"This is such a great time to be in the hobby"

 After the two days at FDIM, I went and spent a couple weeks helping my daughter with a few things around her house.
I did a little computer work on some of the projects I had started, but mostly followed some of the blogs I keep track of.  One of them is by Pete N6QW.  After a couple of e-mail exchanges concerning some of his new projects, he ended one with "This is such a great time to be in the hobby".  I couldn't agree with him more. 

When I started in electronics in the mid 1960's , an instrument with the capabilities of the SNA Jr. would have cost many thousands of dollar and fit in a 19" rack.  Now it is a hand held unit that cost less than $30 to build.  This is mostly due to the fantastic advancement in micro-electronics, especially the new micro-controller chips that are available.  

The first job I had after I got out of the ARMY in the late 1970's was as an engineering technician in a very small company.  One of the  projects I worked on, used what I might consider an early predecessor of the Arduino type controller.  It used a single board computer, with a 4 Mhz Z80 processor, 4K RAM, room for 24K e-prom, and 16 IO pins.  It was about 1 foot square, cost  $250, and you needed a few hundred dollars worth of software to develop anything for it.  Now it is a $3 Arduino Pro-Mini about the size of a large postage stamp, and the software IDE is free.  Along with the Arduino or other micro-controller board, you have all the  peripherals such as LCD or TFT displays , DDS and PLL modules, and of course the many ICs availble.   Some times the hardest part of the design is to decide which of the many options you want to use.
The Internet has made all these parts readily available through the on-line catalogs of major suppliers such as Mouser, and DigiKey.  Other suppliers such as AliExpress and Bangood that offer a large selection of electronics components.  And don't forget eBay where you can get almost anything from around the world.  The Internet has also allowed small companies such as Adafruit, and SparkFun to build a successful business supplying specialty products to an ever growing MAKER market.  Related to Ham Radio, you have suppliers such as Kits and Parts, QRP-labs that offer products that are more directly related to RF projects.  

The Internet also gives you access to information on almost anything you might want.  From product data sheets to service manuals, and individual blogs,  almost anything is available.   Just add DIY to almost any search and you will be amazed with what is available. Want to build your own electron microscope, search "diy electron microscope".  Over 200K hits to choose from.  Of course only a very few might be useful, but there is some great information on what other people have built.

With the smaller solid state devices, construction methods have changed.  You no longer need a machine shop to build something, but it is really nice to have one.  Using methods such as "Manhattan ", "Ugly",or prototype circuit boards, some truly wonderful projects have been built.  My preferred method is to make a Printed Circuit Board.  Layout is very fast using one of the free or evaluation PCB software packages such as KiCad, Eagle, ExpressPCB.  Then using toner transfer, I can etch a nearly professional looking board in a few minutes. A little bit longer, and I can add a usable solder-mask. You will not have some of the nice features such as plated through holes for double sided boards, but with careful layout you can minimize these problems.  Some people have commented that this takes too long, compared to "Ugly" .  But, I have found that it is much easier to trace for errors on a PCB before building than to check something done "Ugly" after it is built.  
If you don't want to etch the board yourself, you can send the design off to one of the many PCB houses to have them made.  One of my favorites is OSHpark.  They take my Eagle file directly, and for $5 a square inch including shipping, I get three solder-masked double sided boards with plated through holes in about a week.  For larger quantities or size boards, I tried one of  Chinese board houses.  For less than $35 including shipping, I got 10  double sided solder-masked boards with plated through holes, around 10cm. by 10cm. in about two weeks. 
One comment I get is that it is getting harder to find through hole leaded components.  I have found that using surface mount devices SMD it is much easier and faster to build most of my projects.   I don't have to drill nearly as many holes in the boards I etch myself. If you use the larger size SMD components 1206 or 805 placement is quite easy.  If I don't have a component in SMD I can just layout a couple large pads, and solder on the leaded component after bending the leads.  If you don't want to go to SMD , you can check out the "Muppet" method championed by K7QO.  Using solder paste and a hot air gun, construction is much faster than having to stuff and then flip the board over to solder through hole components. 
All in all I will have to agree with Pete,"This is such a great time to be in the hobby".  I might even say that this is the "greatest" time to be in the hobby for the home builder.



