[time-nuts] Oleg' s PN test Re: A new member & PN test set

Gerhard Hoffmann dk4xp at arcor.de
Wed Mar 30 19:12:36 EDT 2016


Am 30.03.2016 um 21:20 schrieb Bruce Griffiths:
> Conical inductors are available that are effectively resonance free to 40GHz
> but the largest value is around 10uH. In principle one could wind one's own
> conical inductor with a larger value, However an iron powder (carbonyl iron -
> available from Ukraine at least via ebay) and epoxy mixture. A cone angle of
> about 15 degrees appears to be suitable.
>
> Failing that, the classical method is to use a series string of inductors of
> increasing value. Even then the various resonances need to be damped.
> Lossy Ferrites and resistors can be useful, however one has to be careful not
> to increase the noise at frequencies of interest.

It doesn't take conical inductors to separate the baseband from the 
carrier at 10 MHz. The
world existed before Piconics and their conical L patents. Yes, we used 
them in our 10 GB/s
fiber optic transceivers, just to see what eye diagrams we could 
achieve. But at €38 a pop they
never ever made it into production. It was just too easy to replace them 
with somewhat more cent stuff.

A colleague even rolled his own from wire, epoxy glue and ferrite beads 
smashed in a mortar.
That looked, hmm, ugly, but performed excellently. Now, you get them 
from MCL and Coilcraft.

But for a 10 or 100 MHz lowpass, that's way over the top. Not even if 
you are nuts.

regards, Gerhard




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