19
votes
Accepted
Why do some straight keys have a slider that shorts the contacts continuously?
My understanding is that in at least some telegraph systems, the principle of operation was as in this circuit (where the coils depicted are actually telegraph sounders):
simulate this circuit –...
- 23.7k
17
votes
Accepted
How did hams manage to tune their antennas before VSWR meters?
Mostly, they used RF Ammeters in series with the antenna. The first ones were hot-wire ammeters which were completely mechanical devices. One end of a thin nichrome wire (or other wire of sufficiently ...
- 7,605
15
votes
Accepted
Why are vacuum tubes still used in amateur radios?
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 ...
- 4,429
15
votes
Why do operators mention the band when calling CQ on phone?
I have a scanner capable of HF receive, multiple HF receivers, and several HF SDR transceivers capable of receiving on more than one amateur band slice simultaneously. Lots of contest stations run ...
- 12.9k
11
votes
Why do operators mention the band when calling CQ on phone?
It may have served a purpose in the past, with less filtering in transmitters and receivers, no digital frequency displays &c, e.g. to avoid mistaking a harmonic on a higher band for the ...
- 634
10
votes
Accepted
What does the spark-gap do in a spark-gap transmitter?
The spark gap is a simple, low-tech way of generating high frequencies. It was the only way of generating them before valves and transistors were invented.
As C1 charges up through R1, eventually the ...
- 9,599
10
votes
Accepted
USA/callsigns: Why is California region 6? And the midwest in regions 7-9?
The origins of the amateur radio call sign districts can be traced to 1912 when the Department of Commerce, Bureau of Navigation created nine radio inspection districts to enforce the 1912 Act to ...
- 18.3k
10
votes
Why are vacuum tubes still used in amateur radios?
As far as I know, vacuum tubes are used in newly-manufactured radio equipment (as opposed to still-in-use old equipment) for one purpose: high-power amplifiers. The advantages of vacuum tubes in this ...
- 23.7k
9
votes
How did the terms like QRZ, QTH, and other forms of ham shorthand evolve?
They were created to save time in Morse code communications.
From https://en.m.wikipedia.org/wiki/Q_code:
The Q code is a standardized collection of three-letter codes all of
which start with ...
- 7,605
9
votes
Why are vacuum tubes still used in amateur radios?
Vacuum tubes are neither outdated nor less efficient. See https://spectrum.ieee.org/semiconductors/devices/the-quest-for-the-ultimate-vacuum-tube
The above IEEE Spectrum article talks about a vacuum ...
- 4,901
9
votes
Why do operators mention the band when calling CQ on phone?
Apart from historical reasons it's also a filler. When calling CQ on SSB you probably want to stretch out your transmission a bit because that's what you need to get heard. In theory you could just ...
- 131
8
votes
Why do some straight keys have a slider that shorts the contacts continuously?
Land line telegraph keys are fitted with a circuit closer switch. Radio telegraph keys were not but many radio operators used land line keys because they were so readily available. This includes the ...
- 181
8
votes
Accepted
What replaces the T/R switch in modern transceiver
Receivers and transmitters are still separated today, they are just in the same box. There is still a T/R switch too, integrated in the box.
In many radios, it's a relay, same as they have been for ...
- 50.8k
8
votes
Accepted
What do old unit abbreviations like "mfd" and "kc" mean, and where did they come from?
These were common abbreviations in use for Components, Radio equipment, and Printed publications in the 19th and most of the 20th century.
Mfd = microfarad or μF
kc = kilocycles or kHz. 1,000 cycles ...
- 7,605
7
votes
Why are vacuum tubes still used in amateur radios?
There's one more reason vacuum tubes are still used in amateur radios: personal preference of the amateur building the radio.
Speaking for myself, I understand what's going on inside a vacuum tube ...
- 3,967
7
votes
Accepted
Looking for a book that contained a circuit for receiving (literally) underground amateur radio transmissions
Yes, this most certainly was a thing, and people actually did it.
This type of communication has been done at ELF frequencies in the 3-30 kHz range. Their linear amplifiers were ordinary Hi-Fi audio ...
- 7,605
6
votes
What is the origin, history behind "Ben's Best Bent Wire"?
In the RAF we used "best bent wire" as a test transmission largely because it has a lovely jazz rhythm. Some put "bens" in front, some put another "bent" on the end, but i you send it a reasonable ...
- 61
6
votes
Is the Relay in ARRL still relevant?
The ARRL NTS (National Traffic System) is designed to operate from one local area to another local area (say, across the country) by the process of Relaying messages from one station to another. I am ...
- 2,898
5
votes
Accepted
Is there a practical way for hams to participate in cellular-related technology advances?
Are there any cellular bands that are close enough to amateur allocation for off-the-shelf cellular modems/filters/antennas to work?
Yep, thanks to the fact that what is a GSM band in Europe is the ...
- 14.6k
5
votes
Accepted
How were 1920s hams able to measure megahertz frequency?
[Discovered this via a comment on another answer.]
According to their Wikipedia article:
Lecher lines were used as frequency measuring devices until frequency counters became available after World ...
- 7,092
5
votes
How were 1920s hams able to measure megahertz frequency?
The US National Bureau of Standards (NBS) had a system for basic measurement of frequencies as early as 1911. They used very basic calculations to determine the resonance of an LC circuit. The math ...
- 18.3k
5
votes
What is a panadapter?
A panadapter is a device that adapts the narrow (typically 4kHz) bandwidth of a traditional receiver into a much wider bandwidth, perhaps the entire band. The pan- prefix means all, as in panoramic, ...
- 50.8k
5
votes
Why do so many hams prominently display their callsign in the shack?
There might be other reasons, but in South Africa at least, it's a legal requirement.
Part VII: General Provisions
Subpart 29: Allocation and Display of Call Sign
Where the Authority allocates a call ...
- 9,599
4
votes
Why do some straight keys have a slider that shorts the contacts continuously?
The switch on the side of the key is or rather was used when tuning up a transmitter. In the old days you had to increase drive and dip the grid of the final amplifier. So this is simply a switch so ...
- 139
4
votes
What does the spark-gap do in a spark-gap transmitter?
the spark gap's purpose is to very suddenly change the current in the LC circuit to which the antenna is, in fact, directly connected. the sudden change produces a very strong inductive kick in that ...
- 855
4
votes
When was the first radio transceiver (transmitter/receiver) built, and by whom?
This is tough to nail down since even the term transceiver is subject to interpretation. It is also often the case that a given answer may only be applicable for a specific geography.
But with those ...
- 18.3k
4
votes
Lightbulb as an SWR detector?
Mainstream hams first started to appreciate SWR in the 1940's. In that era some of the first SWR meters started to come on the market. But their accuracy and frequency range was quite limited. Toward ...
- 18.3k
4
votes
Lightbulb as an SWR detector?
I don't know much about this, but for what it's worth I do have a rather distant memory of doing this long ago, before transistor RF power amps became affordable and before I had a way to measure SWR ...
- 311
4
votes
How did the terms like QRZ, QTH, and other forms of ham shorthand evolve?
Here's a quote from https://en.wikipedia.org/wiki/Q_code .
The original Q codes were created, circa 1909, by the British government as a "list of abbreviations... prepared for the use of British ...
- 77
4
votes
What did it mean to "align" a radio?
The process of alignment involves optimizing the settings of variable inductors and/or trimmer capacitors in the set to maximize sensitivity and selectivity. It usually involves feeding the set a ...
- 3,967
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