Pages: [1]   Go Down

Author Topic: Cannibalize and old Sony ICF SW40 to make a QRP rx-tx out of it?  (Read 391 times)


Hi, this is probably off-topic here, but homebrewers are most likely the best ones at making the most of what one has, so I am asking here.

I have an old and battered [Sony ICF-SW40], with basically no resale value. SW reception is dead.

I wonder if I can cannibalize it and reuse any components to make either a crude rx or tx out of it. Or any other ideas that you can possibly have. I have nothing to lose. Thanks.
Logged

W1VT

  • Member
  • Posts: 6071
Re: Cannibalize and old Sony ICF SW40 to make a QRP rx-tx out of it?
« Reply #1 on: March 27, 2021, 06:26:18 AM »

I used to do stuff like that.  I would redesign circuits to use the parts that I had.  Before computers.
Maybe that is why I am so good at Scrabble. Which involves remembering words that use the seven tiles your have. ;D

Zak W1VT
Logged
Re: Cannibalize and old Sony ICF SW40 to make a QRP rx-tx out of it?
« Reply #2 on: March 27, 2021, 06:34:49 AM »

Ok, so what can I do with that?
Logged

W1VT

  • Member
  • Posts: 6071
Re: Cannibalize and old Sony ICF SW40 to make a QRP rx-tx out of it?
« Reply #3 on: March 27, 2021, 07:45:11 AM »

There are two approaches.  One, you can look of the specifications of any transistors you can salvage.  Or, you can make your supply voltage the same as the radio or whatever you got them from, and assume that will work as well. 

If you find an MOSFETs I don't think any were designed for HF.  Not if they are the cheap ones used in consumer devices.  They were designed for television, just like TV dongles.  So, they all pretty much work the same at HF.

Zak W1VT
Logged

N8AUC

  • Member
  • Posts: 1007
Re: Cannibalize and old Sony ICF SW40 to make a QRP rx-tx out of it?
« Reply #4 on: March 27, 2021, 08:04:45 AM »

I started a project like that. Except I started with an old, defunct, AM/FM alarm clock radio. I think the clock radio originally came from Radio Shack, so that will tell you about how old the original radio was. The intent was to build a 40 meter QRP CW transceiver out of it.

Basically, I gutted the thing, saving only the power cord, cabinet, and internal speaker. Everything else went into the trash. I chose not to reuse the internal components, because it was all soldered onto printed circuit boards, and the leads were trimmed too short to be readily reusable. The circuit designs and overall block diagrams were adapted from articles I found in some old Doug DeMaw (W1FB) books. BTW - that guy was nothing short of brilliant. If you can lay hands on the books he wrote, buy them, as they are a wealth of tried, tested, and proven practical information. I built a VFO out of some MPF102 JFETs, and got that working, with a buffer amp to follow it using a 2N3904. The shaft of the tuning capacitor came out the hole in the case where the tuning knob was for the original broadcast receiver. Built a voltage regulator to keep the power distribution busses nice and stable, with the intent of using an external battery supply to run the thing. Also built most of the receiver section, before other life priorities got in the way and I had to shelve the project. The parts I bought, and partially completed project are still around here in a box on the shelf. It was nothing fancy, being built on some perfboard, cut to shape to use all the available space inside the original cabinet, using point to point wiring. One of these days, I hope to get back to it.

Anyways, that's the approach I was taking. Yours may differ, as there is no single right or wrong way to do a project like that. Good luck with your project!

73 de N8AUC
Eric
Logged

WB6BYU

  • Member
  • Posts: 20896
    • Practical Antennas
Re: Cannibalize and old Sony ICF SW40 to make a QRP rx-tx out of it?
« Reply #5 on: March 27, 2021, 08:17:32 AM »

The first question is whether to modify / repair the
existing radio vs. cannibalizing it.  If you want to
make use of the existing tuning and frequency
readout, then modification might be a better
approach.  If you want the adventure of building
your own radio from scratch in a different
case / form factor, then cannibalization may
be a good choice.


The next question is what type of components
it uses.  If it is a dense array of unmarked SMD
chips, you may have trouble getting the parts
off the board, and identifying and reusing them.
While through-hole parts are often easier to
get off the board, if all the functionality is
contained in 3 or 4 integrated circuits, there
might not be a lot of practical difference
between modification and cannibalization,
as the easiest way to use the ICs may be
to keep them on the original boards (which
could be cut apart if you only want to reuse
part of it).

If it is mostly discrete parts, then you could
strip them all out and reuse them.  The
leads will generally be cut pretty short, so
they aren’t always as convenient for
prototyping, but I’ve used a lot of salvaged
parts in dead-bug construction.

As far as functionality goes, the Sony should
contain an audio amplifier that can be reused,
and some IF transformers.  If it is all
discrete parts, then you would also have
some small-signal transistors, though nothing
that would handle 1 W output for a transmitter.
Again, it depends on the circuit:  if all the RF
circuitry is in a single IC, it may be easier
to reuse it for the intended purpose, but
not to build something else.

