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1500 questions
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7 answers

Is the National Calling Frequency actually used?

I know that the national calling frequency is 146.520. Everywhere I go, it does not give a DUP or TSQ. I am not trying to be or, ask a crazy question but is there or not.
Glenn
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Is frequency hopping a viable solution for privacy and security without encryption?

In terms of radio transmission, three major issues seem to arise for various sensitive transmissions: Others do not gain access to the content of the message Others cannot determine the location of the sender Others cannot block (jam) message…
J-S
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7
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3 answers

Minimal info on a SWL QSL

Which is the minimal information I should require to confirm/QSL a reception report I receive ? I know the report must contain my callsign, time, date and band where I was listened. Is it also a requirement to indicate the callsign of the other…
joaquin
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2 answers

Apps and or equipment needed to document local interference?

A neighbor ham user recently started doing something that causes very noticeable feedback/buzzing in AM radio as well as any device that uses a wired microphone (such as a gopro with wired mic). Before I approach this individual, I'd like to make…
a coder
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7
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4 answers

Why can't VHF / UHF be used with ionosphere reflection?

HF radio can be reflected by the ionosphere, giving very long range communications. Why can't VHF / UHF used with ionosphere reflection? Is it due to the attenuation of the atmosphere over that distance with VHF / UHF wavelengths? Or is it to do…
DarcyThomas
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8 answers

VHF/UHF digital single-frequency repeater without duplexers?

Some digital voice protocols are time slotted (TDMA), i.e. the transmitter of a station is not on all the time, and multiple stations may transmit digital voice on the same frequency at the same time by transmitting small digital bursts, one by…
oh7lzb
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1 answer

Using more than 400W in the UK

With a full amateur license in the UK, up to 400W can be used - however, there are cases that might call for higher power, such as bouncing signals off the moon. Is there any way I can obtain permission to use a higher power, even if this is…
berry120
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2 answers

Power dissipation in transmission lines?

I was wondering, does the impedance of a transmission line have any effect on the power it dissipates? I'm familiar with the fact that an impedance equal to the load will provide maximum power transfer (and dissipate just as much power as the load)…
s3c
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2 answers

What are CQ/ITU zones used for?

There are already questions about the definition of CQ zones and ITU zones, but there is no information about what these zones are used for (and Google brings up various maps but no explanation). (Is this something a non-US novice-class amateur…
Georg DO1GL
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3 answers

Broadcasting a WiFi SSID long-distance

Which equipment would be good for broadcasting a WiFi SSID the longest possible range? We're making an orienteering race in a forest and would place a sender somewhere high over the trees, transmitting a WiFi signal into the forest. The SSID should…
sune
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2 answers

Do aprs.fi and APRS-IS use the same credentials?

I have an account/profile on aprs.fi, and now I am trying to use APRSdroid, which requested my credentials. Can I use the password from aprs.fi for it? I am unable to register/submit my application through TQSL because my country is not on the list.…
harayz
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Can I touch the ground of a PWR/SWR meter?

I'm planning to build a 5W PWR/SWR meter very similar to this design by G3YMC, but with two meters: I'd like to put it in this metal box, and use the box as ground. However, the bottom of the box would then also be ground, and I may accidentally…
user885
7
votes
4 answers

Shaving Quartz Crystal for New Frequency

Back in the 1960s during my Novice days I operated on the 40-meter band only with 4 different quartz crystals that determined my transmitting frequency with my Eico 720 CW transmitter. I had heard about other old-timers who would shave (or…
K7PEH
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How is the FM-signal demodulated in my receiver?

I've built a radio receiver and I'm wondering how the demodulation works here. I think it's done by T1 and T2 (I've used BC547 instead of BF494, they're quite similar), but I'd like to know more about it. Source:…
Superlimonade
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2 answers

Using earphones as a dipole antenna

I would like to know how the earphones work as a dipole antenna for a smartphone to receive the FM bands? Usually, one arm of a dipole needs to be connected to the ground and the other arm needs to be connected to the receiver. But in the case of a…
Prabhat Karpe
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