Now that I am back home, it is time to think about some of the other projects I had started, and get busy working on them.

SNA Jr. II update UPDATED 8/29/16

UPDATED 8/29/16
To make it easier for those that want to build their own SNA Jr Ver. II, I have uploaded the Eagle files to OSHPark.com.  Boards can be ordered from them if desired.  If a  couple people want to get together and build some, cost is about $49 including postage for 3 boards.  They can be found under the shared projects as

SNA JR DDS large format ad8307.brd

UPDATED 7/25/16

The SNA JR II took the best in best in show in the home brew contest at FDIM, and because of  many suggestions I wrote an article for QRP Quarterly.  Just got my July issue and found the article has been published.  I put together a Dropbox folder with the documentation needed to build your own. The  Eagle cad files for the board and parts layouts are included.  It also has the latest Arduino sketch and a number of pictures of the construction.  I have also included a document covering the basic operation of the device.
They are available at
https://www.dropbox.com/sh/vqd4kqa4w2keeqr/AAB4Oo0WNCqPWZMIMh0jt-3Ta?dl=0


Just before I went to FDIM I was able to get the SWR function working on the SNA Jr.  With nothing connected to the input to the Return Loss Bridge, I did a sweep and measured the average return loss and stored in the sketch.  I use this value when converting from return loss to VSWR.  I used the SWEEP.R routines to do a sweep of the desired frequency range.  After the data is acquired I  normalize the data using the previously found average return loss.  Using the integer value of the return loss, I use a simple look-up table to find the VSWR.   The display routine now uses the VSWR value and plots  the waveform.  Since I only use integer values for return loss, the plotted wave is a little rough, but more than adequate for normal usage.

Here is a plot of my 80-40 meter end loaded dipole. Sweep range is from 3 to 9 Mhz, so each horizontal division is 1 MHz, and vertical divisions are limited to a SWR of 4:1.   You can see the narrow SWR dip around 3.950 MHz and the low SWR reading of 1.29 : 1 at 7.2 MHz.

Four Days in May 2016

Well because of my schedule it was only Two Days in May, but it was still fun.  I really enjoyed the seminars on Thursday, and was pleased to hear Paul M0XPD mention the SNA Jr. during his presentation.  The WBB was great! You would not believe how much work must have gone into getting everything ready for that.  It was more work than I thought it would be just getting 8 kits of the SWR Power Meter ready for the last club meeting.
Enjoyed the vendor night, although with the limited space it was quite crowded.  I did manage to pick up a couple of things that looked interesting. Also had a chance to talk to several people I had exchanged e-mails with over the last year or so.
After a long day Friday of trying to see as much of the Hamvention as possible, I finally made it back to the hotel in time for club night and the homebrew contest.  The only problem with having an entry in the homebrew contest, was that I did not have a chance to walk around and look at the other entries and club presentations.  But it was still a fun experience.
I spent a lot of time talking about and demoing the SNA Jr.
After suggestions from several people, I am in the process of writing an article on it for QRP Quarterly.  Hope to get that written and submitted within the next two weeks or so.
That's  all for now.

SNA Jr. version II update

Well, after a lot of time working on the top half of the box for the SNA Jr. v.II, I have it finished.  It took quite a bit of time with some small files, but it looks very nice.  The extruded aluminum box is nice and solid, the push button on the rotary encoder has a nice solid feel.  Earlier versions using small tin containers flexed when the button was pushed, and it felt kind of mushy. 

Did some work on the software, and now have most of the basic functionality working with the AD8307 instead of the diode detectors.   With the diode detectors I had range of about 50db, with the AD8307 I have a range of about 10 to -75 dBm.






 5/13/2016
 Finished making changes to get all functions to use the AD8307 and added a simple Frequency Correction  factor to correct for the ~11dB drop in signal output I saw when sweeping form 1 to 40 MHz.  This large drop is probably because I did not include a buffer amplifier, and just take the output of the DDS module through a 100nF capacitor.  I have not had any problems using the instrument for what I want without an amplifier, so decided not to complicate the design.

I added a Watt Meter function for use with a 40 dB. Tap.  It gives the signal in dBm and auto scales to either  a watt or miliwatt reading .  I also keep a peak power reading for each time RF power is detected.  With no power applied the screen flashes NO POWER and resets peak reading after 2 seconds.
 

