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Friday, February 19, 2021

A Problem with the San Jian PLJ6-LED Counter

I had hoped to use this handy and cheap little frequency counter to add some glowing Juliano Blue to the frequency readout on my Quarantine Hodgepodge rig.   I've used these boards with my BITX20, my HA-600A,  and with my DX-100/HQ-100 rigs.  But guess what -- these boards do not work with the BITX40 module board that is the heart of the Quarantine Hodgepodge.  And the reason why is interesting. 

Here is what happens:  First, you plug in the IF frequency of your rig.  In my case 12 MHz.  You connect your VFO output to the signal input on the PLJ6.  You power up the PLJ6.  You then have to select one of two IF frequency options.  One of these options ADDS your IF frequency to whatever it detects at the signal input.  In my case, for a 7.2 MHz signal it would detect a VFO signal at 4.8 MHz. If it were to ADD this signal to the IF freq,  it would readout 16.8 MHz.  And it does.  But obviously that is wrong.  So you go to the other option -- this one SUBTRACTS the designated IF frequency FROM whatever it finds at the signal input.  So here we get 4.8 - 12 =  -7.2   Almost perfect right?  But here is the problem:  The PLJ6 can't handle negative numbers!  So it displays 000000.  Not helpful. 

Here is the manual: 

I didn't have this trouble with any of the other rigs because none of them required the use of negative numbers.  My BITX 20 for example had an IF of 11 MHz and has the VFO running a bit above 3 MHz -- so the PLJ6 just adds the IF to the VFO signal and Bob is my uncle.  Similar problem-free addition takes place with the other rigs. 

I found some discussion on this problem on the internet.  Here is one: 

Some of the respondents didn't seem to understand the problem.  Others hint that the ability to handle negative numbers was as some point in the code for the PLJ6 device,  and may somehow be accessible, but no further info is provided. 

I have already worked up a possible solution, but I'm interested in how you folks would approach this problem.   Any thoughts or suggestions?  I will reveal my solution in the days ahead.   

James West, Inventor of the Electret Mic, has THE KNACK

 
James West (r) with Gerhard Sessler (l)  Bell Labs 1976

https://hackaday.com/2021/02/17/james-west-began-40-years-at-bell-labs-with-world-changing-microphone-tech/

For many reasons, this is a really nice story.  It is about a kid with The Knack, a kid who, like young James Clerk Maxwell, wanted to understand how things work.   It is also a technology story, the story of the invention of a device very important to us: the electret microphone. (Remember the earlier carbon mics in telephones?  I'll bet more than a few of our readers are guilty of stealing a few of those mics from pay phones.)  And it is a reminder of the benefits of helping kids who might need a mentor... or and Elmer.    

Thanks Hack-A-Day.  And three cheers for James West. 




Thursday, February 18, 2021

Phasors and the Propeller Analogy from Walla Walla University


We covered this excellent and very illuminating work before. As a follow-up, student Konrad McClure was kind enough to send me this video, which goes the extra mile with the propeller analogy. 

For me, the most interesting aspect of this is that it provides an explanation of the phase differences between upper and lower sidebands.   I need to study more about aliasing and the Nyquist criteria.  

Check out the video.  It get us a lot closer the an intuitive understanding;  math often falls short in this area. 

Thanks Konrad! 


Please send feedback to Konrad via the comment box below. 

Wednesday, February 17, 2021

Put this Chart on the Wall Above Your Workbench

 

If you are like me and sometimes forget if R=E^2/P or E^2P, this chart will help. Very useful.  

Tuesday, February 16, 2021

My Current Rig: The Quarantine Hodgepodge

 


As I continue to Stay In The Shack,  last week I was looking for something to do. This is what I came up with.   

Left to right: 
-- Speaker
-- Ramsey-kit QAMP20 modified for 40. I now have two MTP3055V MOSFETS in there.  
-- BITX40 Module with a solidified VFO from a Galaxy V (note the knob from a Drake 2B!)
-- Power supply 

It puts out about 15 watts SSB.  I was bracing for attacks from the 40 meter waterfall police, but no, everyone said it sounds great.  I had four very nice contacts yesterday.  It was fun. 

Still to do:  Possibly a San Jian frequency counter to give some Juliano Blue glowing numerals for the frequency readout.  This would be a step up from the Juliano Blue sticky note and  corresponding piece of black electrical tape that currently serves as the frequency indicator. 


Monday, February 15, 2021

Jean Shepherd Works Through a Satellite in a School


Ah,  1975.  Obviously a very different time...  I'm not sure if Shep would fit in well in the classrooms of today.  There was bit of Rodney Dangerfield in his demeanor -- that would likely cause some trouble.
 
But this clip was fun.  Shep was right on target when he talked about how getting your ham license used to mean that you'd "mastered a technical art." 

The OSCAR satellite they were using was 2 meters up and 10 meters down.  There was a Heathkit HF transceiver with a transverter.  And a Simpson multimeter.  That mic was a Turner +3 

Thanks to Steven Walters for alerting us to this.  

EXCELSIOR!   

Sunday, February 14, 2021

Friday, February 12, 2021

A Lifetime of Workshops

 

https://microship.com/consoles/?fbclid=IwAR37yc-NfOrUC93C8QZYXZfakGLf-4eBtPw2php0CpzGHBW3-fb55ciyp0w

It has been more than decade, but we've posted about Steven K. Roberts N4RVE before: 

https://soldersmoke.blogspot.com/2009/09/i-didnt-care-i-had-secret-life.html

https://soldersmoke.blogspot.com/2009/09/knack-on-bike-steve-roberts-video.html

This morning I came across his recent article about the workshops he's had over the course of his life.  Very nice.  Man, I should have held on to that SP-600 I once had.  You folks will like this: 

https://microship.com/consoles/?fbclid=IwAR37yc-NfOrUC93C8QZYXZfakGLf-4eBtPw2php0CpzGHBW3-fb55ciyp0w

Wednesday, February 10, 2021

Microphone Men -- A Really Nice Video


Thanks to Rogier PA1ZZ for sending me this really nice video.  

Tuesday, February 9, 2021

Meet Your New Soviet Neighbor -- With Hallicrafters

 
Thanks to Jeff Murray for alerting us to this.  It is obviously from World War II.   If the new neighbors had S-38s, well, that might help explain why things didn't go so well.  

Sunday, February 7, 2021

A Really Nice Video about a Regen Receiver


Thanks to Stephen Walters for posting the link to this video on the SolderSmoke Facebook page. 
I really liked the way this project was described.  I think this is the work of Ciprian in Romania. 



Really nice.   Thanks!   73  
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