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10
votes
1answer
330 views

Why is the speed of light rounded to 286 Mm in calculations involving frequencies below 30MHz?

I understand that in order to make the maths simpler, frequency ($f$) is expressed in megahertz (MHz) and the velocity of propagation in free space ($c$) for frequencies above 30 MHz is expressed as ...
10
votes
1answer
4k views

How do I discover APRS coverage?

I'm considering adding simple APRS transmitters to my vehicles. I'd rather just put one in and forget about it, but I understand there are areas of the US where a stronger transmitter would be ...
10
votes
1answer
989 views

Can I have multiple inverted-vee antenna fed by a single coax?

A friend who recently received his call is planning to setup an inverted-vee for 40/20m bands. Our take is the signal will take the path of least impedance into the correct length antenna wire. ...
10
votes
5answers
912 views

Are there formulae to calculate capacitance and inductance of an antenna?

How to calculate internal impedance of a dipole antenna? Its resistance has two components ie wire resistance and radiation resistance, both these can be calculated using formula. Are there formula to ...
10
votes
1answer
153 views

Is there a special name (and if so what is it) for this flush-style SMA variant?

I have some radios that have a special antenna connector. It looks like an SMA connector, but the dielectric is flush with the end of the connector: rather than recessed the way "normal" SMA ...
10
votes
3answers
3k views

Why does “high SWR” damage transmitters, instead of “impedance mismatch”?

In the audio realm, where cable lengths are insignificant compared to the signal wavelength, I would understand an impedance mismatch damaging an amplifier as follows: Take an audio amplifier that ...
10
votes
4answers
577 views

Why are commercial SDRs so limited in operating frequency?

I spent a bit of time researching SDRs, mostly looking into the possibility of building an all-FPGA-based TRX. There are a lot of commercial ready solutions; some are cheap, some not, but they all ...
10
votes
1answer
1k views

Is FM modulation still more resistant to noise when given the same bandwidth as an AM signal?

FM modulated radio is much more resistant to noise and can deliver better sound quality than AM radio. But FM signals also use more bandwidth than AM signals. In general a wider bandwidth signal is ...
10
votes
2answers
639 views

Getting Started with Digital Modes on VHF on Linux

I am interested in learning about digital modes using 2m and Linux. I have a couple of older 2m rigs (HTX-212 and an old Yaesu) with no additional hardware, like a TNC. What current resources exist ...
10
votes
2answers
4k views

What is the expected microphone input voltage level of a handheld transceiver?

Ok, so I'm looking to inject some computer generated CW into a little handheld rig by wiring direct into the mic input line. What sort of voltage is expected on this input, are we talking uV, mV or ...
10
votes
3answers
967 views

What is the difference between FCC station and operator licenses?

I an studying for my technician class examination, and I came across this question: What may result when correspondence from the FCC is returned as undeliverable because the grantee failed to ...
10
votes
2answers
264 views

What is the most common amateur identification practice for mobile US amateurs operating in Canada?

When a US Amateur operates in Canada, IT and Canadian regs permit some lattitude on their identification. I have read that some will prefix a "VE3" plus their own home callsign (Ontario, meaning I am ...
10
votes
3answers
711 views

Stealth HF station setup advice

I need some advice on setting up my first HF station in a somewhat restricted townhouse community. If I had a detached house with a backyard I’d probably already have everything setup. But with this ...
10
votes
3answers
467 views

Aside from repeaters, what station types allow automated transmissions?

I know repeaters don't have to have a control operator at the radio in order to transmit given certain conditions are met. Are there any restrictions to setting up automated stations which transmit ...
10
votes
1answer
240 views

What is body blocking, and does it work with a stock HT on a foxhunt?

I've heard that you might not need a special directional antenna to participate in a foxhunt, that some people are able to use their body to help determine the direction of a signal. How does this ...
10
votes
3answers
588 views

How to Evaluate Antenna Data

I found some data on antennas that had been tested for a specific radio. I'm trying to decipher what this data means and how one would go about gathering it. Are there any good resource for learning ...
10
votes
1answer
5k views

How to design a rubber ducky antenna

I am attempting to design an antenna for a 162.4 MHz omni receive only application and am confident it is going to be difficult if not impossible. I have very tight specs on space(6" diameter by 3" ...
10
votes
4answers
911 views

How does an antenna transform impedances along its length?

If I insert some impedance (like a loading coil, or a trap) at the base of a monopole antenna, the effect on the feedpoint impedance is easy to predict: the impedance is in series with the antenna, so ...
10
votes
1answer
789 views

What does a lightning bolt symbol next to an antenna connector mean?

On the back of my Yaesu FT-897, next to each of the antenna connectors, there are lightning-bolt-ish symbols. What do these mean, and is there something I ought to be doing because of that? I have ...
10
votes
0answers
172 views

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 ...
9
votes
5answers
2k views

Non-traceable radio emitters

There are various techniques for locating a radio emitter. But what are some methods to make this really difficult? There is usually a patch to every vulnerability, at least from the world where I ...
9
votes
6answers
30k 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 ...
9
votes
5answers
4k views

Is it illegal to key up and not identify?

So, I key up on a repeater to see if it works, or to see what cool courtesy tone they are using. I don't do anything else. Is it illegal or bad ham radio etiquette to just key up for a second, key ...
9
votes
2answers
2k views

Is Morse code allowed on FM in the USA

Let's say I get my little 2 meter FM handheld out and make a little sine-wave generator with which I pulse a morse code and if I connect it to headphones a speaker, I hear the dits and dahs of a nice ...
9
votes
5answers
16k views

What's the difference between saying “CQ” or “QRZ” in a contest?

