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Fwd Bias LEDs as Varicaps/Varactors
Read the Info from Hans, http://hanssummers.com/varicap/varicapfwd.html And especially this comment with calculations at the bottom...(Jerry) *Adam SQ5RWQ * Note that connecting two LEDs in series
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Chuck Carpenter
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#538
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Re: Elmer 101
Steve, It's been over 20 years, but the original info is still on my qsl web page http://qsl.net/kf4trd. You are welcome to print and use the info as you wish, just not for profit. Good luck Mike
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Michael Maiorana
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#537
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Re: SMT Varactor vs Thru Hole
Eric, Good info, makes sense when you relate the shape to functional applications.? On the O/T about the capacitor plates.? In my Vast Experience (or maybe Half-) I knew that tapered plate style as
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Chuck Carpenter
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#536
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Re: Norcal 40a Toroids
5% is 1.45uH so 0.6uH is well within tolerance. I've been analysing a 20m LPF with my NanoVNA and I found I had to remove a total of 4 turns off the 3 toroids to get a decent return loss and minimise
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Richard Tomlinson G4TGJ
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#535
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Re: Magloop prototype
One good reason to use teflon as a capacitor dielectric, it's easy to know when it has failed. Search for the word "explosively" in this discussion:
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Jerry Gaffke
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#534
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Re: Elmer 101
QRPp journal Vol. IV No. 3 Cheers, Mark.
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Mark - N7EKU <n7eku@...>
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#533
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Re: Magloop prototype
Kurt is onto something with "no solder". Tin-lead solder has 10x the resistivity of copper, tin-silver is not much better: http://eddy-current.com/conductivity-of-metals-sorted-by-resistivity/ More of
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Jerry Gaffke
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#532
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Re: Magloop prototype
No solder...rule number one. Rule number two...no metal other than the loop and coupler. As far as stability. Great point and I can¡¯t yet speak to power more than qrp. It works fine for qrp. As far
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Kurt Loken <kurt.loken@...>
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#531
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Elmer 101
I understand that their used to be a "Elmer 101" box available.? My little Builders group is going to be building SWxx's soon and would like to get a hold of this book for the builders.? Anyone have
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stephen white
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#530
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Re: Magloop prototype
Looks like teflon has a sufficiently low loss tangent, is being used successfully as a dielectric on mag loops. I'm sure a vacuum for the dielectric is preferred, but nothing costs way too much. Could
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Jerry Gaffke
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#529
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Re: Magloop prototype
Hello Jerry, There is more to this capacitor than meets the eye...but at its basics it is indeed controlled separation as a tuning mechanism...but dialectic choice is very important. Your formica
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Kurt Loken <kurt.loken@...>
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#528
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Re: Magloop prototype
Hey, Jerry, Those are all great ideas...until you try them. :) Mag loops don't work (well) unless we build them in ways that only mag loops require. Overlapping strip capacitors, as you describe,
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Kirk Kleinschmidt, NT0Z
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#527
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Re: Magloop prototype
I don't see anything recognizable as a cap in that photo, am curious how you are going about it. Best guess is it's the metalic assembly above the PC board with coax in, a white wire coming out. And
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Jerry Gaffke
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#526
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Re: Norcal 40a Toroids
Thanks to all your replies. There is a lot of valuable information. This is my first toroid and I want to make sure I have it right. I'm winding T3 which is an FT37-61 with 23 turns of #28 and 6 turns
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Paul Egan
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#525
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Edited
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Magloop prototype
Hello all, I¡¯m working on a prototype for a low cost magloop. ?Cost of ALL parts including WiFi/low energy Bluetooth ¡°arduino-based¡± electronics and mechanical assembly for driving the
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Kurt Loken <kurt.loken@...>
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#524
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Re: Varactor Diode C Measurement
Correction, at 9v the 1n4001 graph shows 10pf, not 30pf: wrong:? ?Using the midrange 9v:30pf pair to compute? ?K = 10*sqrt(9) = 30, right:? ? ?Using the midrange 9v:10pf pair to compute? ?K =
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Jerry Gaffke
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#523
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Re: Norcal 40a Toroids
Sorry, this time copied correctly. https://www.edn.com/cheap-and-easy-inductance-tester-uses-few-components/
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[email protected]
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#522
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Re: Norcal 40a Toroids
https://www.edn.com/.../ *test*... *measurement* /.../ *Cheap-and-easy* - *inductance* - *tester* -uses-few-components Howard, n3fel
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[email protected]
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#521
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Re: Norcal 40a Toroids
It's a good idea to wind and measure the inductance of the toriod before installation.? In my experience not all cores are alike especially the five for a dime variety found on Ebay.? Testing of
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[email protected]
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#520
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Re: Varactor Diode C Measurement
The 1n4001 seems to follow the? ?Cj = K/sqrt(V)? ?formula rather closely. From the graph of fig 4 on page 2 of the 1n4001 datasheet at https://www.diodes.com/assets/Datasheets/ds28002.pdf I read
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Jerry Gaffke
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#519
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