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18
votes
6answers
23k views

Using a Morse code key with a computer?

Are there standard ways to connect a hand key (straight or paddle) to a contemporary computing device (PC laptop with no parallel port, Mac, Android, iOS device, etc.) for developing or improving ones ...
6
votes
1answer
1k views

How to calculate UMTS bitrates?

Assuming: Radio frame Subdivided in 15 slots Number of chips: 38.400 Duration: 10 ms; each slots = 666.6 μs and has 2.560 chips Example of channels DPDCH (Dedicated Physical Data Channel) (UL) ...
11
votes
1answer
891 views

How can I participate on Echolink with my Android phone?

I want to use my Android mobile phone to send and receive over Echolink, like if I was using an amateur radio station. How can I do that? I'm a SWL and only plan to listen until I get my license, and ...
9
votes
2answers
756 views

If two antennas of 50 Ω and 377 Ω have VSWR=1:1, then which one is more efficient?

If there are two antennas of 50 Ω and 377 Ω (same as the intrinsic impedance of air) impedance with 0 $\Omega$ ohmic resistance, and they are exactly matched with their transmission line, then which ...
2
votes
2answers
235 views

Technician Class HF Privileges in the USA

What are the current privileges below 30 MHz for holders in the United States of a Technician class license?
2
votes
2answers
2k views

Simplest, smallest antenna for tuning WWV, WWVH?

I'd like to perform some simple receiver testing and calibration (mostly for frequency variance, not signal strength) and have been told WWV/WWVH transmissions can be found throughout most of the US. ...
8
votes
3answers
433 views

What is the permissible frequency error for US amateur radio transmissions?

What are my requirements as a licensed Amateur Radio operator in the US to keep to a single frequency? How much drift can I have during transmission and still be within my license? Does it depend on ...
5
votes
3answers
3k views

Are there any good, consistently receivable signals in the US for HF receiver testing?

Having built my first HF receiver, I'd like to know if I'll need to search around for transmissions that happen to be occurring, or if there are reasonably strong signals I can count on being present ...
3
votes
2answers
1k views

Low Audio out from Kenwood TM-V71A on cross band repeat

Asking this for a web challenged friend: He lives in an HOA restricted townhouse, so no external antennas. He only does VHF FM, so it's not a big deal. To participate in the local nets he uses his ...
8
votes
2answers
833 views

What are some ways to ground a transmitter+antenna in an enclosed attic?

If I want to minimize "RF in the shack" and lightning hazard, what some good ways to ground a transmitter and indoor antenna in a top floor room or attic with no exterior access? (say a multi-story ...
9
votes
1answer
871 views

What are the general effects of a geomagnetic storm on propagation?

Per NOAA/NWS Space Weather Prediction Center, "SWPC Forecasters are anticipating G3 (Strong) Geomagnetic Storm conditions to occur January 9 and 10." What does that mean, very generally, for amateur ...
4
votes
2answers
191 views

What does channel spacing look like in the time domain?

I'm trying to understand how radio works, and the concepts of AM/FM modulation are relatively clear to me. My next hurdle, however, is the following: How does differentiating between signals with ...
8
votes
1answer
4k views

Audio frequency used for Morse code in licensing exams?

Back when Morse code proficiency was required for certain radio licenses, what audio frequency was used by the exam tapes, equipment or examiner that generated the Morse code audio? Was there a ...
4
votes
3answers
2k views

How low a sidetone frequency will allow QRQ CW to be copied?

What sidetone frequency range (or VFO/BFO receiver offset) will allow one to copy CW when trying to learn to copy QRQ? (high-speed Morse code, 40 WPM and higher) It seems like there will be very few ...
2
votes
2answers
1k views

Does increasing the number of turns on a loop antenna decrease frequency operation?

Lets say I want to make a VLF loop antenna for a Sub AM radio band. I don't want a full wavelength because that would be a humongous antenna. Would I wind more turns of wire to decrease the frequency ...
19
votes
5answers
8k views

SDR: Quadrature demodulation vs direct RF sampling

I see that many SDRs use a quadrature demodulator and sample I and Q signals. But is it possible to downconvert the RF signal instead, sample it with only one ADC, and get the same capabilities of ...
5
votes
4answers
167 views

Do signals have to be more separated on higher frequencies?

