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1500 questions
11
votes
5 answers
Non-traceable radio emitters
There are various techniques for locating a radio emitter. But what are some methods to make this really difficult? There is usually a patch to every vulnerability, at least from the world where I come from.
11
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6 answers
Can you use a satellite dish for a ham radio antenna?
Can I use a satellite dish as a ham radio antenna? I was thinking that because there are two unused, working satellite dishes that have all appropriate wires attached conveniently to the roof of my house. Would there be a way to use the dish as a…
hopefulhacker-Reinstate Monica
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11
votes
4 answers
Is "low loss" cable required for HF?
I use RG-58 for all my HF antennas, since it's light, flexible, convenient, and cheap. And super easy to choke. Whenever I have a problem I just loop a few turns of it on a ferrite core and the problem goes away. Since I operate 100W max and all my…
hjf
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11
votes
6 answers
Practical limits to maintaining coherence in an HF channel
Lately I've been thinking about weak signal communication on HF. Very weak, like weaker than even WSPR could achieve.
It would be nice if one could simply take any existing modulation and slow it down to achieve an arbitrarily high Eb/N0 and thus,…
Phil Frost - W8II
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11
votes
6 answers
Why is antenna aperture a function of wavelength?
Wikipedia says:
It can be shown that the aperture of a lossless isotropic antenna, which by definition has unity gain, is:
$$ A_{\mathit{eff}} = \frac {\lambda^2}{4 \pi}$$
We also see this emerge as a $\lambda$ term in the Friis transmission…
Phil Frost - W8II
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11
votes
3 answers
Calculating Doppler Shift for satellites
If I know how fast a satellite is moving through space, how can I calculate the doppler shift for the pass?
Skyler 440
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11
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5 answers
Will electrically joined dipoles of different lengths, at right angles, behave as a multiband antenna?
I haven't seen this done, (which, after more than a century of amateur and professional radio development, is probably a bad sign), but I had an idea the other day for simplifying the setup and feed to cover more than one band without the compexity…
Zeiss Ikon
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11
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4 answers
Real world performance of magnetic loop antennas?
I was investigating about magnetic loop antennas. In a paper about them I found some bold claims:
and
This almost sounds too good to be true, considering a lot of us hams are surronded by city noise and this paper claims the noise would be much…
hjf
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11
votes
1 answer
Why would you need a signal generator to receive early satellite transmissions?
I recently watched, on You Tube, a NOVA program about the British school masters and students who were the first to publish the news that the Soviets had started launching satellites from a new launch site back in 1958. (School Boys Who Cracked the…
John Warren
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4 answers
What is the advantage of making an antenna resonant?
I am constructing a small loop antenna; apprx 4' diameter, will be used with an antenna tuner (mounted at the feedpoint) and 100W transmitter, and hope to use it on 20m, 40m, and maybe other bands if possible. I can add a tuning capacitor to make…
Chris K8NVH
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votes
1 answer
How can I participate on Echolink with my Android phone?
I want to use my Android mobile phone to send and receive over Echolink, like if I was using an amateur radio station. How can I do that?
I'm a SWL and only plan to listen until I get my license, and my brother does have a valid amateur radio…
ReNiSh AR
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11
votes
3 answers
How can I get rid of RFI coming from my house solar panel inverter?
The solar system on my house creates horrible rfi on all hf bands during the day when the sun is out, it goes away when it's not sunny. Any one got any ideas how to get rid of the rfi ? I already tried putting capacitors across the high voltage…
Andrew
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11
votes
4 answers
How do I increase my phone intelligibility?
Listening to various operators at different times, I've sometimes noticed, especially during contests, that some operators are easier to understand than others, and it doesn't all seem to be due to their speech patterns. The audio doesn't sound good…
Adam Davis
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11
votes
2 answers
Why don't monolithic HF transceiver ICs exist?
HAM operators who build their own HF rigs typically do so using discrete components.
However, for VHF and UHF rigs, an operator can make use of monolithic transceiver ICs on the market
For example, there is this one for 30MHz ~ 1200MHz:
AK2401…
watkipet
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1 answer
What is the process of making a voice contact?
I got into Amateur Radio for emergency preparation and to allow me to expand my electronics hobby. Initially I didn't find much value in contesting or making contacts, but apparently there are some valuable skills one can gain from contesting.
I…
Adam Davis
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