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Vintage Radio (domestic) Domestic vintage radio (wireless) receivers only. |
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26th Nov 2020, 12:01 am | #1 |
Heptode
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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. Cheers
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26th Nov 2020, 12:10 am | #2 |
Dekatron
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Re: A Few Radio Related Questions
Which YouTube repairer is that?
I have not come across the term Stacked IF.
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Frank |
26th Nov 2020, 12:14 am | #3 |
Heptode
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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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26th Nov 2020, 1:17 am | #4 |
Dekatron
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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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26th Nov 2020, 1:41 am | #5 |
Heptode
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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
Cheers Jay
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26th Nov 2020, 4:09 am | #6 |
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Re: A Few Radio Related Questions
Not a phrase I've ever heard before.
David
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26th Nov 2020, 11:06 am | #7 |
Dekatron
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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. |
26th Nov 2020, 11:10 am | #8 |
Nonode
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Re: A Few Radio Related Questions
Regarding measuring LO, I always stick it on the LO tuning capacitor.
John |
26th Nov 2020, 1:30 pm | #9 |
Heptode
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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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26th Nov 2020, 1:59 pm | #10 |
Dekatron
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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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26th Nov 2020, 2:29 pm | #11 | |
Heptode
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Re: A Few Radio Related Questions
Quote:
Cheers jay
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28th Nov 2020, 11:09 am | #12 |
Pentode
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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. Keith |
28th Nov 2020, 2:02 pm | #13 | |
Heptode
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Re: A Few Radio Related Questions
Quote:
Jay
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28th Nov 2020, 2:11 pm | #14 |
Dekatron
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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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28th Nov 2020, 2:17 pm | #15 | |
Heptode
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Re: A Few Radio Related Questions
Quote:
Jay
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30th Nov 2020, 7:26 pm | #16 |
Pentode
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Re: A Few Radio Related Questions
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30th Nov 2020, 11:03 pm | #17 |
Octode
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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. Leon. |
30th Nov 2020, 11:09 pm | #18 | |
Heptode
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Re: A Few Radio Related Questions
Quote:
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. Regards Jay
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1st Dec 2020, 10:52 am | #19 |
Dekatron
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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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1st Dec 2020, 3:34 pm | #20 | |
Heptode
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Re: A Few Radio Related Questions
Quote:
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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