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Saturday, 24 September 2016

RTTY Everywhere!

Well,

It's the CQ WW RTTY test this weekend, because of travel tomorrow and other commitments - only a very quick play this year.

Here's the 15M log as a map:



With SFI:86, A:9, K:2, R:49 - the 15M band hasnt been in bad shape today at all.

Local conditions.





I'm off to the Kingdom of Saudi Arabia tomorrow - I think Maggie cat wants to come too!

Good, egh?

Friday, 23 September 2016

TXing WSPR with the Red Pitaya

Well,

You may recall some time ago that I had a fiddle with a Red Pitaya? This was back here in this post.

So further to the WSPR RX I was doing back then, I made a request via Mike Richards G4WNC (He writes the Data column in Practical Wireless) to add a PTT switch to the software. The TX signal was on the output connector and the RX input on the Input connector - I only have one antenna and I wanted to switch between the two.

Well, lo and indeed behold, the code for the Multiband WSPR transciever has been updated here.

I've downloaded the new software which includes an extra module called gpio-output which switches the DIO0_P pin (its pin 3 on the E1 connector) to 3.3V when the device is in TX.

Now, I noted a few things when I downloaded the new files and executed the make command:

  1. The Makefile downloaded ended up with a .1 extension and needed to be renamed.
  2. The new .sh files had the wrong permissions and needed to be chmod ed to be executable
other than that updating the software and re-building was easy. 
To accommodate this I have made a very simple PTT switch (please excuse my TinyCad capability):

which connects to the Red Pitaya Pin 3 and GND on the E1 connector and then feeds a PTT line (grounded during TX) to my TX/RX relay.

The only Relay I had was a latching type so I have made a board from W6PQL to drive the relay from a grounded line:

This board looked like this when I had it under test:



And this is what the latching signal looked like before I added some diodes on the relay coils:


Now, you may remember that I also purchased a board from SV1ASM to add some extra drive to the Red Pitaya output, here it is under test:


Now, this is supposed to give me about 14dB of gain, but my tests suggest it's a bit short. The Tracking Generator is at -20dB in the test below:





It may just be that I am not driving it hard enough in the test above, as I am getting more like 7dB gain. It seems to be good to about 100MHz though - I will look more at this later.

Before I hooked all this stuff up together, I did some tests on the Red Pitaya output lines. This 'scope screen grab is showing the TX output plus the IO line at 3v3 during TX:


And here we have the 'scope connections to the output connector and the E1 lines:


So, hooking all this lot together, we have a mess like this:





I need to make a low pass filter for the output; mine is currently configured to TX on 30M. Once I have the LP filter I will stick this on the air and see how far I can hear and be heard.

This project is now a good starting point for lots of other TX/RX type ideas on the board.... next though I think I am going to have a go at the Vector Network Analyser.

Here's Florrie the Ham cat being almost completely in the way throughout:



 Good egh?

Saturday, 3 September 2016

DG8 Pre-Amp - More gain, really?

Well,

I ordered a DG8 pre-amp for 2M from here last week and it duly arrived. I only ordered the "short" kit as I thought I would probably have a lot of the more common bits needed anyhow.

Here's the completed project:


Here's a close up of some of the surface mount gubbins on the other side of the PCB:


And here's my bench after I had built it - a complete disaster area:





I aligned the pre-amp in accordance with the instructions using a SSB RX but thought the results were quite noisy; I then used the tracking generator and the Spectrum Analyser to align, here's the unit in bypass:




The markers are at 144, 145 and 146 Mhz, here's the aligned version:




I backed the gain off as per the instructions and used my ears to adjust L1, still seems noisy to me.

May have to fiddle some more.the IC-9100 used for my new satellite station can power the pre-amp straight down the coax.

I'm planning to run the amp under the radio bench initially; there's not a very long run of coax to the antenna so I am not sure there is that much to be gained by mast mounting it. Let's see.

Here's Miss Luna Cat, I'm rather hoping she doesn't decide to play "shelf swat" with my Nixie Clock!




Local conditions.

Monday, 29 August 2016

Doppler, Frequency Inversion, What's all that then?

Well,

As I fiddle, I learn. That's the basic idea anyhow.

So, I've been making a few QSOs through these amateur satellite thingamagigs.

There are a series of Japanese birds called the XW-2 series. Their frequency allocation is as follows:

Now, the number on the far left top of that image is wrong and should read 435.000.

