AGD horn find

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Bton-FM
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AGD horn find

Post by Bton-FM » Wed Sep 25, 2019 10:16 pm

I got an AGD traffic sensor off some roadworks men today for free!Are these good for micro links if so what voltage shall I run?(the chips in the bottom are me trying to get the damn thing open as the screws were seized)
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Re: AGD horn find

Post by Gigahertz » Thu Sep 26, 2019 4:34 pm

Never personally used one but from memory others have said the audio wasn’t great?

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Re: AGD horn find

Post by teckniqs » Fri Sep 27, 2019 8:12 am

That's correct, I don't know exactly why but I think the AGD type has a much narrower bandwidth so anything above 10-20% volume just stays the same level but over modulates and distorts.

....I have once seen an AGD Systems gunn being used before but I can only presume the TX diode had been changed.

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Re: AGD horn find

Post by Bton-FM » Fri Sep 27, 2019 8:54 am

oh alright i'll just use it as a test.do you know where i could get a replacement gunn diode?

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Re: AGD horn find

Post by teckniqs » Fri Sep 27, 2019 9:04 am

No I don't because thankfully I've never had to replace one.

....But the one in the horn I saw was probably removed from another gunn like an old Solfan or C&K.

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Re: AGD horn find

Post by Bton-FM » Fri Sep 27, 2019 4:37 pm

Thanks teckniqs I’ll probably buy another Gunn then and use the same waveguide.It’s a bit cheeky but since we are on the topic of microwave have you guys ever used satcans out of an analog tv satellite reciever for recieving microwave links?

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Re: AGD horn find

Post by XXL » Sat Sep 28, 2019 2:55 am

These horns are fine, and really easy to link with because they’re so powerful. You want 7-8v. My audio never distorted on it and it was just as loud as legal stations.

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Re: AGD horn find

Post by Albert H » Sat Sep 28, 2019 3:08 am

I had no real problem with the AGD horns. I sometimes added extension waveguides to them for a really high output power down a very narrow beam. I used about 7.2V (which was roughly the voltage supplied when it was being used as a Microwave Vehicle Detector). I had a few of them with two Gunn diodes (transmit and receive AFAIK), and - with care - it was possible to remove one of them for use in other gear. The best range I achieved for a fully noise-quietening stereo link with these was about 4 miles.
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Re: AGD horn find

Post by Bton-FM » Sat Sep 28, 2019 2:32 pm

Also the circuit board has a PIC16 on it is this for some sort of pll?

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Re: AGD horn find

Post by Albert H » Sun Sep 29, 2019 4:05 am

The PIC was part of the frequency discriminator circuit. A rising reflected signal frequency showed a vehicle approaching, and a falling reflected frequency was a vehicle going away from the detector. The discrimination allowed it to be set up to ignore receding vehicles, and it could also be used for (fairly crude) speed measurement.
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Re: AGD horn find

Post by Bton-FM » Sun Sep 29, 2019 12:16 pm

When I’m desoldering the circuit board from the Gunn diode terminals are there any precautions I should take?
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Re: AGD horn find

Post by Banus_radio » Sun Sep 29, 2019 8:25 pm

That gunn is the nuts !!

I swear by them... Does it have an 'allen key' style tuning screw ?
If so then do the following:

Run it at 5.5v and that thing will need a big temperature change before it drifts. Dont run it at the usual 7 ish volts
Its suppressed so you cant modulate audio as much as an old solfan type gunn but its very sharp and crisp audio albeit a little quiet.

I encoded and run PCM audio through mine and decoded it at the other end direct from the satcan, crisp hiss free stereo audio... boom !
Anthony audio sell 5.8ghz digital audio sender, simple remove the wire from the 5.8ghz can and connect to your microwave modulator board.
The take baseband output from your satcan and feed into the anthony receiver (removing the 5.8Ghz can), tune in the satcan and you have audio.... Tuning into the signal just sounds like white noise ... boom !

Make sure you remove all the plates between the gunn and the horn itself.
Lots of radio hams use this horn. There was a skip load of them about ten years ago from Siemans who fit traffic lights, I had a few!

Lots of radio hams use this setup on the 23cm band and 10ghz band

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Re: AGD horn find

Post by Bton-FM » Sun Sep 29, 2019 8:46 pm

this one has a flathead tuning screw

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Re: AGD horn find

Post by Bton-FM » Sun Sep 29, 2019 8:53 pm

Also where do you get your satcans banus?

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Re: AGD horn find

Post by Banus_radio » Sun Sep 29, 2019 9:32 pm

Look for old analogue pace or amstrad satellite receivers on ebay, remove the cans from them. They are like gold dust these days

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Re: AGD horn find

Post by Banus_radio » Sun Sep 29, 2019 9:34 pm

The flat tuning screw AGS's are heavily internally suppressed and you cannot modulate much audio through them, its very very quiet in WFM mode.

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Re: AGD horn find

Post by Bton-FM » Sun Sep 29, 2019 9:42 pm

what does internally suppressed mean?

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Re: AGD horn find

Post by Bton-FM » Sun Sep 29, 2019 10:10 pm

Here is The screw:
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Re: AGD horn find

Post by XXL » Tue Oct 01, 2019 11:35 am

That’s not the one I used so it might sound like crap. The best ones are the Allen key tune style. Remove all plates from inside, they go fucking miles without drifting. 1 time I couldn’t even see the rig site, even though it was in front of me somewhere. It still linked. They shit at 5 or 6v, don’t bother. Try it yourself, the audio drastically changes at lower voltages and signal strength comes down with it. 7.2v is best but it trial and error really depending on the distance situation.

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Re: AGD horn find

Post by Bton-FM » Tue Oct 01, 2019 5:10 pm

that sounds mental XXL , i'll remove the plates and have a go with it when I get a satcan. It'll probably sound like shite but its worth a try.

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