That sure is a familiar sound from Australia. Back in the 60's and 70's these LDR switched TX's on 27.240 would be placed on the top of gum trees ect. Old transformer wire as an antenna, way up on a tree on a hill gave them quite a range. These days those 27 mhz frequencies are dead and you are lucky to hear a soul.
I have done some experimenting with different crystal oscillator configurations to see if I can get them to do this with success. The series resistor and electrolytic capacitor that goes to ground on this very rudimentary circuit is loaded by the base emitter junction of the transistor until the capacitor discharges and the voltage drops sufficiently until the circuit drops out of oscillation. So noting this I tried the series capacitor and resistor on other circuits and got them to do it. The trick is to avoid loading the RF impedances of the circuit so you don't dampen it's ability to oscillate at RF frequencies and completely kill it. In fact I got the circuit for an old realistic 27mhz walkie talkie and applied the principle to it successfully. It's quite useful to know if you want to make a power efficient beacon as if the following stages are class C, the power draw is almost zero between pulses
Great chirping sound, could be off the soundtrack of a 70s Bond movie! Also, it proves the Envelope Theorem... circuits drawn on the back of an envelope are more likely to work 8^)
I built this and it worked first time. Only exception is for 27mhz I ended up having to use a 60pf capacitor in the LC circuit and my inductor coil is 9 turns of 20awg wire at 11mm length.
Hi vk3ye. Great video. I know you posted this quite a few years ago but I have a few questions if you wouldn't mind. 1. Does the LC tank circuit need to be adjusted to match the crystal you use? 2. In the video I see you mention moving the capacitors to the ground rail? What was the though behind this? 3. For the pulsing. Are you relying on the fact that with the 270k resistor the voltage drop puts the base of the transistor at a level below the VBE(on) value of the transistor and that after the cap charges it will then pulse? Thanks
Interesting project, congratulations. Do you know how can I change the circuit in a way to produce CW (not FM) and insert PIC (call sign recorded) to make a legal propagation beacon? 73!
It's already CW. Just remove the pulsing feature. You should be able to key it by applying keyed DC to the base via the 270k resistor, interrupting the emitter circuit or swiching the collector supply on and off. Be prepared for chirp though unless you add a buffer and key that.
If I used the original circuit (compensated for frequency), could I get it oscillating in the beacon segment of the 6 meter band (or close) with a 16.67mhz crystal in its third overtone like in the newsletter?
Hello. Can a beacon like this be made for operation on 40,66 - 40,70 mhz without use of a rare quartz oscillator? This band is allowed for use in my area and has power limit of 1 watt. Or better can a beacon like this operate in a 149,95 - 150,0625 band? It is limited here by 25 mw only but can be received with two meter HAM tranciever which is easier to get than a 40 mhz tranciever.
Hi vk3ye! I Follow your videos, and I'm trying to repeat some of your experiments, but my circuits are not even oscilating. I suspect of the wire I'm using for making the coils, I guess it's no thick enough(22AWG). The other problem seems that I trying at a protoboard. How thick are the wires you are using for makig coils? Do you think it's still possible to make FM transmitters in a protoboard?
I would use wire about 0.5 mm diameter (not critical). Protoboard with strips introduces capacitance which isn't helpful for VHF circuitry. Open air construction but with short connections may be better. Or on a PC board using continuous copper as a ground plane - again with short connections.
@@omsingharjit Basically an RF amplifier circuit with tuned circuits to pick off the harmonic. If none of this means anything to you, buy a good radio textbook and study basics of circuits for 12 months. Or just buy an FM transmitter kit or made up unit. The Talking Electronics website can help you understand this but you'll need more if you want to start designing circuits.
@@vk3ye yes i am beginner in HF RF but i can understand , that after amplification we will get 2 and 3rd so forth harmonic in higher frequency and by using band pass filter and amplifier we can get that higer frequency Right ! I asked because there's also Two Frequency mixing technique to get higher frequency so i asked which one you are talking about .
So Simple and yet so good. Peter I am making a TV yagi just for the fun of it(I know it will probably cost twice as much as one on the shelf). Just something to show the kids that antennas are not just for Ham. Please could you tell me why is it that purchased Yagis like the Hills 14 etc have a folded dipole of around 200MHz but for the same boom length of around 3 meters have a lot more directors fitted on the boom than say a Yagi using accurate calculations for 200MHz like VK5DJ program? Should I just copy the Hills one or follow a proper calculation? You would think if manufacturers could use less aluminium they would. Thanks
I'm guessing it has extra elements (eg log periodic) so it covers a wide frequency range (ie all the channels). A yagi would only be good for 1 or 2 channels.
