Completing 23cm

Well,

You may recall last time, I was changing my portable setup for 23cm. Well, on my travels I found a Kuhne Electronic PA for 23cm and have installed it in the waterproof enclosure with the rest of the gubbins:

I have a 14dB attenuator between the transverter TX output and the PA input. Thats a bit bigger than I need, but I don't have anything else suitable at the moment. The G4BAO amplifier that I now have here (thanks John) is going to get utilised as a DATV amp (I think).

I've been fiddling with a cheap Chinese board with a variable attenuator on-board. You can control this using the DIP switches on board or by software. I've written a very simple bit of Arduino code and interfaced an Arduino Nano to the board using serial comms:

This allows me to step through from 0-30dB attenuation in 0.5dB steps. Really quite neat for just under £12 GBP delivered from the far east! I may decide to use this to get the transverter to PA attenuation exactly on the money - let's see.

I'd like to introduce you to the best and most useful screwdriver in my possession:

This belonged to my Father who sadly passed away just over 31 years ago:

I'm often heard muttering to myself "now where's Dad's screwdriver". If it's of interest Dad, I still use it regularly!

Local conditions.

23cm Portable

Well,

Following my changes to the 3cm and 13cm setup to become more portable, I decided it was only fitting to re-make the 23cm setup I made back here. I'll reuse the PA and the transverter.

The first stage in this project will be to create a new sequencer, much like the 13cm version, so we can switch the transverter, a VLNA and a co-ax relay.

Here's the design:

and in reality, this looks like this once built on stripboard:

I've already got a G4DDK VLNA for 23cm assembled here, and coax relays aplenty. John, G4BAO is just tweeking my 23cm 60W PA and once I have all the bits, we can mount them in another waterproof enclosure the same as the 3cm and 13cm setups.


As part of the sequencer design, I finalised my latching relay driver circuit and have finished up with this, included in the sequencer diagram above:

So this is what I have so far:

You can see the SG Labs transverter, the sequencer from above, the VLNA and the TX/RX switching - just the PA to be added.

I've tested one of my attenuators to get an exact value at 1296.2 MHz using zero span on my Spectrum Analyser Tracking Generator as a signal generator and concluded a value of 29 dB (its rated as 30dB).

So then I used this in line to my XL Microwave power meter to measure the output:

And in CW with key down on the FT-817 and 5W output, that reads 6.1dBm so we then add the 29 dB for the atenuator and I get 35.1 dBm which is about 3.25 Watts out of the transverter. It's only supposed to output a nominal 2W and 2.5W max - so I'm not too sure whats going on here.

I've set up the transverter to work with full bananas out from the FT-817 whilst on DC power, and the LEDs that indicate input power levels and output SWR are both shining green:

Here's a crazy cat of mine en route to a portable operation:

#GHZbands

23cm from a HillTop - Most definately!

Well,

Following my recent musings about the construction of a portable 23cm station here:

http://g0mgx.blogspot.co.uk/2016/02/23cm-from-hilltop-oh-yes.html

Myself and Vince, G0ORC put it on the air last night in the UKAC contest, here's the result:

Not bad for a first effort, egh?

Local conditions.

23cm - From a Hilltop - Oh Yes!

Well,

You may remember last time I was rambling on about my portable 23cm project; well I had come a little unstuck with what looked like thermal runaway in the PA block.

I managed to acquire a suitable heatsync for the PA and then had another bash at setting the idle current at the 350mA recommended by the PA designer. Eventually, after much trial and error I got the idle current set and there was no hint of the runaway I was seeing before.

So, I took a deep breath and hoked it all up ready for the TX test. The setup was the same as I described last time except I added a power meter at the output of the PA:

I've lashed everything down inside the case in my usual "bodge it and scarper" method and the birds nest now looks like this:

And the whole thing now looks like this:

I'm measuring about 50W output on the power meter, so that'll do nicely.

We've got this Wimo antenna ready for the hilltop which is currently strapped to my Wifes line post:

The return loss of the antenna looks just fine:

By my calculations, if we have 50W out of the linear, that's about 17dBW, the antenna claims 16.something dB gain, even if we call the antenna gain 13dB that makes the ERP about 1KW!

We need to make sure we don't cook too many passing pigeons with this baby.

Local conditions.

23cm - From a hilltop?

Well,

I mentioned a while ago that myself and Vince, G0ORC were planning to have a bash in the UKAC contests. We have a capability for 6M, 2M and 70cm but nothing portable yet for 23cm. So hence the project....

I bought one of these transverters:

http://sg-lab.com/TR1300/tr1300.html

and to go with it a PA kit from G4BAO:

http://g4bao.com/

Here's what I've made so far:

I used a toroidal transformer I had to create the PSU, the requirements are 28V for the PA and 12V for the transverter.

The transverter module itself looks like this:

and the PA, once constructed, looks like this:

Now, the first conundrum was how to test the RX path of the transverter given that my signal generator only goes as high as 1GHz.

What I realised was that my Spectrum Analyser can be set into zero span mode and that makes the tracking generator a fixed frequency. So I set the Spec An to 1296.5 MHz and hooked it up like this:

With the F-817 set to 144.5 MHz I have a strong carrier - so I conclude that the RX chain is working.

Now to test the TX chain - more tricky!

First of all I realised that I can tune the input and output of the PA using the Return Loss Bridge combined with the Spectrum Analyser. Here's the finished result on the input side (after some trimming in accordance with the assembly instructions):

And here is the output side of the PA:

So now to devise a way to test the whole TX chain, this is what I came up with:

Which kind of looks like this:

So we have the RF from the PA into the big block which is a Directional Coupler, the -30dB forward port is feeding the Spectrum Analyser via another 25dB attenuator, then on the antenna side we have 2 x 30dB attenuators to a 50 ohm load. The return loss of this lot is actually quite good and looks like this:

Now, I have tested the transverter without the PA and can see an output at the expected frequency:

There's much less attenuation in the chain for the test above, but when I try and set the idle current on the PA it kind of runs away. By that I mean that as the device heats up so the current drawn increases and just keeps increasing. I think this is because I don't yet have any suitable heatsyncing in place so have ordered something which I will have to wait for before I can continue.

So far, so good though, egh?

Here's our latest addition currled up with her Dad:

Local conditions.