AM receiver convert to ATC receiver

[Archimedes]

Hi all

If I change the tank circuit components (reduce the capacitance and
inductance) and change the transistors to appropriate VHF ones, will I
be able to pick up ATC (Air Traffic Conversations) using this
circuit ?

http://www.electronics-lab.com/projects/rf/006/index.html

Thanks
Shelton.

 

[Don Bowey]

On 4/16/08 9:31 PM, in article
b3b30960-27bc-4d59-924f-4312caffe7c2@x41g2000hsb.googlegroups.com,
"Archimedes" <shelton.dcruz@gmail.com> wrote:

Hi all

If I change the tank circuit components (reduce the capacitance and
inductance) and change the transistors to appropriate VHF ones, will I
be able to pick up ATC (Air Traffic Conversations) using this
circuit ?

http://www.electronics-lab.com/projects/rf/006/index.html

Thanks
Shelton.

Yes I didn't read the article, but the coil and cap of that receiver look
like broadcast band. When you build it, keep all the wires short in the RF
portion of the receiver.

Do you have the means to calculate the needed L and C to cover about 118MHz
to 136 MHZ?

 

[Michael Black]

On Wed, 16 Apr 2008, Bob Eld wrote:

"Archimedes" <shelton.dcruz@gmail.com> wrote in message
news:b3b30960-27bc-4d59-924f-4312caffe7c2@x41g2000hsb.googlegroups.com...
Hi all

If I change the tank circuit components (reduce the capacitance and
inductance) and change the transistors to appropriate VHF ones, will I
be able to pick up ATC (Air Traffic Conversations) using this
circuit ?

http://www.electronics-lab.com/projects/rf/006/index.html

Thanks
Shelton.

Not likely. I doubt you'd ever get that circuit to work at VHF frequencies
no matter what you did with the resonant circuit portion. There are many
problems including wrong impedances for the various parasitic capacitances.

Secondly air traffic stuff is FM I believe.

Military may use FM, I don't know, but airplane related communication is

unique in that it does use actual AM.

A project that saw publication a number of times in the old days took
advantage of that, a "crystal radio" that tuned VHF. It was nothing
more than a tuned circuit and a diode detector feeding an earphone, not
sensitive but useful near airports and since it didn't radiate anything,
even useable (though maybe not legally) on an actual airplane.

The description of the circuit says it's a regen receiver, and those
were never popular at VHF, I'm assuming instability came into play.
You did see superregen receivers there. Either type will radiate, and
that's not a good thing in the aircraft band.

Michael

 

[Archimedes]

On Apr 17, 3:08 pm, Michael Black <et...@ncf.ca> wrote:

On Wed, 16 Apr 2008, Bob Eld wrote:

"Archimedes" <shelton.dc...@gmail.com> wrote in message
news:b3b30960-27bc-4d59-924f-4312caffe7c2@x41g2000hsb.googlegroups.com...
Hi all

If I change the tank circuit components (reduce the capacitance and
inductance) and change the transistors to appropriate VHF ones, will I
be able to pick up ATC (Air Traffic Conversations) using this
circuit ?

http://www.electronics-lab.com/projects/rf/006/index.html

Thanks
Shelton.

Not likely. I doubt you'd ever get that circuit to work at VHF frequencies
no matter what you did with the resonant circuit portion. There are many
problems including wrong impedances for the various parasitic capacitances.

Secondly air traffic stuff is FM I believe.

Military may use FM, I don't know, but airplane related communication is
unique in that it does use actual AM.

A project that saw publication a number of times in the old days took
advantage of that, a "crystal radio" that tuned VHF.  It was nothing
more than a tuned circuit and a diode detector feeding an earphone, not
sensitive but useful near airports and since it didn't radiate anything,
even useable (though maybe not legally) on an actual airplane.

The description of the circuit says it's a regen receiver, and those
were never popular at VHF, I'm assuming instability came into play.
You did see superregen receivers there.  Either type will radiate, and
that's not a good thing in the aircraft band.

   Michael- Hide quoted text -

- Show quoted text -
Hi

Thanks for all the reponses - yes i can calcualte the required
parameters to get this into the ATC band - but im now confused - some
say it will work some say it wont? So will it or will it not ?

