Eric's "Crystal Radio Initiative" Challenge

[Aaron]

Talk to T-Rex

I would like T-Rex to join the conversation if he has any suggestions?

I'll ask him. Are you on skype as well? Email me your skype id and I'll see if I can get you on a skype call with Eric before he leaves.

[LeeBob84]

Looking into what to purchase to wind the secondary with and am really getting confused. I am looking for a 6 AWG size conductor. 1/8th inch copper tubing and 6 AWG welding wire cost about the same. The welding wire is made of many small conductors so should be good for skin effect. I saw some 6 AWG Litz wire on Ebay made of magnet wire but that guy didnt have a long enough length. Might look into a spool of that. A cheap solution is 1/8th inch wide copper tape. Lots of surface area low mass???. And the there is the suggested teflon insulated coax. What would i be looking for in coax that has an outer conductor the right size??? Any suggestions and or pros and cons of each choice would be much appreciated. Today I got an antenna 29 feet into the air and am messing with a standard crystal radio.


oh and I am 15.87 miles away from my thousand watt station with the rift a little closer to me as per attachment on post #38..........and yes have done the PVC pipe trick for trees out here in the desert I will do that for my ground rods when I get them.

Hey Jeff

Sounds like u have some good ideas for conductors, Only thing I would suggest is to stay away from buying anything for now. The trick I used was to scrounge at the dump and local guys with junk in their yard will sometimes sell u bits and pieces for pennies, also an option that I almost took was to use many strands of magnet wire scrounged out of a few old CRT tv's, U can get about two layers of full length turns from one tv depending on the size,I calculated that I was going to need 8 turns of magnet wire to make up the conductor diameter, so I would have needed about 4 tv's about 27" or bigger ... Now that said u may not be able to find the exact conductor diameter for your project. I found that it was easiest for me to do all the math for my frequency following Aaron and Eric's video presentation and the e-book. Then once I knew my conductor length i was able to find something of that length that I had laying around luckly, which was actually quite a bit larger then I wanted diameter wise but its what I had. So I took my conductor diameter and started to work the math backwards till I came up with a form size built for the conductor diameter. That is why my coil is so large. I looked up buying conductors of around the same diameter and it is very pricey for experimentation purposes. I found it much cheaper to buy material to build the form a different diameter. As for skin effect, I am no expert thats for sure. I have read a few papers on it but it was about three years ago now and my knowledge retention is dwindling with the more kids I have lol. I will have to look up those papers again and get back to u. Pretty sure I just googled conductor skin effect at high frequencies. And as for the coax cable. I looked into it as well but I wasn't sure about stray capacitance between the outer conductor lining and the inner wire. It may have an effect on tuning. Hope this helps

[LeeBob84]

I'll ask him. Are you on skype as well? Email me your skype id and I'll see if I can get you on a skype call with Eric before he leaves.

Perfect thanks Aaron I will Email U the info.

[Jeff Pearson]

I do have enough of the pictured wire whatever it is. It has 3 twisted pairs and a copper? foil sheath. The foil sheath is a little large but the entire wire with the insulation is about right to tight wind the thing. I have also thought about using the twisted pairs inside as some makeshift litz wire. I want to wind it with copper tubing but not for any really good reason other than it would look really good with a copper flashing primary. I am kinda leaning towards using the twisted pairs at the moment. If anyone has pros and cons of each choice it would much appreciated

[Aaron]

Q & a

Perfect thanks Aaron I will Email U the info.

Hi Lee,

If you don't mind, can you post a summary of your questions and Eric's answers from the skype call? Will probably help everyone out.

[Aaron]

Tomorrow Live call with Eric Dollard

TOMORROW NOON PACIFIC DAYLIGHT SAVINGS TIME - LIVE CALL WITH ERIC DOLLARD - have questions? Call in and ask him yourself - Conference Call Dial-in: 1-857-232-0155
Conference Code: 582590

[Aaron]

Live call in 1 hour

TOMORROW NOON PACIFIC DAYLIGHT SAVINGS TIME - LIVE CALL WITH ERIC DOLLARD - have questions? Call in and ask him yourself - Conference Call Dial-in: 1-857-232-0155
Conference Code: 582590

Live call in 1 hour.

[LeeBob84]

Hi Lee,

If you don't mind, can you post a summary of your questions and Eric's answers from the skype call? Will probably help everyone out.

Sure thats no problem. I will post it as soon as I can.

[Jeff Pearson]

After trying to research alternatives, I am back to my original notion of winding the secondary with 1/8th inch copper tubing. And will be stopping at Architectural Copper for the primary on my next trip to town.
Correction...Make that 3/16"o.d. copper tubing for the secondary!

