[Michael Black[_2_]]

On Sun, 27 Nov 2011, NT wrote:


If I were designing such a product, I'd do everything in my power to
avoid end user alignment with testgear, for one very simple reason: it
wipes out 99.9% of your potential customers, its business suicide.

Perhaps one could use resonators instead of LCs, if you dont like the
interstation garbage of agced reaction.


And Heathkit is the model for that. They'd prealign tuned circuits,
they'd have certain stages as preassembled modules, they'd build some
relevant test equipment into the equipment (like those tv sets with some
sort of metering in the back). One I always liked was a scanner, they
included some parts to make up a 10.7MHz oscillator and mixer. The
oscillator would provide the signal to align the IF strip, and then you'd
mix the local oscillator with this outboard oscillator/mixer to get a
signal on the signal frequency, to align the front end.

Heathkit of course did design for the beginner, I gather once they had the
instructions together they found people who had never put a kit together
to follow the instructions so they could make sure they made sense (and if
followed properly, would result in a working piece of equipment).
Despite the fuss about Heathkit being for the hobbyist, they always had
taht color tv set, that musical organ, that boonie bike, that were
aimed at people who just wanted something cheaper, and were willing to
put some time into it. But that's why Heathkit shut down the kits, with
time the sorts of things their was interest in got so complicated (and
parts so small) that it was no longer cheap to come up with the
instructions, pack the kit compared to just building it at the factory.

As for ceramic resonators, I think that is a key point. Design is the
overall results. When companies put in ceramic resonators in everyday
radios, they did away with a large part of the alignment, so even if the
resonators were more expensive than IF transformers (I don't know) the
reduction in alignment time was still significant.

As I pointed out, move to a higher IF, you may pay more for an IF filter,
but you can do away with the need to gang the front end tuning with the
local oscillator, which simplifies things mechanically but also gets rid
fo a lot of troublesome alignment. It's relatively easy to get two stages
of front end tuning to align together, just go for a peak, but ganging it
with a local oscillator is more complicated.

The superhet alone is a concept that complicates something to make other
things easier. Make things more complicated, the mixer and oscillator,
and you dont' have to fuss with multiple stages on the RF frequency.

Sometimes the "simplest" solution ends up with more work than the more
complicated one.

Michael