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1500 questions
7
votes
7 answers
End-fed wire antenna lengths
I want to use an end-fed wire antenna, but what would be the best length of wire for the 20m and 40m bands?
Is there a way to work this out?
This is assuming a tuner will be used.
Phil_12d3
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7
votes
5 answers
Using Earth as an RF ground
I have built a simple ground plane antenna for 70cm with a connector, 4 radials, and one vertical element.
The RF ground is connected to the radials, and the RF is connected to the vertical.
It got me thinking, can the actual earth be used, because…
Skyler 440
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7
votes
1 answer
Where exactly does atmospheric noise (QRN) come from?
Where does the noise I can hear on my 28 MHz receiver come from? I'm not talking about the inherent noise produced by the internal circuitry of the radio, I mean the noise received by the antenna. It's always there, no matter where I am, even if I…
Andrew
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7
votes
2 answers
Using radio for musical collaboration -- the line between conversation and broadcasting
I'd like to collaborate (e.g. play together) with other musicians in my local area and/or beyond.
Coronavirus has made in-person collaboration difficult. Latency makes internet-based collaboration difficult.
Is there a legal way for a group of…
mathandy
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7
votes
2 answers
Options for family short range communication in an emergency
I work in an office building about 3 miles from my apartment. I live in a medium sized city in the US.
I have thought about getting a pair of walkie talkies for communicating when the cell phone services are not working (I have experienced this),…
user926
7
votes
2 answers
What does an antenna analyzer tell me about these coaxial cables?
Note: more measurements added after graphs below
I recently acquired a RigExpert antenna analyzer and I am trying to learn how to use it to test cables. I took two cables to start with to try and understand what it shows and what the graphs mean. …
progrmr
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7
votes
4 answers
How can quadrature mixing adjust the phase of all frequencies by the same amount? Can it be done in the digital domain?
This came up in some feedback I got when I tried to answer What is IQ in the context of SDRs? and revealed some of my own misunderstanding.
Initially, I gave an answer something like (paraphrasing):
You could collect I/Q data by taking a second…
natevw - AF7TB
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7
votes
1 answer
What should be the modulation when transmitting APRS signal?
Is it SSB or NFM or other type of modulation?
Harold Chan
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7
votes
3 answers
How to determine frequency and launch angle given a target skip distance?
I would like to communicate with someone 1000 miles (1600 km) away. I'm not sure how to target a specific distance.
(image source)
I assume it's an interrelation of the following factors:
Which frequency I'm using
Which ionospheric layer I'm…
bitsmack
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7
votes
3 answers
Why EME with 100W and a single Yagi-Uda antenna is possible?
Recently I've been reading about EME and there was one thing that surprised me. Many sources claim that EME has path loss for 2m band about 252 dB. In the same time they claim (one, two):
Recent advances in digital signal processing have allowed…
Aleksander Alekseev - R2AUK
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7
votes
2 answers
CW: when I supposed to send "E E"?
I'm new to CW and one thing I couldn't figure out is when I supposed to send "E E". Let's say I'm calling CQ and somebody answers me. The QSO is almost over. Should it be ended like this:
- TNX FER NICE QSO 73 E E
- GDX 73 E E
... or:
-…
Aleksander Alekseev - R2AUK
- 4,272
- 15
- 52
7
votes
1 answer
What exactly was a decremeter and how did they work?
In A Century of WWV, I found this mention of an unusual sounding instrument that may have once been commonplace:
Calibration work was mainly focused on decremeters, instruments designed for measuring the decay, or decrement, of a pulsed radio…
natevw - AF7TB
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7
votes
4 answers
DIY SA612 + RTL-SDR HF receiver: good on laptop, but huge wideband noise on Raspberry Pi
I recently built a SA612 mixer for HF reception. I used an USB-frequency oscilator to shift the incoming frequency up by 28.8 MHz.
I used a random wire antenna outside my balcony and connected it to the center-pin of a car antenna mount, and used a…
比尔盖子
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7
votes
2 answers
Why aren't "ghosts" and intersymbol interference due to unmatched impedance (high SWR) a concern for HF receivers?
In amateur radio, we care about impedance matching when we need to keep the load within the equipment's specification (for best performance, or just to avoid damaging a transmitter), when we want to maximize the power delivered into the load, or…
比尔盖子
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- 17
7
votes
1 answer
Coherent CW synchronization?
When using coherent CW, how is the receiver frequency and/or Morse Code dot clock synchronized to the transmission precisely enough to allow for synchronous decoding?
hotpaw2
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