Watt Scale

milli Watt scale

I want to add some calibration routines if I have time.  Also trying to get some preliminary assembly instructions written for the pilot run of the SWR/power meter before the club meeting this Saturday

SNA Jr. Version II Part 1

I need to visit my daughter and help her with a couple remodeling projects around her house. I set the schedule so I can stop in Dayton for a couple of days at FDIM and decided to build an entry for the home-brew contest.  
With the success I had with the stand alone AD8307 power meter, I thought it was time to upgrade the SNA Jr. with a real power detector.  The SNA Jr. had started out with my version of the K6BEZ antenna analyzer and a need to check some filters I was working on for another project.  I replaced the SWR bridge circuit with a couple simple diode detectors and used the Arduino to compute  gain/loss in dB.  For such a simple project, I was really pleased with the results I was getting.  It was a vary small hand held instrument that I could use as a signal generator, SNA for testing filters.  With  the addition of a Return Loss Bridge I could check antenna SWR.  Then I added a simple pickup coil and a little software I also had some of the functionality of a Dip Meter.

It was very easy to edit the board layout for the original SNA Jr. to remove the diode detector and amplifier, and merge in the AD8307 circuitry from the power meter board.  The board house that I was using for the pilot run of club SWR meter project had a special going on.  Since I know of several people that would be interested in one of these boards I ordered 10 SNA Jr II boards.  It took about 2 1/2 weeks to get the boards, and am really pleased with the way they turned out.  The only issue I had was the spacing of the RF chokes I use to feed DC and signal into and out of the AD8307 circuit.  The ones I had are a little larger than the ones I had used in the stand alone power meter, and I had to bend the leads back on themselves to make them fit.  Other than that everything else works well.
In the original SNA Jr. I used a couple of 4.2 volt Li-ion batteries for power.  Only problem was that I had to remove the batteries to charge them.  In a rebuild of the SNA Jr. I used a 12V battery pack designed for use on security cameras.  This worked well, but I was not getting as long of operation on each charge as I had with the individual Li-ion batteries.

Looking around on eBay for something else I found some 2S Li-ion Lithium Battery 18650 Charger Protection Board Modules.
They are very small and take care of the charging and protection of 2 batteries in series,  there are also other versions available for different size battery packs.



 
I mounted a couple of battery holders , the charge controller board,  connectors and On/Off switch in the bottom half of the extruded aluminum box I bought for the project. The charge controller board is very small and after wiring it up I covered it with a piece of heat shrink and stuck it down beside one of the batteries. 


 I checked charging with a couple batteries and was very pleased with the way it operates.  I monitored charging current and voltage, it charged at about 1.6 amps with a wall wart power supply that put out 10.3 V. with no load.  While charging it put out around 8.6 V.,
and when charge was complete the current dropped to nearly 0 and voltage jumped up to the open circuit voltage. 

I built up one of the boards, and gave it a quick check to make sure everything was working.  Since I did not have the software modified to read the 8307, I checked the output of that circuit with a voltmeter.  




I got around the .25 V. I expected with no input and it jumped up to around .5V. when I touched the input with a screw-driver.  These are just about the same as I was getting with the circuit in the stand alone power meter.  Now that I know it is working I can build the shield box to cover the AD8307 circuitry

After adding the SMA connectors for RF output and input to the detector, I finished building a shield around the AD8307 circuitry using some .008" double sided circuit board.  That has become my favorite for building shields, easy to cut and solder, and stiffer than copper shim stock.  Here is a pictures of everything ready to be assembled, and one showing how tight everything fits in the box




Next to finish a little final fitting on the top half of the project box and mount everything, then on to the changes to the software.  Also thinking about adding a couple additional functions, such as directly computing VSWR instead of just Return Loss.  And add a wattmeter function, using a 40-dB tap to drop the power level down to that required by the AD8307.  Watch for updates, FDIM is less than two weeks away.




