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

[Brett gazdzinski-2]

 

> -----Original Message-----
> From: Brett gazdzinski [mailto:[hidden email]]
> 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: [hidden email]
> > [mailto:[hidden email]] On Behalf Of Fred (FL)
> > Sent: Thursday, May 03, 2007 12:55 PM
> > To: [hidden email]
> > 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
> >
> > __________________________________________________
> > Do You Yahoo!?
> > Tired of spam?  Yahoo! Mail has the best spam protection around
> > http://mail.yahoo.com 
> > _______________________________________________
> > Elecraft mailing list
> > Post to: [hidden email]
> > You must be a subscriber to post to the list.
> > Subscriber Info (Addr. Change, sub, unsub etc.):
> >  http://mailman.qth.net/mailman/listinfo/elecraft   
> >
> > Help: http://mailman.qth.net/subscribers.htm
> > Elecraft web page: http://www.elecraft.com
> >
>

_______________________________________________
Elecraft mailing list
Post to: [hidden email]
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
 http://mailman.qth.net/mailman/listinfo/elecraft   

Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com