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Thursday, 22 March 2018

13cm Complete


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.

Wednesday, 21 March 2018

A new approach to 13cm


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 transvertersequencer, 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?

Thursday, 8 March 2018

Yet more on 3cm (10 GHz)


Following my efforts last time, I managed to get my hands on a 10GHz power amplifier (of sorts):

 This delivers a huge 1W out on 10368 MHz and requires 50mW drive.

According to the transverter manual, I need a sequencer to work this kind of set up properly:

It seems a little strange to me as the Transverter is put into TX first, then the changeover relay and then the PA. I would have thought the relay, PA then transverter so we generate RF last, but hey-ho.

I did a quick design of a simple sequencer:

And here it is prototyped on the bench:

It was giving me about 500ms delay between the relay and the PA on TX:

and about half of that on TX Off:

So I made the circuit on some veroboard and stuck it to the top of the PA:

I also made a latching relay driver from here and bunged it all in a bigger box.

Now, I configured my XL Microwave power meter to read frequency and power and hooked it to the transverter output and adjusted the TX gain to give me 20dBm out. I then hooked that to the input of the PA.

I'm reading about 27dBm out on TX which is 3dB short of target (so half power!). The PA has a voltage point to measure TX power and the sheet that came with it says 2.7V is 1W out, I'm measuring more like 3.5V at that pin so implying that I am over-driving the PA. It's so difficult at these frequencies to know whats accurate and whats not. When I measure the output of the transverter I have to use a 20dB attenuation - I don't know how accurate that is at 10 GHz for a start! Then there will also be losses in the interconnecting cables; so it's all a bit of a muddle.

So I am suitably confused at the moment!

Here's our lovely Florrie Cat proudly sitting in an empty egg box:

Local conditions.

Thursday, 1 March 2018

Arduino CW Beacon


I was messing about on 10GHz and I wanted to get my FT-817 (the IF drive for the 10GHz transverter) to "beacon". As there is no such function in the radio, I wrote some very simple Arduino code and used a Nano to key the CW line to the radio.

I've put the code here if anyone is interested.

It is the most simple thing in the world.....

The two wires from GND and D2 simply connect directly to the CW key jack on the FT-817.

Local conditions.

Wednesday, 28 February 2018

Let it Snow, Snow, Snow!


Interesting view from AntennaCam this morning:

Local conditions.

Friday, 23 February 2018

3cm Again


You may recall my adventures back here on 10 GHz.

Well, today I have decided to resurrect the project and see what happens if I put a dish up on the new mast.

So I got myself a waterproof enclosure, and re-housed the gubbins:

I also have a new mesh dish with a 1M diameter:

Theory says about 37dB or so gain.

I have to pop to the Middle East for a few days, but will get this up in the air when I return.

Here's my very lovely Luna Cat at home in the shack:

Good, egh?

Sunday, 18 February 2018

New Mastamabob


Following several repairs to my mast, I eventually decided to get something stronger and more suitable to the load I have on the top.

My old mast was somewhat like Triggers Broom from Only Fools and Horses; Trigger claims that he's had his road sweeper's broom for 20 years. But then he adds that the broom has had 17 new heads and 14 new handles.

So a new mast was ordered from MM0CUG.

This is all galvanised steel box construction and is much sturdier than the previous. Gary (MM0CUG) made something bespoke for my location to cater for the house apex with a higher tilt point and longer wall brackets. He even drove down from Scotland with the mast on his van and fitted it for me.

So here you can see the motorised electric winch that is used for tilting the mast over and lifting it back to the vertical:

The mast has been concreted in at the base, but is also wall mounted with four very substantial anchor points to the bracket:

And yes, it telescopes too!

Local conditions.

Thursday, 4 January 2018

QRP Labs QCX Transciever


I've been having lots of fun building the QRP Labs QXC QRP transceiver, I've had my first proper bash at a video detailing the construction:

Its a fantastic bit of kit!

Wednesday, 3 January 2018

CAT Control with Logger32


I've been asked a few questions recently about how I auto configure my radios for various tasks using comments over CAT control.

I created a quick video to illustrate this below:

Good, egh?