Back in the saddle again... 40 meters adventures

The last week or two has gotten me back on the air finally.  My goal of having a complete homebrew station is just about done.  At least the HF part of it, for now.

The 40 meter transceiver I'm using is a heavily modified K1SWL SW40+, with redesigned bandpass filters, an arduino-controlled DDS replacing the stock VFO, redesigned RF amp with a MJE-182 final and a headphone amp outboard from the original OPAMP. Other than that, it's a SW40+ built manhattan style on PCB stock. It has a 300 Hz bandpass crystal IF filter and puts out a whopping 1.5 watts.  I could push the MJE182 up to 3.5 watts, but I didn't like how hot the transistor was getting, so I backed the drive down to 1.5W.  At some point, I'll put together a 5W output amp, but I want to see what I can do with what I have first.

To the left of that transceiver is a BITX20 that I hacked together. Again, I've replaced the VFO with an arduino-controlled AD9850 DDS.  The radio appears to work, but it seems I'm never in the shack when 20 Meters is actually open lately, so it hasn't been used on air yet.  More to come on that later.



Here's the BITX20 going into its case

The device with the 4 red buttons is a PIC controlled keyer that started out life as a 4SQRP club style keyer, homebrewed on a piece of stripboard.  I've hacked around so much on the code that it's more my design than the original.  It's not quite as good, I don't think, but at least I tried, right?

Next to that is the audio filter I hacked together a while back.  It originally had a wood case, but I thought better of that and bought a nice little brake from Harbor Freight that I have used to make all the rest of the cases you see pictured.  It makes building equipment boxes really quite simple.

Bending the top cover of the BITX from Galvaneal
 

Not shown in this mess is my homebrew antenna tuner.  It's just an L network for tuning up the only HF antenna that has survived the wind this winter.  The antenna is a 69' end fed wire in an inverted V configuration.  I haven't figured out its pattern yet.  My bet is that the radiation is mostly vertical so it will probably be fairly omnidirectional.  There are lots of trees on my lot though which tends to do funny things.

At any rate, I've made a few QSO's with the 40 meter transceiver.  My biggest disappointment is the high background noise level at my QTH.  I missed a nice QSO into NC last night because of received noise.  I have two strategies that I'm going to try going forward to help deal with the noise.

First, is actually using the active audio filter.  Secondly, I have a receiving loop that I've already put up and a low noise broadband amp built.  I just need to get it boxed up with the appropriate switching scheme and we'll see if that doesn't help with the received noise.

Building an Audio Active Filter Part Two

The finalish result

The audio active filter I built in September has been sitting at my operating position for a while now, doing its job quite well. But, it was past time to put some clothes on the poor thing.  Achieving that goal shouldn't have been hard, but I had a few obstacles to overcome, namely I had no experience in actually using graphics software, I had no idea of how I was going to protect the graphics once I created them and my beloved and ancient Apple emac (running Ubuntu 12.4 for ppc) is dying of the dreaded capacitor problem so common to old Apples.

Getting a computer that works first

I replaced my emac with old Dell GX280 with Debian 7.3 as the OS. I'm not comfortable with where Ubuntu is headed  so I chose to go back to a Debian Linux distribution. The Debian organization does just about the best job of supporting free (as in cost and freedom) software. I finally ditched my ancient CRT monitor in favor of a new ASUS LCD monitor.  The change from the 4:3 graphics format to a widescreen format makes a huge difference when using modern desktops like GNOME and KDE.

My desktop as it looks today

I installed just about every graphics creation program in the distribution and finally settled on two to try to create the front panel: Scribus and Inkscape.  

Creating the panel graphics

Inkscape has a great interface and it's fun to use.  The object creation was very quick and I was ready to print in no time.  And that's when I ran into trouble.  Inkscape was trying to send an unsupported attribute to the printer with each print job. So, I could go no further with Inkscape.  I'll try to debug it later, but I was unable to print directly from Inkscape at that point.

So, on to Scribus.  Scribus is actually intended as a desktop publishing platform and it is overkill for this type of work.  However, the interface is very easy to navigate, the toolset is very complete and it's a breeze to get started. The best part is the detailed attributes that you can place on any object via a sidepanel that is accessed by the F2 key on any selected object.  In my case, where I created the project before I got around to designing the panel, having the ability to specify the location of objects on the front panel down to .001 resolution was very useful. It also prints quite nicely on 110 pound card stock.

Scribus at work creating the panel graphics

Applying the panel

I used a set of punches from Harbor freight to punch out the holes in the card stock panel print. I then used the card stock panel print as a stencil and marked the holes needing drilled onto a piece of OPTIX acrylic that I picked up at Lowes.  Cutting the acrylic to size is a snap...literally.  Just score the acrylic where you want to cut a line and snap it off over the lip of the workbench.  Easy.

Drilling the holes was a little trickier, but still easy to do.  I just marked the holes and drilled them. Drilling acrylic requires starting with a pilot hole and stepping up a size at a time through your drill index until you arrive at the size you need.  It was a piece of cake with no splits or cracks.

One reason I chose the OPTIX acrylic over the plexiglass product is that the acrylic is only 80 thousandths thick and I wanted to hold the acrylic in place with the potentiometer panel nuts.  The thinnest plexi that Lowe's carries is 94 thousandths, which didn't leave me enough threads on the panel nuts. In the alternative, I was going to oversize the pot holes to clear the nuts and drill some mounting holes and use screws to attach the acrylic. In the end, I didn't have to go that far.