I just had a QSO through XW-2C, the linear transponder (the bit that receives speech on the uplink and re-transmits it on the downlink) are actualy at the following frequency ranges:

Uplink:       435,150 -> 435,170
Downlink:  145,815 -> 145,795

Now, the observant amongst you will note that the Downlink frequency I have listed goes from high to low and the Uplink from low to high. Thats because it's a linear transponder with Spectrum Inversion. So as I tune in the 20KHz passband of the satellite I have to tune +ve in the Uplink and -ve in the downlink (or the other way round).

So when the Uplink is at 435,150, the Downlink is at 145, 815 and when Up is at 435,170 Down is at 145,795. Thats all before you add in the complexity that the Uplink is in LSB and the Downlink in USB. And then theres the further complexity of Doppler.

Now, I like to think of things very simply. If you can imagine a Sine Wave shape, with the right hand end fixed and the left hand end moving left, it is quite easy to see that the frequency is being stretched and is therefore decreasing. Similarly, if the left hand end of our imaginary sine wave was being moved to the right, the wave is being squashed and the frequency is increasing.



Therefore as the fixed point (my antenna) and the satellite (moving) get closer together the frequency that I need to tune to receive the Downlink and transmit to find the Uplink are both increasing, similarly when the bird is travelling away from me, the frequency is decreasing. The effect of this change is dependent on the actual frequency itself, so the higher the frequency the more pronounced the shift needed.

Luckily the Sat32PC software calculates the Doppler for me, but I hope the rather simplified explanation above helps explain whats actually going on.


Fun egh?

Friday, 26 August 2016

QED on the Birds!

Well,

Following my last post here, I've managed to complete my first Satellite QSO.

I'm using SatPC32 to control the antennas and also the Radio:


My first QSO was with RN6MA in LN06uo - Thanks Victor!

We were using the XW-2A satellite; uplink on 435 MHz and downlink on 145 MHz.


So much to learn!

Here's a video of the antennas in action:


And here a quick video of the IC-9100 receiving the telemetary beacon from XW-2A showing the auto doppler tuning.


Here's Florrie the Ham cat enjoying some sunshine:

Local conditions.

Monday, 22 August 2016

Some More Bird Time!

Well,

Following the progress last time, today I have finished the LVB Tracker kit.

The kit is complete and the programming of the PIC done; I had some issues with this part of the project. I couldn't get the PicProg executable as supplied as part of the fileset to function - it would appear to program OK, but the verification failed. There were way too many variables involved so I dug out the PIC programmer I purchased way back when and programmed the PIC that way. Once I had figured out all the configuration bit settings I was up and running....


The image above was taken during the calibration process. Basically the rotator control box outputs two voltages which are representative of the position of the AZ (0-360) and EL (0-180). You tell the software when the rotator is at 0 in both AZ and EL and then again when in 360 and 180. It can then calculate the appropriate voltage for anything in between.

I've chosen to use SatPC32 software for tracking the birds, controlling the rotator and also handling CAT control of the radio to automatically turn the antennas (both AZ and EL) when a selected satellite is in reach, and also control the frequency setting on the radio - including the adjustment for Doppler shift as the bird is moving towards or away from my station.


Here's a quick video of my first ever reception from an Amateur satellite. This is before getting the CAT control functional - just the antennas are moving automatically to track the bird as it passes:


And here is a quick video showing the auto tuning for Doppler (no sound):


So now it's time to do some research and some listening before I decide which satellite and how to make my first QSO. Fun egh?

Here's Miss Luna Cat asleep behind one of my monitors:


Local conditions.

Sunday, 21 August 2016

Following the Birds!

Well,

For quite some time I have wanted to try my hand at Amateur Satellites. Now, I plan to utilise my IC-9100 for this task - it is a full duplex radio meaning I can TX on one band whilst RX on the other.

I decided I would build myself a "proper" satellite tracking antennamabob, and here it is up in the air:


There's 3 elements on 144Mhz and 7 elements on 70cm. The antenna has both azimuth and elevation rotation capabilities using one of these:


It's a Yaesu G-5500 rotator; unfortunately they don't supply the necessary hardware to separate the azimuth and elevation rotators - so I had to fabricate something suitable. I've mounted the azimuth rotator way down the pole and utilising these brackets from Barenco and a Yaesu thrust bearing we have a suitable working arrangement with minimum weight at the top.

The plan is to develop a means of automatically controlling the antennas such that they will auto track satellites using PC based software. I've bought one of these kits from AMSAT, here in early construction:


And here ready to wire up and start to play:


So, lots to follow on this topic!

Here are a few of the feline family members:


Good, egh? Local conditions.