FW: [Elecraft] 8 pole vs 5 pole..I knew this would happen

[Brett gazdzinski]

> -----Original Message-----
> From: Brett gazdzinski [mailto:Brett.gazdzinski at mci.com] 
> Sent: Thursday, May 03, 2007 2:02 PM
> To: 'Fred (FL)'
> Subject: RE: [Elecraft] 8 pole vs 5 pole..I knew this would happen
> 
> I think, in the past, it was the first filter,
> before all the conversions.
> 
> When they started with the general coverage receivers,
> plus all mode, the first filter had to be wide enough
> for the maximum signal you would want to listen to, 
> or transmit, say 6Khz for AM, 15Khz for FM.
> So, they saved money by just installing a 15 or 20
> Khz roofing filter, everything was under the one roof.
> You had smaller rooms under the roof (regular filters)...
> 
> I am not sure, but its possible some early rigs did not
> HAVE a roofing filter at all..
> Depending on the first IF frequency, its possible they
> could not make a decent filter even if they wanted to.
> 
> Maybe in the 3rd IF you would have the 'real' filters
> and/or dsp.
> In the beginning, maybe the 3rd IF was at 455 Khz, or
> 262Khz, or 50 Khz. 
> I think drake used 50Khz in some of their stuff.
> 
> The lower you go in frequency, the easier to make 
> and better the filter is, at least in the past it was.
> 262Khz IF transformers could be made much narrower
> than 455Khz ones, hence some companies using 50Khz.
> 
> So you had multi conversion rigs, with general coverage, which
> meant they would go someplace beyond the highest frequency
> you were going to tune for the first IF to eliminate
> images, then they had to use a filter that would pass
> FM...
> 
> Now that computers have invaded radios, you can do all 
> sorts of things with the logic, but only Elecraft seems to
> use it to actually improve the results.
> I think the K2 shows that with its low parts count, single
> conversion, yet great results.
> Until very recently, most ham gear seemed to be quite poor
> despite all they hype and gizmos, jack of all trades, master of none.
> 
> 
> 
> I think 'roofing filter' is a bad and silly name, but there it is.
> 
> Brett
> N2DTS
> 
>    
> 
> > -----Original Message-----
> > From: elecraft-bounces at mailman.qth.net 
> > [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Fred (FL)
> > Sent: Thursday, May 03, 2007 12:55 PM
> > To: elecraft at mailman.qth.net
> > Subject: [Elecraft] 8 pole vs 5 pole..I knew this would happen
> > 
> > I think, still, someone needs to define what a ROOFING
> > FILTER is.   Say for sake of argument - I have a
> > passive or active or crystal filter - and it is to
> > be used as a ROOFING FILTER.   Why is it called this?
> > 
> > Why is the filter itself, called a ROOFING FILTER?
> > And where does the adjective, ROOFING, come into
> > play?
> > 
> > ...... I'm sure I'm dumb on this one - but would
> > like to learn.  Not until the K3 came on the
> > Elecraft scene - did anyone mention or get
> > concerned about the need for ROOFING FILTERS.
> > Now they're all the rage?
> > 
> > Fred, N3CSY
> > 
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