November 20, 2015

First electricity detective?

Q: What is the name of the first electricity detective?
A: Sherlock Ohms
Written by: NJ2X, Michael Maher

November 13, 2015

The ocean is made of waves...

An ocean traveller has even more vividly the impression that the ocean is made of waves than that it is made of water. — Sir Arthur Stanley Eddington
Written by: NJ2X, Michael Maher

November 8, 2015

Vintage Fender Champ Amplifier Restoration

We have been using a weathered looking vintage Fender Champ "silverface" guitar tube amplifier ever since it was given to us by a friend a few years ago.  It had acquired innumerable cosmetic warts and battle scars over the decades as well as a set of extremely dirty/noisy potentiometers and input jacks.  The issues all seemed manageable and we decided this great little amp was worthy of restoration.

Fender Champ Silverface Front View (before restoration)
Fender Champ Silverface Top View (before restoration)
Fender Champ Silverface Side View (before restoration)

Fender Champ Silverface Side View (before restoration)

Planning the Restoration

Our objective for the restoration was to return the amplifier to its original function and beauty. We made a list of the restoration work that we intended to perform:

  • Replace electrical power plug - connector pulled away from the outer insulation
  • Replace speaker grill - original color had faded, dirty, punctures
  • Clean the Fender logo - minor corrosion, dirty
  • Clean the knobs and panel face - dirty
  • Replace the black Tolex - dirty, several large damaged areas
  • Clean all hardware - corrosion and dirty
  • Clean inside of cabinet - dust bunnies and layers of dirt
  • Replace all three potentiometers - super noisy and intermittent
  • Clean both input jacks - noisy and intermittent
  • Replace carrying handle - original handle was missing

Sourcing Parts

We ordered the parts we needed from Antique Electronic Supply including:

  • Black Tolex - we ordered extra in case we made a mistake cutting a piece
  • Original Fender amp carrying handle
  • 250K Ohm audio potentiometer (qty 2)
  • 1M Ohm audio potentiometer

We purchased a 207g spray can of 3M Super 77 Multipurpose Adhesive at our local ACE Hardware.  We used nearly the entire can for the project.  The spray on application worked perfectly for adhering the Tolex to the cabinet.  We had replacement grill cloth on-hand so we didn't need to order it.  We also had a good supply of staples, tacks, and an replacement electrical plug in the workshop.  The total cost of all the parts and materials was about $80.00 USD.


  1. Photograph all sides of the amplifier.  Photographs are excellent reference resource during any restoration.  Photographs can answer questions that your memory cannot, such as, "So where did this do-hicky go?"
  2. Unplug the amplifier from the wall and let it discharge the capacitors which carry potentially dangerous voltages.
  3. Cut the power plug off and discard.
  4. Unscrew the back panels.  Save the screws and panels for reuse.
  5. Remove the grill by prying it off.  It is held in place by heavy Velcro.
  6. Unscrew the Fender logo from the grill.  Save the logo and screws for reuse.
  7. Unplug the speaker.
  8. Remove the speaker.  Store with care to protect the delicate cone.
  9. Remove the metal feet.  Using a flat head screw driver and tack hammer, carefully pry up the feet.  Save these for reuse.  Straighten any points that are bent during removal.
  10. Unscrew the hardware holding the amplifier module in place.  Hold onto the amplifier module case to prevent it from falling to protect the delicate vacuum tubes.
  11. Seek qualified help to remove the amplifier module.  Beware of the capacitors that are potentially storing deadly voltages.  Don't touch anything inside.  Photograph the wiring so you have a reference for how the potentiometers are wired. Store the amplifier carefully out of reach of anyone.
  12. Carefully remove the staples holding an aluminum shield to the inside top of the cabinet.  Retain the shield for reuse.  Discard the old staples.
  13. Remove the knobs and store for reuse.
  14. Vacuum the dust bunnies from inside the cabinet.
  15. Carefully peel the old Tolex off the cabinet.  Try to pull each section off whole if possible since these can help you by providing a template for cutting and reapplying new Tolex.  Save for later reference.
  16. Sand the wood surfaces smooth and clean.  Remove the old adhesive and Tolex residue.  This step also helps remove small nicks and dings in the wood.
  17. Fill any major damage (divots, deep abrasions, missing slivers ...) to the wood and sand smooth.
  18. Vacuum and wipe all surfaces with tack cloth to remove dust and dirt.
  19. Remove and discard all the old staples that were used on the grill cloth and Tolex.


