Broadcast - 8 February 2026
Last club room technical night, Colin VK7ZCF raised a very interesting and quite a different subject.
He started it off with a couple of video presentations from Tony Brock-Fisher K1KP on the topic of Polar modulation techniques in transmitters. Tony took us through the theory behind this concept and its advantage to power usage efficiency, heat dissipation and the potential of smaller transceivers. He developed a prototype called the Polar Explorer being the proof of concept. This culminated in a collaboration with FLEX Radio in the design and production of the Aurora AU-520 transceivers.
When I use the term Polar don’t think of North or South Pole, but think of Cartesian and Polar coordinates, the two different systems used to locate points in a two-dimensional plane. Cartesian using the common x and y axis to define location and Polar using distance from its origin and the angle they make with a reference axis.
Probably the most important factor is that Polar modulation defines the transmitter architecture rather than the emission mode, an RF signal generated using a polar transmitter - such as an SSB waveform - remains fully compliant with the characteristics of that mode.
From the transmitters perspective the incoming audio signal is separated into its amplitude and phase components which are then processed independently. As long as the amplitude and phase paths are correctly time-aligned and the envelope is reconstructed with sufficient fidelity, a conventional SSB receiver will demodulate the signal normally, with no observable difference to the end user.
The Phase component drives the output stage which is running in Class E. That is they are devices which are operated in either a switched on or switched off state, this very fast switching dissipates minimal power. The result is a massive gain in efficiency. The amplitude component of the output wave form is created by varying the operating voltage to the output stage from a Pulse Width controlled supply. Liken it to the efficiency of a switch mode power supply compared to a linear regulated power supply.
This subject is well worth a bit of a “Rabbit Hole” afternoon to look at the progress being made with high efficiency transmitters. There is an paper jointly published by Tony Brock-Fisher and Brian Machesney, K1LI in the March - April 2017 addition of QEX. Entitled “The Polar Explorer - You may never look at your linear amplifier the same way again.” For information QEX is a bimonthly magazine published by the American Radio Relay League or ARRL. It features advanced technical articles on the theory, design, and construction of radio antennas and equipment.
This paper delves into Single sideband being a special case of quadrature modulation, whereby the quadrature (Q) component of the signal is derived from the in-phase (I) component by the mathematical operation of the Hilbert transform. It covers the concepts and implementation leading up to the Polar Explorer prototype.
One interesting paragraph from this this paper and I quote is: “ First dubbed ‘quadraplex telegraph,’ what we now call polar modulation was invented by Thomas Edison in 1874 as a means of allowing simultaneous transmission of four telegraph signals on a single wire.” End quote.
Is nothing new under the sun? Technology has caught up since 1874 and this type of complex processing has become common place. You might be thinking, wow this is the next generation of amateur radio to play with…… But those of us that have carried around a 3, 4 or 5G phone have already experienced this new area of modulation and power saving, as it is currently in use with the phone handpiece and base stations.
URLs included in the text version of the broadcast: The Polar Explorer Paper : QRP Labs : Tony Brock-Fisher, Polar Explorer to Aurora
For those of us that operate on a sub FLEX Radio price budget, check out the latest offering from QRP-Labs. The QMX transceiver, also uses Polar Modulation and in this design it uses a Class “D” output stage, also giving it excellent efficiency. If you are interested and make it to the QRP-Labs website, check out Hans Summers as he has some excellent presentations on the QMX and Polar Modulation.
A final reminder, the Annual General Meeting of NTARC will take place this Wednesday the 11th February 2026 at the NTARC Club Rooms, Rocherlea Scout Hall, Archer Street Rocherlea, commencing at 7.30 pm.
The regular bi-monthly General Meeting will be held after the Annual General Meeting commencing about 8.45 pm. Refreshments will be available after the meetings.
UPCOMING EVENTS
On Air Test and Technical Net session - Every Wednesday night, Test-Net and CW course on 3.580 MHz from 7 pm, then a Technical Net on 3.567 MHz from 7.30 pm till 8.30 pm. Your host for the evening is Nic, VK7WW.
Annual General Meeting & General Meeting - This Wednesday, the 11th February 2026 at the NTARC Club Rooms, Rocherlea Scout Hall, Archer Street Rocherlea commencing at 7.30 pm.
Club Room Technical night - The next session will be Wednesday the 18th February and will commence at the usual time of 6.30 pm at the Club Room Archer Street, Rocherlea.
Coffee Morning - Held every Friday in the NTARC Club rooms. Time is from 10 am to noon.
Finally - If you have any items of news please email them to the Secretary at the following address news@ntarc.net all items to be received no later than 5 pm on the Friday prior to the Broadcast.
That’s all folks,
73, Stefan VK7ZSB
