# All Questions

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320 views

I've just written code for the RTL2832 to receive and decode ADS-B packets (very cool!). I had some confusion about what is actually happening: Is the raw data coming from the USB dongle literally ...
4k views

### Why prefer LC oscillators rather than RC oscillators in RF design?

I don't recall ever seeing an RC oscillator driven RF transmitter or receiver. What prevents people from choosing RC oscillators in RF design?
1k views

### My neighbor is complaining about my transmissions, what can I do?

My neighbor has indicated that they can hear noise from their computer amplified speakers when I'm transmitting. We've done a few tests and it does appear that it's my transmitter that's causing the ...
386 views

### Does modulation affect propagation?

Does the modulation scheme, whether OOK, SSB, AM, FM, a digital mode, etc, affect the propagation of a signal?
555 views

### Why say “break” and “over” on walkie-talkies instead of an automatic chirp?

My understanding of why movie characters say "break" and "over" during radio conversations is based on this answer, which says that people using half-duplex devices often will want to let others on ...
318 views

### Why does the FCC put restrictions on symbol rates?

This answer claims that Mostly, on HF, the FCC has chosen to limit modes of transmission and symbol rates rather than bandwidth Why does the FCC limit symbol rates?
283 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 ...
180 views

### Practical limits to maintaining coherence in an HF channel

Lately I've been thinking about weak signal communication on HF. Very weak, like weaker than even WSPR could achieve. It would be nice if one could simply take any existing modulation and slow it ...
180 views

### Dominant speeds of Morse Communications

5 wpm is easy to learn and better than nothing in emergency. Speed Morse Coding is fine for "sport competition" I am trying to find out which is the typical speed for what I call "conversation" and ...
501 views

### Who funds amateur radio satellites?

I am currently studying for my Technician Exam and I am amazed at the sheer number of amateur radio satellites in orbit. Knowing how expensive it is to launch something into space, and assuming there ...
4k views

### How is “clarifier” control helpful?

My radio-club recently got a Yaesu FT-225RD transceiver and I'm trying to digest its manual (available for download here). This is the first ham radio that I'm learning how to use, so I could be ...
89 views

### Where on the web can I find a calendar of upcoming contests?

For years, I have been using SM3CER Contest Service for HF contests. It is always good to have a backup, so I am looking for more or better. What do you recommend?
162 views

### 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 ...
2k views

### While backpacking, is it worth mounting the antenna to the backpack frame (above my head)?

I am planning a trip with a large group in 6 weeks. We will be spread out in small groups on a trail in a mostly desert plateau landscape perhaps 5 miles apart, but mostly in a straight line. I'm new ...
1k views

### Why is dynamic range relevant for an SDR?

Sometimes I see dynamic range mentioned as a figure of merit for an SDR. For example, I know that the bits per sample used by the analog to digital converter can affect the dynamic range. Why do I ...
3k views

### 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. ...
4k views

### How do I find out what bands are open?

Say the deck is stacked. I'm out in the country with an all-band QRP home-brew rig, and an active antenna. Or say ship-wrecked and marooned on that desert island. The battery only has enough juice ...
367 views

### Do I need to actually lock up my station?

Per §97.103, one is responsible for the proper operation of one's station, which of course includes that no unlicensed person uses it to transmit. I have heard suggestions (no link handy, sorry) of ...
423 views

### What is the best practice when tuning an antenna on air?

I have a magnetic loop antenna that takes a long time to tune and of course, while tuning it, I need to be transmitting. What is the best procedure for tuning on air? I understand I need to check ...
636 views

### Can an amateur use cellular technologies with SDR?

Software Defined Radio is opening up many new possibilities for amateur digital modes. One family of technologies that interests me is cellular. 2G GSM voice/sms and 2.5G GPRS data has been proven to ...
2k views

### Buddipole model comparison

Can anyone give me some insight into the different Buddipole models available? They look pretty similar to me except for the sizes. What would make you choose one over the other?
411 views

### Using MIMO in Amateur Radio?

MIMO, Multiple Input, Multiple Output, is used widely in commercial data transmission. 802.11n and LTE devices use it to increase throughput, link reliability, and channel usage without increasing ...
1k views

### Where can I find the official definition of ITU Zones?

I've been looking around for a spot that has the official definition of what the various ITU Zones are, but can't find one. What is the official definition? I'm hoping for more than just a map, unless ...
243 views

### Which qualities/features does an SDR radio device need to be usable for Amateur Radio?

I know what things to note when selecting an analog amateur radio, but SDR devices have completely different specs, e.g. sample rate and resolution. What do I need to know about the device to make ...
2k views

### How does a “chip antenna” work?

How does a tiny surface-mount "chip antenna" for the 2.x thru 5.x GHz frequency bands work? What allows such a tiny item to radiate or receive RF with some amount of efficiency? What allows a chip ...
720 views

### What is meant by “poles” when discussing filters?

I was looking over the product page for the K3 (dreaming I know) and noticed that they offer a variety of crystal filters. Some are 5-pole and some are 8-pole, other than price, what is the ...
624 views

### Scoring quality of Morse Code “fist”?

When learning, teaching oneself, or training a class in Morse Code sending using a hand key, how can acceptable quality be scored (other than the letters being correct terms of dot-dash sequence)? ...
1k views

### What Part 97 rule allows unattended, automated transmissions, such as APRS weather stations and beacons?

What rule allows Amateur Operators to establish and operate remote, automated stations like APRS weather stations or beacons? Are there different rules specifically for beacons, or do they all fall ...
2k views

### How does a switching mixer multiply the two signals?

I understand what a mixer does, and when I see it in a block diagram it's obvious what purpose it serves and how it fits in the overall design of the radio. However, when I look at the schematics and ...
1k views

### How do I design a round or square coaxial transmission line to have a specific impedance?

Certain Hex Beam antennas use a coaxial center support post to send the RF to each antenna section, which is superior, in terms of maintenance, to a post with screw terminals connected by short ...
316 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 ...
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 ...
911 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. ...
592 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 ...
136 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 ...
563 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 ...
537 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 ...
259 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 ...
596 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 ...
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 ...
419 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 ...
212 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 ...
569 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 ...
4k 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" ...
744 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 ...
898 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 ...
27k views

### What is a Gamma match in the context of the driven element of a Yagi antenna?

How (and why) does a Gamma match work, when used on the driven element of a Yagi antenna? As shown here: (source: http://www.iw5edi.com/ham-radio/?2-element-yagi-for-10-meters-band,49) The article ...
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 ...