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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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Re: Si5351 output power
Hi The phase noise numbers for the RFzero was recorded subject to a 50 ohms load, i.e. no additional 74xx buffer stage: 100 Hz -103 dBc/Hz 1 kHz -128 dBc/Hz 10 kHz -136 dBc/Hz 100 kHz -138 dBc/Hz 1
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Bo, OZ2M
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#518
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Re: Varactor Diode C Measurement
A minor error in my previous post where I said:? "assume our 10v power supply has 0.1v of pk-pk ripple on it" My subsequent calculations for the variation in capacitance assume noise on the power
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Jerry Gaffke
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#517
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Re: Norcal 40a Toroids
I have built a lot of QRP radios over the years, both kits and from scratch.? Including the NC40A from the old group's project.? Have probably wound 100s of toroids in the process and have never
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Curt
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#516
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