Intuitive Repair of a Sony Shortwave Portable

A few years ago my wife got me this nice little Sony ICF-SW7600GR receiver.   On the front it proclaims that it is "AM DUAL CONVERSION" and "PLL SYNTHESIZED."   It has a BFO, and a filter of suitable width for SSB.  It also has a synchronous detector -- it generates an internal carrier that matches the frequency and phase of the carrier being transmitted by the SW broadcast (or ham AM) transmitter.  This helps overcome the selective fading that often plagues AM signals.  Sony advises switching to USB or LSB once the synchronous generator locks onto the carrier.  Pretty cool. 

The BFO is the reason I wanted this receiver. And wouldn't you know, when I dropped it,  it landed EXACTLY on the little BFO fine tune control pot.  It was as if the Radio Gods disliked all the fancy digi PLL synchronous IC circuitry.   

I tried without success to find the value of the destroyed pot.  Finally, last week I just decided to have a look in there to see if I could just figure it out. 

On the board I could see that the pot only connected at two places, so I figured it would be a varactor circuit on the BFO with one end of the pot to DC and the wiper to the varactor diode.  I figured I'd try a 10K pot. 

This seems to have been some good radio intuition.  It works.  I went with a small trimmer because it is less obtrusive and because once I set the BFO in the right spot, I think the de facto channelization of the 40 meter ham band will keep most of the SSB sigs in tune. And the Sony only tunes in 1 kHz increments. If necessary I can move the BFO a bit with a small screwdriver.  I just glued the trimmer pot onto the back of the receiver -- two wires covered by heat shrink run back into the circuitry. 

10k might be a bit too small.  Maybe 100k would be better?  As it is, I can move the BFO above and below the "zero beat" point, and I don't need more range. Mouser has a small trimmer pot with a tuning wheel that looks like it might fit, so I may try for a proper repair. 

K.P.S. Kang's Minimalist VXOs (and one for the BITX)

K.P.S. Kang provides us with some great ideas for simple VXOs.  He includes an intriguing reference for a 5 MHz circuit useable in a BITX.  Tell us more OM! 

http://smallwonderqrp.blogspot.com/2017/07/vxos-simple-minimalists-signal-sources.html

NYC's Radio Row Survives (sort of) in the Bronx

Thanks to our friend (and official lexicographer) Steve Silverman KB3SII for alerting us to this important bit of radio news from the Big Apple.  It seems that a part of old Radio Row was saved and moved -- first to Brooklyn and now to the Bronx.   I got a kick out of some of the comments in the New York Times article about the store:  The insurance company determined that the contents of the store were "non-pilferable." And one young audio enthusiast was quoted as saying that old American tubes "sound better" than Chinese tubes.  I guess they have more presence.  Or brightness.  And less feathering.  Or something.

Here is the 2011 NYT article: 
http://www.nytimes.com/2011/11/20/nyregion/leeds-radio-is-a-haven-for-lovers-of-all-things-analog.html   


To N2CQR  

Jul 17 at 12:26 PM

Bill

Radio Row survives in a storefront in the Bronx, by appointment only.  Leeds Radio was started in 1923 and survives because an enterprising customer bought it from the 72 year old owner.

But this is where you can shop any time for stuff that should be in your junk box:

https://www.etsy.com/shop/LeedsRadio

Yikes, what is the world coming to?

I promise to keep any information about what you actually buy on that site a secret!

73

Steve  KB3SII  ... .. ..

PS  When I was 11 (and WN1ZPT) , my parents visited NYC and gave me $10 and sent me alone on the subway to the real Radio Row.  I was in heaven for a few hours!  Got good stuff too.

Excellent Description of the Electret Microphone

I've been experimenting with electret replacements for the D-104 crystal element.   I found this site with a really excellent description of what lies inside those little electret capsules.  Here it is: 

http://www.openmusiclabs.com/learning/sensors/electret-microphones/index.html

Dino's FB W1FB Crystal Tester

A couple of weeks ago I noted that the complexity of DeMaw's circuit caused many of us to wimp out on this test gear project.  I joked that those who had built the device might be able to set up small businesses to do the testing for the rest of us.  Perhaps our friend Dino can cut a deal with G7WKE to divide up the world market for crystal testing: Dino could have the Western Hemisphere while Rob covers Europe and points East.  