[LeeBob84]

Cri

My skype call with Eric Dollard.

I asked about grounding. He basically said that the deeper you can go with the maximum amount of surface area will give best results. Also using a large piece of conductor to join all grounds on the surface directly below the coil will help in tuning. He also spoke of using trees as a source of grounding, by using a rod driven into the base of the tree allowing the root system to conduct the signal deep below. The bigger the tree usually the deeper the root system. Main thing is surface area as close to the water table as possible.FYI His grounding system is 17 acres.

I asked about skin effect. In my case with aluminum which is a ribbon style conductor making it thin, the skin effect is not an issue. The skin effect is more of a factor in large awg solid round wire conductors at high frequency. In which case is best to use brass.

I asked him about insulated wire compared to non-insulated wire. His recommendation is to have all components of the system as well insulated from air and ground as possible. Insulation on the secondary and primary windings will help with the self capacitance.

I asked him about capacitors. More small capacitors are better then one big cap. He suggested tank capacitors close to my capacitance and a smaller adjustable cap for fine tuning. Best if vac caps are used.

Other suggestions given were to not go overboard with the topload like me lol. All that is needed is a smooth conductor which should never exceed the diameter of your second coil.


Im sure im probably forgetting some stuff but I will post it as I remember.


Thanks for your help Aaron and Eric, can't wait to see this years presentation vids.

[Jeff Pearson]

Just a quick update. Ordered 2 50' coils of 3/16inch copper tubing today...at local lumber yard. Ended up being cheaper than Ebay but it will be a couple weeks. I will need one more 50' coil to wind the secondary, it is about 145'. The Architectural Copper guy was not in today. He is also a river guide so not the best time of year to catch him at store. I had intended to get the copper for the primary today. I also put a longer and higher antenna on the standard crystal radio. It ended up being pointed right at the local radio station and nothing else would tune in. I was getting about 6 stations with it before. 3 of them were strong enough to listen with unpowered crystal earpiece. Been some storms here so antenna is down. gonna point it a different direction next time. A good ground connection is going to be tricky here. The water table could be 1000' down where I am at.

[Aaron]

@Lee

Hi Lee, any updates? Did you get the aluminum and create your grounding system?

[LeeBob84]

Cri

Just want to post an update on the coil. I have been very busy so progress has been slow. Although I have had the time to get my grounding system put in and I am in the process of getting all the connections together for some testing. I have 9holes approx. 3-5ft deep and they are in a star formation with one at the centre. They are spaced about 8ft from the centre and about 6ft from each other. They are all connected like a spider web with 4awg copper. There is also 4 50ft strands of 14awg aluminum welding wire running straight out from each hole buried about 12inch underground. Here are the vids of me pouring some. https://youtu.be/qjVALjfi94E, https://youtu.be/cg4l0VWKoIQ, https://youtu.be/MrU7fDjoAxM

[LeeBob84]

CRI Coil Update

So I connected everything up for testing and have run a few tests on the coil with my frequency generator. My initial tests were not what i was hoping to see as the secondary was resonating closer to 600khz rather than the 800khz I am shooting for. So I went back to my books to look over my initial calculations for the coil to see if i was mistaken, and I have found that somehow I messed up on my calculation for coil diameter. It was calculated originally to be 18 turns at 4'10" to be 247' winding. But when you do the math on that 4.84*3.14=15.2*18=273.6. So this means that I am going to have to reduce the diameter of my coil to 4' 4 1/2" to bring my coil to the desired 247'. 4.375*3.14=13.74*18=247.32. Time to start unwrapping and rebuilding.

[dR-Green]

So I connected everything up for testing and have run a few tests on the coil with my frequency generator. My initial tests were not what i was hoping to see as the secondary was resonating closer to 600khz rather than the 800khz I am shooting for. So I went back to my books to look over my initial calculations for the coil to see if i was mistaken, and I have found that somehow I messed up on my calculation for coil diameter. It was calculated originally to be 18 turns at 4'10" to be 247' winding. But when you do the math on that 4.84*3.14=15.2*18=273.6. So this means that I am going to have to reduce the diameter of my coil to 4' 4 1/2" to bring my coil to the desired 247'. 4.375*3.14=13.74*18=247.32. Time to start unwrapping and rebuilding.

Don't you just love those stupid rookie mistakes I really annoyed myself last week when I measured 44.1cm for a shelf type arrangement, wrote it down on a piece of paper to avoid errors, then went and cut out a piece of wood, installed it, and found there was a big gap. Measured what I had cut - 41.1cm. But luckily I needed a hole to pass things down from above to below the shelf anyway so the gap got incorporated into the design. Typical case of more haste less speed.

Thanks for the updates, I hope the rest is going well!