Uniden SDS100 and SSB

[wbswetnam]

In one of the Uniden forums, a user noted that the SDS100 might be capable of demodulating single side band, the only problem being detecting / calculating the carrier frequency.

What I understand about single side band is that it doesn't have any carrier frequency to begin with. Wasn't this the purpose of the BFO (beat frequency oscillator) in early HF amateur radios, to insert a carrier where there was none?

 

[ab5r]

https://www.electronics-notes.com/articles/radio/modulation/single-sideband-ssb-basics.php

 

[wbswetnam]

https://www.electronics-notes.com/articles/radio/modulation/single-sideband-ssb-basics.php

Hmmm... OK, time for me to pull down my ham license books and review, I guess. Still, can a scanner detect and demodulate a SSB signal?

I read somewhere that in the 1970s and 1980s, some police departments began using SSB as an 'encryption' format instead of FM, because SSB signals were undetectable by scanners. They could transmit in SSB to another SSB receiver set to their normal transmission frequency, and radio scanners would blithely ignore it since scanners were searching for an FM carrier.

 

[jonwienke]

The tl;dr is that the carrier and one sideband are filtered out of a standard AM signal before the RF heads to the final amplifier. Some variants of SSB leave a little bit of the carrier in the broadcast RF so that it can be detected and reconstituted in the receiver, and prevent any frequency shift in the demodulated audio.

A fairly decent guesstimate of the carrier frequency could be inferred from the frequency distribution of the sideband (e.g. pick a carrier freq that keeps demodulated audio between 300Hz and 5000Hz). If there is a vestige of the carrier, then correct demodulation would be easy, just look for a constant-amplitude spike that would correlate to 0Hz in the demodulated audio. No special hardware would be needed, just the appropriate software to demodulate the audio from the I/Q stream. If SDR# can do it with a $20 dongle, then the SDS100 should be capable of doing it as well.

 

[jonwienke]

I read somewhere that in the 1970s and 1980s, some police departments began using SSB as an 'encryption' format instead of FM, because SSB signals were undetectable by scanners. They could transmit in SSB to another SSB receiver set to their normal transmission frequency, and radio scanners would blithely ignore it since scanners were searching for an FM carrier.

An AM or FM scanning receiver won't ignore a SSB transmission, unless it is checking the frequency during a pause between words when transmitted RF power is very low.

An FM receiver will interpret an AM transmission as a dead carrier, due to the capture effect on the carrier. An FM receiver getting a SSB signal will have audio, but it will be badly distorted, as it captures on whatever audio frequency happens to be strongest.

An AM receiver will hear sideband as well, but it will be significantly distorted.

 

[prcguy]

A number of scanner/communications receivers demodulate SSB and AOR, Icom and Yupiteru are a few that come to mind. Police depts would not have switched to SSB in the VHF/UHF or 800 bands as their FCC license would not allow SSB there.

Hmmm... OK, time for me to pull down my ham license books and review, I guess. Still, can a scanner detect and demodulate a SSB signal?

I read somewhere that in the 1970s and 1980s, some police departments began using SSB as an 'encryption' format instead of FM, because SSB signals were undetectable by scanners. They could transmit in SSB to another SSB receiver set to their normal transmission frequency, and radio scanners would blithely ignore it since scanners were searching for an FM carrier.

 

[ka3jjz]

To be honest, I really don't see the point unless you are a ham or are interested in becoming one. They use SSB on frequencies above 25 Mhz in several places, but the limiting factor would be the antenna. On 10 meters, a little duckie is worse than a wet noodle, and on 2m and 432 Mhz, the polarization would be an issue (horizontal vs. vertical for public service work). 6 meter SSB is also possible, but that too is a ham allocation...Mike

 

[jonwienke]

Admittedly, SSB is a niche market, mainly hams and the CB/freeband crowd. And you'd need a base antenna for most of the bands that use SSB. But the point is that the software development needed to add it to the SDS100 would be fairly trivial, and no hardware would be required.

 

[ButchGone]

Actually, there is plenty of SSB traffic to monitor below 30 MHz besides amateur radio. Civil and military aviation communications, for example.
BG..

 

[iMONITOR]

MF/HF-SSB Marine Radio

 

[KB7MIB]

Actually, there is plenty of SSB traffic to monitor below 30 MHz besides amateur radio. Civil and military aviation communications, for example.
BG..

The SDS-100 doesn't go below 25 MHz, so anything lower in frequency is moot.

Between 25-30 MHz, you have CB'ers between 26.965-27.405 MHz, with SSB use usually only found in the top 5-10 channels, and Hams between 28-29.7 MHz, with SSB found above 28.1 MHz

There are the ITU Maritime channels 2501-2510, (25.070-25.097 MHz ship, paired with 26.145-26.172 MHz shore) and Australia has an 11 meter maritime allocation as well (27.680-27.980).

Above 30 MHz, you'll only hear SSB in the Ham bands.

John
Peoria, AZ

 

[Voyager]

The SDS-100 doesn't go below 25 MHz, so anything lower in frequency is moot.

Above 30 MHz, you'll only hear SSB in the Ham bands.

The scanner operation is limits to 25 MHz. There are no SDR specs yet.

While it still might not go below 25 MHz, it's also possible it might.

I would not expect SSB to be a feature that will be part of the normal operation, but it may well be part of the SDR features.