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1500 questions
7
votes
1 answer
Suggested method for boosting 0.05 watt transmitter up to 10+ watts?
Long time ham operator here, new to this particular challenge -
I have a software defined radio transceiver that I'd like to try and use to make contacts on HF, in particular 20-meters. Tuning within the 20-meter band is no problem but the…
Brad Hein
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7
votes
3 answers
What cause the spectrum peak of `center frequency`?
I use gnuradio and fosphor to view the spectrum from USRP B210, default gain set to 34, output looks like concave as below:
Nothing changed just set gain to 35, output become flat, looks like convex:
Whatever center frequency I set,0 frequency…
kittygirl
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7
votes
4 answers
If I tie antenna wire in a knot, will there be damage to the wire?
I'm building HF kits 80m EFHW kit, and in the instructions it directs you to tie a knot in the antenna wire. I'm concerned of damage to the wire. I have found no source as of yet that indicates if damage will or will not occur. I am using their…
Erik Rusell
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7
votes
6 answers
Does an SWR higher than 1:1 necessarily cause additional heat in the transmitter?
Each of the 3 answers to SWR of 1.5 -- use internal antenna tuner or not? in one way or another suggest that an SWR of 1.5:1 will cause additional heat in the transmitter:
The radio may heat up a bit more during transmit with a 1.5:1 SWR, however i…
Phil Frost - W8II
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7
votes
2 answers
HF SSB etiquette when someone is working quick but not contesting and you're not sure they got you?
When someone is working quickly -- clearly trying to work a lot of stations -- but pretty clearly isn't contesting, what's the etiquette when they 73 you and end the contact but you're not sure they were talking to you?
To be specific, I'm listening…
QuantumMechanic
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7
votes
1 answer
Efficient BPSK31 amplification
I'm looking at making a portable system that can transmit BPSK31. I have a limited power budget, so I'm looking at trying to make my final power amplifier as efficient as possible. From my understanding, you can't use a plain non-linear amplifier…
W5VO
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7
votes
2 answers
Doppler Shift Compensation in Inter Satellite Communication
I am currently doing a project in the area of optical inter-satellite communication (GEO-LEO).
I am using a optical carrier of 281 THz, and the Doppler shift corresponding to it is ±7 GHz. I introduced this Doppler shift in the transmitted signal…
Seetharama
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- 3
7
votes
5 answers
Why are an antenna’s nulls sharper than its lobes?
Why, for realistic directional antennas, are its nulls sharper (deeper, narrower, etc.), than the radiation pattern’s lobes (local angular maxima)? Is there some physics or mathematical geometry to EM fields that requires this to be true?
Or is…
hotpaw2
- 13,635
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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
- 225
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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
- 7,690
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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
- 171
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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
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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