I think its working

Well,

Following from my musings last time on the BATC Portsdown project; I think mine is now up and running.

I've been working on a box for the project and the various bits and bobs are now inside:

So, following the suggested test setup I've configured the transmitter to TX on 1255 MHz using 2000KS (thats the symbol rate) and my newly invented DATV receiver from here sees this:

So I conclude it's working. Now to try and stream some video and then think about external amplifiers and filters!

I've decided to initially aim at 146.5Mhz in the NoV only allocation above 2M as my first target frequency.

I've set the Portsdown to tx on 146.5MHz, 7/8FEC with a symbol rate of 333KS. The output close up looks like this:

Checking on the harmonic content we see this:

So I made a LPF (needed!) and now the output looks like this:

In reality the LPF looks like this:

It is a standard 3 inductor design with 22pf at each "end" and 43pf in the middle two locations. The inductors are 3 turns open wound on a 6mm drill bit.

I've hooked up the BATC supplied EasyCap USB device to the Portsdown and I have coupled up my AntennaCam and we can see this on the MiniTiouner receiver we made here:

So, the next thing I need is a TestCard for TX; enter another great use of a Rasperry Pi. I've installed the software called TCANIM from here. I've followed the instructions to the letter but I cant seem to get a video signal out of the Pi AV socket....

Local conditions.

Portsdown where?

Well,

As part of the project I mentioned last time, I've started to construct the hardware for the BATC Portsdown project.

The fist board I have tackled has been the LO filter. This goes post the AD4135 LO which uses the same development board as we used on the 4.4 GHz signal generator.

This is extreme, extreme soldering! I've invested in a flux pen of decent quality from Farnell and that's made my life much easier. Previously I was using some cheap eBay sourced flux which was a load of dingos kidneys.

Here's the results of my days soldering:

There's basically a 2 bit input thats status determines which of the three on board filters are in line (or bypassed on 23cm). I've tested this and can see three filters, not too sure about their shape though.

4M:

2M:

70cm:

23cm:

Looks a bit odd to me, but lets see.

Local conditions.

Telly - really?

Well,

I've started to play with Digital Television and the broadcasting thereof. The fist part of the puzzle was to construct a means of receiving my own signals so I chose the Minitiouner from the BATC of which I am a member.

I bought the PCBs and the bits and bobs from the BATC shop and have built the project:

The transmit side of things will be from the well publicised BATC project the Portsdown. 

There is quite a bit to this project, hardware wise, but initially we need a Raspberry Pi and some software to run something they call "Ugle Mode" whereby you can send a picture across the shack.

Well, it works:

So its time to progress the hardware some more and move forward with the transmitter side of the project.

Interesting start, egh?

A tracking what?

Well,

As part of the fiddling I've been doing on 13cm, I've been using the new to me (read old) spectrum analyser I have. It covers from about 9KHz up to 22GHz.

You may also recall not so long ago, that I made a signal generator that covered up to 4.4 GHz.

As this spectrum analyser has a 1st IF output socket, it struck me that I could probably make some kind of tracking generator to go with it. Actually the IF output will be doing the tracking, all I need is a signal and a mixer.

Some experimentation allowed me to discover that on the low range, the Spectrum Analyser has an IF output of 3910.7 MHz plus the tuned frequency.

I've made myself a simple Arduino Nano and AD4351 combination:

The source code for the above is here. I've not done anything clever at all, just used the Analogue Devices software I showed here to calculate the required registry values and then hard coded them into the Nano.

That gives me the 3910.7 MHz signal required. We then subtract that from the IF output from the Spectrum Analyser using a simple and small Mini Circuits mixer:

Then I've added a low cost return loss bridge from ebay:

Whilst it's not lab grade, in this example you can clearly see the resonant frequency of the antenna that's connected as the Device Under Test:

The difference between the trace with the DUT socket open (the thicker line) and the other trace is the return loss at the specific frequency.

You can see that the open circuit sweep is nowhere near flat - so there are all sorts of issues with this setup, but as a basic antenna analyser up to about 3GHz this works just fine.

All the while, Florrie the ham cat has been sitting on my rotator manual which I am consulting as the display bulb has died:

Local conditions.

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.