At the age of nearly 74 I need to have another look at ferrite rods. Back in the 60s when I was new to radio experimentation, a long wire out of doors and a ground to the house plumbing seemed a 'must'. Some years back, using a kit, I was amazed at the reception from a 2-transistor circuit using a ferrite rod but never followed up the idea. If these things are that good, it will save trying to climb trees etc which in my more mature condition might not be a good idea! Thanks for the inspiration and interesting presentation. Cheers!
I really find this interesting! Put a huge AM loop antenna next to your ferrite rod and you will be amazed what comes in! Perhaps you can do more experimenting with rods, loops, and tuners. Keep up the great work!!!
Thanks for your informative videos. Your wild angry image at the beginning this one never fails to make me laugh, likely because of its contrast to your otherwise level headed demeanor. It took me by surprise. Very funny stuff!
In the last couple of years I've learned a little bit about types 43, 52, and 61 circular ferrite cores for making transformers for 1/2 wavelength transmitting antennas. The beauty of such "EFHW" is that it works all harmonics and the main ones will require little to no tuning/matching once the fundamental frequency is set. But of course now I do believe I'd like to build a ferrite rod antenna for 630m, in case activity there picks up (I won't build the TX antenna and other necessaries until I can actually hear some activity). Thanks for these instructional videos on them. 73
A lot of years ago I put a 60 foor long wire on my high dollar stereo. I tuned it to AM stations and alligator clipped a ham radio band VFO to the AM radio antenna. I had a 100 watt short wave listening radio by tuning the variable capacitor on the VFO..
I am planning on building SolderSmokes Direct Conversion Receiver that Bill, Pete, & others came up with for a high school project. But, I was given a kid's crystal set recently and I aim to build it for indoor antenna use & don't think it includes in its schematic a resistor or capacitor across where the headphones connect, so I grabbed as a screen shot your schematic that included the coil wound on a ferrite rod. Boy, I had trouble getting my phone to grab the screenshot, but did manage. I also partially watched your video last night where you augment the crystal set with a tuned circuit using a transistor which I also want to give a go. Likely, I will try this additional scheme added to the crystal set prior to starting the direct conversion receiver. Why, one might ask. Well by education I am a theorectical math guy thus the deeper an understanding the better & I suspect doing both gives one a deeper understanding.
Hello! Good video! It`s very important to have an air gap between winds: for example when a diameter of wire is 0.5mm - the step can be 1mm or more. The ideal case - a basket winding. I made in past a coil from ethernet cable (one wire from twisted pair). Outer diameter was 80mm, length was roughly 250mm. The capacitor wasn`t exists. I measured wideband of this open LC circuit - and calculated a Quality factor. It was 900!. THe resonance frequency was 3100KHz.
It seems we harvested a D-cell battery center rod in boy scouts in 1963 and slid it in/out of a winding around a correct sized cardboard tube, for tuning.. ? Short wire antenna out side my bedroom window.
5:05 Permeability is the property of ferromagnetic material's ability to concentrate magnetic lines of flux. The higher the "Al" the higher the inductance per unit of number of turns over length
I am new at this stuff, and i have really benefitted from your video series, but i have some problem with my signal amplifier, and impedance matching. I didnt see any, but have you made a video where you go through some of that?
It is very popular to stay with 50 Ohms when you design RF circuits. This is by convention more than reality of what the world or real devices really look like, impedance wise. With conventional devices used in conventional grounded cathode, emitter or source, the impedance the device works best with varies from a few hundred ohms to a few thousand ohms. So we almost always have to do impedance matching. So with a tuned circuit which has a very high impedance, it may work very well into an FET or Tube grid. But with a bipolar transistor or a diode detector, we almost always have to transform down. Thus we tap the coil (ferrite or air wound) or use an RF transformer in the form of another winding with perhaps 1/4 to 1/10th the number of turns.
How about an Rx antenna for 630 and 2200 meter bands? Does one rod type work better down lower than the others--seems all the specs talk about highest frequencies, rather than the lowest ones. 136kHz and 472kHz are in the new ham lowest bands. Maybe use a magnetic loop for TX.
Nice ! Give a tray to a AM demodulation made with on transistor (Ge) without biasing and 100k in collector ... sorry I cant post or attach a schematic but I think you know very well. All the best regards to you ! 73 !
How about using a MOSFET source follower as an impedance-matching device between the LC tuned circuit and the detector? A MOSFET has an extremely high input impedance, so it can be connected across the entire LC circuit without loading it, and the full voltage across the LC circuit will be available across the source resistor, to drive the detector.
After I finished stripping all 175 strands of the Litz wire, 😊 I wrapped a piece of double sided sticky tape around the ferrite rod to allow the Litz wire to adhere and remain tight.
@@MIKROWAVE1 My cat George wasn't very helpful when I had 50 ft. of wire laid on the floor. Nor, was he helpful when he laid across my forearm when I was trying to solder. His 20# could immobilize my arm.
I have some interesting data for you is that you can find about how to wind honeycomb coils and diamond weave coils and basket weave coils by looking in the 1920's magazine Popular radio and Radio news and maybe Shortwave craft. Also I do not know if the website is still around but there is a website called Playthings of the past. You might want to check it out sometime.