The tuning system is probably far too complex
to duplicate, so would either need modification
or something totally different.


As far as modification goes, adding a BFO or
product detector to copy CW and SSB might be
all that would be required (along with repairing
the radio, of course).  By making the BFO
variable, you probably can get around the
1 kHz tuning steps.  Additional filtering would
help, of course, but that could be an audio
filter using a couple ICs (or changing the
components around the existing audio
amplifier circuit).


Looking at the schematic, and the circuit board
inside the case, to see what parts might be
salvageable, might be good initial steps to
help you decide how to proceed.

KB1GMX

  • Member
  • Posts: 2252
Re: Cannibalize and old Sony ICF SW40 to make a QRP rx-tx out of it?
« Reply #6 on: April 04, 2021, 10:14:08 AM »

I've done that, use an old radio as components.
PC mounted (NOT SMT) parts , anything solidstate and all salvaged.
used to strip old computer boards (pre 1970s) for parts too.

From the average radio a tuning cap and RF transistors suitable for a
regen or simple superhet and the 455khz IF canas well for that.  TX you
likely will be power limited but most of the devices at low HF can do a few
hundred milliwatts CW  but you need a crystal or will have to cobble a VFO.
Then again I'm from the days of 6  (sometimes 8 or 10) transistor Am radios.
and used to buy them to salvage and reuse.   Generally the junkbox and
parts cache has to supplement resistors and caps of the correct values f
or the intended project.

The Sony however has a PLL system for the VFO and that may be hard
to reuse.  The other problem is unlike older radios there may be more
ICs and fewer transistors to draw on.  Never seen the inside.

Allison
Logged
Re: Cannibalize and old Sony ICF SW40 to make a QRP rx-tx out of it?
« Reply #7 on: April 05, 2021, 09:42:46 AM »

After giving a 2nd or a 3rd look at this video:
https://www.youtube.com/watch?v=GGBvJZx69uI

I think I don't even need to cannibalize it: I could just let the splatter from a cheap and nasty rock-bound tx (eg the Chinese Pixie) work as a very poor man's BFO for this radio. Reception wouldn't be worse than the Pixie audio stage, wouldn't it?
Logged

WB6BYU

  • Member
  • Posts: 20896
    • Practical Antennas
Re: Cannibalize and old Sony ICF SW40 to make a QRP rx-tx out of it?
« Reply #8 on: April 05, 2021, 01:24:32 PM »

The Pixie runs the oscillator at low power in
receive mode.  Don’t know if there is enough
signal leakage to act as a BFO just from
proximity, but you certainly could tap off
enough signal to make it work.

VK3YE

  • Member
  • Posts: 313
    • vk3ye dot com
Re: Cannibalize and old Sony ICF SW40 to make a QRP rx-tx out of it?
« Reply #9 on: April 05, 2021, 03:23:09 PM »

The Pixie runs the oscillator at low power in
receive mode.  Don’t know if there is enough
signal leakage to act as a BFO just from
proximity, but you certainly could tap off
enough signal to make it work.

Yes, it should be fine.

The main battle with a poorly shielded local oscillator right next to the receiver is not too little BFO injection but too much.
Too much can swamp the receiver and reduce sensitivity.

Although if it's only a little too much (as was the case in my video above) you can get away with just turning the volume up.

You would adjust the trimpot in the Pixie to provide an 800 Hz (approx) frequency offset it needs for the BFO function to work.

Would reception be better than the Pixie? I reckon it would. For a start there will be some front end selectivity. The Pixie has
none (except for the low pass filter) so it had problems if you were near (or even not so near) an AM broadcast station.

Also the Pixie has poor audio selectivity. Some radios have tone controls that could provide a top-cut that helps a little.

It would likely still be poor at night on a band like 40m with many DX signals but during the day with low occupancy it should be fine.

Logged
Peter VK3YE/AK3YE    Youtube videos at VK3YE

Author of 'Minimum QRP', 'Hand-carried QRP Antennas', 'Ham Radio Get Started' and other popular books on ham radio.
All available in paperback or $US 5 ebook. Learn more at vk3ye.com or 'VK3YE Radio Books' on Facebook.

AC2EU

  • Member
  • Posts: 2793
    • McVey Electronics
Re: Cannibalize and old Sony ICF SW40 to make a QRP rx-tx out of it?
« Reply #10 on: April 05, 2021, 04:26:30 PM »

Don't take this the wrong way but, If you have to ask this question on a forum,  the answer is "probably not".
 :D
Re: Cannibalize and old Sony ICF SW40 to make a QRP rx-tx out of it?
« Reply #11 on: April 06, 2021, 01:40:56 AM »

Don't take this the wrong way but, If you have to ask this question on a forum,  the answer is "probably not".
 :D
Don't take this the wrong way, but if you feel the need to answer a question this way, then you're a nasty piece of work.
Logged
Pages: [1]   Go Up