 

[Tom2000]

On Wed, 16 Apr 2008 22:44:46 -0700 (PDT), Archimedes
<shelton.dcruz@gmail.com> wrote:

Thanks for all the reponses - yes i can calcualte the required
parameters to get this into the ATC band - but im now confused - some
say it will work some say it wont? So will it or will it not ?

My guess is that it might work -- sorta -- but never at any useful
level. I see a whole lot of problems with that approach.

One idea that's relatively simple to accomplish, and will teach you a
whole lot, is a tunable converter that you place between a suitable
VHF antenna, such as a groundplane vertical, and a standard AM
broadcast receiver.

I fiddled with one of those as a kid and was able to achieve
surprisingly good performance, after some fiddling. I used a couple
of vacuum tubes. A tunable converter should be a lot easier to build
using toroids and modern ICs. (Look as the SA612 data sheet. You'll
probably get a few good ideas for a converter when you read that.)



Have fun!

Tom

 

[Tom2000]

On Wed, 16 Apr 2008 22:44:46 -0700 (PDT), Archimedes
<shelton.dcruz@gmail.com> wrote:

Thanks for all the reponses - yes i can calcualte the required
parameters to get this into the ATC band - but im now confused - some
say it will work some say it wont? So will it or will it not ?

My guess is that with enough fooling around, you might get something
that will tune a few of the very strongest signals occasionally, but
never very well. You'll never get any selectivity out of it, and it
will be unstable as all get out. All in all, I think you'll be quite
frustrated, if you can ever get the fool thing working at all.

But your desire for a simple air band receiver reminds me of a project
from the old vacuum tube days -- a tunable air band converter that you
connect between the antenna and a standard AM broadcast band receiver.

The converter mixes the air band signals between 108 and 136 MHz to a
fixed IF frequency somewhere in the AM broadcast band. Just tune your
AM receiver to that frequency and tune air band signals by changing
the converter oscillator's frequency.

These days, folks would probably want to build something like that all
fancy and complicated, with PLL tuning and a tracking front end, but
that primitive vacuum tube converter worked pretty well with some very
simple circuitry. It might be funto blow the dust off that old design
and give it a new life.

You could bring that converter design into the 21st century easily and
cheaply using an SA612 chip. The SA612 contains both an oscillator
and a mixer, and is even available as a through-hole part. You could
tune its oscillator with a varactor diode driven by a cheap 10-turn
pot you might scrounge through the surplus channels.

That might provide all the gain you'd need. But if you wanted a bit
more pop, you could use a couple of J310s in cascode as an RF amp.
Shooting from the hip, I don't think an RF amp would be necesssary,
though. I wouldn't use it for my initial design.

You can find the SA612 data sheet here:

http://www.nxp.com/acrobat_download/datasheets/SA612A.pdf

You should get quite a few ideas for a converter design just from
reading the data sheet.

SA612s, J310s, toroidal cores for coils, varactor diodes, voltage
regulators, and all sorts of other good stuff is available from Kits
and Parts:

http://kitsandparts.com/

The idea would be to keep the design really, really simple. Don't add
anything that you don't absolutely need. Feed the antenna directly to
the mixer (through a toroidal transformer, perhaps) and the output of
the mixer directly to the AM broadcast receiver. Let the radio do all
the post-mixer filtering for you.

You might find, through test and experimentation, that your converter
needs something more. If so, figure out what's causing the problem,
sort it out, and fix it.

But I think that a simple SA612 design won't need much debugging.
It's a "high probability of success" project, right out of the can.

Have fun!

Tom

 

[Archimedes]

Thanks Phil - very informative answer - and thanks to the others who
also responded!

