Tag Archives: Michael Black

Chairman of DRM Consortium looks at the current state of shortwave

(Source: Radio World via Maichael Black)

Note that the excerpt below is only a portion of the full article. Read the full piece at Radio World.

Does Shortwave Have a Future?

by RUXANDRA OBREJA

When is the last time you heard a shortwave radio transmission? And why should you put up with possible crackly audio and some interference when we have now internet, satellites, FM and all forms of digital radio?

[…]Shortwave is just short of a miracle, actually. When it is beamed at an angle, it hits the ionosphere. A mirror around the Earth and then it falls like a ball at great distances, beyond the horizon. Thus these transmissions reach listeners over large areas, continents and beyond. Two or three high-power transmitters can potentially cover the entire world.

Shortwave is used not just by international radio stations or radio amateurs but is also essential for aviation, marine, diplomatic and emergency purposes. Shortwave signals are not restricted or controlled by the receiving countries and, as frequencies change in winter and summer, they need to be coordinated internationally.

[…]Digital Radio Mondiale was originally invented to offer medium (AM) and large coverage (HF) and the advantages of the good audio quality and extra multimedia services that can take shortwave into the 21st century. Maybe DRM was ahead of its time. The phasing in of digital broadcasts internationally was not in tandem with the production and sale of receivers, which remains a regional and national business. Since its birth DRM has proven that it is a suitable option for shortwave offering an good digital quality of audio and even short live video at great distance without fading and crackly sound.

Now, at last, there are DRM receivers capable of receiving shortwave, there are broadcasts and interested broadcasters. Quietly and surely shortwave is being re-examined and appreciated for the quality of broadcasts and its potential as a “crisis radio” too. It can become crucial in emergencies when local and regional radio stations, satellite and internet may be off the air due to damage. Broadband is getting cheaper but is limited, 5G will come but not just yet, digital shortwave is here.[…]

Click here to read the full article at Radio World.

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What made the Squires Sanders SS-1R receiver legendary?

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ss-1r

Many thanks to SWLing Post contributor, Michael Black, who reminds us why the Squires Sanders SS-1R receiver (Dan recently spotted on eBay) was so innovative at the time:

It’s legendary because it leaped forward in receiver design, at least at the amateur level, and there was the article in QST in 1963 by Squires about the design. So lots of people knew about the design, even if they weren’t owners.

There’s no RF amplifier, the antenna feeds the mixer trough a tuned circuit. There’s a q-multiplier on that tuned circuit, to improve selectivity (q-multipliers were mostly seen in 455KHz IFs). The mixer was a 7360 beam deflection tube, hard to overload, and a balanced mixer, which was likely a first in ham receivers. After, everyone was using 7360s for receiver mixers, at least until good solid state balanced mixers came along.

I keep forgetting that it is still a dual conversion receiver (except for one band), though presumably to avoid other issues while allowing for a fixed 500KHz tuning range.

But the second IF is at 1 or 2 MHz, higher than the usual 455KHz, a sign of the future, though there were already some SSB transceivers with IFs in the HF range.

It does seem a relatively simple design now, but wasn’t fifty years ago.

The ham band version was the “big seller”, the shortwave version maybe offered because they could. It’s not clear if the front end needed changes to cover the SW broadcast bands. But it would have been an expensive SW receiver, and needing another crystal for each 500KHz tuning segment, a new concept at the time (though a few years later Drake had their SW receivers like that). But that was the trade-off, most receivers did have a 2:1 tuning range, while some were like the R390 , very complicated mechanically and crystals for every band. A subset of 3 to 30MHz meant fewer crystals and a simpler bandswitch but you spent a lot of money for a receiver that wasn’t “general coverage”.

Michael

Thank you, Michael, for the insight! At last glance, the bidding was only at $227.50. I suspect it will go much higher, but perhaps this will end up being a deal for someone.

Click here to view on eBay.

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Michael comments on the Squires Sanders SS-IBS

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Regarding the Squires Sanders SS-IBS Dan recently spotted on eBay, SWLing Post reader, Michael Black comments:

[The Squires Sanders SS-IBS is] a legendary receiver that either brought new ideas to receivers, or brought them to the amateur radio level.

There’s an article in QST in 1963 from Squires about this new stuff, I’ve never seen it so I don’t know if he’s talking in abstract terms, or revealing this receiver.

A big difference is that there’s no RF amplifier before the mixer, and the mixer is balanced. But he throws some of that out by going to double conversion, I assume for tuning reasons. The first IF is 500KHz wide, the first oscillator is crystal controlled and the second oscillator is variable, as seen in top end receivers of the day. The alternative would be a tuneable oscillator that was switched per band (instability from the switch, and the higher the band, the higher the frequency, hence stability) or mixing the tuneable oscillator with a crystal oscillator before feeding the first mixer, which can cause spurs without proper filtering).

The second IF is 1MHz, and having a filter so high was relatively new, though maybe some rigs had moved up to HF filters at the time.

It apparently is fussy about the antenna, or matching, because of the lack of RF amplifier.

Soon there’d be receivers that converted to 9MHz or so directly, saying goodbye to most image problems. Heathkit had a general coverage receiver later in the sixties that had an IF, with crystal filter, at 1680KHz, a relatively cheap receiver with much greater image rejection on the higher bands. The ham band only Heathkit HR-10 used the same IF and filter.

The Heathkit HR-10 (Source: Heathkit Virtual Museum)

Then a bit later, synthesizers arrived that made it much easier to build better receivers.

There was a wave of building using the 7360 balanced mixer used in this receiver, and frontend q-multipliers to deal with the lack of front end selectivity. But as semiconductors and ICs came along, it became much easier for mixers to be balanced or double balanced.