On Jul 9, 6:01 am, clifto wrote:
Andrew VK3BFA wrote:
On Jul 8, 12:35 am, "Polymath" wrote:


I'd been thinking for some time about doing a little experimenting that
involved putting together a few functional blocks which were a little
more involved than ICs, things like IF gain blocks and detectors and
the like. Much faster to A/B test circuits that way.


Yes. This is (usually) IC's on a PCB with the extra bits needed to get
it to work. As long as you have the same impedance for each module, no
worries. And the approach has merit - lacking sophisticated measuring
equipment, its good to have a "reference" IF, RF, whatever module for
A-B comparisons.

I think EMRFD covers this concept quite well....

There has NEVER been a better time to homebrew. We are not relying on
war surplus from a global conflict anymore, and its pretty well dried
up anyway. So many fascinating chipsets out there, a casual reading of
any of the last 10 years of ARRL handbooks reveals this "systems
engineering" approach - treat them like LEGGO blocks....

There is SO MUCH sophisticated good quality test equipment out there
now - most industries are downsizing (gee, I love that phrase) - its
cheaper to send a defective module off for repair (the spare
automatically switches in on a fault condition) to the manufacturer
than maintain highly skilled staff and expensive test gear. So, the
test gear is being sold at RIDICULOUS prices. I recently bought a
Chinese 500Mhz spectrum analyser for $500 - yeh, sure, not as good as
a HP, (refuse to call them AGILENT) but then my 30 year old HP141 etc
was badly showing its age and was out of calibration anyway.....

A good example - the AD9851 DDS chip . Wade through the pages of
waffle, and it comes down to half the pins grounded, some more tied
high, data in from a PC port on 3 lines, bias set by 1 resistor, a TTL
clock module (prebuilt anyway) and a simple LPF on the ouput - voila,
a 0-30Mhz sig gen/sweep gen/VFO with 1Hz increments, and crystal
stability and accuracy. Doesn't need a complex PCB, can easily be
paddyboarded/Manhattan style....

Go for it - don't be scared. The "good old days" were only in your
head anyway, and it took the death of millions to provide us with that
lovely war surplus precision mechanical engineering....what a terrible
price to pay for a nice VFO capacitor and drive....

Times change - the Foundation license has transformed AR - yes, some
idiots, but not nearly as many as the old timers noisily bemoaning
their lost (and rose coloured) past.......all the dinosaurs will
eventually die, do you want to be one? And getting an amateur ticket
30 years ago - how relevant is that now? - good to wallow in antique
technology, but how about moving forward.

My club - its been bloody fantastic. The new F calls, on the
committee, bring new skills and enthusiasm. They can organise a dinner
out - the old timers cannot. They organise technical lectures - the
old timers, with their "I did that 40 years ago" attitude don't. A
long overdue breath of fresh air - should have happened 30 years ago,
and would have except for the moaning and bitching of the "true"
amateurs.

So saying that, I have been licensed for 36 years. I started
homebrewing with valves I scavenged off the rubbish tip, as a kid of
12 I didn't have any money. First soldering iron was second hand,
bought from the local radio club - in retrospect, sold at a fraction
of its value to help a newcomer. Was mentored by WONDERFUL, true
amateurs - generous with their time and knowledge. Are you? Carefully
selecting the least leaky capacitors, measuring and marking old out of
tolerance resistors to build something,anything, to explore radio.
Even scavenging hookup wire from old washing machines and
refrigerators on the tip.

Nowadays, still have a good collection of WW2 vintage gear for
restoration - most of it semi vandalized by idiots doing
"modifications" - I like it, nice BIG components, easy to see and work
on. The classic 70's radios with tube back ends - easy to work on,
parts more readily available than modern consumer stuff on the shelves
currently.

But I also battle with SMD stuff - why, because that too is
interesting - 1 chip does the work of a rackfull of valve gear. Its
STILL the "magic of radio" - and I think a lot of us have got old and
tired and grumpy and forgotten WHY we got into AR in the first place,

Go for it - NOTHING beats the thrill of learning,
exploring,experimenting, and finally getting on the air and saying

"The rig here is homebrew OM"...

73 de Andrew VK3BFA.