 

[Don Bowey]

On 4/17/08 6:02 AM, in article fu7htl$7ha$1@dns3.cae.ca, "Claude"
<claudec@cae.com> wrote:

"Michael Black" <et472@ncf.ca> wrote in message
newsine.LNX.4.64.0804170103550.24809@darkstar.example.org...
On Wed, 16 Apr 2008, Bob Eld wrote:


"Archimedes" <shelton.dcruz@gmail.com> wrote in message
news:b3b30960-27bc-4d59-924f-4312caffe7c2@x41g2000hsb.googlegroups.com...
Hi all

If I change the tank circuit components (reduce the capacitance and
inductance) and change the transistors to appropriate VHF ones, will I
be able to pick up ATC (Air Traffic Conversations) using this
circuit ?

http://www.electronics-lab.com/projects/rf/006/index.html

Thanks
Shelton.

Not likely. I doubt you'd ever get that circuit to work at VHF
frequencies
no matter what you did with the resonant circuit portion. There are many
problems including wrong impedances for the various parasitic
capacitances.

Secondly air traffic stuff is FM I believe.

Military may use FM, I don't know, but airplane related communication is
unique in that it does use actual AM.

A project that saw publication a number of times in the old days took
advantage of that, a "crystal radio" that tuned VHF. It was nothing
more than a tuned circuit and a diode detector feeding an earphone, not
sensitive but useful near airports and since it didn't radiate anything,
even useable (though maybe not legally) on an actual airplane.

The description of the circuit says it's a regen receiver, and those
were never popular at VHF, I'm assuming instability came into play.
You did see superregen receivers there. Either type will radiate, and
that's not a good thing in the aircraft band.

Michael


Here are the facts

Military ground troups and close air support
30 Mhz to 87.975 FM only

Air traffic control
117.975 to 156.000Mhz, AM only

Typo here: ^136.000

Maritime
156.000 to 173.975 ( with some reserved for Sonobuoy operations) FM only

Military
225 Mhz to 399.975 Mhz AM or FM ( they can actually choose wich one for any
freq in this band)
Not interesting in this band as there is a lot of encryption, freq hopping
and other hush hush stuff.

Claude

 

[Joerg]

Michael Black wrote:

On Wed, 16 Apr 2008, Bob Eld wrote:


"Archimedes" <shelton.dcruz@gmail.com> wrote in message
news:b3b30960-27bc-4d59-924f-4312caffe7c2@x41g2000hsb.googlegroups.com...
Hi all

If I change the tank circuit components (reduce the capacitance and
inductance) and change the transistors to appropriate VHF ones, will I
be able to pick up ATC (Air Traffic Conversations) using this
circuit ?

http://www.electronics-lab.com/projects/rf/006/index.html

Thanks
Shelton.

Not likely. I doubt you'd ever get that circuit to work at VHF
frequencies
no matter what you did with the resonant circuit portion. There are many
problems including wrong impedances for the various parasitic
capacitances.

Secondly air traffic stuff is FM I believe.

Military may use FM, I don't know, but airplane related communication is
unique in that it does use actual AM.

A project that saw publication a number of times in the old days took
advantage of that, a "crystal radio" that tuned VHF. It was nothing
more than a tuned circuit and a diode detector feeding an earphone, not
sensitive but useful near airports and since it didn't radiate anything,
even useable (though maybe not legally) on an actual airplane.

The description of the circuit says it's a regen receiver, and those
were never popular at VHF, I'm assuming instability came into play.
You did see superregen receivers there. Either type will radiate, and
that's not a good thing in the aircraft band.

Yes, and then you'd quickly have visitors coming with vehicles bearing
government license plates. A regen-receiver is most definitely not a
good idea in the aircraft band.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[Don Bowey]

On 4/18/08 8:16 AM, in article fuae44$6tg$1@dns3.cae.ca, "Claude"
<claudec@cae.com> wrote:

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:cJMNj.6968$GE1.6102@nlpi061.nbdc.sbc.com...
Michael Black wrote:
On Wed, 16 Apr 2008, Bob Eld wrote:


"Archimedes" <shelton.dcruz@gmail.com> wrote in message
news:b3b30960-27bc-4d59-924f-4312caffe7c2@x41g2000hsb.googlegroups.com...
Hi all

If I change the tank circuit components (reduce the capacitance and
inductance) and change the transistors to appropriate VHF ones, will I
be able to pick up ATC (Air Traffic Conversations) using this
circuit ?

http://www.electronics-lab.com/projects/rf/006/index.html

Thanks
Shelton.

