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2.4 GHz 4W power amplifier MHT1008N

designed by DJ0ABR & DC1RJJ

Matthias, DD1US, November 23rd 2019

In my setup for QO-100 I was missing a medium power amplifier to drive the planned DATV power amplifier.

A friend from the UK, Arved M0KDS, offered me a populated PCB with a MHT1008N amplifier from Freescale

Semiconductor. The design was made by DJ0ABR and DC1RJJ. Thus, I decided to give it a try.

This PA is supposed to give a saturated output power of 10W at a supply voltage of 28V. A description of the

design can be found here: https://www.helitron.de/dj0abr/english/technik/sat/sat_pa_stage1.htm

Here is the schematic of this PA:

Here is a picture of the PA from Arved already equipped with SMA connectors and mounted on a heatsink. I just

took the populated PCB from him.

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I found a suitable milled aluminum encasing in my storage and mounted the PCB into it.

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First I measured the output power as a function of the drive level. I operated the PA at a supply voltage of 24V

and set the bias point to a quiescent current of 155mA. About 25mA are consumed by the bias circuit itself, thus

the drain current of the MHT1008 was approx. 130mA.

The small signal gain is 16.5dB, the P1dB is +36dBm=4W with a drain efficiency of 29%. The saturated output

power is +39dBm=8W at a current consumption of 880mA and a drain efficiency of 38%.

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Next, I measured the small signal frequency response of the PA:

A

1AP

SWT 100 ms

RBW 3 MHz

VBW 3 MHz

RF Att 10 dB

TG Lvl 0 dBmRef Lvl

-20 dBm

Ref Lvl

-20 dBm

NOR

Unit dB

Start 1.8 GHz Stop 3 GHz120 MHz/

-25

-20

-15

-10

-5

0

5

10

15

-30

20

1 2 3

Marker 3 [T1]

16.68 dB

2.45000000 GHz

NOR 0 dB

Date: 21.NOV.2019 18:32:55

The maximum gain approx. 16.5dB and nicely centered around 2.4 GHz. The ripple is probably due to my

measurement setup.

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Then, I measured the frequency response with the PA driven in saturation. Please note that the power attenuator

between the PA output and the analyzer input is 40,8dB which has to be added to the numbers shown in the

graph:

Ref Lvl

0 dBm

Ref Lvl

0 dBm

RF Att 30 dB

A

Unit dBmSWT 5 ms

1MAX 1MA

Center 2.4 GHz Span 500 MHz50 MHz/

RBW 3 MHz

VBW 3 MHz

-90

-80

-70

-60

-50

-40

-30

-20

-10

-100

01 2 3 4

Marker 4 [T1]

-2.08 dBm

2.45000000 GHz

4 [T1] -2.08 dBm

2.45000000 GHz

1 [T1] -1.90 dBm

2.30000000 GHz

2 [T1] -1.77 dBm

2.32000000 GHz

3 [T1] -1.49 dBm

2.40000000 GHz

Date: 21.NOV.2019 17:44:27

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Finally, I checked the input matching of the PA:

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The input matching of this PA is very good. The return loss at 2.4 GHz is 23dB, the VSWR is <1:1.2

In summary the PA is working as expected. If a lower output power is acceptable it can be operated also at a

supply voltage of +12V. The maximum supply voltage is +28V. For SSB an output power of approx. 2W is

recommended to generate a clean signal.

I am always grateful to get feedback and will be happy to answer questions.

Please direct them to the Email address which you will find below.

Best regards

Matthias DD1US

Email: DD1US@AMSAT.ORG Homepage: http://www.dd1us.de