You will need a box cutter with a new blade and scissors for cutting the Tolex and grill cloth.   An electric stapler is very handy.  You will also need flat head and Phillips head screw drivers, a hammer, a roller, and a square.
  1. Gently clean all the hardware and logo using alcohol and cotton swabs.  Use Never-Dull to remove any light corrosion.
  2. Using cotton swabs and alcohol gently clean the input jacks contacts.
  3. Cut a piece of grill cloth about the same size as the original.  Install in the frame using an electric stapler.  Four hands are helpful with this step.  Two hands for stretching the fabric while the other person staples.
  4. Install the Fender logo.
  5. Using the old Tolex panels, cut new pieces.
  6. Apply the new Tolex panels in the following order: left side, right side, top, bottom
  7. To apply each piece, you must spray the surface with adhesive where the Tolex piece will be applied as well as the Tolex itself.  We found a liberal coating of adhesive on both worked best.  Avoid spraying areas that you are not working on since it only makes the job messier than needed.  Take care not cover up the Velcro strips.
  8. Use the roller to smooth out the fit and remove air bubbles.
  9. Using the box cutter and scissors, cut and fit each piece following the old Tolex as a template / guide.  We found it more effective and precise to make the cuts with the piece in place for the purpose of optimizing the fit.  Use your hands to make sure that each corner it good and tight.
  10. Once all the Tolex is in place, let it dry and harden for awhile before proceeding.
  11. Using a small sharp screw driver, poke holes through the Tolex where each screw is supposed to go.
  12. Install the aluminum shield.  Carefully align the shield holes with the cabinet holes.  We used brass flat head tacks instead of staples using the holes left by the old staples.
  13. Install the feet by tapping in gently with a hammer.
  14. Install the handle.
  15. Replace the potentiometers one at a time.  Take care to wire exactly as original.  Inspect visually when complete to make sure there are no cold solder joins or shorts between leads.
  16. Gently clean the amplifier face and knobs with cotton swabs and alcohol.
  17. Install the speaker
  18. Reinstall the amplifier module into the cabinet.
  19. Reconnect the speaker.
  20. Install the speaker grill.
  21. Install the back panels.
  22. Install a replacement power plug.
  23. Test the amplifier.


We were very pleased with the outcome of our restoration work.  The restored amplifier looked just beautiful.  It was a wonderful experience to be able to adjust the potentiometers silently.  All the intermittent issues went away as well.  The amp was quiet and sounded warm and wonderful.  Plugging and unplugging the amplifier from the wall was no longer a scary task.  We were also delighted to find that all the materials we had purchased were perfect for the job.

Fender Champ Silverface Amplifier - front view (after restoration)

Fender Champ Silverface Amplifier - side view (after restoration)

Fender Champ Silverface Amplifier - back view (after restoration)

Restoring the amplifier helped us see just how well Fender designed and built the Champ.  With a little tender loving care the amplifier still sounds great after a having endured decades of considerable apparent hard use.

We would like to extend a special thank you to our friend who gave us this little gem-in-the-rough of a vacuum tube amplifier and the opportunity for a wonderful father-and-son restoration project.

Good DX and 73, NJ2X

© Michael W. Maher and NJ2X.COM, 2015. Unauthorized use and/or duplication of this material without express and written permission from this blog’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Michael W. Maher and NJ2X.COM with appropriate and specific direction to the original content.
Written by: NJ2X, Michael Maher

November 6, 2015

Notably to electrons...

After long reflection in solitude and meditation, I suddenly had the idea, during the year 1923, that the discovery made by Einstein in 1905 should be generalised by extending it to all material particles and notably to electrons. — Prince Louis-Victor de Broglie
Written by: NJ2X, Michael Maher

October 30, 2015

Bad times...

Bad times have a scientific value. These are occasions a good learner would not miss. -- Ralph Waldo Emerson

Written by: NJ2X, Michael Maher

October 23, 2015

Morse on Patent Defence

I have been so constantly under the necessity of watching the movements of the most unprincipled set of pirates I have ever known, that all my time has been occupied in defense, in putting evidence into something like legal shape that I am the inventor of the Electro-Magnetic Telegraph.
From a letter to his brother describing the challenge of defending his patents (19 Apr 1848).

— Samuel F. B. Morse
Written by: NJ2X, Michael Maher

October 17, 2015

DX Technique: Persistence

We have all been there.  You are calling and calling on HF with no reply.  You then start to wonder, "Is anyone receiving me?"  Perhaps you may even begin to doubt your signal is making past your properly line, "Is my signal going anywhere?"

CQ, CQ, CQ, ...

Faced with this type of doubt many hams simply turn the dial or switch bands.  After all, if your signal is going nowhere then why bother?  However, does abandoning the frequency as a strategy make sense if your signal is actually being heard in desirable DX locales?  As in life, good things (i.e. good DX) come to those who are persistent.

"Our greatest weakness lies in giving up. The most certain way to succeed is always to try just one more time." -- Thomas A. Edison

Often the key to unlocking your own personal power of persistence is information.  Information can remove the uncertainty and doubt and help us make an informed choice to stay or move from a frequency.  In the age of the Internet, we now have access to excellent information regarding where our signals are being received.

A wonderful free service that provides remarkable information is "PSK Reporter".  Using PSK Reporter you can quickly determine visually where in the world your signal is being received with just a few clicks.  If you haven't tried it be prepared to be amazed!