Not likely. I doubt you'd ever get that circuit to work at VHF
frequencies
no matter what you did with the resonant circuit portion. There are many
problems including wrong impedances for the various parasitic
capacitances.

Secondly air traffic stuff is FM I believe.

Military may use FM, I don't know, but airplane related communication is
unique in that it does use actual AM.

A project that saw publication a number of times in the old days took
advantage of that, a "crystal radio" that tuned VHF. It was nothing
more than a tuned circuit and a diode detector feeding an earphone, not
sensitive but useful near airports and since it didn't radiate anything,
even useable (though maybe not legally) on an actual airplane.

The description of the circuit says it's a regen receiver, and those
were never popular at VHF, I'm assuming instability came into play.
You did see superregen receivers there. Either type will radiate, and
that's not a good thing in the aircraft band.


Yes, and then you'd quickly have visitors coming with vehicles bearing
government license plates. A regen-receiver is most definitely not a good
idea in the aircraft band.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

Quite correct, it is most likely jail time where you will have hours and
hours of fun designing electronics such as movement alarms
that will detect the proximity of "fellow inmates" . Just swearing on an ATC
frequency will net you a $2,500 fine in Canada, I can't even imagine what
they would do to you if you jammed one of their frequencies.

Claude
Montreal

One of you naysayers should estimate the amount of radiated energy from a
typical regen receiver.

Also, what is the distance from the intended regen location to the airport,
and what would you imagine the comparative strengths would be of the regen
signal and air traffic signals at air traffic receivers?

The regen receiver radiated signal would be lost in the noise.

 

[Joerg]

Don Bowey wrote:

On 4/18/08 8:16 AM, in article fuae44$6tg$1@dns3.cae.ca, "Claude"
claudec@cae.com> wrote:

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:cJMNj.6968$GE1.6102@nlpi061.nbdc.sbc.com...
Michael Black wrote:
On Wed, 16 Apr 2008, Bob Eld wrote:

"Archimedes" <shelton.dcruz@gmail.com> wrote in message
news:b3b30960-27bc-4d59-924f-4312caffe7c2@x41g2000hsb.googlegroups.com...
Hi all

If I change the tank circuit components (reduce the capacitance and
inductance) and change the transistors to appropriate VHF ones, will I
be able to pick up ATC (Air Traffic Conversations) using this
circuit ?

http://www.electronics-lab.com/projects/rf/006/index.html

Thanks
Shelton.
Not likely. I doubt you'd ever get that circuit to work at VHF
frequencies
no matter what you did with the resonant circuit portion. There are many
problems including wrong impedances for the various parasitic
capacitances.

Secondly air traffic stuff is FM I believe.

Military may use FM, I don't know, but airplane related communication is
unique in that it does use actual AM.

A project that saw publication a number of times in the old days took
advantage of that, a "crystal radio" that tuned VHF. It was nothing
more than a tuned circuit and a diode detector feeding an earphone, not
sensitive but useful near airports and since it didn't radiate anything,
even useable (though maybe not legally) on an actual airplane.

The description of the circuit says it's a regen receiver, and those
were never popular at VHF, I'm assuming instability came into play.
You did see superregen receivers there. Either type will radiate, and
that's not a good thing in the aircraft band.

Yes, and then you'd quickly have visitors coming with vehicles bearing
government license plates. A regen-receiver is most definitely not a good
idea in the aircraft band.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
Quite correct, it is most likely jail time where you will have hours and
hours of fun designing electronics such as movement alarms
that will detect the proximity of "fellow inmates" . Just swearing on an ATC
frequency will net you a $2,500 fine in Canada, I can't even imagine what
they would do to you if you jammed one of their frequencies.

Claude
Montreal



One of you naysayers should estimate the amount of radiated energy from a
typical regen receiver.

Also, what is the distance from the intended regen location to the airport,
and what would you imagine the comparative strengths would be of the regen
signal and air traffic signals at air traffic receivers?

The regen receiver radiated signal would be lost in the noise.

