SG Laboratory recently released a 5.7 GHz 10w PA. This amplifier has been developed and produced for industrial use but is matched well for the 6cm amateur band. It is based on the latest GaN power transistor from Cree/Wolfspeed. If you have plans for 6cm, this PA would complement most transverters.

Specifications

The SG Lab 5 Ghz 10w PA output power on 5760 MHz is 10W minimum with a typical output power of 11-12W.  The input power is 10-12mW . Maximum input power is 25mW. The bandwidth is 5.65-5.85 GHz. The PA requires 28V at 1.1A.

The amplifier has monitoring ports for input power, as well as forward and reverse output power from output directional coupler detectors. It has RF sense (RF VOX) always active with <1mW threshold. PTT is activated by connection to GND.

The size of the unit is: 82 x 72 x 22mm without SMA the connectors.

The active component in the PA is the Cree/Wolfspeed CG2H40010F. It is a gallium nitride (GaN) high electron mobility transistor (HEMT) that works up to 8GHz. GaN HEMTs offer high efficiency, high gain, and wide bandwidth capabilities making them ideal for linear and compressed amplifiers. The driver is HMC408LP3E. The CG2H40010F spec sheet makes for interesting reading.

Driving the PA

The maximum input power of the amp is 25mW which means input attenuation is required for most transverters. If you’re using the Kuhne 5.7 Ghz transverter, you’ll need 13dB attenuation to drop the drive to 12 mW. There are several options to do this.

You’ll find some cheap and effective inline attenuators that work to 8GHz on AliExpress. Hrystian at SG Lab has tested these and says they are ‘good enough for this purpose’. The cost arround $3.50 USD.

TX Switching

The PTT line on the PA needs to be grounded to engage TX. If you are using a sequencer, such as the Minikits EME166 where you’ll most likely have a +12v or VCC output, then you’ll need to invert the signal on the TX line. This circuit will do the trick.

The LED is optional but if you want a TX indicator this is one way of achieving that.

The joining of cases

The PA just wouldn’t fit into the existing enclosure so another one was added. This also made an easy swap possible if required. I chose to use a stainless steel flight case detachable hinge and stainless steel locking buckle.

$2.42 for the buckle and $4.69 for the hinge.

The build

I’ve built the PA into a self-contained diecast box as it wouldn’t fit into the existing transverter enclosure. I’ve used a detachable hinge and a clip to fix the PA to the transverter. This way, I can easily detach the PA should I feel the need to run QRP or add a more high-power PA in the future.

My 250mW 6cm Kuhne transverter drives the amp via a 13dB attenuator. Inside the box, you’ll see a 28v DC to DC converter. You’ll find these online for around $30 AUD.

Rob VK3KRD and I were testing these PA over 80km with great success. The PA runs quite cool at full power. With a 28.0v supply, the PA draws just on 1 A. As of the time of this update (8/8) I still haven’t seen a specification PDF from SG Lab. Hopefully, it won’t be too much longer.

I looked high and low for a 2 amp meter but couldn’t find one locally. I did find one on AliExpress which was worth the wait and is now installed on the top of the case.

A final note… the price of this amp as at July 2023 is 384 Euro +10 Euro for shipping. Hristiyan LZ5HP has a 25w version in design too.

The completed build is above. The 12v to 28v converter sits in the middle of the box.

A 10 dB and 3dB attenuator drops the 250 mW down to 12 mW to drive the amp

The PTT switching circuit, as described above, was made into a piece of heat shrink.

Rob VK3KRD’s build

For those who follow my Youtube channel, you may be familiar with Rob’s homemade gear. His transverter feature here used to have a cheap 5GHz drone amplifier. These devices are known to fail without notice so the upgrade to the new PA will be a great advantage. On air, his signal on he band from this newly renovated box packs a punch.

Rob VK3KRD’s homemade 5 GHz Transverter with the SG Laboratory 10W PA

Sparks fly…

Did you find the easter egg at the end of the video? Rob created an unwanted circuit while using his metal pointer while showing us around his homebrew tansverter. No smoke was let out of any of the components, and it certainly was a spectacle.