Build a CB Radio Crystal set
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- Опубліковано 9 бер 2014
- here's an unusual crystal radio build, basically a shortwave set tuned to 8 to 30 MHZ using just 5 turns for the tuning coil and 3 turns for the antenna coil.and connected to grounded Altoids box with diode and phone jack. a ground connection is optional but tends to hum more try it with a house stereo or guitar amp or even a unpowered crystal earphone if the signal is strong enough. Try it out
during skip, or with a friend and CB rig.
Check out my CB crystal radio with a groovy retro 70's faceplate and PL259 connector attached to a 40 foot RG 58 coax cable and a Home made SWR tuned vertical 1/2 wave dipole in a ground plane configuration, very successful when shooting skip with my regular Galaxy CB. • CB Radio Crystal set w... - Наука та технологія
Good job guy. Anyone can spend money and buy a receiver and lots of other guys can spend lots of money buying many parts to build a complex receiver. But you've demonstrated how well and selective such a simple circuit functions. It looks like fun too.
Amazing, I too had CB in the 70's and I built crystal radio's, I guess I just never thought 27mhz would work or I just never connected the dots.. Great to hear the banter, sounds the same as it did before it all went feral. Great stuff old as it is.
Well, now you know. VHF crystal radio variations do exist as well. Modified versions of crystal sets can receive FM even.
Incredible, especially seeing how little parts the are. I always love simple and reliable.
Yes Antron
1/4 wave stainless steel whip
Great video, This is what got me started in RF technology in 1970, I built this in 1971, same exact thing from scrap parts....I retired a Broadcast Engineer and designer. When Satellites and cell phones are gone, We will be right back where we started! I have everything to build anything in my storage.. Thanks-
The cell towers can't come down soon enough.
Super cool project - Now on the hunt to build one. Thanks for sharing!
Great job man !!!!!! I listen that big power station on channel six in the Bahia estate when the propagation is good.....greats from Brazil
I just made a cool addition to my CB xtal set, an optional 12V red LED lamp connected to the audio plug. I just hook up a simple 4 foot wire antenna When I transmit on my regular CB the LED lights up real bright due to the voltages generated in the XTAL set by My strong CB signal transmission . I will be making a new vid on it soon.
That was a crazy background music
I used to fetch in Emerly Moore TV transmisions on a crystal set in 80s so you could pick up anything with right coil and ariel
That's beautiful! I love it!
You need a big knob on that variable capacitor. I wound some house wire around a D cell, 5 turns. I measured the inductance and it was just under 1 microhenry. I calculated that if you put a 47 pF NPO or C0G ceramic disc capacitor in series with the variable capacitor, it will spread the CB band out to the middle of the variable capacitor and make it easier to tune.
Also, put a .01 uF from the hot to ground pin of the audio jack. It will help reduce the hum sensitivity.
Simple, yet ingenious!
muito legaul, bacana mesmo!
Very cool indeed!!
I 'll try to build my own cb radio following the instructions you give here.
soo great, so few of the population is into any electronics, love it
They love to use the technology to play games, watch porn, and screech at eachother, but nobody cares about learning how it works.
As we all know since 2017 the frequencies band conditions above 10 MHZ have been pretty crappy due to the present solar minimum. 2018 was the worst year ever ,especially from September to February signals from the entire shortwave spectrum were a "no show, At present conditions have improved on the lower bands It may be another few years before I can use my CB crystal set again let alone my Galaxy DX959 for shooting skip.
2021 exact opposite, but raining all day for field day. No lightening tho.
The gauge number of turns and spacing makes a difference for it to work right.
I like your make shift screw driver (@ 7:01) ;-) ... LOL // Keep the handle - exchange the worn blade with a new one in a very solid way.
I'm very impressed. Quite creative. Good job!
I'm definitely going to try and make one of these receivers for the CB radio and it would come in real handy for me if I just want to listen to channel 19 on the UK 40 channels and hopefully mine will work the same as yours and I'm really interested in electronics because I'm a Amateur Radio Operator and I have been on it for the last 21 years and I have been on the CB radio for around 28 years now and it's all been really good fun and I have never looked back since I passed the test back in 2001 and I was only 19 when I passed the course and I was so happy when I passed the exam and I got the yellow card from the head tutor and I was very happy. Anyway best 73's for now Stephen M3SNV 73's.
