VK5FQ | 70cm DVB-T PA

Building a PA from ex-commercial PA.

Building a 70cm HD DATV Power Amplifier.

Raising the output power level of my DATV setup.

To broadcast to fellow viewers, amateurs and non-amateurs alike, I needed to increase the power levels of my locally produced DATV signal. Enter the BLF888A RF palette. This palette is designed to produce up to 110 watts of DVB-T (8k OFDM) signal! I can vouch for this! Perfect for local terrestrial work.

The BLF888A is a UHF power LDMOS transistor. It will produce 600 watt CW signal with a 50 volt supply. Has a gain of around 20 dB and efficiency of 30%. I intend to use it locally for DVB-T signals at a modest 50 watt output - just cruising and running cooler.

On board control is done by utilising a W6PQL sequencer, which handles the correct operation and switching of the PA at all times. This PCB includes temperature and fan control, PA output control switching, bias switching, overtemp cut-out, vswr lock-out, etc.

Output RF is filtered with a 270W commercial broadcast band pass filter, which has conveniently, a sample port next to the output port, for monitoring purposes. This is where I connect my spectrum analyser to monitor my RF output waveform.

Home brew is fun...!

This is a great hobby and the opportunity to build and learn goes a long way! To be able to cobble up a HD DVB-T PA using an existing re-purposed PA, some extra bits, both in designing, building and testing, can be as much fun as switching it on and being on-air!