Thanks Peter. It's not a log periodic but I think you are correct, it's about broad banding.This is the antenna I have as a sample to copy off www.radioparts.com.au/product/00681268/dy14-14-element-vhf-digital-fringe-antenna-signal#.V86CODVGTgw It's a Yagi but VHF Hi CH 6-12 is about 180MHz to 220MHzas you would know , so it's a lot to ask an antenna.
Hi vk3ye, I know you posted this video a while back but I had a couple of quick questions I was hoping you could answer. 1. Does the choice of crystal freq effect the values you select for your LC tank circuit? 2,. You mention you wanted the capacitors moved to ground instead of the power rail. What's the thought on this? 3. I think I see how the pulse works. It seems that the BC546 was chosen over other BJTs as it has a relatively low Vbe(on) value and by selecting the 270k resistor the voltage drops brings it below the threshold to turn on until the capacitor can charge? Does that sound right? Thanks for posting this great learning tool.
Hi CG: 1. Yes you will need to change the LC tank circuit with the crystal. 2, 3. Unfortunately I can't answer as I've moved onto other projects. 73, Peter
Haven't tried it but I'd be inclined to short circuit the 3u3 capacitor and put the key in the emitter lead with a 0.1uF capacitor across it. That does however require a reliable oscillator that starts up instantly.
@@vk3ye ahh. I almost wonder if it'd be practical to shrink it down as much as possible and use a super capacitor and some solar cells, about how much power does one of these things use?
Make one for every crystal you have and have an absolute electromagnetic nightmare! Run them all simultaneously into a vertical antenna to get some nice mixing products. What an excellent idea!
Hi Peter, thanks for this video upload. Despite the circuit simplicity, after a few tries/changes I finally got my example to work! Here's a write up..... www.vk6fh.com/vk6fh/beacon simple circuit.htm cheers Frank
I have done many builds of this beacon and have figured out several different things each build. I used both websites and tips from you guys. Maybe you could publish some of my work to your website vk6fh? Just trying to spread knowledge to others. -k0mov
@@derek7017 Hi Derek I'm sure your variations on the beacon design would interest others. Is the information available anywhere in the public domain, Utube, website etc or direct to vk 6 f h at westnet dot com dot au no spaces cheers
FRANK HUGHES I have several videos (need to edit) and a dozen circuit variations etc that I need to compile into a website or UA-cam. I mentioned your website as it’s quite popular over here. I’ve heard about it in my ham group and two other forums. Well, I forgot to say thanks for your work! Which greatly helped me. Thank you & 73 from Saint Louis -k0mov
That sure is a familiar sound from Australia. Back in the 60's and 70's these LDR switched TX's on 27.240 would be placed on the top of gum trees ect. Old transformer wire as an antenna, way up on a tree on a hill gave them quite a range. These days those 27 mhz frequencies are dead and you are lucky to hear a soul.
I have done some experimenting with different crystal oscillator configurations to see if I can get them to do this with success. The series resistor and electrolytic capacitor that goes to ground on this very rudimentary circuit is loaded by the base emitter junction of the transistor until the capacitor discharges and the voltage drops sufficiently until the circuit drops out of oscillation.
So noting this I tried the series capacitor and resistor on other circuits and got them to do it.
The trick is to avoid loading the RF impedances of the circuit so you don't dampen it's ability to oscillate at RF frequencies and completely kill it.
In fact I got the circuit for an old realistic 27mhz walkie talkie and applied the principle to it successfully.
It's quite useful to know if you want to make a power efficient beacon as if the following stages are class C, the power draw is almost zero between pulses
Great chirping sound, could be off the soundtrack of a 70s Bond movie! Also, it proves the Envelope Theorem... circuits drawn on the back of an envelope are more likely to work 8^)
I built this and it worked first time. Only exception is for 27mhz I ended up having to use a 60pf capacitor in the LC circuit and my inductor coil is 9 turns of 20awg wire at 11mm length.
Thanks again Peter. A great little piece of test gear, well described and demonstrated. Cheers Mark VK3PDG
An elegant solution, thanks for sharing.
