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1500 questions
5
votes
1 answer
What frequency to set trap on?
I plan to build trapped multiband dipole so I read lots of documentation I found.
There is one thing that confuses me: various authors recommend setting resonant trap frequency differently: some say trap should be resonant just below wanted band,…
Pedja YT9TP
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5
votes
4 answers
What is the output impedance of a typical solid state ham transmitter?
I've often heard that the output impedance is 50Ω, and the load impedance should be matched to that and also 50Ω. While the reasons for the load impedance to be 50Ω are clear, is the output impedance really 50Ω and if so why? If it isn't 50Ω, what…
Phil Frost - W8II
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5
votes
1 answer
Building a crystal radio with my brother. How does this circuit work?
I'll be visiting home soon after school lets out, and I want to build an AM crystal radio with my little brother. This is the design we'll use:
http://crystalradio.net/beginners/
I'll be doing my best to explain to him how this works. I understand…
BitPusher16
- 153
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- 3
5
votes
2 answers
What ways are there to extend an antenna?
I am using an arduino micro controller with a LoRa radio module to communicate. The shield has 2 ways of connecting an antenna: either a SMA jack or a hole for soldering.
Now my problem is this: I need to get the antenna away from the module…
user5227744
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5
votes
2 answers
What are the requirements of the address given for a US licence?
I'm going to be visiting the US soon (I live in the UK), and since I've heard it's very easy to get a US amateur radio licence and it's something that could be beneficial, I thought, why not?
I see that it requires an address, though. What are the…
Muzer M0SWT
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5
votes
2 answers
What is the purpose of limiting radio output power?
According to article 25, section I, § 4 (25.7) ITU's Radio Regulations:
The maximum power of amateur stations shall be fixed by the administrations
concerned.
In my country this is 500W for CEPT License, 100W for CEPT Novice License, 1500W with…
Hex
- 153
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5
votes
3 answers
How to find or derive the maximum safe input power to a receiver?
A number of my RF devices have a specified safe maximum input power, for example:
"The maximum RX power of HackRF One is -5 dBm. Exceeding -5 dBm can result in permanent damage!" source
"If you look at the R820T datasheet … you can see the max…
natevw - AF7TB
- 7,529
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5
votes
3 answers
How slow is slow telegraphy?
On the UK Band Plan there are frequencies stating “QRS (slow telegraphy) Centre of Activity”. For example, 14,055 kHz on 20m and 3,555 kHz on 80m.
What is considered slow? (<15 wpm?)
How close should you stay to the stated frequencies?
Phil_12d3
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5
votes
1 answer
What is the difference between "Cross Polarized" vs "Circularly Polarized" Antennas?
What is the difference between cross-polarized yagi antennas and circularly polarized antennas?
metropolis
- 61
- 3
5
votes
3 answers
Radio manufactured in United States
I am just beginning with amateur radio and would like to start with an entry level handheld transceiver. I would like to consider manufacturers based in the United States, but I have not found any. Are there any USA handheld ham radio…
jcadcell
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5
votes
1 answer
How can I generate a list of APRS IGates on 30m?
I am investigating using a Tiny Trak 4 with my portable HF radio to self-spot on SOTA activations via APRS on 30m.
I usually self-spot via a text message. When I don't have any cell coverage, I can sometimes spot using APRS on 2m. I am looking for a…
Malcolm VE2DDZ
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5
votes
1 answer
What rules govern robotic teleoperations, when the remote device also transmits back telemetric information?
I was looking through the FCC part 97 rules for robotic teleoperation, and it cites a one-watt figure for "model craft". However, it also allows higher power transmissions for remotely operated stations, and beacons.
The robot in question is a land…
Tyzoid
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5
votes
1 answer
Expected practices for one ham operating under another's privileges?
I understand that in the United States, amateur operators and even non-licensed persons may participate in domestic (and approved international) communications on bands they wouldn't normally be allowed to transmit on, using the privileges of…
natevw - AF7TB
- 7,529
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5
votes
1 answer
Why does path loss decrease as frequency decreases?
The Friis transmission equation can be given as:
Pr = Pt + Gt + Gr + 20 log10 (λ / 4πR)
Where the variables represent:
Pr: Power at the receiver
Pt: Power at the transmitter (in e.g. dBm)
Gt: gain of the transmission system (in decibels)
Gr: gain…
natevw - AF7TB
- 7,529
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- 63
5
votes
1 answer
What would be the typical received power of an "S9" signal?
Obviously, I would expect the amount of power at a receiver would vary greatly based on distance from, and the power/efficiency of, the transmitter. But I don't really have a good sense for what "ballpark" the power would even be in for a "good…
natevw - AF7TB
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