Bill -

Enjoyed seeing someone else who has built Doug’s crystal tester on the blog.  Here’s mine, built this back in early 2007.  Anyone who wants to duplicate the tester can find the article in the January 1990 issue of QST or the updated article in the W1FB Design Notebook (page 192).  Note that the QST article has a missing component value and a missing component (both corrected in the Design Notebook):

(1) R24 is missing its value - it’s marked in the Notebook as 56 ohms.

(2) There should be a 220 ohm resistor connected between the output pin of U2 the LM317T regulator and the top of R1 the voltage adjust pot that is connected between U2’s adjust pin and ground [corrected in the March 1990 QST Feedback column].

I built a FT-243 adapter to let me work with larger crystals.

73 - Dino KL0S

And Now For Something Completely Different: 70cm FM

So there I was, talking to KE5FV on my scratch-built 17 meter BITX, when in walks my son Billy with this walkie talkie.  "Hey Dad, I'm cleaning out my room -- could you use this?"  I'd seen it before but I thought it was some Family Radio Service device that he had picked up.  But no!  It is one of those very cheap Baofeng UV-5R FM transceivers.  I soon found myself scrolling through menus, trying to figure out how to use the strange new appliance. 

I got it on 70cm and soon established contact with a Bill W3HXF -- that was my first ever UHF contact.  We then switched to 2 meter simplex. 

It works fine.   I've been looking for something different.  This could be fun.  Any suggestions on how to make the most use of this thing?

Have You Ever Seen What's Inside a D-104 Crystal Element?

I had not seen this  I must say, I am disappointed.  I had visions a circular collection of shiny Rochelle salt crystals.  But look at this thing.  It is quite flimsy -- not at all what you'd expect from the sturdy D-104 exterior.  It has kind of a "Wizard of Oz" behind-the-curtain feel to it.  Yuck. If I can't find a D-104 element in good shape, I might reach for a dynamic element or -- gasp -- an electret.

Stop Me Before I Commit an Electronic Atrocity!

Sadly, not mine

I like the D-104 mic.  I bought one from Astatic shortly before they went under and it has provided good service with many different rigs for a long time.

I wanted another one, primarily for my DX-100/HQ-100 station.  I saw one on e-bay and a few days later it was here.  Unfortunately the seller was correct when they warned that it showed no output.  I had hoped it was a problem with the amp in the base, but no, it seems that the crystal element is quite dead.  It is an MC320 cartridge marked 7-77.  There is an aluminum sheet at the front that is apparently supposed to be riding atop a center support that connects mechanically with the magic crystals.  But it looks like a circular tent that has poked through the center support and collapsed around it.

Just a few years ago there were some options for replacement elements, but it seems that most of these are gone.  Bob Heil does have a dynamic element replacement kit for about 68 bucks. 

There are many schemes for putting electret elements in the old D-104 head...  I was reaching for the junk box but I stopped myself.  NO!  I will try not to commit this kind of electronic barbarity. (I have already sinned by killing several QF-1 Q multipliers and a couple of Benton Harbor lunch boxes.)  I will instead turn to the SolderSmoke brother/sisterhood and ask if anyone out there has a crystal element that could bring this old mic back to life.  My DX-100 deserves nothing less. 

Anyone have a D-104 crystal element in their junk box? 

Steve N8NM Gets Modular -- With Both Hardware and Software

Steve N8NM has an excellent article on his blog about the benefits of modularity.  He breaks new ground by extending the concept into the software realm.  Check it out:

https://n8nmsteve.blogspot.com/2017/07/sr-16-lets-get-modular.html 

Subscribe to Steve's blog, or link to it.  Hopefully this will encourage him to post more great things like this.

Another LM373 Rig - Pete Is Not Alone!

Bill,

Thanks for coming back to my call. It was a thrill to finally catch you on the air.Like I said my Soldersmoke marathon was amusing and kept me in great company on my round trip drive from Murphy NC to Chicago. While I was in Chicago I emptied my storage garage of goodies that have been there for 12 years, it was like Christmas in June. I uncovered treasures I didn't know I even had and yes I found the box of project boards that kind of or didn't work at all. I now have these treasures to play with and see with renewed eyes what I may have done wrong, or burned up. It looks like a few of these modules can be made into rigs.