Nifty project Peter, I could see it configured to only work at night making it an even more challenging to "fox hunt" :D
I built one on 49.845 MHz, got the crystal and most parts from an old baby monitor set
Grettings, and Good job
Very good job. Congratulations for your effort! Cheers from Brazil (PY2NJ)!
great job... do you have idea purpose for freq 144mhz or 430mhz ?
Hi vk3ye. Great video. I know you posted this quite a few years ago but I have a few questions if you wouldn't mind.
1. Does the LC tank circuit need to be adjusted to match the crystal you use?
2. In the video I see you mention moving the capacitors to the ground rail? What was the though behind this?
3. For the pulsing. Are you relying on the fact that with the 270k resistor the voltage drop puts the base of the transistor at a level below the VBE(on) value of the transistor and that after the cap charges it will then pulse?
Thanks
Interesting project, congratulations. Do you know how can I change the circuit in a way to produce CW (not FM) and insert PIC (call sign recorded) to make a legal propagation beacon? 73!
It's already CW. Just remove the pulsing feature. You should be able to key it by applying keyed DC to the base via the 270k resistor, interrupting the emitter circuit or swiching the collector supply on and off. Be prepared for chirp though unless you add a buffer and key that.
See My Transmitter 1.5v and 1Kilometer Range
👉ua-cam.com/video/gcB-WtNEFCQ/v-deo.html
If I used the original circuit (compensated for frequency), could I get it oscillating in the beacon segment of the 6 meter band (or close) with a 16.67mhz crystal in its third overtone like in the newsletter?
It should work
Nice circuit.
becon mean ! carrier frequency without modulation ?
Hello. Can a beacon like this be made for operation on 40,66 - 40,70 mhz without use of a rare quartz oscillator? This band is allowed for use in my area and has power limit of 1 watt. Or better can a beacon like this operate in a 149,95 - 150,0625 band? It is limited here by 25 mw only but can be received with two meter HAM tranciever which is easier to get than a 40 mhz tranciever.
Checked the FCC and it looks perfectly fine for anyone in the United States
Hi vk3ye! I Follow your videos, and I'm trying to repeat some of your experiments, but my circuits are not even oscilating. I suspect of the wire I'm using for making the coils, I guess it's no thick enough(22AWG). The other problem seems that I trying at a protoboard. How thick are the wires you are using for makig coils? Do you think it's still possible to make FM transmitters in a protoboard?
I would use wire about 0.5 mm diameter (not critical). Protoboard with strips introduces capacitance which isn't helpful for VHF circuitry. Open air construction but with short connections may be better. Or on a PC board using continuous copper as a ground plane - again with short connections.
Great job. Thank you
is it possible to use crystal of frequency range between 88 to 108 so can be listen using digital fm Receiver ?
Custom crystals are usually very expensive but you may be able to multiply up from a cheaper lower frequency crystal.
@@vk3yehow multiply ?
@@omsingharjit Basically an RF amplifier circuit with tuned circuits to pick off the harmonic. If none of this means anything to you, buy a good radio textbook and study basics of circuits for 12 months. Or just buy an FM transmitter kit or made up unit. The Talking Electronics website can help you understand this but you'll need more if you want to start designing circuits.
@@vk3ye yes i am beginner in HF RF but i can understand , that after amplification we will get 2 and 3rd so forth harmonic in higher frequency and by using band pass filter and amplifier we can get that higer frequency Right !
I asked because there's also Two Frequency mixing technique to get higher frequency so i asked which one you are talking about .
مرحبا سيدي ممكن اعرف كيف يمكن تعديل موجة FM في جهاز الراديو العادي وجعله يستقبل أعلى من 108 مع خالص تحياتي لك
So Simple and yet so good. Peter I am making a TV yagi just for the fun of it(I know it will probably cost twice as much as one on the shelf). Just something to show the kids that antennas are not just for Ham. Please could you tell me why is it that purchased Yagis like the Hills 14 etc have a folded dipole of around 200MHz but for the same boom length of around 3 meters have a lot more directors fitted on the boom than say a Yagi using accurate calculations for 200MHz like VK5DJ program? Should I just copy the Hills one or follow a proper calculation? You would think if manufacturers could use less aluminium they would. Thanks
I'm guessing it has extra elements (eg log periodic) so it covers a wide frequency range (ie all the channels). A yagi would only be good for 1 or 2 channels.
