Hi All,

I have been playing with the idea how to make a dual-band transceiver with a single DRA module. I had ups and downs and hence no news from my end. Finally I have done a proven amplifier that works well and does help make a dual-band transceiver with a single DRA module. Read more if interested...

This idea was brewing for some time. You might recall that I did receive UHF signals with DRA818 VHF module (and VHF signals with DRA818 UHF module). While DRA818 module can receive reasonably well outside it's defined freq. range, it cannot transmit sufficiently outside defined freq.range. So idea was natural: make a simple amplifier that would amplify TX signal that is outside defined freq. range. In the mean time I did consider and try many circuits, including small PA by Matjaz Vidmar S52MV from one of his early VHF designs, but I was not pleased with ease of this design. So I did work over my drawers and there I found a couple of M67748L VHF power modules that can deliver up to 7W when driven with 20 mW. This was ideal for my application.

First prototype did not work well, but see the photo od the second prototype that did work as expected. It was driven by DRA818 UHF module that delivers some 2 mW at VHF band - enough to drive TX relay and M67748L module to deliver 1W of output power at 13.8V power supply.

20160404 095439 30perc


This prototype was more a POC - proof of concept and it proved very well! Next PCB will include output filter and necessary connection to controlling AVR. Namely the M67748L has max. input of 40 mW, so we must prevent accidental transmission to PA outside the VHF band. Also I want to make this PA as a stand alone PA for VHF radios. As mentioned this PA can deliver solid 7 Watts with barely 20 mW drive. This will make a nice "boot" to our Weekend radios. More info will follow soon.

73 de Jure, S52CQ