When I lived in Germany, I joined DARC (as you do) and showed my new sausage-noshing friends some examples of my construction handiwork. As
a result of that, they gave it a specific German portmanteau term to describe it: Scheissebau. I haven't looked up the translation but I'm guessing it means 'ingeniously-resourceful.' ;-)
Anyway, here's a prime example. I have several hundred broadcast radio intermediate frequency transformers manufactured in the early 1970s.
https://disk.yandex.com/i/Ym1YrWS2YGTnxw
I was curious as to what IF they were made for. Each of them is
color-coded to indicate this, but I have no chart to de-code this and
online sources conflict in many respects. The obvious answer was to
test them all and create a chart from those findings. This
necessitated the building of a test fixture to accommodate the
transformers, which can be plugged into it and swapped around for
purposes of comparison. Having built this, I then needed to make up a calibration kit to establish a reference plane to subtract the effects
of the hook-up cabling and connections. Fortunately, de-embedding and
whatnot is no big deal as these IFs are low, so the parasitics (which
I'm not proud of) in this construction shouldn't materially affect the measurements.
Here's the fixture:
https://disk.yandex.com/i/NE8B4i5Yh0jWYA
A specimen IF for testing:
https://disk.yandex.com/i/BUpamDpN8us8pQ
The ad-hoc calibration kit:
https://disk.yandex.com/i/CaV7QGfA-KtP_w
On 2/16/25 21:19, Cursitor Doom wrote:
When I lived in Germany, I joined DARC (as you do) and showed my new
sausage-noshing friends some examples of my construction handiwork. As
a result of that, they gave it a specific German portmanteau term to
describe it: Scheissebau. I haven't looked up the translation but I'm
guessing it means 'ingeniously-resourceful.' ;-)
Anyway, here's a prime example. I have several hundred broadcast radio
intermediate frequency transformers manufactured in the early 1970s.
https://disk.yandex.com/i/Ym1YrWS2YGTnxw
I was curious as to what IF they were made for. Each of them is
color-coded to indicate this, but I have no chart to de-code this and
online sources conflict in many respects. The obvious answer was to
test them all and create a chart from those findings. This
necessitated the building of a test fixture to accommodate the
transformers, which can be plugged into it and swapped around for
purposes of comparison. Having built this, I then needed to make up a
calibration kit to establish a reference plane to subtract the effects
of the hook-up cabling and connections. Fortunately, de-embedding and
whatnot is no big deal as these IFs are low, so the parasitics (which
I'm not proud of) in this construction shouldn't materially affect the
measurements.
Here's the fixture:
https://disk.yandex.com/i/NE8B4i5Yh0jWYA
A specimen IF for testing:
https://disk.yandex.com/i/BUpamDpN8us8pQ
The ad-hoc calibration kit:
https://disk.yandex.com/i/CaV7QGfA-KtP_w
I don't think it's meaningful to use them in a 50 Ohm
environment. They were used as collector loads of common
emitter stages, so were driven by a high impedance, say,
20 kOhm or so. The target load impedance on the secondary
varied according to the specific purpose of the stage.
(I think the ones with the yellow screws were optimized
to drive diode detectors in AM radios, and red ones were
AM band LO oscillator coils.)
Jeroen Belleman
On Mon, 17 Feb 2025 10:21:25 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 2/16/25 21:19, Cursitor Doom wrote:
When I lived in Germany, I joined DARC (as you do) and showed my new
sausage-noshing friends some examples of my construction handiwork. As
a result of that, they gave it a specific German portmanteau term to
describe it: Scheissebau. I haven't looked up the translation but I'm
guessing it means 'ingeniously-resourceful.' ;-)
Anyway, here's a prime example. I have several hundred broadcast radio
intermediate frequency transformers manufactured in the early 1970s.
https://disk.yandex.com/i/Ym1YrWS2YGTnxw
I was curious as to what IF they were made for. Each of them is
color-coded to indicate this, but I have no chart to de-code this and
online sources conflict in many respects. The obvious answer was to
test them all and create a chart from those findings. This
necessitated the building of a test fixture to accommodate the
transformers, which can be plugged into it and swapped around for
purposes of comparison. Having built this, I then needed to make up a
calibration kit to establish a reference plane to subtract the effects
of the hook-up cabling and connections. Fortunately, de-embedding and
whatnot is no big deal as these IFs are low, so the parasitics (which
I'm not proud of) in this construction shouldn't materially affect the
measurements.
Here's the fixture:
https://disk.yandex.com/i/NE8B4i5Yh0jWYA
A specimen IF for testing:
https://disk.yandex.com/i/BUpamDpN8us8pQ
The ad-hoc calibration kit:
https://disk.yandex.com/i/CaV7QGfA-KtP_w
I don't think it's meaningful to use them in a 50 Ohm
environment. They were used as collector loads of common
emitter stages, so were driven by a high impedance, say,
20 kOhm or so. The target load impedance on the secondary
varied according to the specific purpose of the stage.
(I think the ones with the yellow screws were optimized
to drive diode detectors in AM radios, and red ones were
AM band LO oscillator coils.)
Jeroen Belleman
Well, all modern test equipment is normalized for 50 or (more rarely)
70 ohms. That is the so-called 'system impendance' and there's not
much one can do about it. However, I really just want to see where the >resonant point is for each of these devices. I only had the time last
night to do one (a green one) which turned out to be 10.7Mhz, so I can
now sell them off as such. I'll do the other colors when I have time.