Fun project!
hi, you're pretty good man. I used a 1n60 and picked up my favorite radio station with your same coil.... just 3 bare copper turns exceeding and "adjustable" with a clip-on. I quoted that because the left over wiring kinda effects the tuning too. have a great time! hitting the subscribe on ya :D
Nice. I use to be an avid CBer back in the 70s. I use to make my own antennas and some of my own gear.
hey man ive got an old pinto 70's cb radio of my granpas and really want to get to using it, but ive got no antenna and i need a cheap, indoor solution, i have coax, but not room for a 10m antenna, any help?
First off you are on 11 meters. I use to make my own outdoor antennas, but seeing how you need one for indoors... you can make one but it's a hassle to get one tuned right.
I have used the older version of this one www.rightchannelradios.com/products/firestik-indoor-cb-base-antenna and it worked well but you need to get it as high as you can to get the best range.
+Kriss Femmpaws i could make one outdoors, i just dont have the option of having a 50ft antenna. i have plenty of coax and copper wire, i just need a crude, simple solution to toy around with some old radios.
thanks a lot, and sorry for my lack of knowledge, im just trying to get into it!
I understand, I also understand not wanting to spend a lot of $$$ For an indoor ant. that firestick is not a bad one
+Kriss Femmpaws i have an old cb antenne for a truck, but i would rather use my radios indoors. thanks for the help!
I gotta try this great idea👍😎
40 years later and still no intelligent signals in the 11 meter portion of the HF spectrun.
Nope, ever since the movie "Smokey and the Bandit" hit the theatres, CB turned to crap and hasn't changed much since then. Small wonder the FCC has abandoned policing 27Mhz (which used to be a Ham band until the FCC stole it away from us).
@@lomgshorts3 back in the 70's was the cb dumpster ...idiots took over..
@@garraper And, later the FCC reduced requirements for hams and the idiots moved to 40 meters.....
Looks like I found the elitist hams.
@@lomgshorts3crying over losing 1 channel out of a million 🤔. Yeah, id imagine that that's exactly why ham radio club membership is all but nonexistent these days. Even at a no code level, nobody wants to get into a hobby where everyone in it is an elitist cry baby. 😒
Pretty cool!!
wow back to the basics, I still like my rci 2900 10m and 11m mod...
This time I used bare copper common house wire. About. 10 turns on a 7/8 deep socket with the tuner at the center tap down and a 9v battery powered fender mini deluxe guitar amp. Tends to wanna pick up FM BCB but with the capacitor. Half shut was getting skip talk of a bunch of truckers telling each other to shut up and that one another radio is too loud.
This very cool and fun.
Thanks for this. So if I add more turns to the wire I will have better chance of picking up more stations?
For what it's worth, the diode is NOT an IN34, but rather a 1N34 (one N34). Easy mistake. I built my first XTAL radio in the mid '50s using a piece of Galena and a cat-whisker and then 1N34 diodes. Later I moved on to building regenerative receivers and superhetdrodynes. Of all the gear I build over the years nothing compared to the first sounds emanating from my Brandes headset connected to the XTAL radio!
Nice video and thanks for taking the time to share it!
73, de Mick WB4LSS
I used a rusty nail and a sharp pin, same with a heavily corroded penny in place of a diode, trying to oxidize a stainless razor blade and carbon rod, not yet.
@@bmcgraw3840 I used one of my Dad's old Gillette Blue Blades that had begun to rust. That corrosion was enough to make a semiconductor along with the pencil lead.
Nice project
Very nice I also thought Crystal radios were only Am radio type radios. That would be a nice project for anyone to build.
It's still amplitude modulation, just on a higher frequency
@@willyb7353 I did not think of that very true. I like the idea you made one in the CB radio band great video.
And how would you add a momentary latching mic?
This is great haha def gonna build one but try n get a momentary mic add on built into it
That's cool. I wonder if you have every built a basic beat frequency oscillator for sideband?
That's really cool
I actually made one of these with a diode from a broken old 23 channel cb!
When I was a kid I wanted to build a "Crystal Television." It would be a very low power standard TV with a power supply that derived energy from the RF TV signal. Having a degree in electronics I think this is doable if you live close enough to the transmission tower.
My crystal radio now has a pair 12 volt LED lights running off a 4 foot vertical wire antenna ,they do light up brightly when I key up on my CB, Not a TV screen by any means but a crystal radio can light up a simple LED if the transmitting antenna is nearby
l c d tv hi hi@@rEdf196
Where did you get this information on how to build? I want to make one of the VHF high band and maybe the 50 Mhz?
