More WSPRing and QRSSing

Well,

After my last ramblings here:

http://g0mgx.blogspot.co.uk/2012/05/back-to-real-homebrewing.html

I've been doing some travelling with work, so progress is not so good. However, I have entered into a dialogue with a number of folk over my observation that the amplitude of the DSS reduces as the frequency increases. Some suggestions to overcome this mainly include AGC type circuitry or utilising pin 12 of the AD9851 to feedback a voltage to set the output amplitude based on a sample of the output (recursion see recursion). The most interesting feedback that I got, however, was not that the amplitude was dropping with an increase in frequency, but that my scope wasn't reading the signals correctly. The theory being that as the frequency increases my scope sensitivity drops off....

I ended up plotting this graph:

This is implying that my scope starts to take a dive, accuracy wise, after about 1MHz, this is the blue line with the y-axis indicating how many dB my scope is "deaf" by. The yellow line is the same signal but through the on-board low pass filter from the DDS module. This seems to imply that the LPF is rather badly designed also. If this theory is correct I need to subtract my scope deafness from the drop in signal out of the LPF. If at this stage we remember that 6dB is half voltage, this is not insignificant!

All rather confusing? My scope is a 100MHz rated fluke which I thought was supposed to be a good quality instrument. So, is this behaviour typical or is my scope a pile of dingos kidneys? I wonder...

I've made a bit of progress boxing the WSPR and QRSS beacon project:

So far, I have tried a number of output amplifiers, the first based on the circuit in my original QRSS beacon, from back in December 2010:

http://g0mgx.blogspot.co.uk/2010/12/qrss-beacon.html

This gives me a nice clean 4v P-to-P voltage out, but I wanted more than that, so either I add another stage or do something else.

I have also tried an output amp based on the Analogue Devices AD8008, this works OK also. I'm off on my travels again tomorrow, so I'll pick this up again when I get back.

All good fun though, egh?

Back to real homebrewing!

You may recall my discovery back here:

http://g0mgx.blogspot.co.uk/2012/04/well-this-looks-just-great.html

So, Ive managed to make some progress. I've modified the software from W3PM from here:

http://www.knology.net/~gmarcus/

and have managed to get the GPS module working and also the DDS drive routines....

The code is written in C for the Arduino; and it's now interfaced to a four-line LCD, the AD9851 DDS module and the GPS receiver. The GPS module isn't in the picture as it's hanging out the window so it has visibility to the sky.

I've started to box the project, and have also built an RF amp to get me a staggering 100mW out...

Progress has been quite good today, I need to think about how I can get the RF levels the same on each band because as the frequency increases, so the amplitude out of the DDS and hence out of the RF amplifier decreases. I'm really not sure how to tackle that one, so I may have to ask for some help here.

Yesterday myself and Vince G0ORC went over to the "Dambusters Rally":

http://www.qsl.net/gb4tcm/dambusters.html

The rally was really good, albeit a bit small, but there was loads of really good radio junk to rummage about in. I picked up all sorts of stuff including this meter which I am rather proud of:

I've cleaned it up, mounted it on some wood, and stuck it in the corner of the shack with some amps flowing through it...

The next step will be to put some lighting inside...

Looks god though, agree?

Why is this just so insane?

Well, in a recent post I mentioned that the 2m/70cm beam antenna here had decided that once horizontal it didn't want to work so well. It was OK when I used it for satellite operation at 28 degrees, but when we put it back to horizontal the SWR went through the roof. I managed to take the head of one of the grub screws that allow you to adjust the gamma match - so that wasn't too handy either. Anyhow, as an antenna for conventional SSB working it's not going to be much cop, as it's a real compromise for both bands.... so......

I bought a 7 element ZL special from moonraker for 144MHz:

http://www.moonraker.eu/

and it duly arrived a few days later.

Now I am no real antenna expert; my understanding of antennas is that you attach a piece of wire to the inside of a length of coax, place the wire on something nearby that's handy - maybe a hedge or something - then you work the world on HF.... not so on VHF!

There were two confusing aspects to this antenna for me; firstly there are two driven elements (which are actually folded dipoles) and the directors (elements) are not ordered smallest to biggest from the front of the antenna to the dipoles. Hmmmm.....