I'm listening to (or let's say I'm trying to participate in) a contest (or perhaps Field Day), using SSB. I noticed that a station would, after completing a contact, sometimes say “CQ” and sometimes ...
9
votes
4answers
38k views

What is the difference between channel & frequency & band in RF?

I am reading about wireless networks basics. I found three terms I cannot find exact definition for: channel, frequency band, frequency. Can anyone give exact definitions for them?
9
votes
4answers
23k views

How can you calculate the frequencies for each band?

I've just started studying for my HAM license a couple of weeks ago, so please excuse me if this is a remedial question... I have the Canadian Amateur Radio Basic Qualification Study Guide (which I'm ...
9
votes
2answers
581 views

Why do we have to hand wind toroids?

Many, if not most, ham radio kits (transceivers, tuners, ununs, baluns) require the builder to hand wind and tap their own toroids. (example) This is a considerable area of stress for newbie builders ...
9
votes
2answers
3k views

Can every antenna be used both for transmit and receive?

Assuming I have an antenna for receiving GPS signals, can I use it also for transmit — to create a repeater in a tunnel (or some place with no reception)?
9
votes
3answers
3k views

Why do so many HF transceivers use a UHF connector?

Just looking around at various rigs online for a fiend. Lots of them look really attractive TS-480, K2, K3, FT-450D, FT-950, IC-78, FT-897 to name just a few... These rigs are mostly HF, albeit some ...
9
votes
4answers
4k views

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?
9
votes
2answers
1k views

Who enacts the FCC's rules and regulations?

I came across an old answer on this site which makes the claim: It would take an act of Congress to change this [FCC Part 97] rule. Is that correct? I was under the impression that United States ...
9
votes
3answers
721 views

Why does “Ethics and Operating Procedures” suggest tuning on a dummy load?

The seminal work "Ethics and Operating Procedures for the Radio Amateur" suggests in subsection II.8.1 to perform tuning only on a dummy load. Sometimes before transmitting it is necessary to tune (...
9
votes
7answers
18k views

Is packet radio possible on Baofeng UV-5R and similar HTs?

I am curious to know if it is possible to do packet radio on VHF/UHF using the UV-5R... I have seen some invasive hardware hacks, but without modifying the radio itself (firmware, hardware) it's my ...
9
votes
4answers
7k views

Operating proceedures: testing an HT against a repeater?

Assuming proper licensing for the frequency, what is the proper operating procedure to test whether an HT works and is within range of a (documented as open, 2M or 440) club repeater? Should one wait ...
9
votes
2answers
759 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 ...
9
votes
4answers
15k views

2m or 70cm FM mobile radio for digital mode operation

Are there any 2m and/or 440cm FM mobile radios that have audio inputs for supporting digital modes, like PSK31 or SSTV? I have a Rigblaster that I use with my HF radio so I could get a mike cable and ...
9
votes
3answers
383 views

Why does ARRL license examination procedure preclude students from discovering what questions they got wrong on licensing tests

I got my Extra-class ticket some time ago. I was able to discover what my score was (the number of questions I got wrong). However, my examiner was not able to tell me specifically which questions I ...
9
votes
5answers
9k views

Home-brew 10 meter walkie talkies?

"When I was in high school, we had 8 hams at once. (Probably rare) 4 of us built little 10 meter walkie-talkies and had great fun using them on Field Day, hiking or around town. It was ...
9
votes
5answers
2k views

How can I prevent my mobile radio from draining my vehicle's battery?

I'm a very absentminded ham. I have a radio mounted in my car, wired directly to the vehicle battery. Fuses and high-gauge wire and all that good stuff. But, if I accidentally leave it on, my battery ...
9
votes
5answers
456 views

Is a Technician license enough to assist in times of emergency?

Is a Technician license enough to assist in times of disaster/emergency or do I need General or higher?
9
votes
3answers
2k views

What kind of antenna has a spiral connected to a reflector like this picture?

The description on the antenna says it is used for satellite communication, but it was taken in 1984. Is this an antenna style that is still in use? What is it called? What kind of gain should be ...
9
votes
3answers
21k views

How would I modify a satellite dish to transmit and/or receive to a Baofeng UV-5r plus? ( A handheld transceiver) If it's possible

I have an old satellite dish just lying around and was wondering how to hook it up to my baofeng uv-5r plus.
9
votes
2answers
294 views

Full UK license visiting US: Can I use frequencies in US but not UK license?

E.g.: 7.2-7.3MHz are Region 2 but not Region 1. My license is "from" Region 1. 1.25 meter band is not available in the UK Operating from aircraft is not permitted in the UK. Would it be if I visited ...
9
votes
3answers
675 views

Why are germanium diodes specified in amateur radio designs?

It's somewhat common to find a schematic that calls for a germanium diode in amateur radio contexts. For example: This is a QSK circuit from the Fldigi manual. And yet, purchasing a germanium diode ...
9
votes
1answer
788 views

Faraday cage in Microwave oven

If I put my mobile phone in my microwave oven and close its door, Should I be able to get incoming calls ? Because, I tried it and I was able to get calls, what does it mean? Does my microwave oven ...
9
votes
1answer
284 views

How Could Superheterodyne Receiver Ever Work?

I am surprised how the Superheterodyne Receiver still works and is still in use after coming to realise the impact of Image Frequencies on its performance. Basically, I'm curious how engineers make ...
9
votes
5answers
4k views

Grounding a second-story shack with an outdoor antenna

My shack is on a second story, really far away from the house ground. To run a ground from my equipment to the outside/ground is a run of at least 60-75 feet. The antenna is at least 100 feet away as ...
9
votes
3answers
8k views

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 ...
9
votes
2answers
930 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?

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