With an old ham radio receiver tuned to a single sideband signal I used to hold a pocket radio next to the receiver and just adjust the tuning until I could hear audio clearly. Has to be the old manual tuning type radio.
yes small wire and tuning caps
Vid is solid!!!
Well done
With a rewound coil can it slip into the ten meter ham band?with any reasonable results?
A very kool video,thanks for putting it togeather for us
Cool dude!
Yes in issue in my area.
Fascinating Radio 101
I made 2 crystal radios (with junk)- my 1st was magnet wire(100 turns) on a small cardboard tube, w/ a var. cap. from another radio, connected to a diode and amp.
my 2nd crystal radio is a SW receiver, w/ the same magnet wire (85 turns) on 2 popcicle sticks (glued together, trimmed to size), connected to a diode, and amp. my SW radio can get N.carolina, Nashville, TN, Havana cuba, and sometimes, China and India! very easy build, and interesting, esp. after 11pm CST!
I didn't follow the schematics, just put components together, w/ a good ground and ant.connection, and they work!
I built a pair of SW xtal sets 22 turns tapped with painted colored tuning dials tuned at 1.8 - 30 MHZ they were intended for HAARP reception recordings but HAARP was shut down before they were complete but I still got lots of HAARP recordings with other xtal sets and conventional SW radios. I will make a video of my crystal sets when SW conditions are good
rEdf196 good luck!
what kind of antenna are you using?
I've straightened 2 wire hangers, connected them to a balun transformer, and screwed that into 2 yardsticks, which I screwed into my wall. this works fine for both my digital tv and Xtal radios.
Just a 70 foot longwire about 12 to 30 feet off the ground, A shorter antenna 20ft long might still work especially in vertical position.for CB. I would hang on to those wire coat hangers their fast becoming old relics since they been overtaken by the plastic revolution..Sooner Science Nerd
good ideas!
i'm in the process of making a smaller SW radio from a small radio (var. capacitor, earphone plug-in,tuning dial, screws).
seems like my diodes are not working right, or my connections are not good.
I did wind a smaller diameter 100-turn coil, and that works good. i'll keep trying diff. things with it.
the wire coat hangers are great for elec. projects, esp. with the plastic insulation!
good luck, and cheers!
Works pretty well if you consider that most CBers are using FM. Was a very active CBer myself here in Germany in the 80s so this brought back some sweet memories :)
I like how quick and dirty your build is :D
Greetings, raBit.
Most CB in North America is AM.
A crystal police signal detector/radio would be cool too!!!!
More like a crystal P-25 digital decrypting detector.
You only hear near cb station and high output with power amplier cb radio station.
Ch 6 will power that good,,
Excellent video . I have salvaged a few "old time" variable capacitors and they are getting hard to find . Is there a place that you could recommend to order variable capacitors and potentiometers ? . Thanks so much for a seriously interesting video .
+Master Tracker You could try checking out Peeble's Crystal radio website or other sites dedicated to the crystal radio hobby. and check for links to electronic parts like variable capacitors , even the hard to find metal old school types can be bought online. Antique Electronics Supply might be a good site to check out as well. I myself have 10 metal vintage 365 pf variable capacitors I have salvaged and collected since I was a kid. but yeah,old school metal variable capacitors are getting harder to find for sure.
would get less noise if you added a counter poise ground to the antenna
That is cool.
Do you need the old school oscalator to make it work?
Is it possible to clean the signals up at all?
Love the background music anyone know who it is pls thanks
I just want to learn hot to build a clip on led light that activates when you hit the mic. Nothing fancy. Just a diy little light for my rig. Can anyone tell me how?
well done very clever!
+Andy Howden years ago I discovered I by accident while tinkering with the coils using bare 14 gauge wire tapping at different turns I stumbled onto some CB radio skip which blew me away. I also made other multi band crystal radios which also tune to CB. Recently. I added a PL259 connector and connected to coax fed vertical ground plane CB antenna and it worked better than a random length longwire antenna.
@@rEdf196 Any chance on getting dimensions and turns of coil? Range of vari capacitor?
on what frequency will it work
How about a list of parts. What value is the tuning coil? How is it powered?
More info is needed
I added a similar comment below. I don't own guitar amps either.
