Re: start without ANY extra roofing filters....

[Fred (FL)]

If my CAD computer design days don't fail me, I recall
8-pole type filters - had much steeper skirts, but
not so hot passbands, sort of ripply.  Having already
forgotten the spec on group-delay (phase?) - I'll
have to look that up.

Fred, N3CSY

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[Jack Smith-6]

Passband ripple is more a function of the filter design parameters--was
it designed as a Chebyshev with 1 dB passband ripple, or a Butterworth
with a flat passband, or a Gaussian with a rounded passband, etc. And,
of course, those parameters govern also how fast the skirts roll off
and, of great importance in many applications, how the group delay looks.

All else being equal (e.g., two filters, same nominal 3 dB bandwidth,
same design parameter, e.g., Chebyshev) the one with more poles will
have better passband roll off, or shape factor.

I can show you some four pole crystal filters I've designed and built
with essentially perfectly flat passbands and others with lumpy passbands.

Jack K8ZOA


Fred (FL) wrote:

> If my CAD computer design days don't fail me, I recall
> 8-pole type filters - had much steeper skirts, but
> not so hot passbands, sort of ripply.  Having already
> forgotten the spec on group-delay (phase?) - I'll
> have to look that up.
>
> Fred, N3CSY
>
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>  

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[Jack Smith-6]

For those having withdrawal symptoms from not having a hot soldering
iron in their hands recently, I'm now accepting orders for a new
kit--the Z100 CW tuning aid.

Build time is between 2.5 and 3.5 hours and the kit is suitable for
beginners as well as experienced kit builders. No toroids to wind,
unfortunatly. But there are 24 LEDs to bend the leads on, so perhaps
that will be an acceptable substitute.

The Z100 uses 24 LEDs to provide a pseudo-spectrum analyzer display.
After a one-time calibration procedure, to tune a CW signal in you
adjust your K2 tuning knob until the two green LEDs in the center of the
display flash. The display shows the degree of frequency error and the
direction of the error. The result is that you can be very quickly zero
beat. I've used it for a couple months in prototype and find it a useful
CW tool.

The Z100 also can be used for tuning RTTY and other digital modes.

It's microcontroller based and will store/recall 16 center frequencies.  
And, I've made available the Z100's complete source code, which is small
enough to be usable with the free Swordfish SE compiler.

I've added a web page describing the new Z100 at
http://www.cliftonlaboratories.com/z100_tuning_aid.htm.

You can see it along with other Clifton Laboratory products at Dayton
this year. I'll be sharing space with Larry's Telepostinc table - Booth
517. However, no sales at Dayton due to Ohio tax restrictions.


Jack K8ZOA
www.cliftonlaboratories.com

>  
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[Ingo Meyer, DK3RED]

Hello Jack,

> I've added a web page describing the new Z100 at
> http://www.cliftonlaboratories.com/z100_tuning_aid.htm.

Looks like an advanced version of the "Son of Zerobeat" at
http://jacksonharbor.home.att.net/zerobeat.htm
from Jackson Harbor Press by Chuck Olson, WB9KZY. ;o)
--
72/73 de Ingo, DK3RED - Don't forget: the fun is the power!

     [hidden email] - www.qrp4fun.de
        DL-QRP-AG #824 - www.dl-qrp-ag.de
       QRP ARCI #11295 - www.qrparci.org
         DARC #2360404 - www.darc.de

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[Jack Smith-6]

Actually, I trace the linage back to HAL Electronic's Spectra-Tune, sold
in the early 1980's.

However, HAL had to use a dozen ICs to accomplish the task, and it was
not programmable.


Jack



Ingo Meyer (DK3RED) wrote:
> Hello Jack,
>
>> I've added a web page describing the new Z100 at
>> http://www.cliftonlaboratories.com/z100_tuning_aid.htm.
>
> Looks like an advanced version of the "Son of Zerobeat" at
> http://jacksonharbor.home.att.net/zerobeat.htm
> from Jackson Harbor Press by Chuck Olson, WB9KZY. ;o)
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