In an old-style valve (tube) communications receiver circuit which utilises
two I.F. stages and uses three I.F. transformers, can someone explain why
the last I.F. transformer (which feeds the diode detector stage) need to
differ in some way to the other two?
Any help would be greatly appreciated.

Theo

The first two feed grids that have a higher impedance than a diode that
is fed by the third.

--
73
Hank WD5JFR
"Theo" wrote in message
...
In an old-style valve (tube) communications receiver circuit which
utilises two I.F. stages and uses three I.F. transformers, can someone
explain why the last I.F. transformer (which feeds the diode detector
stage) need to differ in some way to the other two?
Any help would be greatly appreciated.

Theo

"Henry Kolesnik" wrote in message
...
The first two feed grids that have a higher impedance than a diode that is
fed by the third.

Thanks Hank,
Does this mean that the windings of this third I.F. transformer need to be
different in some way than the previous two, and if so, by how much?

Theo

Theo
The secondary of the IF xfmrm feeding the diode will have a different
winding than the first two. My transformer theory is not up to snuff,
I'm 68 and if I recall correctly a diode has a much lower input
impedance that has to be matched so I'm guessing it will have less
turns. Remember that a transformer reflects the impedance back.
You may want to get a copy of The Radiotron Designers Handbook by
Langford, it covers just about anything you would want to know about
tube radios, over 1000 pages.

--
Thanks & 73
Hank WD5JFR
"Theo" wrote in message
...

"Henry Kolesnik" wrote in message
...
The first two feed grids that have a higher impedance than a diode
that is fed by the third.

Thanks Hank,
Does this mean that the windings of this third I.F. transformer need
to be different in some way than the previous two, and if so, by how
much?

Theo

Henry Kolesnik wrote:
The secondary of the IF xfmrm feeding the diode will have a different
winding than the first two. My transformer theory is not up to snuff,
I'm 68 and if I recall correctly a diode has a much lower input
impedance that has to be matched so I'm guessing it will have less
turns. Remember that a transformer reflects the impedance back.
You may want to get a copy of The Radiotron Designers Handbook by
Langford, it covers just about anything you would want to know about
tube radios, over 1000 pages.

The over 1000-page one is the Fourth Edition, which is the most expensive
on the used market, and the one which has the most hi-fi information in
it.

The discussion of IF strip design is also in the smaller and much less
expensive Third Edition. Some people like the third edition because it
has some information on transformer design which was not carried into
the fourth.

A copy of the fourth edition is available online he
http://geek.scorpiorising.ca/RDH4.html
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" wrote in message
...
Henry Kolesnik wrote:
The secondary of the IF xfmrm feeding the diode will have a different
winding than the first two. My transformer theory is not up to snuff,
I'm 68 and if I recall correctly a diode has a much lower input
impedance that has to be matched so I'm guessing it will have less
turns. Remember that a transformer reflects the impedance back.
You may want to get a copy of The Radiotron Designers Handbook by
Langford, it covers just about anything you would want to know about
tube radios, over 1000 pages.

The over 1000-page one is the Fourth Edition, which is the most expensive
on the used market, and the one which has the most hi-fi information in
it.

The discussion of IF strip design is also in the smaller and much less
expensive Third Edition. Some people like the third edition because it
has some information on transformer design which was not carried into
the fourth.

A copy of the fourth edition is available online he
http://geek.scorpiorising.ca/RDH4.html
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

It would certainly help to see the schematic before jumping to conclusions.
There are many designs out there between American 5 and FT1000D, and you
don't specify.

Over the years I've gone thru several 4th editions but have never seen
any of its predecessors. I'll have to watchout for some.