The two dipoles are fed at 180 degrees out of phase with each other, here you can see the main feedpoint which contains the coax from the radio, a piece of 300 ohm ribbon cable which feeds the other folded dipole and a tuning "stub" - this is in effect an open length of RG58:

These two folded dipoles are sightly different sizes, presumably this offers a broader bandwidth to the antenna tuning point.

Having struggled the pole back down, me and the ever patient Vince G0ORC, we had the new antenna mounted ready to go back up in the air:

You can see the 6m beam and also the new 2m ZL special:

We tuned the antenna on the ground; you chop small bits of the end of the open "stub" for best SWR. It seems to be quite straightforward, once up in the air the SWR was perfect in the SSB portion of the 2m band:

So, the antenna is back in the air, the SWR is near perfect and we could hear PI7CIS all the way from JO22, the directivity of the antenna seems quite sharp, so something is working OK!

Fun, egh?

6m Beam Swap

I decided I should swap the 6m beam that I have up here. A number of reasons for this decision, firstly everyone round here seems to have got used to it being there, so an mysterious increase in size one dark and stormy night was probably going to go un-noticed. Secondly the SWR on the old antenna is not so good.

This 3 element beam came from Lam Communications in Barnsley:

http://www.lamcommunications.net/shop/

I believe it's actually a Sandpiper antenna:

http://www.sandpiperaerials.co.uk/

It went together really easiy and is much sturdier constructed than the two element beam I was using:

http://g0mgx.blogspot.co.uk/2011/05/6m-and-counting.html

The new antenna has gone up OK, it's a bit trickier to lift past the eaves of the house and attach to the pole (thanks to the ever patient Vince, G0ORC) it's in place.

We altered that the beam antenna I had pointing upwards for satellite working to be horizontal. In the process of doing this we wrecked the SWR and lost some of the grub screws from the Gama match. Hey, ho - that's another story.

Here's the new 6m antenna:

Good egh?

It's nearly over (Until the next time)

Well,

After changing the bench last time:

http://g0mgx.blogspot.co.uk/2012/04/even-more-change.html

I've finished finishing the desk (if you get what I mean). I've added some trim to the edge and it's finished it off rather well. Having done that (of course) I then decided that I should stain and wax the shelves to match. Whilst that bit's quite easy; the replacing the shelves without removing any of the equipment was harder. You've seen the trick of removing the tablecloth and leaving the china on the table - it was a bit like that!

The cat seems to approve of the new bench, he stopped of here en-route to his favourite napping position:

Looks ok though, don't ya think?

Even More Change

Well as part of my ongoing attempt to cram as much equipment and other rubbish into my shack, I have had yet another change around. I've thrown away an old set of drawers which included a filling draw, and purchased a proper filling cabinet. This has freed up a big space in the shack which I have now extended my operating desk into. I've also extended some shelves and the results are really quite good.

The desk top itself is simply 18mm thick MDF which I have cut to fit exactly into the available space, I've then finished it off with some "B&Q value" vinyl floor tiles for the grand sum of £8 GBP.

I'm really quite pleased with the results:

I now need to find something suitable to edge the desk with, but the new surface this should cope OK with me spilling tea on it and burning it with my soldering iron!

Not bad, egh?

TS-590 on 5MHz

I've received an NoV (Notice of Variation) to my radio license today; this gives me some restricted and secondary access to the 5MHz frequencies. There is plenty of information on the NoV for the UK here:

http://www.rsgb.org/spectrumforum/hf/5mhz.php

I wanted to open up my European Kenwood TS-590 that I got here:

http://g0mgx.blogspot.co.uk/2012/04/all-change-in-shack.html

I found the details on the mod but thought it would be worth showing others what I have done. The first job is to turn the radio upside down and remove the 10 screws that secure the base:

Then I need to locate the wire link labelled R968 (it's a jumper) and this needs to be cut and separated apart to open up the 5MHz transmit frequencies. This is the jumper before the snip, if you open the image you can clearly see it just to the left of the ribbon cable:

And here it is after the snip:

Immediately in front of the ribbon cable is R900. This needs to be removed to enable full wide TX; I haven't tried this as I have no desire to TX out of band. But the option is there and available if you need it.

Easy, egh?