Example 1: configuring PSK Reporter to determine where your JT-65 signal is being received

  1. Using your web browser navigate to PSK Reporter.
  2. Enter your own call sign in the upper left corner of the screen and click, "Find".  This will take you to a screen with a map and drop down filter options at the top.
  3. Select the band you are using with the drop down next to "On".
  4. Select the mode you are operating with using the drop down next to "using".
  5. Select the time interval you are interested in using the drop down next to "over the last".  We typically use "15 minutes" to limit the results to the last 15 minutes.
  6. Click "Go!" to retrieve your results and update the map.

In the example above, we can see that my JT-65 calls were being received and decoded by stations all over the world as indicated by the yellow call out balloons with time durations.  For example, 3 minutes prior to this query, my JT-65 signal was received and decoded by a station in Canada (VE6ADZ).  My signal was also received 13 minutes earlier by stations in Hawaii and Asia.  My signal was also received 1 minute earlier by a station in Puerto Rico.

This information helped motivate me to continue operating even though I wasn't receiving as many calls as I would like.  I could see quickly that my signal was being received in many of the locations I was targeting such as the US Eastern States, Hawaii, and Asia.

Recently, I was operating JT-65 on 40m in the morning.  I had been calling for about 30 minutes without any DX calls.  I was beginning to feel a little discouraged; however, I could see from PSK Reporter that my signal was being decoded in Asia and this motivated me to continue calling.  Once again the power of persistence paid off and I was rewarded with a contact with 9V1XX in Singapore which is a new DXCC entity for me and Kazuhiko confirmed the QSO via LoTW!  This was an excellent contact indeed.

The next day, I started decoding E21LXK (Thor) at 1546 UTC from Thailand on 20m JT-65.  His signal was weak and according to PSK Reporter my signal was not crossing the gray line to Asia yet.  It seemed it was too early for a contact.  Thailand would be a new DXCC entity for me so I was determined to see if I could make the contact.  Each time Thor would call CQ I would diligently return his call.  The contact would then proceed between Thor and some station in Europe or Asia (none in the US).  Each time I returned his call I would check PSK Reporter and found that no stations were reporting receiving my signal.  I noticed that E21LXK's signal strength was increasing slightly as time went on.  This gave me hope that an opening would appear and provide a window of opportunity to complete the contact.  This went on until 1738 when suddenly his signal shot up as though he was operating from my neighborhood coffee shop!  Excited at my good fortune, I returned his call again and this time Thor replied and we completed the QSO!  Persistence paid off once again.

There are many interesting uses for the information provided by PSK Reporter.  For example, the information is very good for radio experimentation (e.g. power settings, antennas, etc.).  It is quite interesting to adjust your power and see the immediate impact on where the signal is being heard.  It is surprising how little power is needed with modes like JT-65.  This is great fun.

Fire up PSK Reporter, get on the air, and drop your call to see where you are being heard.  There is a good chance you are being heard in more places that you thought and you have better odds at making an interesting DX contact when you are persistent.

Good DX and 73, NJ2X

NJ2X Kindle Edition is now available.

Written by: NJ2X, Michael Maher

October 16, 2015

What God Hath Wrought

What God Hath Wrought. Message transmitted to inaugurate the first U.S. telegraph line (24 May 1844). The biblical text, from Numbers, 23:23, was selected by Annie Ellsworth, daughter of the Commissioner of Patents.   — Samuel F. B. Morse

Written by: NJ2X, Michael Maher

October 10, 2015

NJ2X's Centennial Points Challenge Award Arrives!

I was very excited to receive my ARRL Centennial Points Challenge award this week.

NJ2X's ARRL Centennial Points Challenge Award

I rather like the design of the award certificate with the Hartford, CT skyline in the background.  I earned the Level 3 award with my final score of 9,746 points.  Not too shabby considering that I was unable to operate for most of the first 6 months of 2014.

The ARRL President (Kay Craigie) signed the award and also contributed quite a few points via our contacts.  It was always great fun to hear her on the air working the pileup.

The ARRL Centennial Points Challenge is one of my very favorite contests of all time.  May of us wish there would be a similar contest in the future.  I hope we don't have to wait until 2114 though.


Good DX and 73, NJ2X

Written by: NJ2X, Michael Maher

October 9, 2015

Completed DXCC on Phone

I was very excited to see that my QSO's (17m and 20m SSB) with the DX Expedition E51MKW (North Cook Islands on the Manihiki Atoll) were confirmed today.  Propagation was very poor.  However, the expedition team did a stellar job in pulling stations out of the noise.  I am very impressed and pleased on how quickly the team uploaded their contacts to the Logbook of the World (LoTW).  The Manihiki Atoll is magnificent.  I am considering adding a visit there to my bucket list.

Manihiki Atoll - North Cook Islands

This was the final contact (number 100) I needed to complete my ARRL DXCC Phone award.  All contacts were completed using wire antennas with 100 Watts of power.  Looking forward to receiving the certificate and add another to the shack walls.

Good DX and 73, NJ2X
Written by: NJ2X, Michael Maher

First telephone conversation over outdoor wires

On this day (October 9) in 1876, Alexander Graham Bell and Thomas Watson conducted the first two-way telephone conversation over outdoor wires using telegraph line between Boston and East Cambridge.

Written by: NJ2X, Michael Maher