I removed the nuts from all of the panel controls, slipped on the front panel and finally the acrylic overlay.  I re-installed the panel control nuts and added some spiffy knobs from our friends at Tayda Electronics. 

Unsolicited Plug: Tayda Electronics is AWESOME.  Their pricing is incredible, they have great service and they have a very complete selection of components.

The end result

I did a few things wrong and managed to pit the acrylic by not keeping a clean workspace while I was working with it.  Lesson learned.  Overall I think it turned out pretty spiffy despite the pits. The printout/acrylic overlay is a simple and effective technique and it looks pretty good for a first try.  Next time out, I'll make the graphics more interesting.  I'm thinking maybe a Heath motif or something.

Now I have 2 keyers, a 40M transceiver, a 80M DC receiver, an Elsie 2 LC meter and a data/microphone interface box to give the same treatment... 

More work to be done....

Building an Audio Filter Part One

Fun With a Filter Project

Over the last few weekends I've been putting together an Elecraft AF1 Audio Filter. Ordinarily, I would do the sensible thing --which I suggest you do-- and just order the kit from Elecraft.  They only want $60 for it at the time of this writing, which is truly a bargain. I scratch built it, which took ten times longer to complete and it is not nearly as pretty.

But, I have more parts than sense and I had everything I needed in the junk box. So, with some judicious substitution, I spent several blissful weekends puttering around the shop. Here are the results so far.

Starting Out

Here are my tools of the trade that I used to put the circuit together:

You'll see on the right is my solder station with the ubiquitous Radio Shack Tip Cleaner/Tinner. There's also a big blue glob of FunTak on top of the iron stand that I use to hold tricky components in place while I solder them.

Next comes the usual stuff, i.e nippers, needle nosed pliers, a hemostat, fine tip permanent marker, super glue, screwdriver, a big stash of circuit board pieces and pair of really strong reading glasses.  The glasses are a must for eyes that are 40+ years old.  There are also lots and lots of strong lights around which helps.

Colored Pencils Aren't Just for Kids

One of the things missing from the picture is my green colored pencil.  Every time I place a part on the board, I mark it on the schematic with a green colored pencil. It saves tons of time time later looking for missing wires and unconnected pins.

Marking my way to success!

Ugly Manhattan-ish Construction

I use a combination building method that is part Manhattan-style and part ugly for a result that is all ugly.  By the time the case is finished, no-one will be able to see the depths of ugly that is my completed circuit board. BUT, it worked the first time I turned it on.

You'll probably notice that I've made all sorts of marks on the board itself, notating nice things like tip and ring for stereo jacks and where pads connect to important things like Vcc and off board components. By the way, those jacks are epoxied to the board.  I have used that technique many times before and it's a great way to use through hole parts with ugly construction. My construction style also turns dead bugs upside down.  In  other words, before gluing IC's down to the circuit board, I bend the legs UP so that the part number can be seen and the pin numbering makes better sense to me.  It's a small point, but I think it makes things go faster. It certainly helps with troubleshooting as well.

The Semi-Result

Here is the front view above and the rear view on the right.  I have a very nice pine case to hold the filter. I'm experimenting with printing out a front panel legend that will be protected by plexiglass.  I figure one more weekend and this will be a lot prettier and I won't mind when it gets moved to my operating position.

How does it work?

Like a charm.  The design is simple and it works remarkably well.  In fact, I much prefer the Elecraft design to my MFJ-752C. The MFJ has many more sections and much more complexity, but it doesn't have the presence that the AF-1 does.  The Low Pass Section of the AF-1 doesn't have nearly as much cut as the MFJ and it isn't really useful with my Kenwood TS-430S, but it helps out a lot with a homebrew DC receiver that I like to use. YMMV.

I'll post the completed filter when I get it boxed up this weekend.

Enjoy and see you on the bands!

73

Kenn

KA5KXW

Bumper Sticker Politics

I have been thinking recently about the personification of thought in our culture.  Drive down any street in America and you will see bumper stickers galore, all professing some nugget of political wisdom.  "Guns don't kill people.  People do."  "Don't blame me, I voted for the other guy." "They can have my guns when they pry them from my cold dead fingers."  Obviously, they are intended to make a statement from the car owner's political world view, but they also say volumes about the car owner as well and they are meant to do so.

From my perspective, reasoned political thought can't be distilled down to a bumper sticker --or these days, a Facebook post-- and the problems of today are much too difficult to just stop at these pithy little one liners.  While I won't say everyone who has a bumper sticker on his or her car is an idiot, I can certainly say that the bumper stickers themselves are idiotic. When faced with a complex and intractable problem like gun violence, there should be a vigorous and thoughtful debate about what can be done to solve the problem. 

My favorite bit of political shorthand is the word liberal.  Conservatives use the word in a condescending tone in the same way they might say "child molester" or "sodomite."  Clearly intended to wound the poor victim of such a lowly epithet, it is intended to end arguments with a flourish. The only problem is, modern conservatives not only don't understand the origin of "liberal" they don't even understand the origin of "conservative."  I find myself missing William F. Buckley more and more every day.  It seems he was the last true conservative who understood that conservatism is a response to the finite nature of resources and that they should be conserved. 

Most of all, I'm mindful of G. K. Chesterton who said that "The business of Progressives is to go on making mistakes. The business of the Conservatives is to prevent the mistakes from being corrected."