I’m looking for something that can detect frequencies in the GHz range. I don’t have the money to spend on something as complex as a spectrum analyzer, and I wouldn’t want it to be all that complex, it could be as simple as a hard wired switch that tripped when the correct frequency was detected. So far, I’ve been able to come up with nothing, hopefully some electronics guru will be able to help me.
Doesn’t sound all that difficult. Is this to be a broad spectum detector or a very specific frequency? What exactly are you trying to do with it?
I’d prefer a broad spectrum detector, but could make do with a specific frequency one, it would just change how I would build the rest of it. I’m building a project for my electronics class, and the received broadband frequency will be the triggering mechanism for it. I agree though, it seems like it should be a really simple component that I should be able to find no problem. No luck so far however, despite googling lots of combinations of words pertinent to what I’m looking for. I’m just hoping somebody here will be able to say “oh, all you need is a dewmilated flimeraloo”, and I can then search for that.
Well, the issue is that it is not just one component, unless you count a full high freqency receiver on a chip as one component.
Is there a particular reason it has to be as high as 1 GHz? I know radioshack has FM recievers on a chip that should work well in the 100Mhz range. Of course, this will have a pretty selective narrow band front end on it.
To build a 1GHz receiver with off shelf transistors is moderately difficult. You are at high enough a frequency that component lead length even needs to be considered to make sure it will work right. This is pretty well a radar frequency. Most off the shelf receivers are designed with a very narrow bandpass tuning filter. Most recievers that you are gonna find also have a demodulator built right into them. At this frequency, most receivers will be F.M. It sounds like you just need an amplituted detector. That could be as simple as a high-speed diode and a capicitor, being fed by a tuner and amplifier.
A pin diode and a hunk of wire will do most of the work for you. Maybe add a ceramic disc capacitor for some filtering and feed it into an LED or a multimeter.
Make a half wave dipole antenna of the correct length for the frequencey you want. Between the two halves of the dipole, connect a Schottky diode and an LED in inverse parallel.
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I’ve only shown one diode above, use your imagination to put in the other one.
Both the solutions ECP and Des mention consider a pretty strong signal.
They are essentially what I had in mind for the detector behind the wide band tuner/amp.
What do you plan on using as the transmitter and how far away will it be?
Get your hand off it scotth. What I and engineer_comp_geek proposed may have been what you had in mind, but it wasn’t what you said.
I hope you aren’t serious Desmostylus… Please read the last two sentences of my second post.
Of course, misspelling capacitor probably doesn’t help me much… ugh.
ack… I really need to proof read better… amplituted should have been amplitude
Sorry scotth. I was too harsh.
So, it seems like it would be a bit of work, and not as small as I would like it to be (smaller than a breadbox) if I were to do it this way, which would also only detect one broadband frequency. I could make do with this, but is there really no off the shelf or ready made detector that can detect a range of frequencies?
It will be line of sight distance, powered by a wall outlet (don’t know what it transforms it to though). Transmitter is basically a Doppler shift detector that shoots a fairly coherent beam at line of sight distance that is in the GHz range.
If the transmitter is a Doppler shift detector, it will transmit with a very narrow band on a very specific frequency. Would this be a device that was used to open grocery store doors and such?
Probably, a good place to start for an off the shelf detector is a cheap radar detector from your local electronics store. These detect grocery store door radars very well.
btw, a half wave antenna for 1GHz is
299792458 / 1,000,000,000 = .299792458 Meters for a whole wavelength.
Half of that is about 15 centimeters. Not terribly big.
Radar detectors use a feed horn type antenna rather than a dipole.
Would an off the shelf radar detector be able to tell me what frequency it was detecting (maybe if I hooked something else up to it)? I need to be able to know the frequency being detected reasonably well. Another thing, I know most radar detectors mainly detect X band, which is 10.5 GHz, but will also detect 24 and 32 with more limited capacity, and if my transmitter is not one of those frequencies, it wouldn’t detect it. Best case scenario for me would be to have the detection capacity of lots of antennas wired for different frequencies, so I would be able to detect a lot, and also be able to tell which frequency is being detected. The capacity for that though, not the bulk and tangle of actually having all of those. I guess there really is no ready made GHz spectrum detector that can do that though, at least for under $20K.
I was hoping that something like these would come up.
http://www.spaceklabs.com/Products/Broadband_Detectors/broadband_detectors.html
But, I don’t know if these will actually do what I want them to, and I’ve emailed these guys a couple of times with no answers.
Would an off the shelf radar detector be able to tell me what frequency it was detecting (maybe if I hooked something else up to it)? I need to be able to know the frequency being detected reasonably well. Another thing, I know most radar detectors mainly detect X band, which is 10.5 GHz, but will also detect 24 and 32 with more limited capacity, and if my transmitter is not one of those frequencies, it wouldn’t detect it. Best case scenario for me would be to have the detection capacity of lots of antennas wired for different frequencies, so I would be able to detect a lot, and also be able to tell which frequency is being detected. The capacity for that though, not the bulk and tangle of actually having all of those. I guess there really is no ready made GHz spectrum detector that can do that though, at least for under $20K.
I was hoping that something like these would come up.
http://www.spaceklabs.com/Products/Broadband_Detectors/broadband_detectors.html
But, I don’t know if these will actually do what I want them to, and I’ve emailed these guys a couple of times with no answers.
Ah, you need to be able to discriminate different frequencies with this? Very different ballgame.
What exactly is the the freqency range that must be detected across?
What are the individual freqencies that need to be singled out?
Radar detectors are X and K band, which is 10 and 30 GHz if I recall correctly. I also believe they use filtering to ignore signals out of this range to eliminate false alarms (like supermarket door sensors). I haven’t taken a close look at a radar detector in a long time but they used to tell you which band they were picking up, typically with a different LED for each band and a different chirp out of the speaker.
Something advertised as a microwave oven leakage detector will be a bit more broadband. Most microwaves work around 2 GHz but a simple leakage detector isn’t going to do much filtering (I would think).
The only off the shelf piece of equipment that will receive a fairly broadband signal and tell you what specific signals are present would be a microwave spectrum analyzer, and that’s going to be a little hard on your budget. Just for giggles I searched on ebay and someone does have a spectrum analyzer for about 600 bucks. I doubt you’ll find anything commercial for cheaper than that.
Just an idea…Could you bodge something together out of a cordless phone ? Some of them operate near the frequency you want and you can buy one for a few dollars.