Scott Earle
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Why are vacuum tubes still used in amateur radios?
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15 votes

The last mass-produced vacuum tube was the Cathode Ray Tube, Thankfully those are now going the way of the dodo, replaced with much more practical LCD or OLED displays. (Edit: it turns out the ...

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What is homebrew?
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12 votes

Homebrew is (as the name suggests) when you make your equipment yourself, as opposed to buying it. An amateur setup consists of many components - the largest and most complicated of which are a radio ...

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What does QSL mean in a CW conversation?
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12 votes

Generally, QSL means "I acknowledge receipt". "QSL?" (with a question mark) means "please acknowledge". Sometimes when listening to QSOs you will hear someone say QSL VIA BURO or QSL DIRECT or ...

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What was the origin of the Morse code abbreviations "hi" and "es"?
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12 votes

Many Morse abbreviations and conventions come from before the days of radio, and we are relative latecomers to the game compared to the telegraphy guys. For this question, I found an old reference ...

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Why is Morse code still in use?
10 votes

I love Morse code for these reasons: It's fun. There is something satisfying about pulling a really weak signal out from the noise just 10s of Hz away from another really strong semi-local signal, ...

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Visible radio wave propagation
8 votes

There are visible radio waves. We call them 'light'. We can see a whole range of frequencies of these waves, translated by our brains into something we call 'colours'.

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Why can I hear Morse when not in CW mode?
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7 votes

You don't say where you are hearing the Morse code. You say "on the same channels", but don't specify where you are listening. If you send Morse code using a buzzer, then that generates an ...

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How can I check if my CB radio is AM or AM/SSB?
6 votes

As mentioned in another answer, it sounds like it’s not SSB. The next question is whether it’s AM or FM. “CB” can mean different things in different countries, and you don’t say which country you are ...

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Is there any practical advantage to a parabolic reflector over a high-gain beam antenna?
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6 votes

The issue with using a parabolic dish antenna at UHF is one of size. The 60cm dishes you see on the side of people’s houses are picking up signals at 10GHz, and if you scaled them up for the 70cm band ...

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What equipment and software do I need to read raw civilian GPS signals on my Mac?
6 votes

I will answer this question from a "technology of radio" perspective, because half of the question is very much related to the technology of radio. The other half is related to the decoding of a data ...

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What exactly is a "balanced modulator"?
6 votes

To put it simply, a balanced modulator is a mixer which has two inputs and two outputs. The outputs are (input1 + input2) and (input1 - input2). So, if the inputs are 100kHz and 1kHz, the outputs are ...

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

As a UK license holder operating in the United States, you will be operating under CEPT Recommendation T/R 61-01. According to the CEPT regulations(PDF), it explicitly states that: The CEPT Licence ...

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Can I talk 2 Meter VHF across the United States
6 votes

There is a list of distance records on the ARRL website. Looking at these, I would say that it might be technically possible to hold the absolute minimum of what could be called a ‘contact’ (e.g. ...

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Are QRP transceivers only meant for CW communication?
5 votes

A QRP transceiver is just a transceiver that operates on low power (usually less than 5 watts). If you look at the international Q Code, you will see that QRP simply means 'low power', and QRO means '...

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Restricted line-of-sight communication
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5 votes

As pointed to by Marcus' comment, "line of sight" communication is just that: if you can see it, you can communicate. There are formulae that will calculate the distance to the horizon, given the ...

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How to measure wire for antenna leg | 40m inverted V
5 votes

If I were making an antenna like that, I would add the extra 10" (25cm) first anyway, because when you come to tune it it's much easier to trim the wire than it is to add wire to it later. Also, ...

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What has happened to HF?
5 votes

It is a measurable fact that there is more electronic noise across the radio spectrum now than ever before. However, I doubt that it has directly had much effect on the amount of amateur radio ...

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HackRF + Amplifier = HF/VHF QRP Radio?
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5 votes

Just to answer the second part of the question, you do not want an amplifier that has too wide a bandwidth, mainly to lower the complexity (and hence also the cost) of the amplifier. All users of ...

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How to find transmitting (voice and CW) Amateur stations in UK?
5 votes

The UK band plan for the 2m (VHF) band can be found here on the RSGB website. In the UK, the 2m band is between 144.000MHz and 146.000MHZ. Of note is the section 145.5935 - 145.7935MHz, which are the ...

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Private Channel?
5 votes

There is a way to use radio waves to hold a private conversation. It's called a mobile telephone, and they are available with surprisingly good coverage around the world. We should always use a tool ...

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OK for S/RF light to be illuminated at engine idle?
5 votes

If your car uses petrol (gasoline) rather than diesel, then the ignition system can potentially generate a lot of noise because of the high-voltage system used to generate the sparks that ignite the ...

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What nations still require Morse code testing for Amateur radio license?
4 votes

Thailand For its own amateur radio licences, Thailand has three grades - Basic, Intermediate and Advanced. Basic allows access to the 2m VHF band only, and the higher two grades allow access to HF as ...

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LSB modulation and demodulation
4 votes

USB is basically AM with the carrier suppressed and the lower sideband filtered out. LSB is basically AM with the carrier suppressed and the upper side and filtered out. To demodulate either, you ...

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How proper HIHI sounds like?
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4 votes

People sending HI tend to fall into two camps. Some people send a correct HI, as if they learned that HI means laughter, and they want to send that accurately at all times. The second camp learned by ...

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What gain and power are required for successful DX contacts on 2m/70cm bands in CW?
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4 votes

I will talk about my experiences with 2m here - 70cm is similar, except (and anybody who knows better than me please correct me) there is no sporadic-E at all ever on 70cm. It all depends on ...

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What is "up" and "down", and is it consistent with "top band"?
4 votes

These are just conventions. Back in the day of wavelengths determining the band you are in, the “highest” (i.e. the longest wavelength) band was the 160m band. This is of course not true any more, ...

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Which 10 m antenna will give the most rejection in one direction for received signals which are vertically polarized?
4 votes

I might be missing something here, but one of the antennas in common use that has a very sharp null in one direction (and its opposite, so I guess two directions) is the one used by ARDF enthusiasts ...

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What are the advantages for a receiver that uses an IF compared to direct conversion?
4 votes

There are several advantages to converting to an IF. These include: It is easier to make a multi-band receiver, as you just need to change the RF stage for each band, and everything after the IF is ...

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Is the Nyquist rate independent of the power of the analog signal being digitized?
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4 votes

Completely independent. It is dependent on frequency only. The amplitude of the signal is only relevant when looking at the number of bits used (and the dynamic range). See here for more details.

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Why are 2m and 70cm the common frequencies on HTs?
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4 votes

Worthy of mention is that 432MHz is a harmonic of 144MHz, meaning that the antenna can be much simpler; if it's (electrically) an odd number of half-waves on 2m, it's also an odd number of half-waves ...

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