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Wednesday, 29 October 2014

Transverting some more

Well,

You may recall my discussion a while ago on the best way to get a 144MHz capability here; should I continue to use my FT-847 or transvert from my TS-990.

The TS-990 has an external drive socket "DRV" documented to be a 0dBm output; that's not entirely true. What I have found is that:

  • WITHOUT XVRT selected the output power on the DRV socket is variable from 0dBm to -15dBm with the front panel power control.
  • WITH XVRT selected AND Advanced Menu item 8 ON the power is fixed at -15dBm.
  • WITH XVRT selected AND Advanced Menu item 8 OFF the power is variable between 0dBm and -15dBm with the front panel power control.
However, the TS-990 also has a neat feature in that you can program the offset of the transverter into the rig, thus making the display read the transverted frequency rather than the IF.

So, I joined the list for an Anglian transverter from Sam, G4DDK:


And after seeing him present the design at the RSGB HamFest, mine duly arrived.

Here's the basic transverter module in its screening box:



And the underside:



This will be stabilised by an external 116MHz Local Oscillator generated by a kit from ZL2BKC, based on an Analogue Devices ADF4351 DDS:

you can find details of this project here:


Then finally, there is an 8W PA module for the output:


This is based on the Mitsubishi RA08H1317M module. I've cut the input track and made a 6dB pad at the input on mine:


I haven't yet assembled the PA module, but I have made the heat spreader that the board is bolted too.

The next job was to build and test the low pass filter for the amplifier output stage, it looks like this:


It's pass band looks like this:


and the return loss like this:


All in all, the 2M transverter project is progressing nicely.

Pepper cat hasn't been helping much:


Fun, egh?

2 comments:

  1. My cat isn't allowed on the desk, after some tiny parts "got lost". To be honest, it isn't allowed on the kitchen table either, but that didn't stop different meats to travel from a plate to my bedroom door when no one is around.

    The transverter looks great, I was thinking of building one for my SDR transceiver as well, still haven't decided on the model.

    73 de YO9IRF

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  2. I'm building one of these now, took a look at your 6dB PI circuit just as a sanity check before slicing the board.
    Pepper needs to lay off the cola a bit, don't you think?
    73, mm0gyx

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