Stalno pratim tvoj kanal.od mladosti se bavim iz hobija ovim baš što i ti radiš. Pravio sam dosta sitnih stvarčica. Ne znam da li si primetio.zeleo bih da mi odgovoriš. Ako imaš malo vremena pogledaj www Cooking recepti i na tu adresu mi odgovori.to je moja snajka i ona izvrsno barata sa it i pravi razne recepte za jela iz beograda naše. Pozdrav 73 milan.
I just started building my first crystal radio. I got the kit from United nuclear. This video is interesting but too advanced for me. Is there another video that explains these concepts for the absolute beginner? I don't have room in my apartment for a 30-foot antenna. Will these rod antennas work with any crystal radio set? What's the simplest type of antenna I can build if I don't have room for the 30-foot wire?
OK I get it Michael. Find or make a frame out of a couple of 1 X 6 6 ft Center Notched planks and make a big X that sits upright on the floor. Now wind 6 turns of #14 wire around it spaced 1/2 inch between turns and connect a 365 pF Variable Capacitor to tune it. Now wind a single turn as the secondary to feed the diode and bypass cap and headphones. Experiment wit the position and size of the secondary loop. This beast will hear stations.
@@MIKROWAVE1 Thank you for your reply, but I'm so new to this hobby that it's difficult for me to visualize what you are talking about. Is there a book for beginners that you could recommend for me? This is my very first crystal radio set, and I've never built an antenna before, so it's difficult for me to understand how it all fits together.
And higher. Even the 2 dollar 365 pF Variable capacitors are going for over 25 dollars. The prices will vary depending on demand, the material, origin, and length. They can easily be glued with superglue to make longer rods if you wrap them with clear packing tape before winding. Yes a good quality long Type 61 Rod is going to be expensive from a reseller. And all EBay sellers are basically resellers. I like these little guys to get started. www.ebay.com/itm/274726941594?hash=item3ff700739a:g:MJUAAOSwL6la3A8h
Hello I have question I connect my antenna directly to variable capacitor which then goes to diode versus using antenna loop to couple to inductor I noticed on the antenna direct the capacitance increases by 30% I.e. stations on 600 khz and should be at end of dial are now on middle of dial Any comments please
The antenna has significant capacitance to ground and this is on the order of 100 pF. So in effect it is lowering the tuning range of the radio. It is just like you were adding a capacitor across the tuning variable capacitor. The tuning range will decrease as will the selectivity and that is why this is discouraged. It is better to add a real capacitor or add turns to lower tuning range!
@@MIKROWAVE1 thanks sir reply Well I did math coil 283 uH and capacitor 40 to 320 pf so tuning should be 530 khz to 1490 khz and when I connected the aerial to capacitor leg which goes to diode ....600 khz station was in middle of my dial 0 to 100. The standard basic design shows attaching aerial to cap/coil and when I attached aerial/ground to a 10 turn loop and mutually induct thru the coil 600khz was 90 on dial right about where it should be. I've read a lot in past few weeks re crystal radios and never have I've seen someone mention that effect other than damping . I think it worth mentioning since many people start with the basic design I.e. no tuner or loose coupling or mutual inductance or whatever you wish to call it and connect aerial to coil/cap
@@uncleruckus4060 There are so many variable factors involved in even the simplest tuned circuit, when actually connected to antenna and load. Then bring in form material and diameter, proximity effects, diameter and wire spacing and size, and it gets silly to attempt to model or predict exact tuning with any accuracy. So we get in the ballpark and adjust!
@@MIKROWAVE1 That's why I'll try to do I got a recommendation from RU-vid a few weeks ago for crystal radio video And I've been intrigued ever since When I was a kid it was an oatmeal box and some wire Some of these papers I've read online look like they were written for electrical engineers Volkswagen vs Lamborghini 😆 Thanks reply
Have you ever replaced a ferrite antenna in a tube radio I going to have to ,the original one shattered ,I bought a new ferrite rod what cheap ,and a roll of magnetic wire,If anyone has done this and has any input I would be greatly appreciate it
Fortunately the easy part is done. The LO coil is designed to track 455 kHz lower than the antenna tuning. So most rods are a simple single winding. A more clever design would have a tapped coil or multiple windings. I hope you have a picture or a manual to see the wind type and position. Otherwise just wind say 60 turns of ordinary enameled wire on and give it a try. If too few turns adding capacitance will bring noise up. Once you find the sweet spot where tracking is good with the trimmers, remove the wire and replace it with the same length of litz wire and secure.
@@nor4277 Ron, Litz wire is a special lay up of many smaller diameter insulated wires inside one jacket and wrapped with a synthetic cloth. It fights the skin effect and makes the Q higher in the coil. Find a plastic or cardboard tube a bit larger than the rod and do all winding experimentation on it. Slip it onto the rod when you want to test. Faster and less chance breaking the rod!
Please don't use the term "tuning the antenna" what you are doing is matching the radio to the lead in of the antenna... You "tune" the antenna when you cut it to the frequency that you are going to use it for.
Technically you are absolutely correct. We do use a lot of technically incorrect words in radio. For instance Antenna Tuners used to be called Matchboxes or Matchits.
