[time-nuts] 10 MHz low pass filter

[lists at lazygranch.com]

In the days when I had access to a network analyzer with a chip component fixture (all calibrated of course), I tested components on hand just to see how ideal they were. Chip resistors are quite good. The inductance is basically the electrical length of the device. Caps can be decent. My recollection is Johanson had some really good (low parasitic) caps. Inductors basically suck. 

You will note in most RF board design with lumped elements, they rotate adjacent inductors to reduce mutual inductance. 

10MHz is probably too low in frequency for practical stripline. You could probably do active filters these days, but the power budget would not be trivial. 


-----Original Message-----
From: "Thomas S. Knutsen" <la3pna at gmail.com>
Date: Thu, 21 Jun 2012 01:17:02 
To: <lists at lazygranch.com>; Discussion of precise time and frequency measurement<time-nuts at febo.com>
Subject: Re: [time-nuts] 10 MHz low pass filter

Based on that PCB, I want to see an sweep to at least 1GHz.
The reason is that experience have shown that the inductance (perhaps 10nH)
in series with C2 and C6 would damage the stop-band rejection at UHF.

Used with an OXCO this would not matter, but the desire to make the
ultimate filter is still there.

Thomas.

2012/6/21 <lists at lazygranch.com>

> If the output is buffered, there really shouldn't be a problem.
>
> Incidentally, I can crank out high order LCR filters all day just by
> transforming prototypes out of Zverev. But it has been my experience at
> even 10MHz the parasitics of the elements will throw off the design.
>
>
> -----Original Message-----
> From: Bob Camp <lists at rtty.us>
> Sender: time-nuts-bounces at febo.com
> Date: Wed, 20 Jun 2012 17:49:37
> To: Discussion of precise time and frequency measurement<
> time-nuts at febo.com>
> Reply-To: Discussion of precise time and frequency measurement
>        <time-nuts at febo.com>
> Subject: Re: [time-nuts] 10 MHz low pass filter
>
> Hi
>
> That's a pretty high order filter. The output of most OCXO's already has a
> filter on it. Combining two filters (especially high order ones) without
> isolation between them is not a good idea. The resulting transfer function
> will not be what you expect it to be….
>
> Bob
>
> On Jun 20, 2012, at 4:54 PM, Joseph Gray wrote:
>
> > I came across this filter design recently and thought I'd build a few.
> >
> > http://www.jwmeng.com/AppNote/AppNote003.html
> >
> > I was about to place a Mouser order when I came across someone selling
> > filters, based on the above design.
> >
> > http://www.ebay.com/itm/10-MHz-filter-kit-for-tcxo-gps-pll-/110893777470
> >
> > The price with a board seemed low enough that I ordered a few. I'll
> > let everyone know how they work out.
> >
> > Joe Gray
> > W5JG
> >
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