VERY INTERESTING DESIGN WITH MINIMAL PARTS. AMAZING,AND BRILLIANT ! THIS IS BEAUTIFUL EXPERIMENTATION EXPRESSED IN FUNCTIONING HARDWARE. MARCONI AND TESLA WOULD BE PROUD THE RADIO ITSELF REQUIRES NO BATTERIES A NICE CHOICE OF OPTIONAL AUDIO AMPLIFIER CHIPS WOULD BE THE TDA7052 1.1W OUTPUT. AND IT WOULD WORK NICELY IF YOU DO NOT HAPPEN TO HAVE A GUITAR AMPLIFIER LYING AROUND. A TERRIFIC PROJECT FOR THE 10 METER BAND, IT WOULD APPEAR. - N8DLI
It is ok to cheat-find an am pocket radio, hook up a ground only lead to the earphone jack, snake the lead through the double coil, or into tin, whichever does not shift the frequency, but some are more barebones than that. Line up the internal ferrite antenna with that double coil, and tune super slow on the am pocket radio, once you have already got a loud donald duck sidebander locked in on the cb pedal, and all the sudden an autotune-like cloud comes over your cb pedal, and the pitch phases up or down in pitch to make a nice clear voice. It will drive you mad, because it is like expecting an .ooo5 degree travel, on a plastic, keyed to screwed plastic
coupling, with twice that in slop. Good luck
What is that sucking noise when you complete the project?
Long time ago i did something similar and got up to band I,( first VHF band ) and was able to hear video buzz that was modulated in AM. on the PAL B tv system in Australia,also play alot on my Crystal set listening to shortwave, ,and on that tiny set and a good long maybe over 25 meter random antenna , i was able to listen to Europe,very faint but you could listen to it,but you did needed a lot of patients!. and no amp connected! .So much for people saying that on a crystal set you can only get local Medium wave stations.
This is just a simple version of other SW Xtal sets I made with a range of 1.7 to 30 MHZ using a tapped 22 turns coil and 4 turns on antenna coil tapped on each turn. on a 1 1/2 PVC pipe with colored tuning dials like the classic old time radios. They were used to track HAARP signals which constantly changed frequencies between 2.7 to 10 MHZ The sound quality is very good. Deep bass and low noise they works good for CB too I have heard stations using just an ear phone mostly STANAGs HAARP Radio Havana and my own CB radio I also want to try and make an FM crystal radio soon.
Nice! theres an FM crystal set i have seen somewere in the web
Sydneywave Smith
Don't think so, for one minute..
A crystal or diode can only detect changes in amplitude (Hence A.M. Amplitude Modulation)
Freq Mod is more involved than a diode detector can handle...MUCH MORE.
If the tuned circuit were actually arranged to tune in on a VHF FM station, you
wouldn't hear a thing or even know that you were there because the sound is in frequency modulation. The Amplitude doesn't vary, so the diode (or Crystal) would not detect the changes in freq. which carry the speech and music.
If you are choked off by my remarks, don't cuss ME. I only tell it like it is.
You could of course, spend many years studying Radio Theory and then come back to argue with me but by that time, you would have realised that there was nothing to argue about.
Good luck..
Olde Englande.
***** Look up slope detection. solomonsmusic.net/FM_CrystalRadio.html
Bob Rexford
Why SHOULD I look it up when unlike you, I know exactly what it is, have used it for years as a means of FM demodulation in the absence of a genuine FM demodulator?
If you had a trace of technical knowledge, I could explain to you why your insistence that it WILL work in this very simple circuit, is pointless but if you could understand my explanation, you would not have revealed how little you know, in the first place.
That beautifully produced video, carries no sensible info. whatsoever..I'm baffled why anybody would spend so much time and effort when it simply CANNOT WORK.
There is inadequate means of separating adjacent FM stations let alone provide ANY slope detection.
If you're so stupidly sure, just explain to me
exactly just WHAT slope detection is and where does that circuit supply the necessary conditions for that process? What ARE those required conditions? Whereabouts on the Frequency Modulated signal is it necessary to tune to demodulate anything? If it worked, what would be demodulated and what would you do with the demodulated results.
What deviation is used on Broadcast stations as opposed to communication station which use narrow band frequency mod?
Your anticipated silence will indicate how little you know.
I promise you that I'm not talking Martian, Venusian or Swahili although it may look like it you.
It's no use trying to win an argument simply by pointing ME at site of total rubbish as proof of what YOU say. Just because you've been suckered in by the standard, arrogant Internet Guru nonsense, that doesn't make it factual.
It doesn't work that way.
It may not seem to you to be the load of bollocks that it is but you clearly live your shallow and meaningless life, lurching from one load of total bollocks to the next load of total bollocks.