The other party to air traffic communication are aircraft. Those happen
to roam about quite a bit

Seriously, disregarding the airstrip that's almost next to the office
here we are also roughly in the flight path for Mather Field. Altitude
above our building maybe 1500ft, give or take. If Fedex, DHL and other
pilots would report some weird shhhhht noise everytime they pass a
certain spot, guess what would happen?

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[Michael A. Terrell]

Joerg wrote:

The other party to air traffic communication are aircraft. Those happen
to roam about quite a bit

Seriously, disregarding the airstrip that's almost next to the office
here we are also roughly in the flight path for Mather Field. Altitude
above our building maybe 1500ft, give or take. If Fedex, DHL and other
pilots would report some weird shhhhht noise everytime they pass a
certain spot, guess what would happen?

You would be in deep shhhhht. You might even be charged with
terrorism.


--
http://improve-usenet.org/index.html


Use any search engine other than Google till they stop polluting USENET
with porn and junk commercial SPAM

If you have broadband, your ISP may have a NNTP news server included in
your account: http://www.usenettools.net/ISP.htm

 

[Don Bowey]

On 4/18/08 11:25 AM, in article lI5Oj.4682$iK6.2220@nlpi069.nbdc.sbc.com,
"Joerg" <notthisjoergsch@removethispacbell.net> wrote:

Don Bowey wrote:
On 4/18/08 8:16 AM, in article fuae44$6tg$1@dns3.cae.ca, "Claude"
claudec@cae.com> wrote:

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:cJMNj.6968$GE1.6102@nlpi061.nbdc.sbc.com...
Michael Black wrote:
On Wed, 16 Apr 2008, Bob Eld wrote:

"Archimedes" <shelton.dcruz@gmail.com> wrote in message
news:b3b30960-27bc-4d59-924f-4312caffe7c2@x41g2000hsb.googlegroups.com...
Hi all

If I change the tank circuit components (reduce the capacitance and
inductance) and change the transistors to appropriate VHF ones, will I
be able to pick up ATC (Air Traffic Conversations) using this
circuit ?

http://www.electronics-lab.com/projects/rf/006/index.html

Thanks
Shelton.
Not likely. I doubt you'd ever get that circuit to work at VHF
frequencies
no matter what you did with the resonant circuit portion. There are many
problems including wrong impedances for the various parasitic
capacitances.

Secondly air traffic stuff is FM I believe.

Military may use FM, I don't know, but airplane related communication is
unique in that it does use actual AM.

A project that saw publication a number of times in the old days took
advantage of that, a "crystal radio" that tuned VHF. It was nothing
more than a tuned circuit and a diode detector feeding an earphone, not
sensitive but useful near airports and since it didn't radiate anything,
even useable (though maybe not legally) on an actual airplane.

The description of the circuit says it's a regen receiver, and those
were never popular at VHF, I'm assuming instability came into play.
You did see superregen receivers there. Either type will radiate, and
that's not a good thing in the aircraft band.

Yes, and then you'd quickly have visitors coming with vehicles bearing
government license plates. A regen-receiver is most definitely not a good
idea in the aircraft band.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
Quite correct, it is most likely jail time where you will have hours and
hours of fun designing electronics such as movement alarms
that will detect the proximity of "fellow inmates" . Just swearing on an ATC
frequency will net you a $2,500 fine in Canada, I can't even imagine what
they would do to you if you jammed one of their frequencies.

Claude
Montreal



One of you naysayers should estimate the amount of radiated energy from a
typical regen receiver.

Also, what is the distance from the intended regen location to the airport,
and what would you imagine the comparative strengths would be of the regen
signal and air traffic signals at air traffic receivers?

The regen receiver radiated signal would be lost in the noise.


The other party to air traffic communication are aircraft. Those happen
to roam about quite a bit

Seriously, disregarding the airstrip that's almost next to the office
here we are also roughly in the flight path for Mather Field. Altitude
above our building maybe 1500ft, give or take. If Fedex, DHL and other
pilots would report some weird shhhhht noise everytime they pass a
certain spot, guess what would happen?

I doubt that at 1500 feet the signal from a regen receiver would break the
squelch.

