DP-AMP Sixty One PA Module

DP-AMP Sixty One PA-Module

The PA module of the HVF-1k2 ran absolutely stable and delivered the full performance of the LDMOS from 1.8 MHz (160m) to 50 MHz (6m) without any problems. What could be improved?
Maybe it was time to think about the 70 MHz (4m) band as well? Maybe in the future there will be the possibility of more power there, and I also think that globally and other countries will allow more power in this band.

At 70 MHz I had to look at the input and output again.
What works up to 50 MHz does not necessarily work up to 70 MHz.
The first thing I did was to change the input transformer, the design is no secret, just like the double-core transformer I was already using. This new transformer works up to 70 MHz without any problems and is also easier to obtain.

Since the HF-1200, I had the cross line before the 1:9 transformer in the output circuit. At 70 MHz this no longer worked and I decided to adapt the transformer here too.

No more changes were necessary to be able to transmit from 1.8 MHz (160m) to 70 MHz (4m).

The Sixty One 1k2 PA module is a modern and powerful power amplifier module.
Great importance was attached to high quality and comprehensible measured values.

The Sixty One 1k2 module has the option of fitting a 15dB attenuator for transceivers in the 100W class at the input, making the input less sensitive to power peaks.
As additional protection, TVS diodes (suppressor diodes) have been inserted before the 4:1 transformer to protect the sensitive gates from excessive input power. Four further TVS diodes are located directly at the gates.
Many suppliers do without this protection; it certainly works without it, but you should consider whether you are taking risks if they are avoidable.

In order to determine the temperature as accurately as possible, a digital temperature sensor is installed next to the MRFX1k80H, a DS18B20, which makes the measured temperature available to the connector strip via a one-wire bus. The temperature measurement must take place as close as possible to the LDMOS.
Heat in copper does not spread at the speed of light!
A great marketing trick: measuring the temperature further away from the LDMOS, where the temperature is significantly lower and the manufacturer can sell the power amplifier as much cooler.
Marketing or actually fraud?

The operating point stabilization for AB operation was classically implemented with a stabilized control loop, which has already proven itself in the HF-1200.
There are also wild circuits here that are diligently copied, but what you see there is not clean. In some cases, 0815 diodes are used and the change in the characteristic curve due to the heat far away from the LDMOS then changes the voltage a little.

The BIAS voltage can be switched at the connector strip for transmission. The NTC for temperature compensation is connected there and the BIAS voltage can be checked there.

All materials used are carefully selected, class 1 capacitors in C0G low ESR and with the necessary current and voltage resistance, genuine 18 Ohm cable for the TLT balun and high-quality Teflon coaxial cable for the 1:1 balun in the output.
People often save money here and connect two or three 50 Ohm cables in parallel just to save some money, 17 Ohm cables are readily available!

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