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1

A quarter wavelength of coax (shortened by its velocity factor) is a notch filter if the far end is left open. So leave the far end open; and try feeding the coax from a frequency generator voltage source plus a series resistor at the near end; and sweep the frequency across a slightly wider range than is appropriate for an adjusted quarter wavelength to ...


1

If you are using a monopole antenna, when you hold the radio, your body acts as the image of the antenna to make a full dipole. This works for both transmit and receive. If you are receiving a strong signal, it doesn't make a lot of difference, but if you have a marginal signal, you will notice that it gets a lot worse if you set the radio down or put it ...


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ALL ANTENNAS ARE DIPOLES. THIS MEANS THAT A 1/4 WAVE VERTICALREQUIRES A 1/4 WAVE ADDITION. THAT 1/4 WAVE IS DEVELOPED IN THE EARTH,(HENCE THE TERM EARTHING UR RIG, ANTENNA ETC,). A SIGNAL APPLIED TO AN ANTENNA WILL SEEK OUT THE FIRST AAND BEST FOR IT, TO REPLACE THE EARTH IF IT IS NOT AVAILABLE. CONSIDER A SATELLITE. THE SCRAWNY LITTLE SPIKE, PARABOLA, ...


1

The radiation efficiency of all antenna systems is the quotient of its radiation resistance and the sum of the real (energy-dissipating) resistive losses comprising that system. Some M-o-M software using NEC (Numerical Electromagnetics Code) reports values identified/expected to be radiation efficiency, but including the effects of propagation loss in those ...


2

Ask the radio shop to show you the VSWR of the antennas at the frequencies you use. Have them do it in front of you. That will likely tell you whether the antennas are suitable or not. To ensure an accurate measurement, the antenna must be plugged directly into a VHF (not CB) SWR meter with no coaxial cable jumper between the antenna and the meter. A ...


1

There is an effect on the of the conducting boom on the parasitic elements (directors), see the pdf, which is downloadable: https://www.govinfo.gov/content/pkg/GOVPUB-C13-abad4b77cb9f7a5c73277d0d4b8b1f7d/pdf/GOVPUB-C13-abad4b77cb9f7a5c73277d0d4b8b1f7d.pdf Section 3.4 shows experimental result on optimum length of the parasitic elements in wavelength as a ...


1

For HF, a loop antenna doesn't require being tall. For UHF/VHF, you commonly want something vertically polarized. But they can be short enough that you might be able to hide one inside something (attic, etc.)


2

J-Pole or vertical dipole are good choices for VHF/UHF. There are good chances that you can reach a local repeater with an antenna right in your shack: In my case the repeater is ~10 km away and I have no problems reaching it with 5W and a cheap antenna, Nagoya NA-771. Please note that there are many fake NA-771's, see How to identify the genuine and fake ...


0

For VHF/UHF, I did some J-pole's made out of twinlead (old style flat 300 ohm TV antenna cable.) Just google Twinlead J-pole. For HF, the attic trick is a good one, as is the use of stealth antennas. Flagpoles make good verticals :) When I lived in the apartment (sometimes called a flat) I had a 40m/15m coaxial dipole strung around the living room. I ...


2

Even though you're asking about "tall antennas," I'm guessing that your wife is more concerned about the appearance of an antenna than its actual height. Search the Internet for "stealth antennas" and you'll find a lot of options for outdoor antennas that aren't very noticeable. Another option is to put an antenna in your attic, if you have one. Either of ...


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