HF PA amplifier kit: instructions decrypted from Chinese

DIY 45W SSB HF Linear Power Amplifier Amateur Radio Transceiver Shortwave Radio Development Board Kit


I just finished building this kit that I bought online (link above).  In my opinion it meets the main requirements of a kit for hams: 1) cheap 2) fun to build 3) it actually works.

So what’s the catch?  The instructions are either in Mandarin Chinese or in Google Translate English.  Amusing to read but difficult to follow.  So with lots of cogitation, head scratching, questions to several other hams, and the assistance of the boffins at Bletchley Park we are offering CAARC website readers a decrypted version of the kit instructions.

The first paragraphs are given below as a “teaser”.


These instructions are my attempt to put the “manual” supplied for download on the seller’s website into more conventional English.  They are based primarily on the “RF‐AMP‐2078 debug instructor V303”  (sic) downloaded from the website.  You will note that the schematic is dated 5 August, the BoM sometime in September and the PCB is marked “20151229”.  I found more than a dozen inconsistencies in values and markings between the PCB and the documents.  Also there appear to be several “typos” on the PCB silk screening.   I have endeavored to sort this out and update my documentation to match the PCB supplied with the kit.


It is no doubt feasible for an experienced builder to successfully assemble the kit using only the schematic and the silk screening on the PCB.  My objective is to make this inexpensive kit available to a wider audience of radio amateurs, who may feel less confident about building their first MOFET PA without some additional guidance.  Anyone who does not have previous experience soldering the small SMD parts used in this kit is advised to practice first. 



amplifier under test

A pdf file with the complete instructions will be linked to this post within the next few days.  Watch this space. 




Solar Powered projects

The objective of this project was to create an independent WSPR beacon transmitter.  As such it should operate completely independently – no computer in the shack, no internet time server and no power from the grid.


I found that a U3S kit + GPS kit both from QRP Labs met my requirements for a transmitter with internal controller, GPS disciplined frequency synthesizer and GPS timing.  WSPR operates on 2 minute time segments and timingGPS + U3S must be accurate to a very few seconds or no one will be able to decode your transmission.  Similarly the frequency band for WSPR signals is only a few hundred Hz wide, so if your frequency is not exact;  no reception.


The photo at left shows the transmitter (bottom of the box) and GPS (top shelf) mounted in a weatherproof PVC electrical box.  The box is mounted on a steel plate, that allows the assembly to be attached to the 2″ pipe mast with U bolts.  (This transmitter puts out approximately 500 mW on 30m with a 25% duty cycle — 2 minutes on, 6 minutes off; the antenna is a dipole with the mast providing the center support.)

temporary panel installation


After getting the transmitter and GPS to work successfully inside the shack, I started my quest for independent power.  I started with a 5W solar panel and a 7 AH gel cell battery.  The 12V battery voltage is knocked down to 5 V for the transmitter using a low cost buck regulator module (internet shopping).  In the photo above, the smaller 5W solar panel is shown on the left hand chair next to the newer 10W panel that eventually came in the mail.  The charge regulator is on the right hand chair just in front of the battery.  This arrangement was almost good enough so I sprung for a larger, 12 AH battery.  The 10 W panel and the 12 AH battery easily carried the transmitter through the night until the morning sun could re-start the charge cycle.

mounting bracket clamped together

So it was time to fabricate a bracket that would hold the solar panel on the mast.  I wanted the bracket to be adjustable so I put a leaf hinge at the top.  The mounting holds the panel at an angle by moving the support arm from one hole to another.  A position for any season.

I used 2 mm mild steel plate for the bracket.  The solar panel is held in place by aluminum U channel that was left over from my main antenna tower project.  I believe that suitable aluminum profiles should be available from any aluminum window manufacturer.  I took considerable care positioning the plates and the hinge before welding it together.  After I cleaned up my welds and removed as much rust as possible from the plates I gave them a coat of galvanizing spray followed by blacSAM_2401 croppedk enamel spray.

