Hi.
I have seen this item on Ebay : Ramsey ABM1 Pssive Aircraft Airband Monitor Kit :
Does anybody have a schematic, or an idea on how one of these operates (Without a LO). I find it a bit pricey (for a South African), so I would like to try build one of my own.
I do quite a bit of electronics work, but have not had extensive experience with radio circuitry.
Thanks Peter
On 03/25/2009 11:58 PM, kolbep sent:
Hello Peter:
It could be a TRF receiver:
Pete
-- 1PW @?6A62?FEH9:DE=6o2@=]4@> [r4o7t]
Thanks Don.
I take the Google flame, I really did not spend more than a minute googling for the info..
Thnks
Ya got to love Google
don
"Receives the entire band with no tuning!"
IOW, it's a bandpass filter followed by a detector, which means you can't tune out anything you don't want to hear.
-- http://www.wescottdesign.com
Yeah, I believe the reason their radio "works" is that the aircraft band still uses AM, so no local oscillator is needed for detector.
I'm surprised that it's a "patented circuit and design." :-(
---Joel
Sounds pretty much like an un-tuned crystal radio (with perhaps an amplifier/buffer stage in front of the crystal so that it doesn't need a seriously-long antenna).
Hard to tell from the posted link... the on-line version of the manual has a blank page where the schematic would be.
If I had to guess, I'd guess that the claims in the patent are written pretty narrowly - it'd be a "novel" combination and application of otherwise well-known circuit elements.
--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
I think this is to allow you to listen to radio traffic while on board aircraft without interfering (there's no local oscillator). However, try explaining this to a stewardess or air sheriff; "Its not a superhet, lady, its just a passive detector with audio amp"....
M
His e-Bay listing gives the title of the patent abstract as "Aircraft band radio receiver which does not radiate interfering signals" - put that into Google Patents and you find US Pat. 5361405 filed Nov 30, 1990 for what is just a TRF receiver. How can you get a patent for that?
. Only if by "novel" you mean it has the "feature" of letting the strongest signal override all others, yes. I'd think hard about buying into that "feature".
(It is a "feature" if you can't design out a boo-boo.)
Jim
-- "It is the mark of an educated mind to be able to entertain a thought without accepting it." --Aristotle
-- Just pay for it; the USPTO is a disgrace. JF
The patent is for a TRF receiver with the audio output tied to the antenna input through an earphone, a cap, and an inductor,
if that makes you feel any better.
Cheers, James Arthur
Here are some examples:
be kind to your local pilots and avoid super-regens.
Usually a good Rf preamp and proper case design kills the LO leakage issue.
Steve
They say they have a patent, and they do:
It does look like a wideband TRF receiver. I don't know why they were granted a patent on it.
Sylvia.
I believe the secret is TRF - Tuned Radio Frequency receiver. Tuned front end, amplifier feeding a tuned coupling to next amplifier etc for prolly at most 3 tuned sections, thenthe detector.
Simple; write it up and file it. Done a lot.
But since ther is a parts list and PCB layout, the schematic could be derived.
Answer...they filed, period.
Could be. But if so, the patent examiner should be fired.
Sylvia.
Go look at the job experience requirements for patent examiners, its disgusting. Many if not most of them have zero commercial experience.
The ones I have delt with could not read the radiation pattern chart of a led, nor understand Snell's law. The initial application was denied because said examiner had granted a patent on another LED design that DIDN'T work and used it to shoot down ours.
We got a commercial unit of the other design and put it on a goniometer and plotted the pattern, and it did not match the granted patent by a long shot. Software modeling proved it could not work. You must be wrong said the examiner. Then our lawyer hand carried a video of the tests to DC, and had a meeting with the examiner's supervisor. Amazing how fast that got cleared up, but costly. They still messed with the claims.
Only problem is the patent with the bad engineering still stands and is still licensed, and the lame parts are in bulk commercial production.
The wiki covers it here for the job requirements:
Its sad and a national disgrace.
Steve Roberts
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