 

[Bob Monsen]

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:lI5Oj.4682$iK6.2220@nlpi069.nbdc.sbc.com...

Don Bowey wrote:
One of you naysayers should estimate the amount of radiated energy from a
typical regen receiver.

Also, what is the distance from the intended regen location to the
airport,
and what would you imagine the comparative strengths would be of the
regen
signal and air traffic signals at air traffic receivers?

The regen receiver radiated signal would be lost in the noise.


The other party to air traffic communication are aircraft. Those happen to
roam about quite a bit

Seriously, disregarding the airstrip that's almost next to the office here
we are also roughly in the flight path for Mather Field. Altitude above
our building maybe 1500ft, give or take. If Fedex, DHL and other pilots
would report some weird shhhhht noise everytime they pass a certain spot,
guess what would happen?

One of the nice things about AM, and the reason they use it for aviation, is
that power wins. If two signals are colliding, the more powerful one will
always be heard.

There are various "unicom" frequencies around the US, which are used by
pilots at uncontrolled airports for announcing positions in the traffic
pattern. Since the frequency space is not all that big, they tend to
overlap. You can often hear folks announcing at airports up to 100 miles
away. However, there is never any problem, since the near transmitters just
blast over the far ones.

I'm guessing the regen receiver outputs less than one mW through its power
wires. That isn't going to be a problem for anybody unless the OP decides to
start messing with the design, and somehow manages to build a far more
effective transmitter. If he puts it into a metal box, he'll be safe.

OTOH, he'll never get it working in the AM aircraft band, since the circuit
itself really sucks.

He should instead buy something like this:

http://cgi.ebay.com/Blue-Emergency-Solar-AM-FM-S-W-Aviation-Weather-Radio_W0QQitemZ380018212225QQihZ025QQcategoryZ146512QQtcZphotoQQssPageNameZWDVWQQrdZ1QQcmdZViewItem

For 35 bucks buy-it-now, not a bad deal. It also does weather, AM broadcast
band, FM broadcast band, and shortwave, and even works from a crank so you
can work out while listening to the ATC folks vector jets around.

If the OP really wants to hack at something, I'd suggest an old Cessna
transceiver. Just don't plug in the microphone, and power it from 24V.
Should be fun to play with. This actually will get you arrested if you mess
up and jam a frequency, though. There is one on sale at eBay now for $10,
but it'll go for more.

I landed at Mather once when it first went GA. Very creepy. The runway is so
wide that it feels like you are much lower than you really are. A 172 feels
like a gnat on a surfboard.

Regards,
Bob Monsen

 

[Bob Monsen]

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:66t2bnF2lnc18U1@mid.individual.net...

"Bob Monsen"


One of the nice things about AM, and the reason they use it for aviation,
is that power wins. If two signals are colliding, the more powerful one
will always be heard.


** That is how FM behaves - ie the "capture effect".

AM does no such thing - " colliding " signals simply combine in the
receiver and are heard together.

Weak signals are heard in the background of strong ones.



...... Phil

Thanks for the clarification. However, I'm curious about this.

An FM signal is really just a frequency shift on the carrier. As I
understand it, the transmitted signal is the carrier frequency shifted in
proportion to the amplitude of the sound that will get transmitted (for
mono).

So, given two transmitters on the same frequency, you end up with two
varying carriers. If your receiver is just receiving both signals, mixing
them down to a lower frequency, detecting the shift, and converting that
into an amplitude, the detector must be doing this locking on. Do you know
how it works? How does it lock on rather than just outputting a mess?

