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540 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 ...
672 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 ...
272 views

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 ...
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 ...
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 ...
69 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), ...
589 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 ...
241 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 ...
1k 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 ...
10k 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 ...
3k 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 ...
254 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. ...
121 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 ...
198 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 ...
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 ...
178 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 ...
63 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 ...
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, ...
922 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.
259 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 ...
127 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 ...
81 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 ...
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. ...
624 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 ...
2k views

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 ...
828 views

Why do some DX listen on a different frequency than they transmit on?

I've heard some DX indicate "CQ up 5" for instance, indicating that they are listening on a different frequency than they are transmitting on. What are the reasons one might want to do that?
122 views

What prevents automation in contests?

It seems that using a CW skimmer with an SDR one could fully automate a contest station, and even handle multiple contacts simultaneously in the case of pile-ups. Has this been done or discussed ...
608 views

What range of mismatch can the internal tuner on the TS-480SAT accommodate?

A fellow ham recently acquired a TS-480SAT. His working condition is complemented by an inverted-vee for the 20m band around 10m above ground; solid 59+ reports. Trying to tune the same antenna on ...
1k views

Why is the 70cm band commonly referred to as the 432MHz band?

I keep reading and hearing the 70cm band (420-450 MHz depending on local regulation) referred to as the 432 MHz band, particularly by older hams. Why?
75 views

Optics for open-air visible spectrum communications

I want to communicate 2.7 miles from a peak on a mountain. I will be using a very bright LED and some type of photo-element (photo multiplier tube, avalanche photo diode etc.) to receive the amplitude ...
249 views

Optically clear RF shielding?

Is there a material suitable for use as RF shielding that would allow at least 50% light transmission in the visible range? Thinking about a sensitive light receiver.
183 views

How is a second radio managed when operating SO2R (Single Operator Two Radios)?

I am relatively new to contesting, and I have heard of a category called SO2R (Single Operator, Two Radios). Are they really talking about 2 radios, or just 2 VFOs in one radio? Running one radio ...
2k views

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 ...
113 views

During a radio contest, how do I determine if a station is “too faint” to be worth trying to contact?

Suppose I hear a station during a contest that is an eligible contact, but not necessarily a multiplier (worth points, but only a nominal amount of points). This station is relatively faint, (maybe 2-...
596 views

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 ...
157 views

How do I maintain my frequency during a contest?

Suppose I am operating a busy HF contest, and I have found an open frequency to call CQ. I make a number of contacts, and then suddenly another station starts to call CQ right on top of me. The other ...
296 views

How do I find a frequency to call CQ on during a contest?

I know that in many contests, sitting on a frequency and calling CQ is a very effective strategy to rack up points. However, during very popular contests it can be very difficult to find an open ...
321 views

What information should be on a QSL card?

Like it says in the title. When you design a QSL card (intended for use for both local VHF-and-up contacts as well as international HF contacts), what information needs to be present, and what ...
61 views

What are some reliable sources of propagation forecasts?

Where can I go to find propagation forecasts? How useful are propagation forecasts over time? For instance, I've been told by meteorologists that weather forecasts three days out generally ...
26k views

Is there a simple, DIY, antenna suitable for HF receive only?

So the antenna I'm thinking about doing might be* way too large for my property. Is there another simple, cheap, DIY antenna I could try on my receiver? I know I'm going to want to hook it up and ...
904 views

What impedance matching do I need between my 300Ω feedline and Softrock receiver?

I will be assembling a Softrock Ensemble II HF receiver, and I know I'm going to want it on air as soon as I build it, so I'm challenging myself to build an antenna for it first. The plan is to do a ...
914 views

Can I transmit anything inside a Faraday cage?

Can I perform any transmission regardless of my license as long as I'm inside an RF sealed enclosure, such that no RF will be detectable from my transmissions off my property? I imagine the answer is ...
238 views

Can I use two antennas and coax to couple RF into my aluminum sided house?

I have an aluminum sided house, and when I'm using my HT I typically need to be near a window for it to work well. Would I gain much if I put an antenna on the roof, an antenna in the middle of my ...
513 views

What SDR software is available that provides internet control?

I plan to use a SoftRock Ensemble RX II to receive HF transmissions. I'd like to be able to use it wherever I am when I have a few minutes, though, so I'm wondering what software exists that would ...
415 views

What is this short, wide band signal?

I've observed a signal I'm unfamiliar with, and am wondering what it might be: The period of time it lasted is 5 seconds, and it occurs irregularly. You might be able to see it too via WebSDR. How ...
472 views

How is full duplex implemented without swamping the receive circuitry?

I've seen a few references to full duplex SDR radios, and I'm wondering how can one transmit and receive at the same time without overwhelming the receiver, and without heavy filtering such as the ...
3k views

What are the I and Q in quadrature sampling?

For some reason I've long believed that given I and Q, one corresponds to amplitude, and one to phase, so I thought that I could hold one steady and create AM, or hold the other steady and create FM. ...
218 views

How do I increase my phone intelligibility?

Listening to various operators at different times, I've sometimes noticed, especially during contests, that some operators are easier to understand than others, and it doesn't all seem to be due to ...