That is why you and your clever-devil ilk so easily expose your crass stupidity and ignorance.
Final simple question "Where is the so-called slope and how steep?"
Untrained know-alls make me wanna PUKE.
desculpe, no video tem o esquema, muito obrigado
What are the parts and where can i find them?
What about putting the whole circuit in a metal container (of course antenna would go through some hole like cables here)? Would it also reduce the noise from AC mains, or does it work only when there's screen between LC resonator and diode?
I tried it years ago with a lower frequency shortwave xtal set but found out the coil doesn't work at all being enclosed in metal but tuning capacitor and diode seem to work fine, but the coil likes to be in the open.
Very cool project, but if there is an amplifier in the circuit the term crystal set is not applicable. At least, it used to apply to pasdive circuits only. Ty for posting.
is fun project is completed
This is a simple but very interesting project... Can i ask you the capacity of the variable capacitor? It is 365pF?
Thanks for your reply.
Just by looking at the cap with the Mark 1 eyeball, it seems to be a 365pf.
Anyone else have an opinion?
yup! thats it! sometimes they might be 400pf they will work!
I have the exact same cap. Yes it is 365pf.
is this good for mhz?
neat project, kinda noisey though, would like to see one made to pick up cellphone conversations since they block out that feature on a police scanner,
THAT would be a challenge: cell phones run 850 Mhz or above...plus, the phone itself puts out very little radiated energy.
Plus - the signal is not analog; crystal sets are impressive, but not a device that will get this job done.
Plus ( ;-) ) the signals are blocked out for a [legal] reason.
No joy there.
Add a Parts List to the description. Not everyone owns a guitar amp. I played percussion. A simple speaker design could work. Does wire gauge size matter? I appreciate what you did. You could have reached a broader range of viewers new to HF/VHF (RF) communications here.
I have the same mixer as you! lol
why LOL ?? what's funny about him having the same mixer ??
You are awesome
CAN I USE A DIY "audio amp"? what kinds of amps could be conencted to this?
try lm386
Is there a paper with the schematic and component information I can download? Your video is vary vague on the values of the parts.
Nice.
How much the value of the variable capacitor?
365 pf
How long was your receiver antenna wire, and how far was the cb transmitter from it?
Next room
Awesome project....lol whats w the tunes tho?
I wish you would show exactly where you hooked up on the opposite side of the tuning capacitor I can read a schematic but you could have shown that on camera a little better do you use both of the back screws pointing toward the can? . Or do you just hook it on to one of the screws on the tuner, capacitor? I can't see it you never show it because you never point the camera toward it after it's finished I'll just have to figure it out with the schematic the two screws on the other side you don't use because I can see that I can see where all of the grounds go I can see where the antenna goes but I cannot see if you use Both screw terminals or one
it is a 1n34 not a in34 diode, you should try and make a loop antenna for it so no ground needed...
JUST MAKE SURE IT IS A "GERMANIUM DIODE" THEY ARE EASY TO FIND ON E-BAY. THAT IS RIGHT, IT IS A 1N34 GERMANIUM DIODE, NOT in34.
Had he had experience with semiconductors he wouldn't have made that error. The "1" refers to the number of junctions of the device. For instance, a 2N2222 is a two junction device of a common transistor. The 1N34 he shows is the common version used for communications gear. I have seen another version of it that looks radically different, it's a ceramic bead with short pin on both ends, and one of the pins will have a removable cap which could be put on either end. It's used in radar equipment.
@@lochinvar00465
Yes that would be a microwave or hot carrier diode and some of those can be quite a bit more sensitive than a 1N34, and yes it's quite obvious that this guy has very little knowledge of electronics at all, I'm sure that is not his design, he kept referring to the tuning cap frame a negative and the stater plates as the positive, last I checked RF was AC and at that frequency changes polarity 27,185,000 times per second at least on channel 19. It drives me crazy when someone like that, puts up a video and tries to teach others how to do something like this and don't know how, referring to AC components, be it line power audio or RF as having + & - is just messed up because you end up teaching others wrong. Infact he himself just may be one of those who was taught Wrong by someone else who didn't know.
gota do it now!
for this project, would u please let's know about the length of antenna? thx.