"Scott Dorsey" wrote in message
...
Henry Kolesnik wrote:
The secondary of the IF xfmrm feeding the diode will have a different
winding than the first two. My transformer theory is not up to snuff,
I'm 68 and if I recall correctly a diode has a much lower input
impedance that has to be matched so I'm guessing it will have less
turns. Remember that a transformer reflects the impedance back.
You may want to get a copy of The Radiotron Designers Handbook by
Langford, it covers just about anything you would want to know about
tube radios, over 1000 pages.

The over 1000-page one is the Fourth Edition, which is the most
expensive
on the used market, and the one which has the most hi-fi information
in
it.

The discussion of IF strip design is also in the smaller and much less
expensive Third Edition. Some people like the third edition because
it
has some information on transformer design which was not carried into
the fourth.

A copy of the fourth edition is available online he
http://geek.scorpiorising.ca/RDH4.html
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Hey JB
I assumed since the query was in this group it wouldn't be a FT-1000 and
not an AA5 because it has only one IF. It would be nice to know what
radio but anxious people making queries and get carried away and I'm
one..
Hank
"JB" wrote in message
...
"Scott Dorsey" wrote in message
...
Henry Kolesnik wrote:
The secondary of the IF xfmrm feeding the diode will have a
different
winding than the first two. My transformer theory is not up to
snuff,
I'm 68 and if I recall correctly a diode has a much lower input
impedance that has to be matched so I'm guessing it will have less
turns. Remember that a transformer reflects the impedance back.
You may want to get a copy of The Radiotron Designers Handbook by
Langford, it covers just about anything you would want to know about
tube radios, over 1000 pages.

The over 1000-page one is the Fourth Edition, which is the most
expensive
on the used market, and the one which has the most hi-fi information
in
it.

The discussion of IF strip design is also in the smaller and much
less
expensive Third Edition. Some people like the third edition because
it
has some information on transformer design which was not carried into
the fourth.

A copy of the fourth edition is available online he
http://geek.scorpiorising.ca/RDH4.html
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

It would certainly help to see the schematic before jumping to
conclusions.
There are many designs out there between American 5 and FT1000D, and
you
don't specify.

Henry Kolesnik wrote:
Over the years I've gone thru several 4th editions but have never seen
any of its predecessors. I'll have to watchout for some.

I see the second and third editions at hamfests a lot. They are often
black and less than half the width of the 4th edition so you might not
see it unless you're looking for it.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"Scott Dorsey" wrote in message
...
Henry Kolesnik wrote:
The secondary of the IF xfmrm feeding the diode will have
a different
winding than the first two. My transformer theory is not
up to snuff,
I'm 68 and if I recall correctly a diode has a much lower
input
impedance that has to be matched so I'm guessing it will
have less
turns. Remember that a transformer reflects the impedance
back.
You may want to get a copy of The Radiotron Designers
Handbook by
Langford, it covers just about anything you would want to
know about
tube radios, over 1000 pages.

The over 1000-page one is the Fourth Edition, which is the
most expensive
on the used market, and the one which has the most hi-fi
information in
it.

The discussion of IF strip design is also in the smaller
and much less
expensive Third Edition. Some people like the third
edition because it
has some information on transformer design which was not
carried into
the fourth.

A copy of the fourth edition is available online he
http://geek.scorpiorising.ca/RDH4.html
--scott
The forth edition is available in PDF form from Pete
Milette's site:
http://www.pmillett.com/
Along with many other classic books including
K.R.Sturley's two volume book on radio receiver design. The
organization of the site is a bit confusing so a bit of
poking around in needed to find everything. The quality of
his scans is excellent but the files are _very_ large and
really require a high speed connection to be practical.
I also recommend the 4th edition of the Radiotron, I
think I have two, the one I bought new fell apart from use
(rebound it). The 3rd edition, which is much smaller, also
has a lot of useful information in it.
I agree with the statements made about the final IF
transformer but not all detectors offer low impedance to the
transformer although this is true of straight diode
detectors. Both of the above books have thorough discussions
of AM detectors and their relative merits.

--
Richard Knoppow
Los Angeles
WB6KBL