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Sunday, 17 February 2019

Es'hail-2 - really?


I've just lashed together a first attempt at receiving the downlink from Es'hail-2.

If you have been asleep, the is the first ever Geostationary Amateur Satellite and is a bit fab 'n' groovy!

I'm just using an Amazon sourced LNB:

I've stuck it on a dish I had lying in the hedge and attached it to an Azimuth and Elevation rotatormabob - you may remember that setup from here.

There's an LVB tracker with computer driven elevation and azimuth control.

I pointed the dish in very roughly the right part of the sky and then tuned around where I expected the signals to be, with the narrow band transponder downlink at 10489.550 - 10489.800. I've subtracted the 9750 local oscillator in the LNB.

I then found some signals and used the rotator controller to peak the signals - I've ended up at 149 degrees to the south and 18 degrees elevation - there will be many, many errors in my setup at thus time.

I'm a bit off frequency, and also drifting a touch. I need to add external frequency lock to the LNB. I've also started to setup an uplink based on the system we made here.

But I've certainly found it:

So the low beacon on the narrow band transponder is sending:

5i 5i 5i de qo-100 BK dl50amsat

and I am receiving this at a constantly drifting down frequency, currently at:

739.306 MHz on my SDR. So I add the 9750 MHz Local Oscillator and we get 10489.306 MHz

If should be between 10489.550 and 10489.555 MHz so I am a bit out of bonk and drifting.

Next job - lock the LNB to a frequency reference!

Much more to follow on this topic!

** UPDATE 1 **

I've modified my LNB to take an external 25MHz frequency - so I can feed it with a locked reference.

This has been done in accordance with the instructions here.

I'm feeding the LNB with some cheap co-ax from Amazon and I have replaced one of the "F" connectors with a BNC and attached it to my Leo Bodnar reference which I have set for 25MHz.

According to the instructions (well, read box) from the LNB:

Model: OQSLG Green HQ
Input: 10.70 GHz - 12.75 GHz
LO: 9.75 / 10.6 GHz (10.6 with 22KHz signal on coax)
0.1dB noise ratio
Gain: 60-65dB
Horizontal 18V; Vertical 12V

Now, with the 25MHz external reference, the low end beacon on the Narrow Band segment of the satellite is exactly on frequency:

I'm still worried about LNB skew as switching to horizontal doesn't null out this beacon completely = not even sure if it should, but I am definitely not seeing the DATV beacon yet so more fiddling is required.

** UPDATE 2 **

I've fiddled and now can receive the DATV beacon:

This is really quite fantastic!

Sunday, 13 January 2019

FT-990 CAT Interface


Very much in line with what I did back here; I have today knocked together a PC interface for my FT-990 with its new control board from here.

I've included a audio interface and RTS driven PTT just for good measure - I don't think for a minute I'll use it though.

The construction is very simple on veroboard, and it allows me to read the transceiver frequency automatically from Logger32.

Here's Miss Pepper Cat and Miss Florrie Cat doing what they do best:

Friday, 11 January 2019

A collection of FT990s - A gaggle?


I've had an old Yaesu FT-990 for quite a while; its a delightful analogue radio with very few modern bells and whistles.

Now, I've previously opened up and admitted I suffer with TEAS; I suspect the diagnosis may be wrong and actually it's GAS that I have got (Gear Acquisition Syndrome) it seems to be more far reaching that just test equipment.

I've got myself another FT-990.

There is some logic behind this madness, the ROM version in mine was 1.2 and that doesn't allow CAT control from my logging software. The second radio I have is at version 1.3 which does.

This is the inside of the new rig, which is extremely clean and tidy.

It has two filters fitted, one is an Inrad SSB filter and the second is the wider 500Hz CW filter.

The image below is the "control board" and this contains the CPU and ROM with the software version:

So, all I have done is simply swap these boards between the two radios. I also notice that the one I use on the bench is much dirtier inside. The case on the latest acquisition is a little scruffier so I guess we will stick as we are. I also notice my existing rig has this modification at the back. It's clearly switching am RF path, bit I haven't tried to figure out which one or what it does. There's a relay on the underside of the bit of veroboard and it is doing something under certain unknown conditions. I need to investigate further.

Anyone know what that mod might be?

I'd also be interested in anyone who wants a FT-990 V1.2 ROM fully working. It's only going to gather dust here.

Local conditions.

Saturday, 5 January 2019

TS-890 and Data Mode Configuration


Following my video last time, I have been asked by a few folk to do some more. Here is a video on Digital Mode configuration for the rig:

and another one with a few more bits 'n' bobs:


Monday, 31 December 2018

TS-890 Again


I've been asked to put a video together on why I love the TS-890; well here it is:

Sunday, 30 December 2018

OCXO Update


You may recall back here where I built a VE2ZAZ GPS disciplined OCXO as a frequency reference for my shack. This was back in 2013 and the unit has pretty much trundled along, doing its thing ever since.

My recent fiddling here resulted in my realisation that a more accurate 1PPS signal is achievable by putting certain GPS receivers into a fixed location mode for timing applications.

So, I decided to invest in a decent enclosure and re-build the frequency standard. I have effectively swapped the PSU, GPS receiver and the OCXO itself.

This is the internal gubbins of the new unit:

This is the main PCB - the wire you can see from a PIC pin is to a reset switch on the back panel which clears the alarm condition manually. A firmware mod included this but the PCB is prior to this change.

This is the MAX232 device and regulator which converts the PIC comms into RS232 levels for the PC.

This is the PSU board and the OCXO itself:

And finally this is the GPS receiver parked in the corner:

The config of the system is fairly complex, but for those playing along at home, these are the settings I used to get the system into a stable state. I first forced the DAC value to be close using my test gear and manually adjusting the value, then I left the device running overnight with these parameters:

Then now the unit is settled, I have changed the config to be thus:

The unit itself looks like this at the front, there are two 10MHz outputs plus a selectable 1 or 5 MHz output:

The rear of the unit has two further 10MHz outputs:

I have more than enough "bits" here to make another one of these; anyone want one?

Friday, 28 December 2018

Stationary Mode - Really?


I've been fiddling quite a bit this week with frequency standards (man with two watches never know correct time et cetera). All of the GPS based frequency standards rely on the 1 PPS signal from the GPS receiver, and the accuracy of this can be improved by putting the GPS receiver into "Stationary" mode i.e. not moving. This mode is intended for timing applications and is clearly the correct mode for any fixed GPS being used as part of a frequency reference.

I have recently bought a couple of GT-U7 GPS modules from Amazon. They are as cheap as chips and the documentation for the chipset can be found online. This documents the process of squirting a bunch of data down the serial comms link to the GPS module to put the receiver in "Stationary" mode.

So, in order to do this I have stolen some C code and modified it a bit (the Syncronisation command being looked for wasn't correct) and stuck it on my webspace.

I've connected the GPS module to a Raspberry Pi:

Its just the TXD and RXD lines of the Pi Serial0 connected to the GPS TX and RX serial lines.

You need a bit of jiggery pokery on the Pi before you can use the Serial Port in the way we want:

  1. Edit the config.txt file in the /boot directory and make sure you have the line enable_uart=1
  2. Edit the cmdline.txt file in the /boot directory (make sure you keep only one line in this file) and remove the text "console=serial0,115200" - this removes the need for a login when you connect to the serial port
Once you have done that, reboot your Pi and then from the comand line:

>sudo gcc Stationary.c -o StationaryMode
>sudo chmod +x StationaryMode

And the software should respond with a message to say the configuration has been updated and saved correctly.

What could be simpler?