468 dived by the frequency
how to make germanium diode ?
you don't, you buy them, they are cheap
6:04: And that, boys and girls, is a soldering _gun!_
Others have asked but I haven't seen an answer from the poster of the video. .. perhaps it's waaayyy down in the comments, but what is the value of the variable capacitor? I have plenty of the 365pF variety on hand and three 200pF mini mylar dielectrics. The coil would be about 1.3" diameter using a d-cell to wind. To get the highest Q from the air core I suppose it should be about 1.3" long. 5 turns covering 1.3" and being 1.3" in diameter would yield only about .56uH. The description mentions that the set covers 8MHz to 30MHz (the entire CB Band would be covered by 26 to 28MHz). Anyway, to cover 8MHz to 30MHz with a .56uH coil would require a capacitance range of 50pF to 707pF including stray capacitance. A dual gang 365pF air variable with both sections paralleled would suffice. I'm just curious as to the actual values used here in this video. It's also possible that my calculations are off. A 365pF varicap should allow it to cover 11MHz to 30MHz. If stray capacitance is 50pF, the it would probably cover about 10.4MHz to 30MHz. Note that my calculations may be wrong so don't take them at face value without checking them. I'm going to attempt to assemble one of these :-)
+Robert Turner The Value of the variable capacitor I used is ,I would guess to be a typical AM type 365 pf single gang. A lower pf value might work too, it would not tune as low in frequency but would be easier to tune in CB, that being said, the selectivity would be nonexistent the entire CB band and the outer bands too will likely come in just as strong but usually channel 6 comes in due to the big power of their booted transmitters.
+rEdf196 cool. I've been sitting here winding coils for the am band and experimenting. Then I saw your video and thought about putting one of those together, but I've got to work in a few hours so I'll try it later. I actually have a 365pF variable capacitor that I just made from a veggie can...
It's not "I"n34 -- it's 1N34 or 1N34A
Also, you should mention that the wire is 16 Gauge solid, and not stranded.
the gauge amount of turns and spacing makes a difference for it to work right.
Some beginners don't know the difference. They will someday if they persist in learning radio electronics. I teach the Radio merit badge to Boy Scouts, most do not know the difference, either.
very easy build ..but is it a AM set or will it put up FM signals 26.96.5 to 27.99.1
electron0002 Tt can receive FM by using "slope tuning".....tuning to one side of a FM signal will enable a AM receiver to receive FM. There are FM broadcast band crystal sets that work on this principal.
build one for 2 meter ham, i'[d like to see how one for that band is assembled. probably very complicated, but would be interesting to see one built for 2 meters DX AM though lol. i have a couple of older cbs i could also get the rocks out of too lolk. be VERY interesting to try i know that much
You would need a slope detector circuit (some extra capacitors and resistors) for 2 meter ham in addition to different coils if you wanted to detect the FM and much higher frequency. CB works well as a Crystal set because it is AM.
At 11:15 that's some stereotypical CB shit right there
Merci !!!
12 gauge is used for normal working in houses... 16 no..
Would this work using say 20 gauge solid wire
Yes 20 gauge or thinner will work just as well as 14 gauge house wire ,but of course with thinner wire you will need to wind it around a either a 1 1/2" PVC pipe or even a empty toilet paper roll will work good too.but dont go wider than 1 1/2" peak frequencies range tends to drop sharply with wider coils.... Oh ,by the way are you the famous John Arthur the founder of the now defunct A.C.E The Association of Clandestine radio Enthusiasts? A pirate radio Monthly magazine which operated from 1982 to 2005 I was a subscriber to that mag from 1994 to 98 back in my hardcore pirate radio QSL collecting days.
doe this project require a power source?
The only power source is the long wire antenna as with all other crystal radios with the exception of a powered guitar amp or stereo amp to hear the mostly weak CB signals but sometimes with very strong signals it is possible to hear noise using an unpowered crystal earphone or possibly some vintage 2000 ohm headphones.
1N34A diode is more sensitive.
gostaria do esquema num desenho, e qual faixa que ele sintoniza
Ele colocou um desenho do esquema no final e aparentemente, ele sintonizou a banda de 11 metros.
clever
i build one but why do pick up am radio stations no where near 27-28 mhz
diode want work with any sensativity at 27mhz , hes coning i tested diodes and never heard a squeek even plugged into my tower with big antenas . its a con
You are picking up what is called "image frequencies" from strong AM radio stations nearby. This happens when you do not build an antenna tuner to go with your crystal radio. The tuner acts like a "bandpass filter" to your crystal set. Several designs are available from the Crystal Set Society along with much better crystal radio designs. Give them a try!