RIP Chopsey

My beautiful Chopsey cat died this morning.

He was our git bastard cat from hell and we loved him dearly.

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

Finishing 3cm

Well,

Following my musings back here, I've finished the portable 3cm thingamabob:

I've moved the sequencer to be on top of the transverter box and added some surplus heatsyncs to the PA module.

I've even made a metal sheet and drilled it so it all fits on the arm of the dish.

I've also been up to Alport Heights today to test the portable 13cm setup:

Here's a clip of the reception of GB3ZME from the top of the hill:

#GHZBands

Good, egh?

13cm Sked

Well,

Just running a quick test before heading for the hills tomorrow for 13cm sked with @G4ASR.

#GHZBands

13cm Complete

Well,

I've received the PA for the 13cm masthead project and added it to the box with a heatsync and suitable input attenuation:

I haven't stuck it down in the photo hence its a bit wonky.

The documentation with the PA suggests that about 5.1V on the monitor pin is close to PA saturation so I have adjusted my input attenuator to give just over 5V from the PA monitor port with CW key down.

With the output connected via these two attenuators:

to my XL Microwave power meter I am reading -2 dbM so that's about 38 dBm or 6.3 watts - it should be closer to 10 Watts.

To check the value of the attenuator at 2320 MHz, I used the spectrum analyser and tracking generator I made back here in zero span at 2320 MHz, and compared the signal with and without the attenuators, I measure a signal of +10.4 dBm without the attenuator and -29.2 dBm with. So that makes the attenuator 39.7 dB - so pretty much on the money.

Local conditions.

**UPDATE** 

I kept finding my TX/RX switching was going into some kind of oscillation on RX. The unit would rapidly switch between TX and RX until I pulled the power. Oddly (and still somewhat a mystery) this only happened when the +ve voltage to the VLNA was connected to the sequencer. No VLNA power, all fine, attach VLNA power, TX/RX oscillation.

There is a VOX feature in the transverter that switches to TRX on detection of RF on the input; changing that to have a long detection time (a jumper on the transverter board) has cured the problem.

I have no idea either.

As SG labs don't seem to link the transverter datasheet on their site anymore, it's included here for reference.

A new approach to 13cm

Well,

You may recall back here where I built a 13cm capability. I've decided to go about it a different way.

Instead of sending lots of RF up lossy coax with a fixed station arrangement, I'm going to generate less RF but right next to the antennamabob and make the whole setup portable.

So here we have 13cm take 2:

In here we have the transverter, sequencer, the VLNA, a SMA relay and driver, plus this PA will also fit; but I dont have the PA yet. The wonky board you can see is a FET driver to switch the PA bias supply on during TX; that will be mounted on top of the PA once I have it here.

I've hooked up my XL Microwave power meter to the output of the Transverter via a 40dB attenuator and I am measuring:

about 32.5 dBm so close to 2 watts - exactly on the money of the transverter spec.

The PA needs a 1W drive so I will have to attenuate the TX signal by 3dB to get that correct.

Good, egh?