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Thursday, 30 October 2014

Transverting some more, some more


Following my progress last time:

I've kind of finished (ready for test) the Anglian transverter.

Here's the finished article:

Here's the main transverter module:

This is the external DDS LO which stabilises the in-board LO:

And this is my hideous looking changeover relay for the 144MHz socket.

There's an Omeron relay on the underside of the board, even so it looks pretty hideous to me!

These are the things I am not so sure about:

  • The case is metal but plastic coated. Have I got a good ground connection to the front, back and main parts of the case - should I add some specific earth tags on each part of the case?
  • The changeover relay - need I say more!
Fun though, egh?

Wednesday, 29 October 2014

Transverting some more


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?

Saturday, 4 October 2014

Finalising the Conundrum....


A few things to report....

Firstly, when I was at the National HamFest the other weekend, I found myself a signal generator. It's a HP8648A and looks like this:

It covers 100KHz up to 1GHz and appears to be calibrated in agreement with my Spectrum Analyser. That's good enough for me and at last I have a Signal Generator where I can specify the output amplitude in dBm!

I've been fiddling today with the transverter project I started back here:

and have been making the final component which is a 10W PA to give a reasonable level or RF out. Here's what the PA looks like:

It's based on a 2SC2539 final transistor which is mounted on a reasonable heatsync between the two copper boards you can see. The PA seems to be working with a nice clean output:

The driver transistor (which is a poor old 2N3866) is running hot, hot, hot! I need to find a better component for that bit as otherwise it's going to cook. Something with an isolated can would be ideal so I can solder it to the copper board - that would make an excellent heatsync.

I've stuck the project together now and it's looking like this:

I need to run some more tests on the output to check for harmonics and other spurious emissions, but I think this is good for an on-air test now.

The only other thing to report is that I left my FT-DX3000 WSPRing on 40M last night, I set the RF out to the lowest setting (5W) but also reduced the audio drive so the output was reading 2W on the internal meter. This is the map of heard/hearing this morning:

Florrie cat's not been helping much, sleeping behind the radio PC monitor:

The other three spent most of the afternoon upside down in the kitchen:

Good, egh?

Local conditions.

Friday, 3 October 2014

WSPRing again - Shhhhhh


Before I headed off to the work QTH yesterday, I left one of the radios in WSPR on 20M. Here's what I found when I got home:

Now, none of these can be considered QSOs but it sure gives a good impression of the propagation through the day and the station capability.

I'm more than impressed.

Good, egh?