Reply by Jerry Avins May 28, 20102010-05-28
On 5/27/2010 11:30 PM, robert bristow-johnson wrote:

   ...

Hey, Kid, I was 4 years out of high school when you were born, then. Had 
I followed a normal path, I'd have been a college senior.

> after reading and hearing "OIL SPILL"..."BP"..."MASSIVE ENVIRONMENTAL > DAMAGE"..."EUROZONE COLLAPSE"..."STOCK MARKET IN THE TOILET"..."IT'S > ALL OBAMA'S FAULT"..., i need a giggle before going to bed. > > g'night all. with any luck, there will be a world waiting for us in > the morning.
Good night! Jerry -- Engineering is the art of making what you want from things you can get. �����������������������������������������������������������������������
Reply by robert bristow-johnson May 28, 20102010-05-28
On May 27, 4:32&#2013266080;pm, Jerry Avins <j...@ieee.org> wrote:
> On 5/27/2010 3:30 PM, Rune Allnor wrote: > > > On 27 Mai, 21:25, Jerry Avins<j...@ieee.org> &#2013266080;wrote: > > >> I remember doing the math for stagger-tuned IF strips in the early > >> 1050s. > > > Er...? > > I was only one key off. :-) >
i dunno Jerry. yer older than me and i date back to the 1050s. January 1, 1056, in fact. after reading and hearing "OIL SPILL"..."BP"..."MASSIVE ENVIRONMENTAL DAMAGE"..."EUROZONE COLLAPSE"..."STOCK MARKET IN THE TOILET"..."IT'S ALL OBAMA'S FAULT"..., i need a giggle before going to bed. g'night all. with any luck, there will be a world waiting for us in the morning. r b-j
Reply by Clay May 27, 20102010-05-27
On May 27, 2:14&#2013266080;pm, BobG <bobgard...@aol.com> wrote:
> Whats the rule of thumb for how far to detune the two outside filters > for third octave bandwidth? Is the middle filter supposed to have a > little less gain to flatten the passband out? Is the Q of all 3 > filters the same? Do the skirts roll off at 18dB per octave? (I > searched for 'triple tuned' but no hits, so I hope I dont get flamed > for asking)
Most here have given the answers, but if you wish to look at analog approximations, the "Active Filter Cookbook" (Don Lancaster) has great tables, nomographs, and design guidelines for stagger tuning. Clay
Reply by Steve Pope May 27, 20102010-05-27
Jerry Avins  <jya@ieee.org> wrote:

>On 5/27/2010 3:57 PM, Steve Pope wrote:
>> Sure. Tune precisely to a strong RF signal, and trim the >> little IF filters until you see a maximum at their output >> on a scope.
>That gets you maximum sensitivity at the expense of distortion at higher >volumes. Low distortion is achieved by stagger tuning to broaden the >response. This is best done with a sweep generator, but if one is good >at it (I was once) it can be done fairly well by ear.
I totally forgot about "stagger tuning". Yes, you do not want all your pole pairs at the exact same place to get a nice flat passband.
>> I haven't done this for maybe 40 years but that doesn't >> mean it isn't still done.... > >It's been longer than that for me.
Steve
Reply by Jerry Avins May 27, 20102010-05-27
On 5/27/2010 3:30 PM, Rune Allnor wrote:
> On 27 Mai, 21:25, Jerry Avins<j...@ieee.org> wrote: > >> I remember doing the math for stagger-tuned IF strips in the early >> 1050s. > > Er...?
I was only one key off. :-) Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
Reply by Jerry Avins May 27, 20102010-05-27
On 5/27/2010 3:29 PM, Tim Wescott wrote:
> On 05/27/2010 12:25 PM, Jerry Avins wrote: >> On 5/27/2010 2:14 PM, BobG wrote: >>> Whats the rule of thumb for how far to detune the two outside filters >>> for third octave bandwidth? Is the middle filter supposed to have a >>> little less gain to flatten the passband out? Is the Q of all 3 >>> filters the same? Do the skirts roll off at 18dB per octave? (I >>> searched for 'triple tuned' but no hits, so I hope I dont get flamed >>> for asking) >> >> Do you perhaps have analog filters in mind? The design procedures for >> digital filters don't usually go in that direction. >> >> I remember doing the math for stagger-tuned IF strips in the early >> 1050s. It wasn't all that hard, but I don't remember off hand. There's >> an old paper in the Proceedings of the IRE. > > Whoa! Jerry, I knew you were old, but I didn't realize you were _that_ > old. For that matter, I didn't realize that they were building IF strips > in the middle ages. > > Were you in England for the Battle of Hastings? What was it like?
Oops! Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
Reply by Jerry Avins May 27, 20102010-05-27
On 5/27/2010 3:57 PM, Steve Pope wrote:
> glen herrmannsfeldt<gah@ugcs.caltech.edu> wrote: > >> Does anyone tune the IF section of FM tuners to correct >> for any drift? (Especially after 30 years.) > > Sure. Tune precisely to a strong RF signal, and trim the > little IF filters until you see a maximum at their output > on a scope.
That gets you maximum sensitivity at the expense of distortion at higher volumes. Low distortion is achieved by stagger tuning to broaden the response. This is best done with a sweep generator, but if one is good at it (I was once) it can be done fairly well by ear.
> I haven't done this for maybe 40 years but that doesn't > mean it isn't still done....
It's been longer than that for me. Jerry -- Engineering is the art of making what you want from things you can get. &#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;&#2013266095;
Reply by Steve Pope May 27, 20102010-05-27
glen herrmannsfeldt  <gah@ugcs.caltech.edu> wrote:

>Does anyone tune the IF section of FM tuners to correct >for any drift? (Especially after 30 years.)
Sure. Tune precisely to a strong RF signal, and trim the little IF filters until you see a maximum at their output on a scope. I haven't done this for maybe 40 years but that doesn't mean it isn't still done.... S.
Reply by glen herrmannsfeldt May 27, 20102010-05-27
Jerry Avins <jya@ieee.org> wrote:
(snip)
 
> Do you perhaps have analog filters in mind? The design procedures for > digital filters don't usually go in that direction.
There not being a comp.asp newsgroup, it seems that analog questions end up here. When I was in high school I had my grandfather's Heathkit vacuum tube amplifier and tuner to play with. I have written about them before, the preamp that is powered by the amplifier through an octal socket connector. Among other features, there are about four choices for phono equalization, though I was reminded that RIAA was always the right one. (I never tried to find any really old records.) -- glen
Reply by glen herrmannsfeldt May 27, 20102010-05-27
Tim Wescott <tim@seemywebsite.now> wrote:
> On 05/27/2010 11:14 AM, BobG wrote: >> Whats the rule of thumb for how far to detune the two outside filters >> for third octave bandwidth?
(snip)
> It sounds like you're trying to make a filter in 2010 using design rules > from 1940. There's nothing inherently bad in this, but there are > certainly faster ways.
When I bought my first FM tuner 30 years ago (which I still have, though don't use so much), I was told that I would have to retune the IF every some number of years. Of course I never did that, though I did buy the service manual for it. Does anyone tune the IF section of FM tuners to correct for any drift? (Especially after 30 years.) -- glen