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?

I'm about there!

Well,

You'll remember last time I started modifying the 13cm PA I had acquired. Well, I think it's about done.

What we have is the modified PA, an Arduino Nano plus some software to monitor:

• PA Temperature
• Forward power
• Reflected power
• Bias current (driver, Left and Right PA MOSFETs separately)

and trip if anything goes out of bonk.

The Amplifier now looks like this:

I've just to wire up the Analogue inputs in this image. There are three "status" LEDs on the front panel; one for "All OK", one for "It's gone horribly wrong" and a final one for "TX". If you connect the serial cable to the Nano then there is a status line repeatedly output giving the details of all the inputs read and their values.

The connector on the main board of the Amp is configured like this:

and it was therefore a fairly simple case of wiring the various pins to the I/O of the Nano and writing some code. I stole a lot of the ideas for the code from Mike G0MJW - but there are quite a few differences between what I have ended up with and what Mike created a few years ago.

The 9V line to the bias and other bits of the board is permanently on; the 28V line is also enabled all the time but switched bu a FET switch under software control. This switch is the same as the one in the sequencer, it's just altered slightly for 28V:

I've stuck the source code here if anyone is interested.

Time now for some testing.....

**UPDATE**

A couple of minor software mods (updated on the link above) during testing and all seems to be OK. I am not entirely convinced about the scaling values used to convert from the ADC readings into the value units, but time will tell.

Here's the whole system - there's an IF cable from there to my IC9100 which is used on 70cm as the rig for the transverter:

**UPDATE 2**

I found that the cheap Chinese sourced FET I was using to switch the 28V line had failed, but my software didn't pick up on this. I've changed the device for a Farnell sourced component and also added an extra digital line to the Arduino to monitor the voltage on the 28V supply to the PA. There's a potential divider added to the FET switch board to provide 3.3V when the 28V line is high, this is in turn connected to pin 9 of the Arduino and the code linked above modified accordingly. There is an additional trip condition when the 28V line is High and we are in RX or the 28V line is Low and we are in TX.

Here you can see the potential divider I have added to the FET switch to monitor the 28V line status:

And here is the finished article:

Finally - All coming together

Well,

There have been many musings recently all building to a 13cm (2.3GHz) system:

1. The Transverter
2. The VLNA
3. The masthead enclosure and switching
4. The antennamabob
5. The sequencer

So now I'm trying to glue it all together!

The case is a bit tall, but it's all I had. I created a very simple PSU based on a 723 voltage regulator and a 2SC5200 as a pass transistor - I have tried to over-rate the power supply (please excuse the terrible layout below):

That plus the transverter and sequencer we played with previously.

The Gubbins basically remains the same as designed:

So, there is a VLNA at the masthead next to the antenna and two co-ax feeds back to the shack - one for TX and one for RX. The TX is 15mm Web-600 and the RX line Westflex 103.

This is all driven from 423 Mhz multi-mode transceiver - I plan to use the IC9100.

Now for the linear amplifier, I picked up one of these for basically scrap metal value:

There is information on modifying the unit for our purposes here.

As ever, the first thing required is to take it to bits, once you get the bottom off this is revealed:

then that board comes out and slung to one side:

then we remove another million screws and get the screen out of the way:

and then the top of those two boards gets slung:

Now we need to lift a cap off the board and connect in where our RF feed will be:

Now for the bias for those lovely MOSFETS....  here's the board with my bodged bias circuit:

I reached out through the UK Microwavers Yahoo! group and have received some very useful information including this:

I've added an Arduino Nano into my enclosure and may have a bash at reading some of those control signals:

And throughout, Florrie the Ham cat has been assisting:

Next, a bit of testing.....

Local conditions.

The VLNA, Oh Boy!

Well,

I think I have finished the build of the VLNA for 13cm; having constructed the project I am wishing I had bought a ready built and aligned unit. This was the hardest project to date, mainly because of the very tiny components. I really struggled to get the input matching network parts in place - and have no test gear to actually measure the return loss or noise figures of the final build.

It looks like this:

You can see the input network components in the image above; it kind of looks like the instructions from G4DDK @DXING, but I have no means to actualy measure or test the input return loss.

Lets see.

More Sequencing Secrets

Well,

I've added a FET switch to the sequencer I made last time. The FET switch will provide +12V on RX to the masthead and will be used to switch the masthead relay and also power the VLNA.

The schematic looks like this:

and it's built on the same bit of veroboard as the sequencer:

It switches very quickly, here in blue is the PTT being enabled and in Yellow the power supply that will head up the mast:

So we will then have 200+ ms delay before EVENT 1 from the sequencer:

which will be used for things like turning on the PA bias and enabling RF 'n' stuff like that.

All in all this is coming on nicely.

Local conditions.

So, your mixing what?

Well,

I mentioned in this post that I needed to find a way to test the TX of my new transverter.

I've bought myself one of these:

It's a mini circuits mixer, that is rated to 2GHz but probably works to a fashion well beyond that. Electrically it looks like this:

So, as a test I have my new USB signal generator set at 2000 MHz connected to the RF port.

The HP Signal Generator from here is connected to the RF port and set to 900 MHz.

Now, given that this mixer should do what mixers do, the IF port should have the sum, the difference and all associated other components and harmonics:

The main point here being that 2000 MHz - 900 MHz = 1100 Mhz, which is clearly visible on the spectrum analyser.

So if I take the output of my 13cm 2.3GHz transverter and do some jiggery pokery with attenuators and then mix it with my 900 MHz sig gen signal I should be able to see it on my spectrum analyser at 1.4 GHz.

That should work, egh?

Counting all the way to 13cm

Well,

You may have realised that I had something in mind when I made the Signal Generator up to 4.4GHz recently? Well, the idea is to use that to test a new transverter I have for 13cm:

This is another most excellent piece of kit from SG Labs. You may remember that the transverter used in this 23cm project came from the same place.

So, this transverter has a number of options for the LO, but with that set to be 1870 MHz, and my new Signal Generator set at 2301 MHz:

Lo, and indeed behold, on 431MHz we see a strong carrier:

Now, this transverter even came with a PCB antenna for 13cm:

So, the next thing is to try and test the TX side; not too sure how I am going to manage that yet, but I am sure I will find a way!

I have an ultra low noise amplifier from G4DDK ready to construct also for this band, plus a surplus telecoms PA block that should give some power. I also seem to have a 13cm Wimo antenna sat on my desk:

So, lots more to follow on this topic!

Local conditions.