An Attenuator from Fred KC5RT

Fred, KC5RT, sent me an electronics "CARE Package" with lots of really useful stuff, including an attenuator with switches.  All I had to do was find a box and some connectors.  An appropriate box was quickly found in my junk box (TRGHS).  So Fred's attenuator was added to my attenuator arsenal -- thanks to Farhan for getting this started.  

I've already put Fred's attenuator to good use: Instead of building an RF gain control for my Q-31 receiver, I just put the attenuator between the antenna and the receiver.  

Thanks Fred!  

ON6UU's DB4020 EA3GCY Rig

Hi,

Recently I got the EA3GCY newsletter,  it announced a new kit DB4020,  a 2 band transceiver kit covering 40 and 20 mtrs.  I know Javier EA3GCY’s kit are good so I ordered one.  A week later it arrived in a brown enveloppe in which I found all components and printboard wrapped in bubblewrap,  it was all well packed and after checking all components all was accounted for,  all components were indeed there.

8 toroids have to be wound,  following the instructions it was piece of cake,  no problem,  

After several hours of work - relax max style - I got everything in place to test,  hurray,  no smoke !!!!  So now the SSB part was ready,  I have 7W on 40 and 3.5W on 20mtr.  Good power for qrp sota,  wff or just garden activity.  A fortnight later I got notice that the CW part of the kit was ready and another week later it arrived here,  I soldered the 2 boards as soon as possible to get a multimode 2 band transceiver.   The 2 boards are the CW interface which also holds the KB-2 keyer,  the second board is the 500-600HZ CW filter.   The KB-2 give the user 4 memories,  beacon function and some more functions.  Good thinking to include the keyer,  it makes life easy when you’re on an activation. 😊   I opted to make the filter switchable,  I like to be able to listen broadband too,  very simple,  cut one leg of the 13 pin connector on the bottom of the CW interface and put a switch on both ends.

After some figgling around I also got the box ready,  a military grade plastic box with wall thickness of 5 mm,  this box should be able to withstand a lot of shocks and a drop to the ground.  I also made a docking station for a laptop battery which holds some 5Ah and which should be able to give me a lot of hours of listening and some 2 to 3 hours of operation.  I had an old laptop which the screen was broken and had some other malfunctions,  I have taken the battery connector out of it,  luckily I still have another laptop which still works and this is the charging station for the batteries …. ..  😊   The docking is only to test,  I will box it up in maybe a some box where I can then maybe also fit a end fed solution or tuner for coax fed antennas.

A new radio also needs a new CW key so I made one out of an old relay,  painted the base green to fit somewhat the box et voila,  here is the result of the complete portable station.

The key can be fitted to the box by means of a bolt and a wingnut.  A short cable goes to the CW connector of the transceiver.

I had a lot of fun constructing this kit,  the box,  the docking and the key.   For 180€ you get a arduino nano controlled CW/SSB transceiver with 2 bands on which most of the activity is and you also get a keyer with memories.   Good deal I think.   More info is available on EA3GCY’s website.  Javier is also very quick in responding to questions,  he ask for opinions and offers almost an Elecraft style of service.

I made some video’s which are on youtube :

https://www.youtube.com/watch?v=Y9sUbyAlF00&t=12s

https://www.youtube.com/watch?v=hGDwLdkr3HU

https://www.youtube.com/watch?v=ZiMnpfte4cI&t=35s

https://www.youtube.com/watch?v=oLYIgVv7So8&t=130s

The kitters website :

https://www.qrphamradiokits.com/

https://www.qrphamradiokits.com/transceivers/db4020-dual-band/#cc-m-product-12710260049

Best 73

Frank

ON6UU

"The All Japanese 6" Receiver

One of the great things about having a "miscellaneous" box in an otherwise well-ordered junk collection is that rummaging through that box will often send you off on fun and interesting radio adventures.  I was rummaging yesterday and I came across the guts of the little AM radio that used to be mounted on my bicycle handle bars.  I last mentioned this in 2011 : 

http://soldersmoke.blogspot.com/2011/08/bike-radio.html

I was just about to cannibalize this board.  The IF transformers were almost certainly at 455 kc and I could use a few of those.  But then I started thinking and Googling and trying to figure out the circuit.  That all led me this the site that provided the diagram below: 

http://www.angelfire.com/planet/funwithtransistors/Book_TS_CHAP-7.html

Six transistors, four transformer cans, two audio transformers.  Yea, that's pretty close to what I was seeing on my board.  So of course I had to see if I could get it going.   I hooked up a 9V battery.  I connected the pot wiper connection directly to the connection at the top of where the pot had been (it had disintegrated).  It works!  It is inhaling nearby WFAX, Falls Church, Virginia. 

You will notice that the transistors in the circuit above are PNP.  I had assumed negative ground and had hooked the battery up accordingly.  No smoke was released and the thing worked, so I guessed that I had assumed NPN correctly.  Sure enough, perhaps aware of the PNP ancestry, the manufacturer had marked my board "BC123 NPN"! 

The author of the book I linked to above dubbed this circuit the "All Japanese 6"  -- an obvious allusion to the All American 5.  

I see real potential in these AJ6s.   A few mods to the front end and you could be shortwave listening, perhaps on 31 meters!   

BTW:  The space on my handlebars formerly occupied by that little AM radio is now taken up by a Bluetooth speaker that plays tunes streamed to my I-phone from Pandora as I make my way down the same old Washington and Old Dominion bike path.  Progress. 

A Swedish Homebrew uBITX built in Dubai

It was great to get an update from Martin.  He has moved his workshop from Dubai back to Sweden.  We have seen lots of homebrew BITX monobanders, but very few homebrew multiband uBITXs.  Check out Martin's.  Very FB.   The input from Farhan was very cool, as was Martin's wise decision to follow Farhan's suggestion and to pause construction once the receiver was working.  As Martin put it, "I halted the build for a couple of days and just enjoyed listening."  Thanks for the update Martin. 

Dear Bill and Pete,

Here comes a long overdue update from my workbench, my last update was back in March 2017 when I had completed my first transceiver project.

http://soldersmoke.blogspot.com/2017/03/fb-ibew-hb-dc-cw-de-uae-a65dcs.html

I did not stop building and quite soon after I completed the CW transceiver Farhan posted the first schematics of the uBitx, why not? Why not get into a multiband CW-SSB transceiver as my next project.

After completing the receive part I was amazed... 

I halted the build for a couple of days and just enjoyed listening.

When it was time to start on the filters and the main RF Amp I sent Farhan an email asking about the way forward, he responded like this on May 17th 2017

"martin,

first, let me congratulate you, i suppose you are the first one to build a ubitx after me! second, i am not happy at all with the transmit line up, the drivers were not doing a good job above 14 mhz. i have replaced the 2n2219s with parallel 2n3904s. i also had to add two more LPFs, for proper harmonic suppression. i am headed for dayton today. once in dayton, i will try to find time to send you the latest circuit diagram. 

once again, congratulations on a wonderfully constructed ubitx."

Wow, what a shot in the arm for a fairly new home brewer!!! I was now back full speed with solder melting. I completed the filter bank and the RF amp, this is where I am starting to move away from the published diagram, I believe it is good to make it your own a little.

The end result was great, I worked many many stations in Europe and Asia with this little machine both SSB and CW.

In 2019 we decided to move back to Europe, the workbench and all boxes with parts and junk together with the rest of the household found their way into a 40ft container and was sent of to Sweden.

The A65DC Laboratories became SM0P Laboratories, the iron is still always hot and there is something brewing here all the time.

Thanks for a brilliant show boys,

Martin SM0P

Q-31 Receiver Filter Fix with the NanoVNA

The picture above shows my problem. As predicted by the Murata data sheet and as warned by R.A. Penfold, that nice 455 kc ceramic filter has a significant response at around 640 kc.   This caused me to hear Brother Stair twice as often as I should have.  Clearly a spur exorcism was called for. 

Click on the picture for a better image.  As noted last time, my first idea was to build a series 640 kc trap LC circuit and put it ahead of the ceramic filter.  But I had trouble getting the desired high Q.  So I then thought about putting a wider 455 kc filter ahead of my 12 kc filter.  I would, of course, need one that did NOT have the 640 kc spur.  I found a 455B filter in my junk box.  I used the NanoVNA to look at its response.  No spur at 640 kc!  Yea!  

Next I put the two filters together, 455B first, then the 12 kc filter.  Success!  You can see on the NanoVNA that there is no spur at 640 kc. 

With close to the desired termination impedances, the passband at 455 kc looked pretty good.  I just put 1500 ohm resistors in series at the input and output of the dual filter combo. 

It worked.  Spur exorcised!  I no longer hear each SW broadcast stations at two spots on my dial.