I originally intended putting the gel cell battery in the lower PVC box.  After I determined that I needed a larger capacity battery I used this box for the charge controller and the 5 V buck regulator.  The 1.8W Canadian Tire panel shown on the right was not used in the final system.

The 12 AH battery is sitting on the ground inside a plastic box from the Dollar Store and weighted down with a brick.  I will eventually get round to something more elegant, but it does work.

The whole system has been up and running 24/7 for some days now and appears stable.

You can see the WSPR beacons by going to http://wsprnet.org/drupal/wsprnet/map

Select the 30m map and a time period of 30 minutes. Click on any station call sign to see who is hearing who.



In summary I will list the components or modules I found suitable for making an independent power system:

  • Solar panel of sufficient power rating
  • Battery with sufficient storage capacity
  • Charge regulator
  • Regulator to drop the battery voltage down to that required by the circuits being powered (if necessary)solar panel with transmitter
  • Weatherproof boxes
  • Sturdy mounting system


Some possible applications:

  • repeaters
  • beacons
  • remote antenna tuners






Voltage Regulator Modules

regulator board


A whole range of small regulator boards or modules are available from your favorite on-line shopping sites for very little money.  I gave the most recently arrived unit a quick once over.

The on board voltmeter is fairly accurate but if you need to adjust voltage exactly I suggest a good multi-meter.

I measured quiescent current at 25 mA (compared to 5 mA with a 7805).

Voltage regulation was good; switching an 11 ohm load at 5 volts did not result in a noticeable drop.  The regulator IC stayed cold – at least until the load resistors started smoking.test setup

I put my scope across the load and found an interesting [Eastern Rockies] waveform about 0.5 V at 10 KHz.

output waveform

There is one 220 uF electrolytic across the output.  The scope suggests that some additional output filtering is in order.


All in all a useful piece of kit for only a very few dollars.

Carl VE6VG


Our dear friend and fellow amateur

Carl VE6VG passed away December 26, 2015 in Red Deer.

The service will be held on  Tuesday Jan 5, 2016 at 2:00pm at the Innisfail United Church.



All Band portable antenna

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RAC Bandplan Dec.1, 2015


New CAARC Executive for 2015 – 2016

The Annual General Meeting was held on Wednesday Nov 18th at the Red Deer Search and Rescue. Congratulations to the members who were elected to the new executive.new exec

CAARC Executive for 2015 – 2016
Past President   Bob King VE6BLD

President– Stephen Lee VA6SGL

Vice President– Rod Lins VE6XY

Secretary– Sandy Jacobs VE6SND

Treasurer– Karen McKinney VA6LDY


  1. Brian Davies VE6CKC
  2. Garry Jacobs VE6CIA
  3. Greg McKinney VA6GMC
  4. Jeff Low VA6JL
  5. Mike Mailiot VE6MIM


Skip MacAulay VE6BGT

Emergency Coordinator
Jeff Low VA6JL
Bob King VE6BLD
Bob King VE6BLD
Net Control
Bob King VE6BLD

using “bargain” coax connectors

die on incorrectly threaded so239


I bought a package of 10 SO-239 chassis connectors on eBay at a great price.  The connectors looked good, teflon insulation, gold plated pins.  However it was not possible to thread a PL-259 male connector on more than 2 or 3 turns.

I then understood why the price was so low.  I decided that the solution was to re-thread the connectors.  I looked for a die at local tool stores but no luck –  I was told that 5/8-24 was a thread used in electrical connectors but not commonly used by machinists.  Checking on Amazon it became clear that the proper die was available at reasonable cost as a “gunsmiths” die.


As soon as it arrived I tried it.  I did not have a holder for this size die so I used a “Quick-clamp” with rubber pads.  I used lots of cutting oil and took my time cutting the threads.  The result was a bare brass thread which easily took the Amphenol PL-259 connector.

I don’t know if the manufacturer in China used a 16 mm die in place of 5/8″ or if they failed to take the thickness of the nickle plating into account when cutting threads.  Whatever the reason now I have the tool to make it right!


The photos tell the story.  73 and keep on building.  Earl VA6TJ



die on correct conn after rethreading rethreaded it worksu