Hey all, first post here (:
So I'm currently trying to put together a circuit that is tuned to receive data in the air at 1030 MHz.
Using the equation RF = 1/(2pirt(LC)), I get
1,030,000 Hz = .....
LC = .000393
Now I assume I choose a capacitor and then solve for the inductor's value, but I don't have a clue how to determine what rating capacitor I should use.
First things first. 1030 MHz is not the same as 1,030,000 Hz, you are off by 1,000.
Silly me, I skipped kilohertz. But that just changes the LC so my question is still valid.
Mikedub:
Silly me, I skipped kilohertz. But that just changes the LC so my question is still valid.
Just chose a C value and see if the resulting L value is something you can actually make or buy. If indeed you are talking about 1030Mhz both the C and L will be very very small.
retrolefty:
Mikedub:
Silly me, I skipped kilohertz. But that just changes the LC so my question is still valid.Just chose a C value and see if the resulting L value is something you can actually make or buy. If indeed you are talking about 1030Mhz both the C and L will be very very small.
So the relation between L and C are more important than the values themselves?
Also, the purpose of this circuit is strictly just for amplifying signals on the selected frequency, correct? And I would still be processing data straight from the antenna as opposed to from the LC circuit?
Mikedub:
retrolefty:
Mikedub:
Silly me, I skipped kilohertz. But that just changes the LC so my question is still valid.Just chose a C value and see if the resulting L value is something you can actually make or buy. If indeed you are talking about 1030Mhz both the C and L will be very very small. Or put another way, any C and L value will resonate at some frequency.
So the relation between L and C are more important than the values themselves?
Yes, for any specific frequency there is a near infinite combinations of L and C that will resonate at that frequency. In practice however you have to use values for L and C that can be actually implemented. Put another way any specific L and C value will resonate at some specific frequency.
retrolefty:
Yes, for any specific frequency there is a near infinite combinations of L and C that will resonate at that frequency. In practice however you have to use values for L and C that can be actually implemented. Put another way any specific L and C value will resonate at some specific frequency.
Okay I get it, I'm pretty math oriented. I actually amended that post as well:
Also, the purpose of this circuit is strictly just for amplifying signals on the selected frequency, correct? And I would still be processing data straight from the antenna as opposed to from the LC circuit?
Also, the purpose of this circuit is strictly just for amplifying signals on the selected frequency, correct?
No.
You are putting together a tuned resonant circuit there is no amplification going to happen.
And I would still be processing data straight from the antenna as opposed to from the LC circuit?
No.
What are you actually trying to do? That frequency is ridiculously high and requires special microwave techniques to construct. It is not something you can knock up on a bread board or even a PCB without specialist software.
Grumpy_Mike:
Also, the purpose of this circuit is strictly just for amplifying signals on the selected frequency, correct?
No.
You are putting together a tuned resonant circuit there is no amplification going to happen.And I would still be processing data straight from the antenna as opposed to from the LC circuit?
No.
What are you actually trying to do? That frequency is ridiculously high and requires special microwave techniques to construct. It is not something you can knock up on a bread board or even a PCB without specialist software.
Basically I'm doing some experimental things with aircraft transponders (Aviation is my degree). The particular component this thread is about is meant to detect certain signals on 1030 MHz, which is the frequency that Air Traffic Control sends pulses on for the purpose of tracking aircraft in Class B and C airspace (Class A is starting to use ADS-B, which I want to do for a future project [and has been done on Arduino already]). I realize I will need a transmitter component as well, but I'm taking this just one step at a time.
Also, I don't see how 1.030 GHz is ridiculously high...a common cordless house phone is 2.41 GHz right?
Mikedub:
Also, I don't see how 1.030 GHz is ridiculously high...a common cordless house phone is 2.41 GHz right?
Common indeed, but containing immensely sophisticated radio frequency circuitry, a complete design field in itself.
Some radio amateurs with a particular interest in this area develop proficiency in designing and implementing such circuits over the months and years.
Yep, anything above the 432Mhz ham band is still considered pretty exotic by hams. At 1030 MHz the L & C tends to just be controlled length and width of PC traces on special PCB substrate, indeed complete bandpass filters tend to just be printed on the PCB needed very tight tolerances.