 

SWR Power meter update UPDATED 5/7/16

Because of a family emergency I had to make a two week trip to the winter wonderland I escaped from about 30 years ago.  I was not able to do much on the SWR Power meter I am working on that the local QRP would like to kit.  I was able to get back in time to get a board stuffed in an Altoids tin and take it to the monthly club meeting.  
The club member that has been testing my early prototypes seems to be happy with the results he was getting with the latest version that incorporated a diode compensated amplifier to improve linearity and low signal response.  The power readings he was getting were linear from less than .5 watt to over 50 watt, and were good up to 6 meters.
I will stay with this hardware and just have to do a little clean up on the software and couple things I want to add.  Just in the process of ordering parts for a pilot run of 10 units for some club members to assemble and test on their own.  If that works out the club will probably start selling the kit along with the kit they presently have.

Including a picture of a prototype board mounted in an Altoids tin this time.  For the Altoids tin I am using edge mount SMA connectors. They are nice and small and easy to install.  There are adapters from SMA to BNC and most other types of connectors available fairly inexpensively through the auction sites.

Will let everyone know how the pilot run turns out.  
For now I am spending most of my time working on something for the home-brew contest at FDIM.

Just a quick update on the pilot run of boards. The boards I got from China look really nice. Finally have all the parts in and built one to test.  Found that the display boards I received use a different driver chip.  I found the appropriate driver that was compatible with the Adafruit libraries I use, but runs at a slightly different resolution.  So I have been rewriting some of the display functions to reflect the changes.  Shouldn't take too long, and also doing some  clean up of the code at the same time.

 
 

Sweeperino Jr. Part 1

Now that I have the SWR meter nearly finished, I want to get back to working on the spectrum analyzer.  I will need to build and align several filters that are higher in frequency than either the SNAJr. or the Chinese SNA cover.  Lookng at some posts by Asher Farhan on his blog, he has a simple SNA that he called the  Sweeperino.


  http://hfsignals.blogspot.in/p/sweeperino.html  

This uses the same AD8307 power meter I had used before and a SI570 for the signal generator.  His version has a 2 line LCD display for frequency and measured power level , and uses a pot for tuning. There is a PC program for doing a display of the sweep, same program is also used for the SPECAN display.


Since I was only interested in displaying the sweep while aligning filters, I did not need the display or tuning pot.  I wanted to save the last si570 I have on hand for the spectrum analyzer, so I used a Adafruit si5351 breakout board I had left from another project.

   The power requirements for the si5351 board and ad8307 are very low, and could be powered directly from the 5 volt output on the Nano.  I used some 100uH. molded RF chokes with additional filter capacitors to feed power to the 5351 and 8307 .  I had used this before in the stand alone power meter, and with shielding was able to get a -74 dBm noise floor.
When I built the power meter I found it was fairly difficult to solder the SMD parts without a solder mask, very easy to have shorted traces.  After I finished etching a double sided board, I decided to try adding a solder mask. 
I found two methods of doing solder mask at home, the simplest appears to be using UV curable paint.   I watched a You-Tube video that makes it look like it should be fairly easy.

https://www.youtube.com/watch?v=Vj_cdBZO1Tk

Other than the paint, the only other thing needed was a UV light source, although you could probably just take it out into the sun to cure.  Looking around for UV light sources, I found a small unit that is designed for use with UV curable finger nail polish.  This was under $10.00 and can be powered from a USB port or USB power cell.  This unit has a push button that turns the light on for 30 seconds at a time, this will make timing the exposure very easy.


I printed up a stencil of where I wanted the mask to leave bare copper on a plastic overhead projector sheet.  Then got everything all ready to give it a try. I did a couple of quick tests on some scrap board to get the exposure time down. About 2.5 minutes seems to give good results.

Using a small plastic card as a squeegee and a piece of plastic cut from a zip lock bag, I spread a thin layer of the UV paint on the board and aligned the stencil with the etched pads.  I exposed the board to UV light for 2.5 minutes, and then removed the stencil and the piece of plastic.  Using a paper towel with some rubbing alcohol, I cleaned off the un-hardened paint.  After checking the mask, I exposed the completed board for another couple of minutes to make sure everything was hardened.










 
The board looked pretty good, with only a small area where the mask came off the ground plane area.  Not as pretty as a commercial board, but looks like it will do what I want it to do.  Looking at the area where the SMD components for the power meter circuitry will go, everything looked very nice.  I think this will make it much easier to solder in the SMD parts using my hot air gun.  I used the same process and masked the bottom layer of the board.

Next to build up the board, and get the Arduino software working with this configuration.