Radio Receiver w/o local oscillator

[kolbep]

Hi.

I have seen this item on Ebay : Ramsey ABM1 Pssive Aircraft Airband
Monitor Kit :

http://cgi.ebay.com/Ramsey-ABM1-Pas...hash=item360030188040&_trksid=p3286.m20.l1116

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

 

[1PW]

Hi.

I have seen this item on Ebay : Ramsey ABM1 Pssive Aircraft Airband
Monitor Kit :

http://cgi.ebay.com/Ramsey-ABM1-Pas...hash=item360030188040&_trksid=p3286.m20.l1116

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

Hello Peter:

It could be a TRF receiver:

<http://en.wikipedia.org/wiki/Tuned_radio_frequency_receiver>

Pete

 

[TheM]

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.

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

 

[Andrew Holme]

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.

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?

 

[James Arthur]

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?

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

 

[[email protected]]

Here are some examples:



1. [email protected]
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More options Mar 26, 6:30 pm
Newsgroups: sci.electronics.design
From: [email protected]
Date: Thu, 26 Mar 2009 15:30:29 -0700 (PDT)
Local: Thurs, Mar 26 2009 6:30 pm
Subject: Air Band
Reply | Reply to author | Forward | Print | Individual message | Show
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there are lots of these on the net:

http://www.vk2zay.net/article/127

http://www.uoguelph.ca/~antoon/circ/aviarx/aviarx.html

be kind to your local pilots and avoid super-regens.

http://www.techlib.com/area_50/pilarsprojects.htm#Air Band Radio

Usually a good Rf preamp and proper case design kills the LO leakage
issue.

Steve

 

[Sylvia Else]

Hi.

I have seen this item on Ebay : Ramsey ABM1 Pssive Aircraft Airband
Monitor Kit :

http://cgi.ebay.com/Ramsey-ABM1-Pas...hash=item360030188040&_trksid=p3286.m20.l1116

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

They say they have a patent, and they do:

http://www.freepatentsonline.com/5361405.html

It does look like a wideband TRF receiver. I don't know why they were
granted a patent on it.

Sylvia.

 

[Sylvia Else]

Answer...they filed, period.

Could be. But if so, the patent examiner should be fired.

Sylvia.

 

[[email protected]]

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:

http://en.wikipedia.org/wiki/Patent_examiner

Its sad and a national disgrace.

Steve Roberts

 

[Sylvia Else]

---
No.

The examiner's not to blame, the turning of the USPTO into a profit
center is.

The examiner is still supposed to apply the rules. It may not be his
fault if he's been employed to do a job that he's incapable of, but he
should still be fired.

Sylvia.

 

[Greegor]

No AGC, ghastly biasing.

John

Doesn't it work as advertised?

Can a crystal radio be set up to monitor
the entire aircraft band?

 

[krw]

I once answered an examiner questioning my patent application with,
"You're too stupid to understand" ;-)

He granted the patent.

You aren't the only one to use that strategy successfully.

 

[krw]

---
What you don't seem to understand is that the rule is, except for what
seem to be some rare cases,: "Open the floodgates!"

Such being the case, if the examiner is too judicious or argues too much
against the issuance of the patent, _that's_ how he's likely to lose his
job.

He may indeed argue until he's blue, but it takes his time every time
he does. in the end, he's measured by income (i.e. patents granted),
not office actions. You tend to get what you measure.