It is easy to make an insensitive, but completely workable detector for signals with frequencies > 1.0 GHz, based on the old crystal radio technique. The antenna is simply an LC circuit that is also the antenna, and consists of a full wave circular or square loop, which you can make in about 30 seconds with a piece of bare wire. Or you can make a PCB loop/antenna. See WiFi detector. - Sensors - Arduino Forum and The Creative Science Centre - by Dr Jonathan P. Hare
jremington:
It is easy to make an insensitive, but completely workable detector for signals with frequencies > 1.0 GHz, based on the old crystal radio technique. The antenna is simply an LC circuit that is also the antenna, and consists of a full wave circular or square loop, which you can make in about 30 seconds with a piece of bare wire. Or you can make a PCB loop/antenna. See WiFi detector. - Sensors - Arduino Forum and The Creative Science Centre - by Dr Jonathan P. Hare
Thanks for the references! I definitely want to do PCB because I want it to be a presentable project. This is mostly for fun (and I want to show the Federal Aviation Administration how outdated this technology is now). When you say insensitive, what are we talking here? As far as I know these are pretty powerful pulses because they do span large distances (about 25 nautical miles if I remember correctly, or about 30 statute miles)
Mikedub:
When you say insensitive, what are we talking here? As far as I know these are pretty powerful pulses because they do span large distances (about 25 nautical miles if I remember correctly, or about 30 statute miles)
So if you are within a few hundred meters of the transmitter and the antenna is pointing at you, a "crystal set" will probably detect the pulses.
{Have you noticed the periodic "zzzzzt" noise you get in radios and such when you are near the airport radar, corresponding to when the antenna rotates in your direction?}
Paul__B:
So if you are within a few hundred meters of the transmitter and the antenna is pointing at you, a "crystal set" will probably detect the pulses.{Have you noticed the periodic "zzzzzt" noise you get in radios and such when you are near the airport radar, corresponding to when the antenna rotates in your direction?}
Yes! The pulses are actually set up so that the second "ping" is there to make sure that the third is "heard" with the leading edge of the beacon.
I don't see how 1.030 GHz is ridiculously high...a common cordless house phone is 2.41 GHz right?
Common but produced by large teams of specialist engineers with very expensive test equipment.
You need at least a good quality spectrum analyzer costing some where in the region of $6000 + as well as a dam good scope in the same price bracket and a LCR bridge. Components at these frequencies are also very expensive in very small quantities especially the connectors.
The closest ham band is 23cm or 1296MHz so the same sort of techniques apply.
Attached is an example of what you need as a simple preamp. Note the construction and the curved and zig zag tracks all these shapes are calculated. Do you think as some one who asked about calculating a resonant capacitor is capable, at the moment, of designing this?
Don't get me wrong, you can design something like this but in about five years time when you have acquired the right skills and test equipment.
Hi Mikedub
Remember that there will be a very large difference in the strength of the signal returned by the aircraft transponder compared with the transmission from the ground radar that is pinging it. A simple loop / diode detector may pick up something when close to an airport radar but I doubt it would be sensitive enough to detect aircraft responses (which I inferred is what the you want to detect).
How about taking a different approach to the project? Get a cheap SDR dongle to handle the RF side of things. Then focus on identifying the transponder returns from the baseband output of the SDR and decoding the data in them. I think that is probably how the ADS-B Arduino projects you mentioned have done it.
Regards
Ray
When you say insensitive, what are we talking here?
Try it and see! The dimensions of the loop are critical so some trial and error will be necessary. Start by making a cell phone detector (note there are four common frequency bands). If you dispense with the LED and instead measure the weak pulses from the detector, as described here The Creative Science Centre - by Dr Jonathan P. Hare you can easily detect the transmissions of a cell phone in the same room. The transmission power of a cell phone might be a watt or so and I would expect airport beacons to be several orders of magnitude more powerful, leading to a correspondingly larger range to detect the transmitter.
and I want to show the Federal Aviation Administration how outdated this technology is now
What will you suggest as a replacement?
Actually, no. The only agency that receives aircraft responses is ATC. The airplanes do not communicate with each other on this current method. They do in ADS-B, however.
jremington:
What will you suggest as a replacement?
Additionally, the replacement I would suggest for this current method is something encrypted (to prevent terroristic acts).
Grumpy_Mike:
Do you think as some one who asked about calculating a resonant capacitor is capable, at the moment, of designing this?
I found this free software which supposedly can design planar inductors, but I'm not sure how to use it http://www.saturnpcb.com/pcb_toolkit.htm
Mikedub:
[quote author=Hackscribble link=topic=242632.msg1739318#msg1739318 date]
A simple loop / diode detector may pick up something when close to an airport radar but I doubt it would be sensitive enough to detect aircraft responses (which I inferred is what the you want to detect).
Actually, no. The only agency that receives aircraft responses is ATC. The airplanes do not communicate with each other on this current method. They do in ADS-B, however. [/quote]
Mike, I wasn't suggesting that airplanes did communicate with each other. But I had misunderstood you anyway. I thought you wanted to receive the aircraft responses to SSR pings from ATC radar (e.g. the 4 digit octal transponder setting).
Now I realise you want to build (at least part of) an airborne SSR transponder. Have I got that right?
Do you want just to detect the presence of transmissions on 1030 MHz? Or do you need to detect and decode the radar pulse train from ATC radar that triggers a transponder to respond by transmitting its code?
You may already have references on the Mode A and Mode C protocols, but if not, I found this transponder manual which has a useful explanation.
Regards
Ray