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1500 questions
5
votes
5 answers
What about the digital mode ROS causes some to consider it spread spectrum?
The FCC disallows amateur spread spectrum communications below 220MHz. At the moment the relatively new digital mode, ROS, is considered, by some, to be spread spectrum. So this mode is getting little to no use in the US.
It doesn't seem much…
Adam Davis
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5
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2 answers
What organizations in the USA can I join to participate in emergency preparedness?
I want to get involved in emergency preparedness. What organizations, if any, are there in the United States that support disaster recovery and emergency management?
dcaswell
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5
votes
1 answer
Can X-rays be used for communication?
I keep increasing my frequencies and want to get up the spectrum more and more. My current project is pointing a powerful focused LED from a peak and I will try to pick it up with a telescope and some sort of photo detector to receive the AM light.…
Skyler 440
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5
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2 answers
Is the 3-cm band serviced by any commercial main-stream ham radio transceiver?
Wikipedia writes to say
The Radio Regulations of the International Telecommunication Union allow amateur radio operations in the frequency range 10.000 to 10.500 GHz, and amateur satellite operations are allowed in the range 10.450 to 10.500 GHz.…
VU2NHW
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5
votes
5 answers
Signal path to maximize RFI rejection in an urban environment
Urban ham here (Cambridge, MA - FN42ki - KC1JZE) looking for tips to make this hobby possible in the city. I rarely can hear both sides of HF phone transmissions, and have yet to make contacts despite dozens of attempts on 80/40/20m using commonly…
Jeremy Gilbert
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5
votes
1 answer
Impedance matching using Smith Chart and relationship to reflection
I've been reading the impedance matching chapter of Bowick's excellent RF Circuit Design book and I have a question.
For those who haven't read this book (or have but can't remember!), the chapter discusses L and 3 element matching networks (very…
Buck8pe
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5
votes
1 answer
Are there any Alternatives to Packet Radio for sending digital data?
Recently, I asked a question about using an Arduino to send packet radio. I noticed that the top record speed for packet radio is 1 megabit/second, on a modified radio. Someone mention on stack overflow that the normal speed is around 120…
itisyeetimetoday
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5
votes
1 answer
How different is Q-factor of SMD inductor from regular one?
I am trying to figure out if it is possible to replace inductors like this
wound by 0.1mm (diameter) copper wire
with multilayer 0805 SMD inductors.
Those are supposed to be used inside band-pass filters. Right now there are 2 coils but I am…
k1zmt
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5
votes
1 answer
For air coax calculation, what is correct diameter metric vis-à-vis tube stock thickness?
I am interested in creating a square outer-conductor with round inner-conductor air coax post for a hex beam antenna. I found the extremely useful information at:
How do I design a round or square coaxial transmission line to have a specific…
photosynthesis
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5
votes
2 answers
Using a Deceased Club Member's Call Sign for Field Day
The Secretary of our club passed away unexpectedly last week. With Field Day rapidly approaching in the U.S., the board is wondering if there is any legitimate way for the club to use the deceased member's call sign for Field Day operations.
We can…
Lance
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5
votes
1 answer
Will stainless steel bolts work with my copper antenna?
My antenna is copper, elements and the beam. I would like to bolt them together where they cross. Would stainless bolts work? Just sweating them together lets them twist and move some in high winds.
arkieguide
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5
votes
4 answers
Are Americans the only hams with four-letter callsigns?
Some American hams are lucky enough to have four letter call signs such as: K1JT
Are American hams the only ones with the possibility of a four letter call sign? Is there another country that grants four letter call signs to individuals on a regular…
RoboKaren
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5
votes
1 answer
Help understanding the information field in an APRS-IS message
I'm looking at the raw packet data from http://aprs.fi. I see packets such as these:
ROSLDG>APN390,HEBOWX,OR2*,qAR,MKSRDG:@015805z4501.34NF12351.41W_000/000g000t053r000p000P000h92b......U2k
W7KKE-9>TTRSUT,NEWPRT*,OR2-1,qAR,W7GC-3:'4].…
watkipet
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5
votes
2 answers
Weak signal digital modes and clock synchronization
Why to some weak signal digital modes (jt9, jt65, etc.) require knowing a clock time? Does knowing this clock time provide any gain in signal detection ability? (lower required S/N?)
What clock synchronization accuracy to what master clock source…
hotpaw2
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5
votes
3 answers
Why are 2m and 70cm the common frequencies on HTs?
Why do most HTs have 2m and 70cm as the two bands? Is it just out of history or tradition, licensing restrictions, or is there something in the transceiver or antenna design that would make these the two obvious frequency bands of choice?
RoboKaren
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