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1500 questions
13
votes
6 answers
Calculating Antenna Length on the FCC Exam vs. in Reality
I have seen the following formulas for calculating half and quarter wavelength antennas:
Formula for $\frac{1}{2}$-wavelength antenna (in free space):
\begin{equation}
\mathrm{Length~(feet)} = \frac{492}{f_{MHz}}
\end{equation}
Or is…
Dan
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13
votes
5 answers
Is an antenna analyzer necessary for building antennas?
I'd like to try my hand at building a few antennas for VHF/UHF use. I'm going to be going approximately from established designs, but obviously the final result will require some tuning. I don't currently own either an SWR meter or antenna…
David KF4MDV
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13
votes
1 answer
Is there any legal recourse against unauthorized usage of a private repeater in the USA?
Can the FCC revoke an amateur license for unwelcomed use of another amateur's private/closed repeater system?
It's clear that private repeaters are allowed, per 47 CFR 97.205(e):
Limiting the use of a repeater to only certain user stations is…
natevw - AF7TB
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13
votes
3 answers
How do I troubleshoot a Baofeng UV-5R that won't receive?
I have a couple of Baofeng UV-5R radios. I have a profile in Chirp that works great on one of them, and I foolishly pushed that profile straight over to a UV-5R without checking firmware versions. Chirp crashed, and now the radio won't receive. …
Benson
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13
votes
1 answer
Hanging a dipole from a tree not code compliant?
I just got off the phone with my town's electrical inspector (in Massachusetts), and he informed me that you are not allowed to hang anything electrical from "vegetation". He said if I did this with my dipole, that it would not pass inspection. He…
kr4sh
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13
votes
4 answers
Why does ice on a wire dipole affect the SWR?
We just had snow and ice overnight and my wire dipole was coated in ice. Why does the ice covering negatively affect the SWR of the antenna?
Ron J. KD2EQS
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13
votes
2 answers
Is there an optimum Antenna Feedline Length for mobile installations?
I bought a ham radio antenna mounting kit for my car that includes ~16' of coax. One end has a trunk lip NMO antenna mount, the other end has a re-solderable PL-259.
I asked the sales person if it is best to shorten the coax after installation to…
BenSwayne
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13
votes
1 answer
How do Radio Regulations and Frequency Allocations Apply to an Ionosonde?
An ionosonde is a special HF radio transmitter that periodically transmits a signal that sweeps across a large portion or the entire HF spectrum to identify the propagation of radio signal in the ionosphere, currently they are operated by various…
比尔盖子
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13
votes
3 answers
Testing blind license applicants
My friend is blind and would like to take the amateur radio license exam.
I understand that the question and the four possible answers can be read to them, and that is fine. The one question that we are still not sure on is, When it comes to block…
peter
- 131
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13
votes
3 answers
Bandwidth of a CW signal?
What is the RF bandwidth of a typical CW signal? How is the signal bandwidth affected by WPM and/or transmitter rise-time?
What is the narrowest bandwidth that can still be copied by a human? Or what is the narrowest receiver audio filter that…
hotpaw2
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13
votes
4 answers
Why do today's transceivers use LC filters rather than crystal filters?
Going through a number of schematics for today's receivers (Elecraft KX3, for example) I note that most use LC circuits for filtering. The wikipedia article for Crystal Filters suggests, however, that crystal filters are used in high quality…
Adam Davis
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13
votes
2 answers
Do volunteer exam coordinators provide accommodations for applicants with visual impairments?
I am a prospective HAM, and I recently began reading the ARRL's third edition of their Ham License Manual, published in 2014.
Anyhow, under
WHO CAN BE A HAM
They mention that there are ham operators who may have disabilities that might affect how…
HeavenlyHarmony
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13
votes
3 answers
UHF FM power amplifier design without expensive software
I'm designing a small UHF data transceiver for the 70cm band, based on a Silicon Labs EZRadioPro Si4463 IC. Modulation is FM, 12.5kHz channel step. The concept is similar to SiLabs' AN656 application note but with a different power amp BJT as the…
philpem
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13
votes
4 answers
Can I operate in the United Kingdom with a US license?
Can my license from the United States be used to operate while I'm in the United Kingdom?
Timtech
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13
votes
1 answer
Is it a good idea to build your own radio transceiver today?
With all the advances in the field of electronics, microcontrollers, etc., is it a good option today to build my own amateur radio transceiver (or transmitter/receiver)? Why might one choose to build over buying, or the other way around? How should…
kR105
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