Using the Eyal Gal 10GHz module in a ham radio transverter

The core of my transverter project is a 10 GHz Eyal Gal module acquired in eBay the last year. These units have a receiver converter and a transmit power amplifier in the same enclosure.

Because the design frequency of the module is 10.4 to 11.7 GHz, it works unmodified at 10368 MHz, which is a clear advantage for use at ham radio.

There is not too much information about these modules except the info published by G8CUB here and here, this post from M0DTS and this datasheet. It is convenient to read all these documents before continue reading this post.

There are many models of this module out there. My module is a model 6031-22, so the information in this page information only applies to the -22 suffixed modules and it is entirely based in my own experiences with the module using as reference the information provided by G8CUB.

Outside

The module is a large block with a bottom plate used to dissipate heat, five SMA connectors and two pin based connectors, one for the supply voltage and another one for the control lines. The pinout of the module is:

Pin	Function
A1	n/c
A2	+8V
A3	-12V
A4	GND
A5	n/c
A6	+12V
B1	n/c
B2	Detector output
B3	TX Gain
B4	GND
B5	TX mute

Inside

At one side of the module you can find the module's markings, and a pair of outlines: One for the power amplifier and the other one for the receiver converter. The outlines are soldered so no chance to open them and take a look inside.

The other side is more accessible. There is a cover hold by several screws. After removing all of them, you can put the cover away and take a look at the control board of the module:

Inside the 10GHz Eyal Gal module. (click to enlarge) 

There are some interesting things on this board. There are three LM2941S regulators. The one at the bottom left of the above picture is connected directly to the +12 volts line through the eight 82 ohms resistors, all of them connected in parallel. It is obvious they form a 10 ohms current sensing resistor. The other two regulators are connected to the +8 volts line through a power mosfet (U6) to turn them on or off. This mosfet is controlled by the TX mute line.

There is an AD8058 (U2) and surprisingly, an AD8310 logarithmic amplifier (U3). This logarithmic amplifier is rated DC to 440MHz, so How can it work at 10-11GHz? My guess is the output amplifier uses a directional coupler with a rectifier diode, and this rectified DC is applied to this logarithmic amplifier to get a convenient dB ready value.

There is also a 78L05 (U5), several operational amplifiers (U1, U10) and some unknown integrated circuits.

Powering the Eyal Gal module

The Eyal Gal module needs three different voltages to work: +12, +8 and -12 volts. The 6031-22 variant uses the +8 volt line to supply the transmitter section, so it can draw over 2 amps of current. As suggested by G8CUB I used a 78T08 regulator, a 3 amps variant of the well known 7808 voltage regulator and works fine. The +12 volt line is connected directly to the battery / power supply and for the -12 volts I use a small DC-DC converter capable of 250mA rescued from an old 1Mbit Ethernet card..

The Eyal Gal module as receiver

To use the Eyal Gal module as 10 GHz receiver you only need to power it up with the three required voltages, add from 2 to 4 mW to the LO IN port and tie to ground the TX mute signal to disable the TX side. I'm using around 4.5mW of LO power at 9936MHz for a IF of 432 MHz.

I can't measure conversion gain neither noise figure, but the module can raise more than 10dB the noise floor of a FT-817 used as IF. Also placing a small SMA 50 ohms dummy load at the RX port produces an additional 2.2dB of noise floor. I know that does not mean anything but it is usually good a receiver can "hear" the noise produced by a dummy load.

The preliminary tests I have made indicate the module RX performance is quite good. Please, note there is no way to disable the receiver side in the module: It is always on, so keep sure your TX-RX switch/relay has adequate isolation!

The Eyal Gal module as power amplifier

In TX mode, the Eyal Gal module is only a power amplifier. This means you must provide a clean 10GHz signal to be amplified. The main advantage of this power amplifier is it has a lot of gain, around 50dB, and the output power can be over 1W. This means you only need a signal around -20dBm to get full output power.

Fortunately this huge gain can be adjusted using the TX Gain pin. This pin admits a voltage between 0 volts (maximum gain) up to 5 volts (minimum gain) so you can accommodate the amplifier's gain to suit your needs.

Applying 5 volts at the TX Gain pin reduces the gain to the minimum, a value close to 0dB, or even a little negative value. The amplifier's input range is unknown, although in the datasheet the IP3 point and 5th order intermodulation values are tested with two 19dBm input tones, this seems a lot for me. I'm applying a +9dBm (8mW) 10368MHz signal at the amplifier input and I can set the TX gain easily to get the full output power. +10 to +13 dBm (10 to 20mW) as maximum input power seems to be a safe value.

The amplifier has a monitor with logarithmic output, you can easily monitor the output power from ridiculous values to full power. This monitor output has 40mV/dB sensitivity.

I made some rudimentary linearity tests. I found to get acceptable linearity power, output must be keep under 1.2 - 1.3 watts. In this way I can use all modes, including AM. The module can produce almost 2W of power, but that is only usable on CW / FM modes, and probably this would push the module well beyond its limits, so it is not a good idea. Expect an output power reduction (gain reduction) when the module gets hot, so for precise TX output adjustment, adjust it after some TX periods, when the module is warm. Use a large heatsink to dissipate all the heat you can from the module, even with a fan.

A last note of caution: the amplifier has some response at 9936MHz, so make sure your signal is clean enough before applying to the amplifier's input port. Otherwise you will see how the detector output is indicating some power when it shouldn't.

Proposed interface

Taking into account all the information presented in this post, my interface to the Eyal Gal module is like this:

In my transverter I have two 12 volts lines: One active at RX, and another one active at TX. The 12V RX line mutes the power amplifier using a small signal NPN transistor, for example a BC547. The 12V TX line feeds a small 78L05, whose output is applied to a 10K adjustable resistor who sets the amplifier's gain, this is, the transverter's output power.

The detector output feeds a small meter (0.5mA full scale) used to monitor the transverter output.

Conclusion

This Eyal Gal module is a nice unit. Its only drawback for me is the power consumption (heat) and the associated output power reduction. My complete transverter + FT-817 draws 1.5 amps in RX and nearly 5 amps on TX. The module reaches easily 50-60 °C during operation. I would like it to dissipates less heat and draw less current but using a car battery there is no problem at all while in portable operation, even during long periods of time. Powering it at 13.8V only increases the heat, so try to avoid it.

Last update: June 29, 2014.