Thanks Peter. It's not a log periodic but I think you are correct, it's about broad banding.This is the antenna I have as a sample to copy off www.radioparts.com.au/product/00681268/dy14-14-element-vhf-digital-fringe-antenna-signal#.V86CODVGTgw
It's a Yagi but VHF Hi CH 6-12 is about 180MHz to 220MHzas you would know , so it's a lot to ask an antenna.
Argento Goldspier z
i asked so many people that if it's possible to make Rf Spectrum analyser using crt tunner and Arduino ?
i think it's possible , can you built this ?
Can't help sorry.
@@vk3ye tell if its possible ?
Hi vk3ye, I know you posted this video a while back but I had a couple of quick questions I was hoping you could answer.
1. Does the choice of crystal freq effect the values you select for your LC tank circuit?
2,. You mention you wanted the capacitors moved to ground instead of the power rail. What's the thought on this?
3. I think I see how the pulse works. It seems that the BC546 was chosen over other BJTs as it has a relatively low Vbe(on) value and by selecting the 270k resistor the voltage drops brings it below the threshold to turn on until the capacitor can charge? Does that sound right?
Thanks for posting this great learning tool.
Hi CG: 1. Yes you will need to change the LC tank circuit with the crystal. 2, 3. Unfortunately I can't answer as I've moved onto other projects. 73, Peter
Could I use a 2n2222 as place of the bc548?
Yes
@@vk3ye Ok thank you
73, DE KA4SEY
ooof thank god now i can pop them out like flys and drop em all around town because i have a big bag of them sitting around in my shed.
After eliminating the r3 resistor and the inductor; would it be possible to connect a keyer between the transistor's base and battery's ground?
I can't find an R3 resistor - the diagram at 1:26 only has R1 & R2.
oh, sorry, I meant R2 :)
Haven't tried it but I'd be inclined to short circuit the 3u3 capacitor and put the key in the emitter lead with a 0.1uF capacitor across it. That does however require a reliable oscillator that starts up instantly.
Where would I find out more about similar frequencies for these types of experiments? VK6OP.
ACMA website. Or search for 'low interference potential devices class licence'
much appreciated Peter, thankyou.
Mera Transmitter dekhiye in Hindi 1.5v and 1Kilometer Range
👉ua-cam.com/video/gcB-WtNEFCQ/v-deo.html
great! .....How long does the battery last?
A pretty long time.
Thanks
But how does it work though???
Here's a pdf of the project
docs.google.com/uc?export=download&id=1w0n6MBUHw1RtzepFIFAacoQiMndKLH3T
where in Australia can you buy 36.864 MHz crystal
Maybe Rockby? Haven't checked lately though.
just use a 27 mhz one from a toy RC car, it works too.
Out of curiosity, but what could one of these things be used for?
Fun! People might modify it for stuff like animal tracking.
@@vk3ye ahh.
I almost wonder if it'd be practical to shrink it down as much as possible and use a super capacitor and some solar cells, about how much power does one of these things use?
BRAVOOO
Great video as always - Now I know what to do with all the spare crystals I have. :) 73 de ZS1CDG
Make one for every crystal you have and have an absolute electromagnetic nightmare! Run them all simultaneously into a vertical antenna to get some nice mixing products. What an excellent idea!
Hi Peter, thanks for this video upload.
Despite the circuit simplicity, after a few tries/changes I finally
got my example to work!
Here's a write up.....
www.vk6fh.com/vk6fh/beacon simple circuit.htm
cheers Frank
Thanks Frank - enjoyed reading about your experiences.
I have done many builds of this beacon and have figured out several different things each build. I used both websites and tips from you guys. Maybe you could publish some of my work to your website vk6fh? Just trying to spread knowledge to others. -k0mov
@@derek7017 Hi Derek I'm sure your variations on the beacon design would interest others. Is the information available anywhere in the public domain, Utube, website etc or direct to vk 6 f h at westnet dot com dot au no spaces cheers
FRANK HUGHES I have several videos (need to edit) and a dozen circuit variations etc that I need to compile into a website or UA-cam. I mentioned your website as it’s quite popular over here. I’ve heard about it in my ham group and two other forums. Well, I forgot to say thanks for your work! Which greatly helped me. Thank you & 73 from Saint Louis -k0mov
@@derek7017 Thanks Derek, good luck with your experiments! cheers Frank