I also found a couple of antennas that I traded for that never made it up.

Also the bigger surprise was how many parts I had kept especially the ICs that were intended to beused in rigs like the LM373's that Pete has talked about. I have one test circuit board to test the LM373 that just needed the oscillators so with my SI5351 breadboards I have what I need to get this going.

Now that I'm settled into my new QTH in the wilds of western NC I will noodling and tinkering moreto get my little DSB rig on the air and an LM373 based SSB rig too,  using mostly or all obsolete/vintage parts. This is something I have been noodling about for sometime now.

I also will get my MMM finished.

Thanks again for the QSO and I look forward to working you again. Now to melt some solder.

73,

Skip Davis. NC9O

---------------------------

Pete's LM373 page: http://www.n6qw.com/LM373.html

The Radio Laboratory at Bandung, Java -- SSB in 1927

Anton PA0AST alerted me to this important piece of radio history:

The first phone radio between Indonesia , the city of Bandung ( Dayeuh Kolot, Jalan Radio 1 ),  and Holland , Radio Kootwijk  were made  in SSB already in 1927... Before that time they had only a CW  1 Mega Watt spark transmitter in Malabar.
One of the receivers still exists in a museum in Amsterdam (cdvandt ). It is 3 meters in length and 2 meter in  height....  All made with plug-able units with 1 tube inside .

The transmitter was 10 kW. Ua was 6kV was made by dynamotors. Transmitting Tubes locally made by craftsman in a workshop.  Both  buildings as well  in Bandung and in Kootwijk still exists .

Anton

The old images come from:
http://www.cdvandt.org/bandung-lab-kwk.htm

At the other end was Radio Kootwijk in Holland. 

Before you jump to the English version of the page, be sure to check out the Drone video of the site, and the audio file of the Morse transmissions: 

http://radiokootwijk.nu/     Thanks to PA0JWU for the wonderful site.

Quite an impressive shack!  My favorite part is the note indicating that local residents cleaned out the cooling pool and used it for swimming each summer.

AC9JQ's Mini Digi VFO/BFO Al Fresco with OLED (and noise test)

From Dean AC9JQ:

Just completed the VFO/BFO/Arduino/OLED module for my radio.  I also have the LPF, BPF and crystal filters completed and tested.  Next will be the audio amplifier and NE602 modules.  I will probably build one of the NE602 modules and test things out as a DC receiver.  My ultimate plan is to have the rig no more that 1"x3.5"x3".  I still have a lot of "stuff" to stuff into that size of box.  I'll keep you posted.


I have been able to contain the entire Arduino/Si5351/OLED into a small cube in the front.  The rest of the radio has to fit on two levels in the rest of the area behind the Arduino/Si5351/OLED.  I think I will build the audio section and on NE602 mixer and run it as a direct conversion first to vet out any noise or other problems.  Bill, that small coax that you pointed out will really help on this build.  I used a small piece as a power feed-thru and will use it to feed out the VFO/BFO signals, thanks again for that pointer.

I decided to test for noise on the TIA transceiver test bed.  See the video of the results.  Not too much noise.  I'm only using my indoor magnetic loop for an antenna.  Video is kind of sloppy, but taking off the antenna and turning up the volume shows how little noise is left in the system.  Now time to stuff the rest of the radio into the tight quarters.

https://youtu.be/kXf7-7FtxEU

I purchased OLED from ebay.......

http://www.ebay.com/itm/401234789687?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

0.91'' 128x32 IIC I2C Blue OLED LCD Display DIY Module DC3.3V 5V For PIC Arduino | eBay www.ebay.com IIC interface. OLED display, no need backlight, self-illumination, the display performance is better than the traditional LCD display, also lower consumption. VCC: Power (DC 3.3 ~5v). Display Color:Blue. | eBay!

They are nice and compact, although as time goes on, I'm sure they will be harder to read.  I'm hoping to have an alfresco version in a week or two.  I used much of Pete's code from the shirt pocket transceiver upgrade, modified the code to address the smaller display and add USB/LSB capabilities. 

73's  Dean AC9JQ