The magic of GPS time for the QMX+

It's almost magical to watch how UTC time drops down from the GPS satellites onto the QMX+ ! Here's 1.5 minutes condensed to only 11 seconds showing just that.

A first-time activation of a POTA park

As a latecomer to the Parks on the Air program, I didn't think there were any unactivated parks in the vicinity of where I live just southwest of Oslo. But the other day I found one which had been attempted, but with too few contacts to count as an activation. I managed more than the required ten, so that is a first for me.

When you love radio and want to do more hiking: POTA

I love amateur radio and I would like to do more hiking - so what's more natural than to take part in the Parks On the Air (POTA) program. I've only recently discovered POTA and how it combines the two: amateur radio and hiking.

Today I went to a park not too far from home. In addition to a short drive it took about a one hour walk in the terrain each way to NO-0497, "Furuåsen og Hagahogget". There is a magnificent view over the Oslo fjord from a trekking cabin there: Hovdehytta. It has a history going back to 1922.

Garden portable with the QMX+

Just a few days ago I had my first SSB QSO with the QMX+. It was from LA to PA - Norway to the Netherlands - on 20 m using a vertical quarter wave antenna.

 

The speaker/microphone is a "For Kenwood" Chinese speaker mic bought for a Baofeng some years ago. I replaced the microphone element with a more sensitive one that I had in my junk box. 

Surprisingly, the speaker gives (almost) adequate volume without an amplifier. The speaker is 8 ohms and connected via two 33 ohm* resistors from the left and right audio outputs of the QMX+. The resistors are the only components in the little square box that the speaker-microphone connects to. Initially I felt no need for any more audio amplification, but after some more use, I see the point in more power output as the audio easily gets distorted when the volume is increased.

Why didn't I come up with this simple upgrade to the QMX+?

This is an upgrade to the QMX+ which is so simple that I keep saying to myself: why did it take so long for someone to come up with it?

It consists only of doubling the PA transistors. The original 4 BS170s are paralleled with 4 more as shown in my implementation in the image. Very simple!

It is, as far as I understand, the brain child of Roelof PA0RDT and is described in detail on the QRPLabs website. I essentially followed those guidelines, and got more or less the same results as reported there.

There are several advantages:

• Approximately doubled output power
• More robustness to applied voltage. My QMX, wired for 9 Volts, now runs fine on 11 and more Volts, with a current limited power supply (approx. 2 Amps). 

I have had many FT8 contacts with it - where the transmitter is on continuously for 13 seconds - and have not had any problems. The only downside that I have heard of is slightly reduced power on 6 m due to the effect of the increased gate capacitance with two instead of one transistor.

QMX+ mechanical improvements

My QMX+ has some minor mechanical improvements:

1. Slimmer knobs. I decided to replace the knobs as I often touched the bottom one while adjusting the top one and vice versa. The slimmer knobs solved that. I found knobs on AliExpress with the same looks, only a smaller diameter as the image shows. Unfortunately they don't have screws, so they aren't so well attached as the original ones.
2. Folding laptop feet which I first saw on the AE5X blog.

A QMX+ coming together

I got an unassembled QMX+ for Christmas this year, and here are pictures of it coming together. First the winding of toroids for the low-pass filters: