hpr-knowledge-base/hpr_transcripts/hpr4685.txt

Episode: 4685
Title: Listening to SSB stations in the early 1980s
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr4685/hpr4685.mp3
Transcribed: 2026-07-31 16:16:45 (official HPR transcript)

---

This is Hacker Public Radio Episode 4685, for 2026-07-17
Today's show is entitled, "Listening to SSB stations in the early 1980s"
The host is Lennart Benschop and the duration is 00:15:12
The flag is Clean, and the license is CC-BY-SA
The summary is "Lennart tells how he could listen to SSB stations on shortwave on a radio without SSB capability."
Listening to SSB stations in the early 1980s, I'm Leonard Benschop, I'm an embedded software engineer in the Netherlands.
In 1980, I was 13 years old, and we had a grondic tube radio in the house that had a single shortwave range from 5.9 to 15.5 megahertz covering the 49 to
19 meter broadcast bands. And between those broadcast bands, you could hear all strange noises like heavily
distorted in intelligible speech, and number stations, and telek signals, and more signals of some
short, and then you had this very crowded islands, the shortwave broadcast bands that were
completely filled to the brim with signals. You couldn't have enough selectivity on a shortwave radio.
There were so many signals on the band. The 49 meter band in particular had a signal on every
multiple of 5 kilohertz, wherever you tuned. Whatever time of the day it was, 24-7, this band was
overcrowded. In 1980, they legalized CB radio in the Netherlands, and then I had a desire to own a radio
on which I could listen to those stations. I didn't need to have a transmitter for it, but I wanted
to be able to receive those things. And in 1981, I got the opportunity to buy a transistor radio
with 5 bands, made in 4 shortwave bands, covering the entire range from 1.6 to 30 megahertz. I think
the brand name was Silver. The radio had a fine tuning knob, which was very convenient. It was
all analog. It had an LED signal strank meter, which I think 5 LEDs to indicate. Signal strank
in a bar graph. It wasn't selective enough for shortwave broadcasting, but then you couldn't be
selective enough at that time. It didn't have a way to receive SSB. I could tune to the CB radio,
CB radio in the Netherlands was in FM, narrow band FM. The radio could only receive AM mode signals,
but if you off tuned a bit, you could still hear the signal. It wasn't as good as a proper FM detector,
but you could hear quite a few of those stations anyway. And then, of course, I had more broadcast bands.
16 meter band could be heard with radio South Africa on it. It was one of the few Dutch language
international stations outside of the Netherlands itself. Really nice to hear that from so far away.
That nothing to do with the apartheid regime in South Africa itself. That wasn't important.
The content of the program wasn't important, but you could hear a Dutch language stuff from
that long distance. And that was great. Then I wanted to hear radio emitters
and also marine traffic, like a scavening radio, marine telephony. And all these things were in SSB.
And they invented SSB as a way to save bandwidth and transmit a power. If you have an AM transmitter
and you look at the transmitted spectrum, it has two side bands, an upper N lower side band,
both contain the same modulation information. And then it has in between them carrier frequency,
with lots of signal power concentrated at carrier frequency. The carrier frequency itself contains
no information. You need it to demodulate the signal, but you don't convey information with it.
What were the professional users related radio emitters doing? They filtered out one of the
side band that saved a lot of bandwidth and they filtered out or just
constructed their modulator in such a way that the carrier signal wasn't transmitted. But what was
left contained one side band, all the information you need, but you couldn't demodulate it
without reconstructing the carrier frequency signal. And that was exactly what the proper SSB
receivers do. They reconstruct the carrier frequency with internal oscillator. But my radio didn't
I could have bought a different radio that had a BFO. The internal oscillator was called BFO
for Marscoat and SSB signals. But my radio didn't have one. Some radios were on the market,
way above my budget, like the Kenwood R1000, the JZFRG 7700. That was even a Sony portable radio,
the ICF 2001, that looks very nice in brochures. It got good reviews. It covered all the way from 150
kilohertz longwaves to 30 megahertz and then FM from 76 to 108 megahertz, very desirable radio.
But maybe if I had one at that time, I wouldn't have liked it because it had no tuning knob.
I had that scale of precisely tuning in an analog dial, pushing buttons and then
there was muting all over the place while tuning. And I needed to hear the signal while you were
tuning. That was our radio was supposed to work. It's it's a bit like you don't put the blind
fold on if you start walking. You want to see what's going on while you're walking. And it's
like the same. You want to hear what's going on while you're tuning your radio. So muting is a very
deaf idea, but still many of those digital portable radios with the up and down push buttons
