Netgeek wrote:

snip

But seriously - let's look at the potential utility of a fairly "mindless"
NAV receiver as it might apply to the non-instrumented-rated,
day-VFR "Sport" or "Recreational" pilot. First off, these guys
believe that GPS coupled to a simple moving map display represents
not only the holy grail - but they'd be willing (foolishly) to bet their
lives on this sole-source nav capability (never mind simple "dead
reckoning" or other elementary - e.g. "follow roads" forms of
navigation). If the batteries run out on the GPS - or the guys at
Cheyenne Mountain pull the big red lever marked "scramble GPS"
for whatever reason - they're in big trouble.

If that happened, and that's a pretty big if given the US government
is forcing GPS as the defacto navigation standard for just about
everything, the accuracy would be reduced to such that it would be
impossible to make a precision approach.

The remaining accuracy would be more than enough to find an airport,
especially since Sport and Recreational are limited to day VFR.

Standard VOR-based
equipment would give them a way out - but they don't have it ('cause
it costs too much) and they wouldn't know how to effectively use it
anyway ('cause they aren't instrument rated). Some form of relatively
simple (albeit far from accurate) NAV capability would at least give
them a last chance to drag out the sectional and try to determine roughly
where they are - hopefully close enough to find a place to put down.

Sporty's sells the SP-200 NAV/COM handheld for $299.00 with a $14.95
rebate if you use your AOPA credit card. It has VOR and LOC with a
digital CDI display and 2,280 channel COM. You still would have to
know what 235 FROM means.

IMHO anyone not flying a big turbine with multiple redundent everything
that doesn't have a handheld just in case is foolish.

My ridiculous little experimental project is to try and come up with a
"poor man's" (and perhaps "stupid man's 8-) nav capability based on
VORs which is inexpensive and SIMPLE. There's no OBS nor any
other "normal" features (e.g. ability to drive a CDI) - but it kicks out
enough info relative to a few nearby VORs so that you can at least
determine what planet you're on 8-).... and provide a few hints as to
*where* you are on that planet...

GPS replacement? Absolutely not. TSO'd NAV receiver replacement?
Nope - not that either. Inexpensive (enough so that you might actually
install one) and simple (enough so that you could derive some useful info
with little training) - that would be the goal.

In the meantime, it's really a personal educational and entertainment
toy to play with, and nothing more ("amateur", "homebrew", etc. - so
it's relevent here, right?)......8-)

I appreciate your thoughts and comments, Len! You obviously have a
wealth of experience to draw upon and I thank you for sharing it. Despite
more than 25 years in product development, most of this is new territory
for me (and I'm enjoying the learning experience!). I've never done an
RF design - well - at least not "deliberately"!!!

Regards,
Bill

Decoding the bearing can be done with a PLL running as a 360X frequency
multiplier on one 30 Hz signal and using the other to gate a counter
which is feed the multiplied signal.

I built such a beast in '75 as a senior project with a NIXIE tube
display. Available compenents have improved a lot since '75.

If I were to do something like this today, I think I would look for
someone's receiver module and use a microcontroller to control the
receiver and do most (maybe all with DSP) the decoding, feeding it all
to a PDA with a database of VOR frequencies and locations and use the PDA
to generate a map display.

It would be a fun project.

--
Jim Pennino

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