# All Questions

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### 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 (...
20k 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 ...
1k views

### What should I do if my call is being used by someone else?

I've been contacted by others who want to verify a DX with me, but I was not operating at that time! It appears that someone made several contacts using my callsign for a short window of time one day....
284 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 ...
2k views

### What is the definition of DX?

I always believed that DX meant out of one’s own country, and in the continental US that can be pretty far. However, tooling around on the bands I’ll often hear people calling DX inside the US receive ...
718 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 ...
8k 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 ...
1k 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 ...
393 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?
1k 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 ...
14k 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 ...
245 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 ...
505 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 ...
766 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 ...
136 views

### What is the decimal in Morse Code?

The ITU's International Morse Code recommendation ITU-R M.1677-1 specifies a "Full stop (period)" as ".−.−.−", however it falls short of specifying a decimal point. Even the examples, though they ...
215 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 ...
2k 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 ...
6k 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 ...
3k views

### What causes ground losses in a HF antenna system?

This applies to mobile and fixed installations. What are ground losses, and how can they be minimized? It seems to involve proximity to the ground, but what is the mechanism that causes loss? Does ...
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. ...
1k views

### AIS and RTL-SDR Dongles

I am looking for an Windows-based AIS Decoder for RTL Dongles. Currently, there is a solution available using GNU Radio and SDR# but it is complicated to set up and keep running. ADSB has a dedicated ...
964 views

### What did it mean to “align” a radio?

I've heard older hams talk about "aligning" their equipment. E.g. "I sent it to a guy for alignment" or "that rig probably needs to be completely aligned before you use it". As a kid, sometimes I ...
924 views

### Are hashes (such as md5) legal in the US

If I were to implement a remote computer control system using amateur radio, would using hashes (such as md5, sha-*, etc...) for authentication be permissible under the United States rules?
1k views

### Remote SDR on the internet other than WebSDR?

Besides WebSDR, what remote Software-Defined-Radio stations (for shortwave or amateur bands) might be available for open public access over the internet? What protocols do these SDR stations use to ...
1k views

### What is the largest gauge (thinnest diametre) wire I may use as an antenna?

A follow-up to Good wire for wire antenna? I'm QRT at present - thanks to fooling around with just a couple of diodes and PVC capacitors instead of a well-regulated supply. The antenna I used earlier ...
144 views

### Why are there so many coaxial cable impedances?

Why do we have 50, 75, 62 and 92 Ω coaxial cable, to name a few? Why not just one standardised cable? Is there some technical reason or did Mr. Coax and Mr. Cable have a disagreement, like Mr. Tesla ...
423 views

### RigExpert AA-35 - Interpreting The Information

I have a new RigExpert AA-35 antenna analyzer. 1st one I have had & 1st time trying to use an analyzer on an antenna. My questions are very basic and general, but I am having difficulty in ...
2k views

### What is an antenna tuner? Why bother with resonant antennas in the first place?

There are a lot of antenna tuners on the market that have various capabilities in terms of how they can allow random radiators to work with our transceivers. What exactly do they do? My ...
365 views

### How to operate on HF if an AM transmitter is only 540 feet away?

I'm a General Class Licensee, and due to pulmonary disease I cannot operate voice. I am also about 540 feet from a 24/7 1 kW AM station. The signal is so pronounced that most audio devices in the ...
311 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 ...
6k views

### What is dBm and why is it used rather than watts?

Reading through an RF power amplifier datasheet, I found the sheet only referenced dBm output power, rather than watts. What is dBm? How do I convert it to watts? Why, or when, would you use dBm to ...
242 views

### In-house repeater?

At one time I was active in the local SKYWARN program, but then we moved and I find myself 10 miles from the local repeater. Given the various obstructions between it and me, I can't really hit it ...
397 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 ...
3k views

### Does a balun need to be made with coax?

The short version My understanding is that one of the main reasons to use a balun with coax is to prevent the outside of the shield from becoming part of your antenna system. If that's the case, won'...
9k views

### How does the baofeng radio eliminate squelch tail?

All tests are performed in Carrier Squelch mode on all radios without any sub-audible tone or digital squelch involved. Scenario 1: The Baofeng handheld radio Keys up. Another Baofeng is listening. ...
328 views

### Why do SDR control apps have two frequency settings?

Why do many SDR control apps have two frequency settings, even when the app is designed or set up only for listening to or decoding one signal? Should the two SDR frequency controls be set ...
1k views

### Cleaning relay contacts?

I have an old transceiver. I have a problem where ocassionally the received signal will drop out when switching from transmit to receive. I've narrowed it down to the transmit/receive relay. When ...
3k views

### How much RF energy do trees and branches absorb?

For the 20m - 10m and 6m bands, will having my dipoles below the tops of trees (I live in redwood forests) drastically affect the RF power out or radiation patterns of my dipoles if I can still get ...
120 views

### What is the purpose of the German CW exam if it is not required to use CW?

To receive the amateur radio license Klasse A (HAREC) in Germany it is since 2005 not required anymore to pass a CW exam, due to a corresponding change in the Radio Regulations. However, the exam is ...
277 views

### Tuning a wire antenna by folding

Last weekend we tuned a quad loop for 80 m and 40 m. Instead of cropping, we folded the isolated wire using cable ties as shown in the picture below. After folding several quite large sections of the ...
409 views

### Is there a convention for SSB frequency selection?

I know that the amateur bands are not channelized. I know that anyone can pick an arbitrary frequency and they're not wrong, and you are not obligated to have a calibrated VFO. But if everyone picks ...
1k views

### How to combine two 50 Ω antennas such that they appear as one 50 Ω load?

I'm looking for a simple way to impedance match an array of two 50 Ω antennas so that when they are combined they appear as one 50 Ω load. Assume that both antennas are identically constructed, are ...
2k views

### Are satellites Left or Right hand circularly polarized?

I'm thinking of building some helical antennas for satellite work. I want to know which way to wind them. If satellites are spinning randomly, how can we know if they are left hand or right hand ...
2k views

### How does SDR demodulation differ between wideband and narrowband FM?

What is the difference between software demodulation of an IQ signal between wideband FM and narrowband FM? Both seem to look at the 2nd difference in unwrapped phase angles of IQ samples.
298 views

### CW on phone band

In the U.S., regulations permit CW operations throughout the amateur bands. That makes the phone section of a band look tempting when the CW/digital part of the band is busy with a contest. I wonder ...
5k views

### What is the electrical shock risk of an antenna?

I've seen people refer to avoiding touching an antenna or bare transmission line that might be transmitting. What voltage potentials and currents are commonly found on typical ham radio antennas? Do ...
441 views

### What is the procedure to obtain an amateur radio licence in Australia?

What and how would I go about obtaining a licence for HAM radio in Australia? Do the licencing regulations vary significantly from state to state?
1k views

### When is APRS use considered commercial?

I've heard that APRS is only allowed for non-commercial use. I was thinking of a building a weather station that uploads data via APRS (so far, non-commercial). If I then include data from that ...