Richard W. Solomon wrote:

Dick, it is really easy to build one.  The wonderful (free!) filter
design program ELSIE will give you all the help you need.  I would have
thought an hour or so with a couple of toroids would do the trick.  Even
just a Low Pass filter would usually do to turn a square wave into a sine...

Dan

ac6ao / g3ncr

Dan Rae wrote:

It's actually much better to use an LPF than a bandpass filter if you
don't have subharmonic energy to deal with.  An LPF with a cutoff midway
between the fundamental and the 2nd harmonic will show much less tempco
(in the form of phase shift over temperature) than a bandpass filter.

John

James Lux, P.E.
Task Manager, SOMD Software Defined Radios
Flight Communications Systems Section
Jet Propulsion Laboratory
4800 Oak Grove Drive, Mail Stop 161-213
Pasadena, CA, 91109
+1(818)354-2075 phone
+1(818)393-6875 fax

You mean the ever popular BBP-10.7 for $41?
Hard to beat that price for something comparable.

You might even be able to use some wonky little filter feedthrough with a suitable cutoff frequency.

John Ackermann N8UR wrote:

John

Another approach is to use relatively high Q traps/bandstop filters to
eliminate/minimise the unwanted harmonics together with a low pass filter.
The high Q traps contribute little phase shift and phase shift tempco at
the fundamental.

Bruce

If you're simply looking for purity of signal maybe a crystal filter.

Intersil application note AN9815 is interesting.

Darrell

----- Original Message -----
From: "Richard W. Solomon" w1ksz@earthlink.net
To: time-nuts@febo.com
Sent: Thursday, January 08, 2009 10:11 AM
Subject: [time-nuts] 10 MHz Band-Pass Filter Needed

Mini-Circuits

https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts

A quick filter would be a series resonance circuit.  My notes show that
on a circuit that was 10 Mhz and terminated into 50 ohms load, I used a
10uH choke and a 22 pF cap.  Both of these items were off the shelf ,
the cap was a silver mica 5%.

Brian KD4FM

Darrell Robinson wrote:

A crystal filter may not be a good choice for phase stability unless an
oven is used.
Some of the older frequency standards used crystal filters within an
oven to cleanup the output signal.

The limited crystal dissipation as may raise the phase noise floor of a
low noise OCXO significantly.
The implementation shown in AN9815 is particularly poor in this respect.

A low Q resonant LC filter using low tempco components will have greater
phase stability.
Whilst obtaining capacitors with relatively low tempcos is relatively
easy, the tempco of most off the shelf inductors is usually unspecified.

The significance of the increased phase instability and /or raised phase
noise floor depends on the application.
If one is multiplying the output to 10GHz then even minor temperature
fluctuations will be a concern.

Bruce

Darrell Robinson wrote:

2009/1/9 Bruce Griffiths bruce.griffiths@xtra.co.nz:

There is the other issue of xtal jumps occuring randomly (?) which
could cause rapid phase changes.

73, Steve

--
Steve Rooke - ZL3TUV & G8KVD & JAKDTTNW
Omnium finis imminet