Atlantis wrote:
W dniu 2010-08-22 01:24, Dave M pisze:

National LM3820N AM radio chip. BG Micro has them available for
$3.00 for a tube of 25 The chip is obsolete, but still presents an
interesting project. (...) The datasheet gives design and layout
(PCB) for several versions of a BCB AM radio. You can be as simple
or complex as you wish.

Thanks for suggestion. I will search for this chip, but I am not quite
sure if it's widely available in my country (Poland).
Usually I still use polish ICs from CEMI semiconductor factory
(unfortunately they're not existing any more) + some Russian and
western parts, depending of their avalaibility. Most of those
polish and russian, that I have in my supplies are equivalents of
western integrated circuits.

As I said in my post, these chips are obsolete, so I'm sure they aren't
widely available. BG Micro sells them for $3.00 US per tube of 25, plus
$15.00 US (minimum) for shipping to countries other than Canada. If you're
interested in trying them, I have a most of a tube of them in my parts bin.
I used a few of them for 40 & 80 meter receivers a few years ago, and still
have about 20 of them left. If you wish, I'd be glad to mail you a few to
experiment with.

Ordering from BG Micro might be a bit expensive for you, but I'd be glad to
send you a few, gratis. If interested, contact me directly at the address
below.

--
David
dgminala at mediacombb dot net

W dniu 2010-08-23 00:52, Dave M pisze:

$15.00 US (minimum) for shipping to countries other than Canada. If you're
interested in trying them, I have a most of a tube of them in my parts bin.
I used a few of them for 40 & 80 meter receivers a few years ago, and still
have about 20 of them left. If you wish, I'd be glad to mail you a few to
experiment with.

Thank you for your offer. I will remember it, but first I would like to
try find it in local electronic stores.
And I still prefer a little bit more complicated and challenging
constructions, with each stage on separate transistor or IC. I found
only few polish publications from early 70's amateur radio press. All of
them consist germanium transistors, manually made coils and few
transformers in AF stage.

There recevers for 40 and 80 meter band, which You mentioned... What was
that? Superheterodyne? Homodyne?

Atlantis wrote:
W dniu 2010-08-23 00:52, Dave M pisze:

$15.00 US (minimum) for shipping to countries other than Canada. If
you're interested in trying them, I have a most of a tube of them in
my parts bin. I used a few of them for 40 & 80 meter receivers a few
years ago, and still have about 20 of them left. If you wish, I'd
be glad to mail you a few to experiment with.

Thank you for your offer. I will remember it, but first I would like
to try find it in local electronic stores.
And I still prefer a little bit more complicated and challenging
constructions, with each stage on separate transistor or IC. I found
only few polish publications from early 70's amateur radio press. All
of them consist germanium transistors, manually made coils and few
transformers in AF stage.

There recevers for 40 and 80 meter band, which You mentioned... What
was that? Superheterodyne? Homodyne?


They were superhet receivers, since the LM3820 is basically a superhet
design. The chip has poor sensitivity, so I had to add an RF preamp stage
to get the performance up. I thought about trying to run it as a TRF
receiver, but ran into trouble biasing the oscillator stage so that the
mixer would work. It was more trouble than it was worth.
The final build was decent, but not great. Sensitivity was around 3uv, even
with a good FET preamp stage. I used them for about 18 months before
abandoning them for a better receiver (an old Heathkit unit), which I still
have and use occasionally.
You should be able to make a pretty good BCB receiver with these chips,
since the in-band noise will swamp the receiver if you try to make it more
sensitive. You can find good preamp designs for BCB on the web if you wish
to experiment. You might be able to get a bit more sensitivity by making
the RF tanks more selective (higher Q inductors and capacitors, high
impedance FET preamp stage, etc).

--
David
dgminala at mediacombb dot net

Hey OM:

I am looking for the same thing but with 1 volt tubes I'd like to
duplicate the old Zenith trans oceanic radio. Now there was a radio
that is proven.
Not a single solid state device if I recall, great if there is ever a
EMP that takes out all the solid state radios.
For some reason there are plenty of 1 volt tubes out there even though
they haven't been made for sum 40 years.

But I digress. Get a Howard Sams TR manual, there will get you the
schematic. The real old radio's were hard wired no PCB. I know you can
find a schematic that is all transistors, bipolar though, no FETS in
those days, and I know they are still making germanium transistors
which are great for front ends.

73 OM
de n8zu

On Fri, 27 Aug 2010 10:29:51 -0700 (PDT), raypsi
wrote:

I am looking for the same thing but with 1 volt tubes I'd like to
duplicate the old Zenith trans oceanic radio. Now there was a radio
that is proven.

Heptodes like 1R5 or DK91 were used in battery powered superhets, so
googling for these might bring up something interesting.

Paul OH3LWR

On 27/08/10 20:22, Paul Keinanen wrote:
On Fri, 27 Aug 2010 10:29:51 -0700 (PDT),
wrote:

I am looking for the same thing but with 1 volt tubes I'd like to
duplicate the old Zenith trans oceanic radio. Now there was a radio
that is proven.

Heptodes like 1R5 or DK91 were used in battery powered superhets, so
googling for these might bring up something interesting.

Paul OH3LWR


They are around, I sold a number of those battery radio valves recently.
The other thing to look out for are the miniature valves that were used
in deaf aids.


Charlie.

--
M0WYM
www.radiowymsey.org

Sales @ radiowymsey
http://shop.ebay.co.uk/gnome7763/m.html?