Netgeek 2009-11-02 16:08:15
[First post after lurking for quite some time…8-)…]
MANY years ago I built up quite a few kits that I got from RST (thanks to
Jim Weir!) and really enjoyed it while learning alot. But that was more than
20 years ago. In looking around lately I can find very little that would be
suitable for DIY. As a product designer for the last 25 years I realize
that much of the technology has moved beyond the capabilities of the average
DIY type (surface mount, custom ASICs, etc.) – BUT – is there anything out
I would like to build a number of things (e.g. remotely controlled VHF
receivers, ADS-B, etc.) but it looks like I’ll have to go it alone and
design them from scratch. I’d be interested in hearing from any of you about
things you’ve seen out there as well as any potential interest in getting
involved in DIY avionics.
Sure, most of the off-the-shelf stuff is cheap and available, but if any of
the new NASA/FAA initiatives really come to pass (AGATE, SATS,etc.) there
could be a real need for modular, inexpensive widgets and functional blocks
that could be integrated easily into a custom “system”.
Any pointers/comments most welcome!
Karel 2009-11-02 16:10:57
Can only say I have been thinking along much the same way.
Only I am not acquainted of AGATE, SATS and whatever.
But I have lots of thoughts on a bus system with
solid state gyro’s and pitot/static, GPS, auto-pilot &C
Lots of thought yes
and of course not the time to do anything with them…
KA from Europe
Scott 2009-11-02 16:11:59
For VHF stuff, http://www.hamtronics.com
Of course these are geared toward us ham radio guys, but they have
receivers for FM up to 902 MHz, I believe. Fairly simple stuff with
schematics, so it’s easy to add capabilities to use them as remote
control receivers, etc. if you are technically inclined, which it sounds
as though you are…
Gotta Fly or Gonna Die
Georgeb 2009-11-02 16:14:03
Aviation radio is AM … fwiw
Netgeek 2009-11-02 16:16:05
Interesting that this is still the case. In fact, the majority of the “old
school” stuff is fairly low tech when you get right down to it. If you take
a look at what is required to interpret ILS signals – fairly simple. Same
with marker beacons, etc. (and alot of it AM still). What I’m interested in
is how to take some of the newer proposals and concepts and make them
simpler/cheaper so that virtually anyone can actually use them (starting
with myself of course 8-)…
As an example – I found an article that mentioned a “SAAS” system proposal
(as part of NASA’s SATS program). Basically this is a GPS augmentation
system intended for small airports (Small Airport Augmentation System). We
already have WAAS (Wide Area Augmentation) and I don’t know what happened to
LAAS (Local Area Augmentation) – but SAAS was intended to deliver a low-cost
system that could provide a “virtual ILS” at any small airport. The accuracy
was on the order of around 0.2 meters horizontal and 0.3 meters vertical –
allowing approaches to the smallest of airports (or grass strips, I
suppose?) to Category I (1800 ft. runway visual and 200 ft. ceilings)
minimums without mega-bucks worth of additional equipment….Wow!!! – not
far removed from the next step of an autoland system in light aircraft.
Assuming that you already have a decent on-board, panel-mounted processor
and display – you can start with something like the Mountainscope software
for enroute stuff – www.pcavionics.com , then you could add on some
TCAS-like functionality (using an ADS-B receiver) and then some precision
approach capability (using SAAS or equivalent) – and all of this for only a
few thousand bucks…
I’m planning to start some development on the various blocks so that I have
something to play with: Air Data, AHRS, ADS-B and see where it leads (maybe
nowhere, but what the h***?)…
Thanks for the pointers so far.
Georgeb 2009-11-08 16:19:59
It isn’t really a “still the case” issue; the technology for FM is
agreed to be better and to offer many advantages. One if its major
advantages is the very significnat disadvantage that keeps it from
FM has that WONDERFUL capture ratio. The stronger signal completely
takes over the receiver. A weaker signal on AM lets the receiver know
that there are 2 signals, considered a safety necessity AFAIK. It
will take some digital modulation with sophisticated algorithms to
replace the antiquated AM here.
I believe that will come rather soon. In reality, WAAS is better than
expected, and could likely get you to ground effect 98% of the time
,,, and CFIT 2%. I’ve never seen my WAAS handheld (non-aviation) off
by more than 20 ft in elevation when it had a full view of the sky …
South Carolina … and that, I understand, matters.
Jim weir 2009-11-10 06:10:41
All of which proves if you repeat an old wive’s tale long enough, it will be
Going to FM (or any other form of modulation not compatible with double sideband
full carrier AM) is NOT a safety measure. It is simply trying to figure out how
to change the entire world’s aviation communications system at one precise time.
shared these priceless pearls of wisdom:
A weaker signal on AM lets the receiver know
->that there are 2 signals, considered a safety necessity AFAIK.
Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
Netgeek 2009-11-10 06:11:43
Point taken – So when are you going to come out with the “new and improved”
VHF AM transceiver we’ve (or at least “I”) have been waiting for? I built a
few of your radios about 18 years ago – been waiting for the “updates”
Surely you haven’t given up just because a bunch of nerds can’t grok how to
do surface mount ???!!!
I’d like a “black box” VHF thingy that can speak (and respond to) something
like CAN bus – if you have any suggestions I’d love to hear them. Perhaps a
direct digital synthesis thing (ala Analog Devices) – or along the lines of
the work being done by flex-radio.com ???
Come on, Jim, jump in there and impart some wisdom (or at least some
Netgeek 2009-11-10 06:11:48
Good point – so AM is not going to go away any time soon…. easy stuff,
just sort out the amplitude of different modulated stuff and the ILS works…great!
Well, that “CFIT 2%” is surely a bother…8-)…. Never mind the FAA, I
don’t think many pilots would be very happy with that spec either!
So, my questions are:
What happened to LAAS? (Probably dropped once WAAS was implemented – better
results and all)…
Who’s working on the SAAS – if anybody? What are the specs and where are
I keep finding announcements from NASA/FAA that there’s going to be an SAT
public “demo” this spring in Virginia. But *what* are they going to demo,
*who* is involved, *details/specs* of the technology decided upon (?), and
how do others with an interest participate? If this is all publicly-funded
and all – and intended to promote the public’s use of the proposed SATS
system – where are the specs and how do others participate?
All questions that bug me somewhat – but I’d be happy enough if Jim Weir
just jumps in and puts up his $0.02 worth regarding the comms stuff 8-)…!