Someone told me that 10 meters was the biggest band because you can fit the most channels in it. He said that in higher frequencies like 2 meter etc, you have to separate the signals more apart for ...
3
votes
1answer
191 views

How can I communicate with VLF ground waves [closed]

I willing to try really hard on working with Very Low Frequency waves to get a signal through the earth a few Km. How can I go about putting a signal at the frequency (probably near 10 kilohertz) ...
4
votes
1answer
361 views

How to avoid Bluetooth intereference?

I'm thinking about dropping a bluetooth module into my Softrock receiver so I can use it with my computers and portable devices wirelessly. The receiver runs from 1.8MHz to 30MHz, and the bluetooth ...
6
votes
2answers
183 views

What happens when I and Q are switched?

In https://ham.stackexchange.com/a/1068/9 it's shown that one can use $$ r = \sqrt{I^2+Q^2} $$ to decode AM signals from a direct conversion receiver. It appears that, in this particular case, I ...
4
votes
1answer
179 views

What is the record for highest successful (automated) CW transmission rate?

I understand high speed CW is used with meteor scatter, because the path only exists for a few seconds after the meteor passes. I was wondering if automated high speed CW has an effective "speed ...
3
votes
3answers
4k views

What effect will placing two receiving antennas next to one another be on the received signals

I'm planning on using 2 receivers that operate on the same frequency. So there's no confusion I'm talking about WiFi signals (but I'm trying to do some cool amateur radio stuff with it!) so the ...
6
votes
3answers
1k views

"Coaxial capacitors in line” in E4E04?

I've been studying the U.S. license examination question pools. For the most part, it is reasonably obvious what the questions and answers mean even when I am not yet able to come up with the answers ...
8
votes
3answers
12k views

How can I reduce the noise coming in from an RTL-SDR dongle?

I've recently received an RTL-SDR dongle, and I'm picking up a lot of noise that is probably coming from my PC, especially a lot of "spikes" on the 2M band. I've already started using a USB extension ...
5
votes
5answers
2k views

Simple DIY AM receiver for 25/28 MHz

I'd like to build a simple AM receiver for 25 and/or 28 MHz to receive DCF77-formatted time code. It doesn't have to be extremely sensitive or selective - the local clock oscillator will keep time ...
5
votes
2answers
80 views

Website for Sat details

I used to use the Amsat website for finding out the status of Sats and other info, like operating frequency etc. It was proving useful, and I like the pass predictor also. Seems nowadays though there'...
2
votes
0answers
562 views

The knob on rabbit ears [closed]

So I was reading some fiction about where the character bought a television and "and the fanciest pair of rabbit ears available. The rabbit ears even had a large tuner knob built in to it that I'm ...
2
votes
1answer
690 views

Is there a rtl-sdr wrapper for the funcube dongle?

I would like to use some software packages, such as rtl_433, that are written with the RTL-SDR library with a FUNcube Dongle instead. Is there a wrapper that would allow the FUNcube Dongle to be used ...
5
votes
3answers
319 views

Does a Canadian amateur radio operator’s certificate expire?

I obtained my Canadian Basic with Honours certificate in the late 90's and haven't done much with it since. Was looking to get back into the hobby. Has my certificate expired? Do I need to take the ...
13
votes
2answers
3k views

How does one read a ferrite datasheet?

Datasheets for ferrite materials are usually filled with incomprehensible graphs with greek letters. For example, Fair-Rite's 73 material: What's a $\mu'_s$ and a $\mu''_s$? What do these numbers ...
8
votes
1answer
3k views

What's an appropriate core material for a loopstick antenna?

A loopstick antenna, if you don't know, is a coil of many turns around a high permeability core. They are frequently encountered in AM receivers and look like this: This particular example is ...
1
vote
0answers
71 views

Data encoding puzzle [closed]

I have a usb stick that communicates with a medical device. I am attempting to decode the communication. I have figured out the basic radio parameters (916.5MHz, ook, bit rate, preamble, sync words), ...
5
votes
1answer
620 views

Do vacuum variable capacitors have higher Q than air variable capacitors?

Do vacuum variable capacitors have higher Q than air variable capacitors? They are not commonly seen in tuners or crystal sets. But they are mentioned as superior to air variables for resonating ...
5
votes
1answer
257 views

Does the Crystal Radio really work?

