Generating RF for 2405 MHz from Portsdown

[G8GKQ]

I have been doing some tests on generating RF at 2405 MHz (for Es'Hail 2). For the tests, I used a standard (factory-built) V2 Portsdown Filter Modulator board as supplied by the BATC Shop. The F-M board was driven from an ADF4351 through an LO filter board.

The results were initially inconsistent, until I realised that the filter-modulator board was oscillating at about 750 MHz when driven with higher levels of local oscillator RF at 2405 MHz. The level of the ADF4351 output can be adjusted in the Portsdown console (Advanced System Set-up, ADF4351 Levels) and I had set the level for 1255 MHz and above to 3 for (so I thought) maximum output. In fact the 7 dBm that I was seeing on my power meter was all at 750 MHz.

On reducing the LO level to level 2, the power meter dropped to -6 dBm and I am confident that this is all at 2405 MHz. The default level setting of 0 gave less than -10 dBm, so it is worth playing with the level to achieve maximum stable output.

The MER on MiniTioune (1MS, Serit Tuner) was initially 16 dB, but could be increased to 21 dB by band-specific adjustment of the potentiometers on the F-M board.

Of course, the ADF8345 QPSK modulator is only in-spec up to 1000 MHz. Far better results would probably be obtained by substituting an ADF8346, which would need less drive and have better performance at 2.4 GHz.

Given these results, and the fact that I will probably also want to use narrow-band modes on Es'Hail 2, I will be building an up-converter (from 70cm) for my Es'Hail 2 station. However, I would be interested to hear of anyone who has gone down the direct route to generating high power at 2405 MHz.

Dave, G8GKQ