I want to feed a single pulse of, let us say, 10 to 100 microseconds duration, into a short length of waveguide and detect that pulse upto 1000 metres away in another short length of waveguide set to be more or less co-linear with the first piece of waveguide. Can anyone suggest how I might implement this?
R
Please can you supply a bit more information, in particular:
What exactly are you trying to do?
Is there a good reason why want to use waveguide?
What is the carrier frequency of this pulse?
Gareth
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That probably can't be done. No reasonably sized waveguide (smaller than Central Park, say) will propagate signals that slow.
Why do you want to do this?
John
1000
might
Transfer instantaneously a start signal to some mobile electronic equipment which is in line of sight upto 1000 metres away.
I do not want interference by or to other radio transmissions but other options are possible. It is just too inconvenient to run a wire except for the shorter distances. For short distances the start signal by wire is a momentary low triggering pin 2 on a 555.
Flexible but around 2 gigahertz. The waveguide can be of any size that is reasonably portable and aimable and the carrier wave should match it. For preference it will be just outside any recognized band.
Roger
1000
might
The 'pulse' might be a brief period of carrier wave or even a brief gap in the carrier wave. Pulse was probably a poor choice of word on my part. It has to start some other electronic equipment which measues time intervals in milliseconds (not microseconds!).
See above.
Roger
Apologies if I have misunderstood your post, but I don't think waveguide does what you think it does.
Are you thinking that you can confine your pulse to a narrow beam so that it can only be picked up by another bit waveguide of 1km away which is carefully aligned? If that is what you are thinking it doesn't work like that. a signal from an open ended waveguide will have a beamwidth of ~60 degrees.
If you want to confine your signal to a narrow beamwidth you need a large antenna. The beamwidth, in radians, of an antenna is approximately the wavelength divided by the antenna diameter. at 2 GHz the wavelength is ~6", so you need a very large antenna if you want a narrow beamwidth.
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Oh. If you modulate a microwave carrier it becomes feasible. At 1km distance, horn antannas or parabolas might be better, or yagis for UHF range.
Line-of-sight optical is interesting, too.
John
message
I would like to explore all options.
Very interesting but it might require telescopic sights on the light source and receiver.
The transmitter moves every few minutes.
Roger
"Roger Dewhurst" I want to feed a single pulse of, let us say, 10 to 100 microseconds
** Err - where did you get the mad idea that a wave guide will create a narrow beam beyond the guide ?See anyone do it ?
Or have you just decided in your infinite Kiwi ignorance that the name alone tells you that.
Baaaahhhhhhhhhh ....
...... Phil
You can buy wireless modems, with small whip antennas, that will work that far.
John
If you modulate the start signal instead of using a simple pulse, you could easily make it such that only the matching receiver can demodulate it properly. True, it won't be as "instantaneous" since you may need to send several symbols to generate a decent code, but at 2 GHz you ought to be able to send quite a few in the time windows you mention.
Best regards,
Bob Masta D A Q A R T A Data AcQuisition And Real-Time Analysis
You could build waveguide feedhorns, but you probably wouldn't get enough gain to go 1 Km. Get a couple of parabolic dishes, and use the feedhorns to drive them, and it should be a snap.
Good Luck! Rich
How easy is it to feed the signal into one feedhorn and get it back from the other? Are there easier ways to achieve the required end result? Long lengths of cable will do it but they are a nuisance to move around. The signal is required to start a seismograph. The first part of it is a 555 acting as a Schmitt trigger and timer.
Roger
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