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Old 25th Nov 2020, 11:01 pm   #1
Radio Scotland
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Default A Few Radio Related Questions

I frequently hear my favourite youtube radio repairer referring to a ''stacked I.F'' What exactly is it ?

And where is the best place to hook a scope up to monitor the L.O ?

Just a few questions off the top of my head, They'll be more as time rolls on Ha.


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Old 25th Nov 2020, 11:10 pm   #2
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Default Re: A Few Radio Related Questions

Which YouTube repairer is that?
I have not come across the term Stacked IF.
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Old 25th Nov 2020, 11:14 pm   #3
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Default Re: A Few Radio Related Questions

I've never heard of it either and as far as i can tell neither has google

Shango066
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Last edited by Radio Scotland; 25th Nov 2020 at 11:25 pm. Reason: Spelling correction
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Old 26th Nov 2020, 12:17 am   #4
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Default Re: A Few Radio Related Questions

Sounds like a way of describing a typical AM/FM IF strip with its dual tuned transformers "stacked" on the IF anodes or collectors.

A neat way to use the same active devices at two widely separated frequencies without recourse to (costly) switching arrangements.
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Old 26th Nov 2020, 12:41 am   #5
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Default Re: A Few Radio Related Questions

Sounds about right as he uses the term when working on AM/FM Radios with the type of transformers you mentioned


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Jay
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Old 26th Nov 2020, 3:09 am   #6
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Default Re: A Few Radio Related Questions

Not a phrase I've ever heard before.

David
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Old 26th Nov 2020, 10:06 am   #7
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Default Re: A Few Radio Related Questions

Me neither.

I could have worked out what was meant by stacked IFT's, but not stacked IF's.

As to where to stick a 'scope probe. how about the oscillator section of the tuning gang?

Or, wind 10 turns of wire of a suitable diameter, connect to 'scope, and slip it over the end of the oscillator coil?

Bear in mind that either of the above will alter frequency slightly, so use a x10 probe for minimal loading.
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Old 26th Nov 2020, 10:10 am   #8
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Default Re: A Few Radio Related Questions

Regarding measuring LO, I always stick it on the LO tuning capacitor.
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Old 26th Nov 2020, 12:30 pm   #9
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Default Re: A Few Radio Related Questions

Must be an american phrase or a shango066 expression as he can be a bit off the wall at times. thanks for the replies and the info regarding hooking up a scope to the LO.


Much appreciated.



Jay
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Old 26th Nov 2020, 12:59 pm   #10
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Default Re: A Few Radio Related Questions

Are you sure it's not "staggered tuning"?

It means tuning subsequent IF stages with offsets in each direction to widen the pass-band.
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Old 26th Nov 2020, 1:29 pm   #11
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Default Re: A Few Radio Related Questions

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Originally Posted by rambo1152 View Post
Are you sure it's not "staggered tuning"?

It means tuning subsequent IF stages with offsets in each direction to widen the pass-band.
No. I'm certain its ''Stacked'' Thanks for the reply rambo.


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Old 28th Nov 2020, 10:09 am   #12
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Default Re: A Few Radio Related Questions

Hi
Stacked IFs are used in valve US TVs. Two stages of the IF are in series across the HT supply so each one can be operated at lower voltage also a.g.c applied to the lower stage will also control the gain of the upper stage.
Shango066 is a TV man.
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Old 28th Nov 2020, 1:02 pm   #13
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Hi
Stacked IFs are used in valve US TVs. Two stages of the IF are in series across the HT supply so each one can be operated at lower voltage also a.g.c applied to the lower stage will also control the gain of the upper stage.
Shango066 is a TV man.
Keith
Thanks for the explanation keith. But anytime iv'e heard him using the term he's been referring to radios.


Jay
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Old 28th Nov 2020, 1:11 pm   #14
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Default Re: A Few Radio Related Questions

The statement “Stacked IFs” is ambiguous, I thought about the stacked HT supply very often supplied to other stages by the Sound output valve in USA TV’s, then there is the case with radios FM AM transformers . Others noted by Keith with two IF stages actoss the HT.

Have you a link to the video you heard the comment in, perhaps that would give us what Shango means by the term.
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Old 28th Nov 2020, 1:17 pm   #15
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Default Re: A Few Radio Related Questions

Quote:
Originally Posted by Nuvistor View Post
The statement “Stacked IFs” is ambiguous, I thought about the stacked HT supply very often supplied to other stages by the Sound output valve in USA TV’s, then there is the case with radios FM AM transformers . Others noted by Keith with two IF stages actoss the HT.

Have you a link to the video you heard the comment in, perhaps that would give us what Shango means by the term.
No unfortunately i don't. I Tend to binge watch his videos. But i know iv'e only ever heard him using the term when working on AM/FM Radios,


Jay
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Old 30th Nov 2020, 6:26 pm   #16
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Default Re: A Few Radio Related Questions

Quote:
Originally Posted by RadioScotland View Post
Must be an american phrase
Nope. I've never seen or read it before seeing this thread.
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Old 30th Nov 2020, 10:03 pm   #17
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Default Re: A Few Radio Related Questions

I can't throw any light on the term "stacked IF".

A reasonable way of coupling a 'scope to the oscillator valve in many cases is to drop a screening can over the oscillator valve, without allowing it to contact its earthing skirt.

There is usually enough capacitive coupling to the oscillator anode to get a good trace via a 'scope probe connected to the loose can. This will work even with an internally screened valve such as the ECH81 without pulling the oscillator frequency very much.

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Old 30th Nov 2020, 10:09 pm   #18
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Default Re: A Few Radio Related Questions

Quote:
Originally Posted by Leon Crampin View Post
I can't throw any light on the term "stacked IF".

A reasonable way of coupling a 'scope to the oscillator valve in many cases is to drop a screening can over the oscillator valve, without allowing it to contact its earthing skirt.

There is usually enough capacitive coupling to the oscillator anode to get a good trace via a 'scope probe connected to the loose can. This will work even with an internally screened valve such as the ECH81 without pulling the oscillator frequency very much.

Leon.
Looks like the mysterious stacked IF will forever remain a mystery.

Thanks for the above info. But i'm more of a transistor man. But i'll keep it in mind if i ever progress to valves.


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Jay
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Old 1st Dec 2020, 9:52 am   #19
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Default Re: A Few Radio Related Questions

What about a comment to shango66 on a relevant video? Maybe you'll get a response
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Old 1st Dec 2020, 2:34 pm   #20
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Default Re: A Few Radio Related Questions

Quote:
Originally Posted by RadioScotland View Post
I've never heard of it either and as far as i can tell neither has google

Shango066
Given that "shango066" is a colonial I guess he uses expressions with which may be unfamiliar...
My take would be the i.f. transformers of the a.m. and f.m. stages being in series between the ht supply and the anodes of the common i.f. amplifier valve(s.)
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