I am in 12th std, the reason why I am mentioning this is that we are given a PROJECT to do in Physics subject. And then one day I searched the internet and found this amazing thing called 'Crystal ...
9
votes
2answers
2k views

How might one realize a first order, two dimensional RF field antenna for HF?

I just coined the term "field antenna". It is by analogy to the lightfield camera or the soundfield microphone. Essentially, it is an antenna that captures not only the strength of an RF field, but ...
21
votes
2answers
12k views

What makes a 5/8 wavelength vertical desirable?

An ordinary 1/4 wavelength vertical is smaller and resonant without any loading coil or matching network. What's the advantage to a 5/8 wavelength vertical? Why 5/8 in particular, and not something ...
9
votes
3answers
4k views

Is a multiple-wavelengths antenna possible in UHF and up?

I know that in the High Frequency regions of the ham bands, the antennas have to be sub-wavelength because most people just can't put up a 160 meter full-size antenna. Let's say we're in the 23 ...
5
votes
1answer
270 views

Relicensing after a decade, can I reacquire my old call sign?

The background, I got a US Tech+ license back in the 1990's when I was in middle school. At the time I did it for the novelty of getting licensed in something and not a bit to imitate my brother. ...
8
votes
1answer
123 views

What is the logic behind RG cable codes

What is the logic behind the names of different RG cables? The Wikipedia's Coaxial cable page has a list of different coaxial cable standards but I cannot find the internal logic of the naming. I ...
9
votes
4answers
209 views

Are there ways for people with receivers to participate in contests?

At the moment I only have an HF receiver (or I will when I build it, hopefully soon). Are there any contests I can participate in, or ways for me to participate in a contest without borrowing a ...
16
votes
3answers
2k views

I hate contests. How can I avoid them?

There's nothing worse to getting home, turning on the radio, and being unable to find a clear frequency that isn't full of a bunch of meaningless QSOs where somehow everyone is 599 and no one has ...
2
votes
1answer
181 views

What modes are used for transmitting motion pictures video?

SSTV permits transmission of single images, or if one desires image sequences at a very low framerate. Are there specific Amateur Modes that are meant for real time (motion pictures) video ...
4
votes
1answer
66 views

How much should we invest time in collecting multipliers in the big contests?

In most big contests, the total score is calculated by multiplying the number of QSO points by the amount of worked DXCC entities ("countries"), or prefixes. What would be a good strategy to divide ...
15
votes
2answers
8k views

What does a noise blanker really do, and what are the side effects?

Most HF rigs have a noise blanker (NB) feature. It does reduce some types of noise (car ignition noise and such). How does it really work? I've read it has negative side-effects with strong signals, ...
3
votes
3answers
1k views

SSTV on repeaters?

Just a simple question and the answer is probably no, but am I allowed to transmit a picture using SSTV on an FM 2 meter or 70 centimeter repeater? I am in the United States.
6
votes
3answers
263 views

What does a first-time operator need to know when looking for a DIY kit?

When I was growing up, I lived about three blocks from a Heathkit, and envied every device on the shelves. Now that I'm older, am teaching myself electronics and have a background in film and ...
1
vote
2answers
132 views

Will swapping receiver polarity on a spiral antenna change right hand to left hand polarization?

I'm evaluating a helix antenna, and wanted to try out a reverse circular polarization than it's designed for. I do know that it's balanced and has no other components that would preclude polarity ...
2
votes
2answers
82 views

Does propagation affect magnetic and electric fields equally?

In the HF bands loop antennas are common, which, if I understand correctly, emit most of their radio energy into the magnetic field, whereas most dipoles emit largely into the electric field. To take ...
1
vote
1answer
85 views

Can I filter after modulation when using a square wave oscillator? [closed]

Most designs appear to filter most of the harmonics out of the oscillator before modulation, then apply additional filtering as needed for the specific modulation they are using after modulation. ...
3
votes
1answer
664 views

Why are loop antennas placed horizontally in HF

I am thinking of a large (circumference $\approx \lambda$) loop antenna at low (HF) frequencies. At higher frequencies the loops are used as quad antennas that have relatively high gain towards the ...

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