I made a mistake here. The inductance is proportional to the square of the
turns.
Amidon uses the following formula:
Turns = 1000 * Sqrt(desired L (mH)/Al)
Where Al = the inductance value at 1000 turns specified by Amidon
So in my case I have 10 turns. Al = 2160
So the correct amount of inductance is .216 mH or 216 uH.
73,
Jon
NA9D
-------------------------------------
Jon Ogden
Sales Engineer
Cain-Forlaw Company
847-202-9898 (Voice)
847-202-9896 (Fax)
jon.ogden@cain-forlaw.com
> -----Original Message-----
> From: Jon Ogden [mailto:jon.ogden@cain-forlaw.com]
> Sent: Tuesday, June 26, 2001 11:36 AM
> To: 'EDWARDS, EDDIE J'; Jon Ogden; 'RFI'
> Subject: RE: [RFI] Touch Light Update #3
>
>
>
> According to the Amidon literature I have in front of me, the
> FT-50B-77 has
> a value of 2160 mH per 1000 turns. So that would mean that
> 10 turns is
> 21.60 mH. So that's way to big. However, it still didn't
> stop the 20M RF
> from messing with things.
>
> You'd think it would since it's a rather large impedance at
> 14 MHz, but it
> didn't.
>
> 73,
>
> Jon
> NA9D
>
> -------------------------------------
> Jon Ogden
> Sales Engineer
> Cain-Forlaw Company
> 847-202-9898 (Voice)
> 847-202-9896 (Fax)
> jon.ogden@cain-forlaw.com
>
> > -----Original Message-----
> > From: EDWARDS, EDDIE J [mailto:eedwards@oppd.com]
> > Sent: Tuesday, June 26, 2001 11:18 AM
> > To: 'Jon Ogden'; 'RFI'
> > Subject: RE: [RFI] Touch Light Update #3
> >
> >
> > > -----Original Message-----
> > > From: Jon Ogden
> > > > Have you tried a "micro" Henry choke on the sense line?
> > > No I have not. I had assumed that the sense line wrapped
> around the
> > > torroid
> > > would end up looking similar to using a choke in series
> in the line.
> > > Perhaps I am mistaken. Ten turns of the wire around an
> > FT-50B-77 (half
> > > inch
> > > torroid using the 77 material) didn't do much to solve the
> > problem. Maybe
> > > it's not the same as a choke actually in series with the line.
> > >
> > I'm not sure how to calculate the inductance of the FT-50B-77.
> > Anyone know if it's the same as the FB-(77)-1024 listed in
> > the ARRL RFI
> > book? And if so, what are the "A-sub-L v Mix No." values
> > listed in table
> > 2.2? Seems to indicate nanoHenries. So then FB-77-1024 is
> > 5600 nanoH or
> > 5.6 microH? For how many turns? One? So many questions!
> > If it is one
> > then would've been 10 times 5.6 for 56 milliH. That might
> be too much
> > inductance and reactance for the sensing line. But this is
> > all a complete
> > guess without the answers to my questions.
> >
> > An actual inductance value for the FT-50B-77 would be helpful to
> > know for sure.
> >
> > 73,
> > de ed -K0iL
> >
>
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