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To SDR or To Not SDR? Follow Up and Personal Observations 12 - February - 2010

Posted by k9zw in Amateur Radio, K9ZW, K9ZW Just Rambled.
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This is a second post expanding on To SDR or To Not SDR? Is That Really Even a Question?

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A few thoughts on Bleeding Edge vs Leading Edge, Connectivity Issues, and the reality that part of the SDR is a personal computer who’s hardware & operating system will be evolving.

As a lead in, I want to be clear I am writing about “Full SDR (Software Defined Radio)” technology, not receive only processing of intermediate receiver products, CAT-less (Computer Aided Transceiver – basically full control of the Transceiver from the computer desktop) or receive only components that maybe part or all SDR, but lack SDR transmit capability.

I’ve had people comment that their “IF-tapped XYZ Transceiver plugged to a computer soundcard with their PC running audio processing of that analogue tap’s output” is somehow an SDR, and even more an SDR equal to the big-boys.

Sorry, it isn’t.  It is a neat thing, to computer process an IF-tap’s receive output – very cool!  But it is not a full blown SDR transceiver.  If you differ, lets set a Sked and talk SDR to SDR on the air… oh woops, sorry I forgot these “SDR” lack SDR-transmit….  Well maybe we can email…

All humor aside, there is a real risk in adopting a lifespan-limited SDR offering – of buying into a Bleeding Edge design that will be come unsupported.

That same fear of buying into a dead-end bound design was the number one reason I had never given serious thought to the first SDR products.

What made the SDR platform come into focus for me personally?

Two items – Ultimate Performance and Economics

Ultimate Performance in not only has SDR evolved to meet every technical achievement that conventional transceiver designs offer, but arguably the state of the art has been moved & improved upon by SDR. Having had extended opportunity to use the top of the line conventional gear I had developed pretty lofty tastes for performance, especially in receiver ability.

I’m not the only one to identify the unique, and software improvable performance lead of SDR – well known testing labs have documented the measurable figures and even our government has jumped onto SDR for mission critical intelligence work by adopting the FlexRadio Systems CDRX-3200 32-receiver 100kHz to 100MHz streaming Channelizing Digitizer Receiver.

In the case of the SDR design I am using the SO2R (Single Operator – Two Radio) design is integrated into one device in way not available in a conventional transceiver pair with SO2R interface.

In terms of station integration, including bringing other station components like rotor control, antenna switching, audio recording, Watt/SWR Metering, Digital Mode, Amplifier, Logging Programs, DX Spots, and audio processing under control, the SDR opportunity allows a single shack interface through the computer. If you noticed I mixed hardware items and station software in my list – on purpose as once put to the machine their virtualization becomes an interoperability playground independent of whether the components are hardware, software or a mixture. That the various programs can share control hooks to work together is an opportunity in interoperability very difficult to achieve in the shack with non-computer based assistance (please be certain that the stand alone station aids for integration are actually small purpose built interfacing computers, or distributed processing if you will.)

In the area of Ultimate Performance there is little opportunity to implement certain SDR features in the shack on a practical basis.

Binaural audio features make use of the human mind & ears ability to gain intelligibility by the way of the head-related transfer function or HRTF, an improvement in reception not available at this time in the hamshack other than through SDR.

Having built in diversity reception is otherwise presently not achievable in the hamshack with mass market single transceivers.

The transmitted voice processing, equalizer, compender, compression and other tweaks is available in the hamshack in stand alone gear, though three pieces of specialist kit would be needed.

Economics then comes into play. With computer my present SDR setup investment is around 1/3 of what would have been spent to achieve the same feature set, the few unique SDR features set aside, at the same performance levels. When used in the SO2R configuration that 1/3 drops to more like 1/5th the investment.

That isn’t to say that a good station with conventional gear couldn’t be put together at a similar price point as my SDR setup, but such a station would not share either the performace specifications, much of the feature set, nor a fraction of the station integration.

Even when evaluating Ultimate Performance and Economics, a fear of buying into a limited life product and the knowledge that the operating system & hardware of the PC portion would be evolving played heavy on my mind.

That was before I realized I was holding more a fear of uncertainty, as the updatability is the most significant product feature of SDR.

True that someday down the road, ultimately my particular SDR purchase maybe tomorrows “boat anchor.” Actually I rather hope that our hardware keeps advancing, and I would obviously be 100% assured of having bought tomorrow’s “boat anchor” if I were to purchase any conventional transceiver currently made.

So perhaps my fear was of having a “short cycle” to obsoleteness? What sort of timeframe should I plan to “amortize” my SDR purchase over, predicting the future as best one can?

Contemporary conventional transceivers seem to be roughly on five-to-eight-year, give or take, manufacturing life-cycles before upgrades & model improvements overshadow the previous offering. Recently influences like the RoHS rules and earlier than expect processor end-of-life announcements & subsequence unavailability have modified this with a couple of premium transceivers going short cycle.

In the case of some of these rigs they are now basically unrepairable if they were to loose one of their embedded processors – onboard computers on a chip – and have become bargains for those willing to take the risk.

Did I mention that virtually none of the current conventional transceivers have a significant feature upgrade path (I would argue that the Elecraft transceivers are one of the exceptions to the locked design)? Maybe the SDR having the option to adopt computer improvements (there is no obligation of course) is an asset, rather than a liability?

The PowerSDR software, as it moves into “Deep Impact” (the working name for the newest versions) is multi-platform for both software operating system and hardware.

So it is unlikely I will find my investment seriously painted into a corner anytime soon.

Of most concern is the IEEE 1394 Firewire Port of the present design. The PC industry has an on/off history in supporting Firewire, as many clone manufacturers did not want to apy the small licensing fee, nor comply with the QC standards of Firewire. Currently some makers don’t offer it, some add it to their premium – especially media server type – PCs, and many offer it either as standard or a factory option.

Perhaps down the road a future version of USB might be more desirable (though I would think not until its throughput exceeds Firewire and until it moves its I/O overhead off the processor), which gasp – gasp – might mean I would need to update my SDR unit if I wanted to directly use say USB 6.0 as the native SDR-PC interface. Try updating your 2002 mainstream transceiver’s hardware to update connectivity – it isn’t going to happen.

Now to be fair I do want to be clear that as much as I am pleased to be operating with the Flex-5000A SDR radio I bought 18 months ago, I do enjoy being on the air more than worrying about on what specific radio, I have kept a full complement of conventional transceivers & computer controlled transceivers (not SDR, just controlled), have homebrew & QRP radios, and am in the midst of setting up a 1970’s style vintage station.

Adopting the leading edge doesn’t mean you have to forego the legacy gear that pleases you.

My question is what delights does the future offer that put my SDR transceiver into that revered status as a legacy? And how rewarding it is to be using that technology today!

73

Steve
K9ZW

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Comments»

1. Paul Coats - AE5JU - 12 - February - 2010

Thank you, Steve, a very good writeup! You have addressed every one of my concerns as posted in the Comments of the first article.

You’ve given me some things to think about on this.

2. Philw KA1GMN - 13 - March - 2010

I’m thinking seriously about an SDR. Thanks for sharing your thoughts.


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