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To directly answer your question, the ideal antenna length for maximum radiation is dependent on the wavelength.
For example, CB wavelength is approximately 11m. The ideal antenna is half of that for a dipole antenna. However, most CB (and HT) antennas are monopoles, which split the antenna in half and use its mount as the other half, so the ideal CB ...
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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 ...
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To answer the last part of the question, the detector for an AM receiver is basically a rectifier, which rectifies the RF and the signal that it was modulated with.
Once the RF has been rectified, it has superimposed on it the original signal that the carrier was modulated with. This is then usually put through a low-pass filter to turn the "rectified RF ...
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The tuner is whatever allows the frequency to be selected. Tuners usually involve some kind of resonant circuit.
For a very basic AM receiver like you describe, the tuner is probably nothing more than an LC circuit, with one or both of the inductor or capacitor being variable.
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The radiation pattern of an antenna laying on the ground can be easily approximated for the transmit case: it's roughly equivalent to a dummy load. Unless of course you are in Antarcitca: ice is transparent enough to HF that it's basically invisible. But I don't think there are any retirement centers in Antarctica.
For a receive application, you might hear ...
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It depends on the type of the antenna.
Mobile antennas are often monopoles. A monopole is self-resonant when it's a quarter wavelength long. A quarter wavelength is good:
smaller, and the feedpoint impedance will be capacitave and may require a matching network. Matching networks introduce loss.
larger, and the radiation pattern grows lobes that go up ...
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Ground losses introduce additional attenuation in the path between the stations. Reciprocity applies, but this additional attenuation is more of a practical problem for transmitting than it is receiving.
Say the ground losses amount to an additional 20 dB of attenuation. To offset this additional loss, you can add a 20 dB amplifier.
For receiving, you'll ...
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You can transmit, and it might work.
One of the magic things about HF is that the path loss is often so low, because of the reflection from the ionophere, that even terrible antennas work OK. You'll find tons of stories of people working the whole of europe with a loop of wire around their desk, or a coathanger, or something.
This is not to answer directly,...
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A small horizontal loop will have two sharp nulls: one pointing straight up and one pointing straight down.
That may:
Help reduce losses in the soil directly beneath it
Reduce the NVIS radiation directly overhead. On the lower bands, that could be a disadvantage if you want to work nearby stations, say, within a couple hundred miles.
Lower the radiation ...
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If you mount it horizontally, it will be omnidirectional horizontally polarized.
Because it loses its directionality, you also lose some of the gain, although this may not be all that significant.
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RE: This antenna is showing only 30% radiation efficiency. What causes it to be so low? ... Is a radiation efficiency of only 30% the expected result for a radiator slightly less than half its ideal size?
The value for the Radiat-eff. result in the 4nec2 display includes losses based on the amount of the originally-radiated r-f energy remaining after ...
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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 ...
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The optimal length for a HT whip antenna would be ¼ λ.
The smaller rubber ducky, with its comparable performance, would win hands down for its convenience and ease of use.
The performance of either would be enhanced by adding a ¼ λ flexible-wire counterpoise, popularly known as a 'rat tail' or 'tiger tail'.
A ring-type lug, attached at one end of the ...
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I had a 15" whip for my 2m HT that I thought performed quite well. Unfortunately I dropped my radio and that managed to snap the antenna. I have yet to replace it.
You're gain isn't really proportional to the length. Rather, it's about the electrical resonance of that length. Think about humming an A really loudly next to a guitar. You can make the A string ...
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Although reciprocity and conjugate matching are physics facts there are certainly examples where an antenna system that is poorly matched will suffice for receive only use, ie on an HF band with high noise levels where the receiver is nowhere near it's limits of sensitivity and the receivers own noise levels are swamped by the received noise. Personally I ...
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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 ...
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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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