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 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. I don't feel any need for any audio amplifier.

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.

Radio amateur endorses my latest book

Last fall I published the book "The Imagined Conflict". One of the endorsers is John Lennox, with whom I share the radio amateur hobby. His callsign during his most active days was GI3NSP,  at present it is G3NSP. 

Here's his commendation from the book's webpage:

“Holm’s book is an excellent addition to the literature on science and religion. With a delightful Scandinavian flavor, and with the keen insight of a practicing research physicist, Holm takes a balanced, three-pronged approach to the topic—historical, scientific, and philosophical. This book is a model of fair enquiry, and I thoroughly recommend it to anyone interested in understanding how science and the Christian faith can both coexist and thrive in fruitful dialogue.”

—John C Lennox, Emeritus Professor of Mathematics, University of Oxford

Thanks, John!

 

Do deer like antenna wires?

Our garden is frequently visited by roe deer. They like to trek along the little brook that runs at the edge of the garden. Usually that has few consequences.

But this weekend as I was about to contact stations during the CQ160CW contest, I noticed that nobody could hear me. I heard many stations, but nobody seemed to hear my signal.

The Imagined Conflict

I have a new independent blog named after my book "The imagined conflict". The book was published in November 2025 and is a revised translation of a book first published in Norwegian in 2021 and in a second printing in 2022. 

The new blog may be reached by clicking here.