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Sunday, July 2, 2017

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.

I purchased OLED from 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

Saturday, July 1, 2017

G7WKE's Crystal Tester

Wow, this is an example of dedication to the cause.  I think many of us wimped out when confronted with the complex circuitry of the test device prescribed by DeMaw, but Rob G7WKE actually built the thing, and did a great job on it.  I'm tempted to suggest that Rob might want to set up a small business leasing this rig out to less dedicated filter builders.  Or perhaps he could have batches of crystals sent to him for DeMaw-ian analysis.

Hi Bill,
 
After listening to you and Pete discussing crystal filter design during SolderSmoke 197, I thought you might be interested in my latest project.

This is the Crystal Tester from January 1990 QST that is reprinted in W1FB's Design Notebook, which I believe is the circuit you and Pete were referring to.

It all appears to function as it should, so the next step is to sit down quietly with a pile of crystals and hopefully start along the road to a working filter!

73s
Rob G7WKE.



 

Thursday, June 29, 2017

Smoke Test Failure!


This is why you need fuses!  And reverse polarity protection!  Yikes! 

The Workshop at AA8V

Field Day was a big success for me this year.  I was in category "1E" which meant that I was home in the air conditioning, but doing my bit for emergency service by using a gel cell as my power source.  A SOLAR CHARGED gel cell.  So don't anyone call me a slacker, OK?

I was on my HW-8 and made a total of two contacts.  The second was with AH6AX.  I wasn't fooled -- I knew they weren't in Hawaii.  But the op gave me his home call:  WB8YYY.  Curt is a SolderSmoke listener.  In a follow-up e-mail he alerted me to the web site of AA8V.   Great stuff.  Thanks Curt.

Here is the AA8V workshop:

http://faculty.frostburg.edu/phys/latta/ee/workshop/workshop.html#electronics1

AA8V was on the QSO Today podcast not long ago. 

Monday, June 26, 2017

FDIM: Bob Crane Interviews Ashhar Farhan VU2ESE

At Dayton,  Bob Crane interviewed our friend Farhan VU2ESE.  Farhan shared insights on the BITX, the Minima and future rigs. 

Farhan was inducted into the QRP Hall of Fame at this year's FDIM event.

You can listen to the interview here:

http://soldersmoke.com/FDIM17VU2ESE.mp3