It'll be interesting to see the difference in construction between a
10.7Mhz and a 455khz one. Interesting for *me* at any rate, although I
accept that others might fail to see the point of this. Each to his
own!
On Mon, 17 Feb 2025 13:31:28 +0000, Cursitor Doom <cd@notformail.com>
wrote:
On Mon, 17 Feb 2025 10:21:25 +0100, Jeroen Belleman
<jeroen@nospam.please> wrote:
On 2/16/25 21:19, Cursitor Doom wrote:
When I lived in Germany, I joined DARC (as you do) and showed my new
sausage-noshing friends some examples of my construction handiwork. As >>>> a result of that, they gave it a specific German portmanteau term to
describe it: Scheissebau. I haven't looked up the translation but I'm
guessing it means 'ingeniously-resourceful.' ;-)
Anyway, here's a prime example. I have several hundred broadcast radio >>>> intermediate frequency transformers manufactured in the early 1970s.
https://disk.yandex.com/i/Ym1YrWS2YGTnxw
I was curious as to what IF they were made for. Each of them is
color-coded to indicate this, but I have no chart to de-code this and
online sources conflict in many respects. The obvious answer was to
test them all and create a chart from those findings. This
necessitated the building of a test fixture to accommodate the
transformers, which can be plugged into it and swapped around for
purposes of comparison. Having built this, I then needed to make up a
calibration kit to establish a reference plane to subtract the effects >>>> of the hook-up cabling and connections. Fortunately, de-embedding and
whatnot is no big deal as these IFs are low, so the parasitics (which
I'm not proud of) in this construction shouldn't materially affect the >>>> measurements.
Here's the fixture:
https://disk.yandex.com/i/NE8B4i5Yh0jWYA
A specimen IF for testing:
https://disk.yandex.com/i/BUpamDpN8us8pQ
The ad-hoc calibration kit:
https://disk.yandex.com/i/CaV7QGfA-KtP_w
I don't think it's meaningful to use them in a 50 Ohm
environment. They were used as collector loads of common
emitter stages, so were driven by a high impedance, say,
20 kOhm or so. The target load impedance on the secondary
varied according to the specific purpose of the stage.
(I think the ones with the yellow screws were optimized
to drive diode detectors in AM radios, and red ones were
AM band LO oscillator coils.)
Jeroen Belleman
Well, all modern test equipment is normalized for 50 or (more rarely)
70 ohms. That is the so-called 'system impendance' and there's not
much one can do about it. However, I really just want to see where the >>resonant point is for each of these devices. I only had the time last
night to do one (a green one) which turned out to be 10.7Mhz, so I can
now sell them off as such. I'll do the other colors when I have time.
It'll be interesting to see the difference in construction between a >>10.7Mhz and a 455khz one. Interesting for *me* at any rate, although I >>accept that others might fail to see the point of this. Each to his
own!
Rip some open and see what's inside.
I agree that you might not learn much in a 50 ohm environment. I'd
play with a signal generator and an oscilloscope and a few resistors
and caps to get into the right frequency and impedance ballpark.
Just an ohmmeter will figure out a lot.
Well, all modern test equipment is normalized for 50 or (more rarely)
70 ohms. That is the so-called 'system impendance' and there's not
much one can do about it. However, I really just want to see where the resonant point is for each of these devices. I only had the time last
night to do one (a green one) which turned out to be 10.7Mhz, so I can
now sell them off as such. I'll do the other colors when I have time.
It'll be interesting to see the difference in construction between a
10.7Mhz and a 455khz one. Interesting for *me* at any rate, although I
accept that others might fail to see the point of this. Each to his
own!
On 17-02-2025 07:01 pm, Cursitor Doom wrote:
Well, all modern test equipment is normalized for 50 or (more rarely)
70 ohms. That is the so-called 'system impendance' and there's not
much one can do about it. However, I really just want to see where the
resonant point is for each of these devices. I only had the time last
night to do one (a green one) which turned out to be 10.7Mhz, so I can
now sell them off as such. I'll do the other colors when I have time.
It'll be interesting to see the difference in construction between a
10.7Mhz and a 455khz one. Interesting for *me* at any rate, although I
accept that others might fail to see the point of this. Each to his
own!
A long time ago, when the Earth was much younger, FM didn't exist where
I live but there was an AM station transmitting at 540kHz.
I used to take a 455kHz IF transformer, replaced the built-in 200pF cap
with 150pF and used it as the collector load for an RF transistor (an
AF117 IIRC). I tuned the IFT directly to the station and the secondary
fed a Ge diode (usually OA79) detector. The DC output from the detector >served as an AGC bias while the audio signal went to an amplifier. I had
a very narrow range of parts to choose from and the amp was usually an
AC126 driving an AC187/AC188 complementary pair or a pair of AC128's in >parallel push-pull with an output transformer..
The RF input side was a coil of solid copper wire (I didn't have Litz)
on a ferrite rod, paralleled by another 150pF cap and tuned by sliding
the coil along the ferrite rod.
I must have built at least half a dozen such "radios" with some
variations and gave them away to friends. It was a lot of fun.
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