Thanks,
Bob Monsen

 

[Joerg]

Don Bowey wrote:

On 4/18/08 11:25 AM, in article lI5Oj.4682$iK6.2220@nlpi069.nbdc.sbc.com,
"Joerg" <notthisjoergsch@removethispacbell.net> wrote:

Don Bowey wrote:
On 4/18/08 8:16 AM, in article fuae44$6tg$1@dns3.cae.ca, "Claude"
claudec@cae.com> wrote:

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:cJMNj.6968$GE1.6102@nlpi061.nbdc.sbc.com...
Michael Black wrote:
On Wed, 16 Apr 2008, Bob Eld wrote:

"Archimedes" <shelton.dcruz@gmail.com> wrote in message
news:b3b30960-27bc-4d59-924f-4312caffe7c2@x41g2000hsb.googlegroups.com...
Hi all

If I change the tank circuit components (reduce the capacitance and
inductance) and change the transistors to appropriate VHF ones, will I
be able to pick up ATC (Air Traffic Conversations) using this
circuit ?

http://www.electronics-lab.com/projects/rf/006/index.html

Thanks
Shelton.
Not likely. I doubt you'd ever get that circuit to work at VHF
frequencies
no matter what you did with the resonant circuit portion. There are many
problems including wrong impedances for the various parasitic
capacitances.

Secondly air traffic stuff is FM I believe.

Military may use FM, I don't know, but airplane related communication is
unique in that it does use actual AM.

A project that saw publication a number of times in the old days took
advantage of that, a "crystal radio" that tuned VHF. It was nothing
more than a tuned circuit and a diode detector feeding an earphone, not
sensitive but useful near airports and since it didn't radiate anything,
even useable (though maybe not legally) on an actual airplane.

The description of the circuit says it's a regen receiver, and those
were never popular at VHF, I'm assuming instability came into play.
You did see superregen receivers there. Either type will radiate, and
that's not a good thing in the aircraft band.

Yes, and then you'd quickly have visitors coming with vehicles bearing
government license plates. A regen-receiver is most definitely not a good
idea in the aircraft band.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
Quite correct, it is most likely jail time where you will have hours and
hours of fun designing electronics such as movement alarms
that will detect the proximity of "fellow inmates" . Just swearing on an ATC
frequency will net you a $2,500 fine in Canada, I can't even imagine what
they would do to you if you jammed one of their frequencies.

Claude
Montreal


One of you naysayers should estimate the amount of radiated energy from a
typical regen receiver.

Also, what is the distance from the intended regen location to the airport,
and what would you imagine the comparative strengths would be of the regen
signal and air traffic signals at air traffic receivers?

The regen receiver radiated signal would be lost in the noise.

The other party to air traffic communication are aircraft. Those happen
to roam about quite a bit

Seriously, disregarding the airstrip that's almost next to the office
here we are also roughly in the flight path for Mather Field. Altitude
above our building maybe 1500ft, give or take. If Fedex, DHL and other
pilots would report some weird shhhhht noise everytime they pass a
certain spot, guess what would happen?

I doubt that at 1500 feet the signal from a regen receiver would break the
squelch.

From a regen that misbehaves it certainly can.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.

 

[Bob Monsen]

"Phil Allison" <philallison@tpg.com.au> wrote in message
news:66ta4oF2mg9r9U1@mid.individual.net...

** Capture effect is almost entirly due to the " limiting " that occurs
in the IF amplifier stages.


...... Phil

Thanks for the info.

Regards,
Bob Monsen

 

[Don Bowey]

On 4/19/08 5:28 PM, in article
C6wOj.2082$pS4.1634@newssvr13.news.prodigy.net, "Joerg"
<notthisjoergsch@removethispacbell.net> wrote:

Don Bowey wrote:
On 4/18/08 11:25 AM, in article lI5Oj.4682$iK6.2220@nlpi069.nbdc.sbc.com,
"Joerg" <notthisjoergsch@removethispacbell.net> wrote:

Don Bowey wrote:
On 4/18/08 8:16 AM, in article fuae44$6tg$1@dns3.cae.ca, "Claude"
claudec@cae.com> wrote:

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:cJMNj.6968$GE1.6102@nlpi061.nbdc.sbc.com...
Michael Black wrote:
On Wed, 16 Apr 2008, Bob Eld wrote:

"Archimedes" <shelton.dcruz@gmail.com> wrote in message
news:b3b30960-27bc-4d59-924f-4312caffe7c2@x41g2000hsb.googlegroups.com.
..
Hi all

If I change the tank circuit components (reduce the capacitance and
inductance) and change the transistors to appropriate VHF ones, will I
be able to pick up ATC (Air Traffic Conversations) using this
circuit ?

http://www.electronics-lab.com/projects/rf/006/index.html

Thanks
Shelton.
Not likely. I doubt you'd ever get that circuit to work at VHF
frequencies
no matter what you did with the resonant circuit portion. There are
many
problems including wrong impedances for the various parasitic
capacitances.

