Product detector for communications receiver ?
J M Noeding
but I haven't found any proof when product detectors were used for the
first time.
A note in QST 1950 mentions the application of 6BE6, but it should
indicate that older types like 6K8 or 6SA7 has already been used.
Some early German application uses ACH1 (triode hexode)
Have QST on CD, but only the period 1950-1959 and few loose magazines
for the period 1947-1952, so I would be grateful if somebody could
send me a circuit diagram or article from before 1950 as gif file to
be used on my planned website on www.noding.com
73
Jan-Martin
LA8AK
--
remove ,xnd to reply
carltons
Hi Again J-N,
I would guess that the place to go would be to an archive of Western Electric
as they are the ones that came up with sideband in the 1920's. Have you tried
a web search on this?
Steve
WB4CZR
Plantation, FL
RF is a royal pain.
Peter O. Brackett
It all depends upon your definition of "product detector".
My definition is that a product detector is a device whose output contains
at least one componen that represents the "product" (i.e. the
multiplication) of the incoming signal and a locally generated carrier.
This is a functional definition, of what a product detector does, not how it
does it.
If you use the above definition, product detectors are probably very very
very old... i.e. even a diode pumped with a local BFO fills the bill.
--Peter K1PO
"J M Noeding" <la8a...@online.no> wrote in message
news:3c40db44....@news.online.no...
carltons
<ab...@ix.netcom.com> wrote:
> Jan:
>
> It all depends upon your definition of "product detector".
>
> My definition is that a product detector is a device whose output contains
> at least one componen that represents the "product" (i.e. the
> multiplication) of the incoming signal and a locally generated carrier.
> This is a functional definition, of what a product detector does, not how it
> does it.
>
> If you use the above definition, product detectors are probably very very
> very old... i.e. even a diode pumped with a local BFO fills the bill.
>
> --Peter K1PO
Peter,
I also thought that maybe Jan-Martin was looking for any "mixer" type of
detector, but then I thought that maybe he wanted the other types of detectors
which are more of the multiplier type such as a single balanced detector.
Those, of course, produce more of the desirable signals and less of the useless
products that you just end up throwing away. There had to be something before
the 7360 type of detector.
Steve
WB4CZR
Peter O. Brackett
Ah... vacuum mulitpliers! Sigh!
What did the world do when the last 7360 was manufactured?
I often thought that one should be able to make a similar kind of solid
state device using MOSFET technologies.
i.e. a MOSFET with one source and two drains, and a gate geometry that
forces the carriers to switch channels. Probably worth a patent
applications don't you think?
Then there are the modern Gilbert multipliers and other such "long tail"
semiconductor circuits that work just fine... so don't pine for 7360.
Best,
--Peter K1PO
"carltons" <mots...@mediaone.net> wrote in message
news:motsteve-130...@dplane-176-88-250.pompano.net...
Michael Black
> remove ,xnd to reply
>
At first, I thought I couldn't come up with anything earlier. But
Don Stoner, in his "New Sideband Handbook" which came out in 1958,
says that Murray Crosby "invented the product detector". But
he doesn't mention a date.
Later in the book, it has a schematic for a phasing adaptor. Since
the associated text mentions such a thing being originally described
by Norgaard in the GE Ham News for July/August 1951, and then a more
commercial version was introduced as the Central Electronics Model A
"Slicer", it's not clear which the schematic comes from (or if it's
a newer design). But it just uses a 6AL5 diode for each channel,
as the mixer to translate the sideband down to audio.
In the ARRL's "Single Sideband for the Radio Amateur" (a collection of
articles from QST), first edition that came out in 1954, there's
an article by O.G. Villard, "Demodulation and Selectivity in SSB
Reception". It says the article is "from" an article in QST
for April 1948. There's no mention of "product detector" but
he does talk about frequency conversion for SSB (and, points out
why it would help for straight AM, I guess paving the way for
synchronous detectiion). There is a circuit, just a balanced mixer,
using two 6L7's. He does mention the stuff about turning down the
gain in an old receiver, or to the same effect, making the BFO stronger.
Certainly, that is mixing; there are all those old 432 and 1296 MHz
converters that fed the antenna into a single diode mixer.
I turn the page, and there is a circuit labelled "The Product Detector".
The blurb says "Here is a useful detector for SSB reception, devised
by Murray Crosby, W2CSY. It gets its name from its operation --
the output signal is proportional to the "product" of signals in two
channels". The book says this is from an article "An All-purpose
Super Selective IF Amplifier" in QST for March 1953. If that's the
article I think it is, it is an intriguing scheme. Anyway, it uses
three triodes, from 1.5 12AU7's.
Right under this, there is a passage that looks like it is new
writing for the book:
" 'Product vs Envelope Detectors'
The interesting and significant thing about a product detector is
that there is no output with the BFO turned off. Unlike an envelope
detector, where two or more signals coming in will give a beat or beats,
the product detector requires that the BFO voltage be present. Thus
it is very similar to a mixer or converter stage, which also gives
no output unless oscillator voltage is applied.
The advantage of the product detector is consequently that the
output voltage consists solely of beats with the BFO and not
cross-modulation beats between signals."
Later in the book, there is an article by Norgaard, which
is "from 'Practical Single Sideband Reception' in QST for
July 1948". This is about using phasing for SSB reception,
and he again uses 6AL5's for the mixers, making sure the
BFO is strong enough.
Maybe that helps? I don't have a scanner. I do wonder
what was used in commercial circuits, especially since SSB was
being used by AT&T long before it became common in ham radio.
I do remember reading that the ring modulator came out of
telephone use, though I can't remember where I would have read
that. But I have no idea whether they were used at the receiving
end.
Michael VE2BVW
J M Noeding
wrote:
Thanks to all.
I phoned G3VA Pat today, since he mentioned (TT Radcom June 2002) a
product detector using ECH35 (6K8) which has been used in an Eddystone
receiver since WW2. I said it is probably no product detector since
the input levels are not proper for ssb, but it is interesting
although Telefunken made a similar circuit in 1936 using ACH1Gr. So I
will provide some text and circuit diagrams to Pat. Hope it is
allright to quote some of the information given, particularly by
VE2BVW and G3RZP?