Home made HF PWR/SWR-meter - revisited

Three years ago I played with a Stockton Bridge and made (just because I had it on my shelf) a nice portable HF power meter and SWR meter with cross-needles.

In the first iteration, it was meant to work with QRP radios; it has an impressive 5-600 mW range but on a second thought, I though what if I can use it for a broader range.

And I put a double potentiometer to change the range. 

But that was not a reliable solution because the range was somehow too "variable" and I never knew the real power.

So, a new iteration was born.

The PWR and the SWR voltage came from the Stockton bridge to a set of 2 x 4 * 1 MOhm potentiometers that will set the range for each position on the switch.

The switch is a dual pole-4 position and the ranges will be 10 W, 50 W, 100W and 200 W.

The calibration was made with a NRP-Z11 power sensor. While it is not a very reliable measurement tool, it helps to see the approximative value of the average or CW power. The 10W scale is pretty precise but the others are not so good.

The values are consistent through 1.5 MHz - 80 MHz.

QCX CW

 YO3HEX, Dexter gave me a nice present! 

A QCX CW pocket transceiver. 

It is able to put around 4-5W into one band and it is working only CW.

It was an awesome project for an afternoon and, after some 4-5 hours, the radio was ready, tested, the fine tuning made and on the second day I already made two CW contacts!

Here are some pictures from my work:

An eagel eye will notice the OpAmp misplaced (the right-side one).

One ferrite toroid snaps. Broke in three parts. Fortunately, I got a lot o this Type 2 toroids. Unfortunately, they are at my second lab, too far away for a lazy ham like me...

This is why I used ol' SuperGlue..

The project is completed. The OpAmp, still upside down.

 

Powered the TRX, current surged to around 1.5 Amps. Fortunately, I start all my experiments on my special design lab power source so no irreversible damage occured.

I found the fault pretty easy, the area was warm. I took out the OpAmp, put instead a 2x4 socket to check if the original circuit survived. 

I took the time to change the LCD with a Yellow-Green one and the original contrast trimpot with a 10KOhm one for a better range of contrast.

After I put the circuit on the right position, there was no damage so I took out the socket and placed the OpAmp directly on the PCB.

The broken toroid is doing well after SuperGlue surgery! 4W at 12V, this is nice.

Thanks to Mihai, YO3ISL, the radio got a nice case!