Secondly air traffic stuff is FM I believe.

Military may use FM, I don't know, but airplane related communication is
unique in that it does use actual AM.

A project that saw publication a number of times in the old days took
advantage of that, a "crystal radio" that tuned VHF. It was nothing
more than a tuned circuit and a diode detector feeding an earphone, not
sensitive but useful near airports and since it didn't radiate anything,
even useable (though maybe not legally) on an actual airplane.

The description of the circuit says it's a regen receiver, and those
were never popular at VHF, I'm assuming instability came into play.
You did see superregen receivers there. Either type will radiate, and
that's not a good thing in the aircraft band.

Yes, and then you'd quickly have visitors coming with vehicles bearing
government license plates. A regen-receiver is most definitely not a good
idea in the aircraft band.

--
Regards, Joerg

http://www.analogconsultants.com/

"gmail" domain blocked because of excessive spam.
Use another domain or send PM.
Quite correct, it is most likely jail time where you will have hours and
hours of fun designing electronics such as movement alarms
that will detect the proximity of "fellow inmates" . Just swearing on an
ATC
frequency will net you a $2,500 fine in Canada, I can't even imagine what
they would do to you if you jammed one of their frequencies.

Claude
Montreal


One of you naysayers should estimate the amount of radiated energy from a
typical regen receiver.

Also, what is the distance from the intended regen location to the airport,
and what would you imagine the comparative strengths would be of the regen
signal and air traffic signals at air traffic receivers?

The regen receiver radiated signal would be lost in the noise.

The other party to air traffic communication are aircraft. Those happen
to roam about quite a bit

Seriously, disregarding the airstrip that's almost next to the office
here we are also roughly in the flight path for Mather Field. Altitude
above our building maybe 1500ft, give or take. If Fedex, DHL and other
pilots would report some weird shhhhht noise everytime they pass a
certain spot, guess what would happen?

I doubt that at 1500 feet the signal from a regen receiver would break the
squelch.


From a regen that misbehaves it certainly can.

Yes, just about anything and everything that misbehaves can can cause a
problem. When I lived in Ketchikan, AK, I received one of those
salmon-colored FCC QSL cards from a listening station at Point Reyes, CA due
to a misbehaving multiplier in my HT9. Got a 579 on my second harmonic.

 

[Varactor]

On Apr 19, 2:05 pm, "Phil Allison" <philalli...@tpg.com.au> wrote:

"Bob Monsen"



One of the nice things about AM, and the reason they use it for aviation,
is that power wins. If two signals are colliding, the more powerful one
will always be heard.

** That is how FM behaves  -  ie  the  "capture effect".

AM does no such thing  -  " colliding " signals simply combine in the
receiver and are heard together.

Don't know abou that. When two stations broadcast over each other its
generally just distorted garbage. I speak as a pilot, not from theory.

 

[Don Bowey]

On 4/20/08 4:00 AM, in article
5ddef92b-5533-42f9-936f-8e27e87ca416@v26g2000prm.googlegroups.com,
"Varactor" <Moreflaps@gmail.com> wrote:

On Apr 19, 2:05 pm, "Phil Allison" <philalli...@tpg.com.au> wrote:
"Bob Monsen"



One of the nice things about AM, and the reason they use it for aviation,
is that power wins. If two signals are colliding, the more powerful one
will always be heard.

** That is how FM behaves  -  ie  the  "capture effect".

AM does no such thing  -  " colliding " signals simply combine in the
receiver and are heard together.



Don't know abou that. When two stations broadcast over each other its
generally just distorted garbage. I speak as a pilot, not from theory.

Also speaking as a pilot AND a ham of many years, I believe that a trained
ear can ignore the heterodyne whistles of combined signals and hear the
underlying messages. Even when one signal largely overcomes another, it is
easy to recognize that a second station was there, inviting a follow-up
call.