Measuring Audio Frequencies with a Guitar Tuner

Here’s a little hack that serves no real purpose.  I’ll tell you about it anyway.

I recently built the T-Tone Code Practice Oscillator (CPO) kit from Morse Express.   It’s a handy little addition to the shack for adjusting straight keys or testing keyers.  After building it, I just adjusted the audio frequency for a pleasing tone.  Most people would have just left it alone at that point.  I’m not most people.

I started to do some thinking, which is a dangerous practice that can sometimes lead to unexpected consequences.  I wondered how the frequency of CPO compared to the sidetone of my FT-817.  There was no particular point to this mental exercise other than idle curiosity.

Now, I certainly could have keyed both the CPO and the FT-817 and done a comparison by ear.  I could have just adjusted the CPO by ear to match the FT-817.  But what fun would that be?  I was curious about the exact audio frequency of the FT-817’s sidetone, so I opted to do some experimenting.

Having been playing guitar for more than 50 years, I have acquired a gadget or two over the years.  One of those gadgets is a clip-on guitar tuner.  I can clip this clever device on the headstock of my guitar and, by sensing vibrations, it will tell me what note I’m playing and whether the pitch is sharp or flat.  I figured I could use this thing as an audio frequency meter of sorts.

First, I laid the guitar tuner on top of the FT-817’s speaker and keyed up.  That indicated that the pitch of the sidetone was an F note.  Consulting a conversion chart I found on the Internet, that equates to 699Hz.  I seemed to recall that the FT-817’s sidetone was somewhere around 700Hz, so that seemed about right.  I was sure I was in the right octave.

Guitar tuner on top of the FT-817
Guitar tuner on top of the FT-817

Next I took the lid off of the CPO and clipped the guitar tuner on it.  It initially indicated that the CPO was tuned to F#.  That equates to a frequency of 740Hz.  I tweaked the CPO’s frequency adjustment pot to F, matching the FT-817.  A side-by-side comparison of the CPO and the FT-817 showed that I was successful.

Guitar tuner clamped onto the lid of the code practice oscillator
Guitar tuner clamped onto the lid of the code practice oscillator

So, what’s the point of all this?  None really.  Is there a practical use for this?  Probably not.  Does it really matter that my CPO matches the sidetone of my radio?  Nope.  I just had one of those “I wonder what would happen if…” moments.  Now I know.

72, Craig WB3GCK

MS2 Straight Key Magnetic Mount

As I mentioned in an earlier post, I bought the little American Morse MS2 straight key intending to somehow magnetically attach it to the clipboard I use for portable operating.  It took some thinking but I came up with a workable solution.  I might come up with a better solution in the future but, for now, it should suffice.

What I set out to do was build a wooden mount that could attach the MS2 that held two magnets that lined up with the steel washers on the clipboard.  I had a couple of “super magnets” that I planned to use.  The problem I ran into is that the magnets are almost too strong to attach directly to the washers.  My solution was to enclose the magnets within the wood base.

Super magnets used for the MS2 straight key magnetic mount. Boy, these things are powerful!
Super magnets. Boy, these things are powerful!

I cut a 1×3.25-inch piece of 1/8-inch plywood.  Then I drilled two 3/4-inch holes just deep enough to fit the magnets.  After placing the magnets in the holes, I glued on a thin wood veneer.  This puts some extra spacing between the magnets and the washers on the clipboard.  After drilling a mounting hole for the MS2, I sprayed on a couple of coats of paint.

MS2 straight key magnet mount wood pieces prior to assembly
Wood pieces prior to assembly

After letting the paint dry, I went to attach the key to the base.  Oops!  I drilled the mounting hole from the wrong side of the mount.  My first inclination was to putty it in and repaint.  However, I decided to leave it there as a constant reminder to always measure twice and drill once!

MS2 straight key attached to the magnetic base
MS2 attached to the magnetic base. Don’t look too closely or you might see the drilling mistake I made.

The mount actually works well.  The concealed super magnets hold the key firmly to the clipboard without the need for excessive force to remove it.  Once I free up some time, I’ll give it a thorough test out in the field.

MS2 straight key mount attached to the clipboard
The finished product

72, Craig WB3GCK

American Morse MS2 Straight Key

For many years after I first learned the code in the Navy, I was a die-hard straight key user.  Unfortunately, back in the 90s, I started to experience some wrist pain and switched to using iambic paddles.  Recently, after working one of the Straight Key Century Club (SKCC) K3Y special event stations, I was inspired to sign up with SKCC and dust off my straight keys.  Hopefully, I will be able to get my old straight key fist back in short order.

Since I do most of my operating while portable, I wanted a straight key that was easy to pack and use while sitting on the ground along some trail somewhere.  I was looking for something small that I could add some magnets to for use with my little clipboard.

After doing some research, I decided on the American Morse MS2 miniature straight key.  I built a set of Doug Hauff’s (W6AME) NorCal paddles from a kit many years ago and they are still in regular use.  Doug’s machine shop produces some precision stuff.

The kit arrived a few days after I placed my order.  Following the manual’s precautions, I emptied the parts into a baking pan.  Some of the parts are pretty small and would disappear forever if dropped on the carpet.  Even with my aging eyes, it only took about 45 minutes to assemble the kit.  (A younger person with better eyes and steadier hands could have done it faster, I’m sure.)  You need to supply your own cable and connector, so I dug an old audio patch cable out of my junk box and cut it in half.

American Morse MS2 straight key after initial assembly
American Morse MS2 straight key after initial assembly

The key is 2 inches long by 1 inch wide and is made from machine aluminum.  The contact gap and spring tension are fully adjustable.  The key (with my cable attached) only weighs about 2.7 ounces (76 grams).

The finished MS2 straight key with cable attached. The cable is one half of an 1/8-inch diameter audio patch I had in the junk box.
The finished MS2 straight key with cable attached. The cable is one half of an 1/8-inch diameter audio patch I had in the junk box.

After adjusting the contact spacing and the spring tension, I was surprised at how great this little key feels.  The knob is a little different from most keys, but I was able to easily adapt to it.  As expected, the overall quality of the key is outstanding.

My next project will be to attach some sort of base to it with magnets spaced to line up with the washers on the clipboard I use while portable.  More on that in another post.  I’m looking forward to making some SKCC contacts from out in the field.

72, Craig WB3GCK

Clipboard Keyer

I purchased a set of Palm Mini paddles for portable operating a while back. I love the magnet base, which attaches nicely to the side of my little YouKits HB-1B transceiver. However, in some situations — like sitting on the ground or operating from inside my truck — that isn’t always the most convenient arrangement for me. Here’s a little hack I came up with to solve that problem.

Figure 1. Washers attached to clipboard
Figure 2. Paddles attached to clipboard

I purchased an inexpensive 6-inch by 9-inch, acrylic clipboard at my local office supply store. I used some GOOP adhesive to attach two steel washers to the clipboard, as shown in Figure 1. I made sure that the washers lined up with the magnets on the base of the paddles. Figure 2 shows the paddles attached to the clipboard. Figure 3 shows the clipboard in use during a recent outing. For transport, the little clipboard fits in the small plastic container I use for the HB-1B and accessories.

Figure 3. Clipboard & paddles in use

For less than $2.00, this little accessory makes portable operating a bit more convenient.

73, Craig WB3GCK