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1500 questions
6
votes
2 answers
How is phone cable with iron called?
In in Russia I saw a phone cable called "field cable" (провод полевой П-274-М). It is a loosely twisted pair with some iron strains added alongside with copper ones.
I tried to lookup something similar but I failed to find it.
I used phrases like…
k1zmt
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6
votes
1 answer
How to stack circular polarised antennas
I'm interested in stacking a pair of circularly polarized "crosshair" antennas. Do I construct such as both antennas are in phase with one another then match the two signals in phase via the coax line, i.e. equal length, or should I rotate one by…
Ben
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6
votes
5 answers
How can a tuner pick up a specific frequency?
The point I'm confused about is the antenna. Depending on the environment, there are tons of different frequencies passing through you (FM, AM, 4G, SAT, etc). The electrons in the wire will move as the radio frequencies pass by. One wave will move…
Derpy
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6
votes
2 answers
How does a digital demodulator know which level it is reading?
I have recently started getting into wireless digital communications and I read about QAM modulation.
But I am a little confused as to how the receiving demodulator would know which symbol it is reading.
For example with 64-QAM there would be 8…
YellowBadger
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6
votes
1 answer
Secure communication over Amateur-band HSMM / 802.11 in the United States
I'm quite interested in 802.11 over amateur radio frequencies; however, all I have done at this point is reading (I don't have a ham license yet). The conventional wisdom (espoused in this ham.SE answer) is that you cannot encrypt radio…
Mike Pennington
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6
votes
1 answer
How to estimate input and output impedance of an amplifier?
I'm trying to figure out how to design power amplifiers which input and output are properly matched to 50 Ohm. My thinking was that the most bullet proofed approach would be to model an amplifier in LTspice and estimate R as U/I on both input and…
Aleksander Alekseev - R2AUK
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6
votes
4 answers
What nations still require Morse code testing for Amateur radio license?
Going a bit further I'll ask, for which licenses (all or just for licenses for HF operation) and at what speed (5 WPM, 10 WPM, none specified)?
The reason I ask is because every so often I'll see people from the USA wanting to visit another nation…
MacGuffin
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6
votes
4 answers
50Ohm Coax presents 50 Ohms of impedance on which frequency?
Either there's a simple answer that I'm not finding in a spec sheet somewhere, or, I'm asking the wrong question!
Adam Palmer
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6
votes
3 answers
Is it ethical to accept sponsorship for QSL cards?
We all know that in general commercial activities are not welcome on amateur radio bands.
One thing that somewhat related to that came up in a discussion I had with some operators:
Is it ethical to accept money for printing and sending QSL cards in…
AndrejaKo
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6
votes
1 answer
How to prevent cracking the capacitors in my diplexer?
Just made my first 2m/70cm diplexer. Important: I aim to be able to use this up to 50 Watts.
S21 from the LP section:
Having access to regular distributors such as Farnell/Element14, Mouser, Digikey,... I searched for RF capacitors with a voltage…
Dieter Vansteenwegen
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6
votes
4 answers
Any reason not to choose a discone antenna over a Wide/ MultiBand mobile antenna for TX/RX operations
We are setting up a all-band radio in an emergency com center that's intended most for amateur band use, but since its' for emergency use will also be used in the public safety bands; (150-170)MHz, (470-512)MHz, (700/800)MHz, and possibly others if…
Frank
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6
votes
7 answers
Space Requirements
As I progress in my path to getting a ham license I notice that a lot of radio enthusiasts avidly talk about their radio shacks (or do they call it cabins?).
Do I need that much space to start?
Do I have to set up an antenna outside?
Will it work…
hopefulhacker-Reinstate Monica
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6
votes
2 answers
Why does capacitive loose coupling increase selectivity?
There are multiple ways to couple antennas. It is said that an antenna is capacitive loose coupled if a small capacitor is used between the antenna and the parallel resonant circuit (like C2 in the image below).
Such a loose coupling will increase…
dudekowsky
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6
votes
1 answer
What's the difference between an APRS "item" and an APRS "object"?
What's the difference between an APRS "item" and an APRS "object"?
A kenwood manual says Objects have timestamps, items do not. What does that mean, and how should it be used?
Also in general: What is a good resource for learning about APRS?…
Thomas
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6
votes
4 answers
Why is gain used?
It always confused me why 100 watts out of your transmitter could radiate 200 watts coming from a high-gain antenna.
Why is the term gain used instead of directionality?
Skyler 440
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