[Boatanchors] SDR unit

[Robert Nickels]

On 3/21/2014 6:47 PM, Jim Wilhite wrote:
> Sadly we live in a throw away world where only manufacturers can 
> afford the equipment to repair individual boards.

I've been biting my tongue on this thread but that's only got me a sort 
tongue ;-)   Jim's comment above is directly on point  I think, because 
it reflects a major shift in the way these products are designed.      I 
think it's silly to lump SDRs in with Boatanchors anyhow - they may 
accomplish the same task of sending and receiving RF but they represent 
entirely different design philosophies and business goals.

I suspect many of the pioneers of the "boatanchor companies" would be 
amazed to learn that their products have lasted this long and are still 
in use.    Like everything, they were designed to certain 
price-performance targets and although they weren't designed to last 
forever, the mindset at that time was that repair and maintenance would 
be ongoing until they were replaced (preferably by a new model from the 
same company).    Simpler designs generally meant fewer things to go 
wrong, and designs that were easier to troubleshoot and  repair.

Although this thread is about "SDR", the problems of maintainability, 
having the proper tools and skills for SMT repair, etc are not unique to 
SDRs.   It's a fact that many components are not even offered in 
through-hole packages anymore, and this situation will only get 
worse.    Collecting, restoring, and using boatanchors is one way to 
enjoy radio without having to deal with SMT.  I've found it far more 
frustrating to find replacement parts for some radios built in the 70s 
and 80s than those built 30 to 60 years prior.

All modern radios are "SDR-like" to varying degrees, a trend that 
started with the use of DSP to replace hardware long before standalone 
SDR transceivers came on the market.   RF hasn't changed - it still 
takes a good RF front-end for a QSD decoder to provide high performance 
in an SDR,  and cleanly amplifying low-level RF signals to bend the S 
meter on the other guys radio is no different regardless of how the 
signal is generated.    Standalone SDRs offload much of the signal 
processing to cheap hardware like PC soundcards and CPUs.    When those 
big fat ICs fail, you shop for a new computer, not a new radio.

But SDRs are designed to be continuously improved by software upgrades. 
   Eventually improved performance is going to mean new hardware as 
well, when you take away the RF stuff that you'd need anyway, SDR 
hardware is cheap.  The Tayloe demodulator that is at the heart of many 
SDRs is built around a 25 cent IC, and full multi-band SDR kits can be 
had for $150.     "Cheap" does not apply when it comes to high 
performance 24 bit A/D and D/A converters - but those are not yet in the 
mainstream for SDR users, just like the Collins PTO was only found in 
premium products when it represented the state-of-the-art.   But the 
good news is, SDRs will follow a Moore's Law-like curve to become 
cheaper and more capable.

The DVB-T dongles that are the heart of the "cheap and easy" SDRs I've 
written about provide amazing performance for $10.   Truly throwaway 
technology, even though I've yet to have one fail.   These low-end SDRs 
perform as well as a $400 receiver did when I was first licensed in 
1965, but cost what an S-38 did back then.

> I agree keep boatanchors around to teach the logic of repair and 
> understanding of circuits. 

Absolutely right.   I find myself in awe of innovators like Wes Schum 
and Tony Vitale every time I work on a phasing type SSB exciter and 
realize that they were able to do with WWII surplus hardware what now 
takes a bazillion transistors and unfathomable quantities of ones and 
zeros to accomplish!   Perhaps the ultimate irony (or compliment) is 
when I use the capabilities of a modern "throwaway" SDR to align a 1950s 
era transmitter.

73, Bob W9RAN