it's almost as good as a lambda antenna but much more conveniently to handle. I understand that more complicated antenna designs can be better than a simple lambda wire, but how can a lambda/n wire be better? I don't doubt what you are saying, I'm just curious how this can work.
- aexaey 11y agoLinear monopole antennas are very easy to reason about. Imagine (or actually draw) a sine wave graph, and then fit your antenna along the X axis of the graph. Now look at "signal" amplitude at the antenna's extremities. You'll notice that 1/4 wavelength antenna will give you the strongest signal, while 1/2 and full wavelength will apparently give no signal at all. The only reason that full-wavelength piece of wire picks up anything at all are build imperfections - wire length not perfectly matched to wavelength, not perfectly straight, not perfectly aligned with signal source, signal reflections hitting it from different angle, etc. Thats why olympus refers to performance of full-wavelength piece of wire as "random piece of wire"-kind of performance. On the other hand, linear dipole would be 1/2-wavelength (or 2 times 1/4-wavelength), as it is just two 1/4-monopoles put together.
- weinzierl 11y agoThis makes sense. Thank's a lot.