have excessive muting while tuning. That's not nice and nothing feels like a real tuning knob.
The one on our two radio even had a flywheel behind it. That feeling despite this being way too
white frequency range. My own new transistor radio wasn't much better in that respect. It also
had frequency bands of 10 megahertz wide, but you had true analog tuning and that was important.
But I didn't have a BFO in my radio. If I was better at soldering, I could have
constructed one to build into my radio. But there was another trick. And all radios essentially
that are made and factored commercially between the 1930s and early 2000s are super hetero-dine
receivers. They have a local oscillator that mixes the incoming signal with the oscillator and
then it produces the difference and some frequencies difference frequency. That's the one we
want to have. That's fed into a selective single frequency filter. The IF, the intermediate frequency,
and then you have a fixed bandwidth, selective filter and amplifier and detector. And that's how
the radios work. So if you tune a radio medium-wave radio to one megahertz, one thousand kilohertz
and you tune the local oscillator to around 1450 to 1417 megahertz. The IF, the intermediate frequency,
is roughly in the range for 50 for 70 kilohertz. You tune the local oscillator to that frequency.
If you put a radio nearby, you tune one radio to one thousand kilohertz and another radio to
something around 1450 to 1470 kilohertz, you were here the signal of the local oscillator.
And if there's station in that range, you can hear that local oscillator interfere with that station.
And I thought, well, if that happens, couldn't you use that signal to as a stand-in for the
carrier frequency? Yes, something like a BFO. And I wanted to hear the marine band, the lower part of
it between say 1800 and 2000 kilohertz and an ordinary medium-wave radio had its local oscillator
all the way up to 2050 kilohertz. So it could cover that range. And indeed, I could tune
to say 1850 kilohertz on my portable radio, tune a different radio to 450 kilohertz lower. And
low in the old, I could hear that interfering signal from the local oscillator. And I could tune it
to the missing carrier frequency and make intelligible speech out of that as a B signal.
Great. And if I used a tube radio as the second radio, the second harmonic of the local oscillator,
would tune to over 4 min. And then I could cover the 18 meter emitter band, the 18 meter emitter band
was a very desirable band for me to hear. It had some Dutch language stations in it. You had the
veron station every week in the 18 meter band in SSB, PI4AA, and Papa India for alpha, and it had
a bulletin and I wanted to hear that. And I could hear that. Great. And then, if I had not a radio
with short-wave range, I could use it as a BFO for the 14 meter hand band around 7
megahertz and the 20 meter hand band around 14 megahertz. And that worked kind of.
Was a bit finicky and you had to vary the distance between the two radios to make the BFO signal,
the local oscillator signal just strongly enough that it makes properly with the signal you want
to receive. But that was doable. Until 1985, I didn't have anything else to hear as its base
stations on. In 1985, I got a communication receiver on non and R107. I had that radio for. I think about
a year or so alone. It's tuned from 1.2 to 18 megahertz in three bands. It was stone death
of 10 megahertz, so I couldn't hear the 20 meter emitter band on it, but 80 meter was great. Never had
such good 80 meter reception ever since. I only had an indoor antenna, but I had a ground connection
and the wires were laid out optimally for the 80 meter band. And yes, that was a great experience
to hear emitors in that band. Of course, in those days you had number stations, you had the
Russian wood packer that was an over the horizon radar that obliterated complete sections
of the shortwave spectrum. It was a Russian over the horizon radar. Everybody hated that one,
but you had to live with it. That trick, though I kind of discovered it myself, was kind of well-known
in the time. I read about it several times. It was especially widely used in countries where
SSB capable receivers were restricted or were like Middle East countries, or where they weren't
simply available to consumers, like the Soviet Union. It wasn't prohibited by law, but nothing
wasn't sale to mere consumers, emitors were supposed to build their own equipment. And
using two radios meant you didn't have to modify your existing radio, you didn't have any
illegal equipment in your house, and in some countries that made the difference.
This is all I want to tell for today. I hope to speak to you next episode.
You have been listening to the Hacker Public Radio podcast, at hackerpublicradio.org.
Today's show was contributed by a HPR listener like yourself.
If you ever thought of recording a podcast, then visit the HPR site to find out how easy it really is.
Hosting for HPR has been kindly provided by anhonesthost.com, the Internet Archive, rsync.net, and the HPR Community Content Delivery Network.
Unless otherwise stated, today's show is released under a Creative Commons Attribution-ShareAlike 4.0 International (CC BY-SA 4.0) license.