Software Defined Radio fiddling

I had some time these past few days to have a reasonable fiddle with a new SDR I acquired – the Watson W-SDRX1 mark 3. This is essentially one of the RTL style SDRs with a switchable HF front end and two aerial inputs, one for HF and below, and one for VHF and above. Coverage is 100kHz to 2GHz.

VHF-wise it works just the same as the RTL-SDR dongle from eBay. Gqrx plays well and with the wide screen on my Linux desktop it shows a good bandwidth.

But it took me a while to figure out how to get the HF side working. The paperwork suggests the cutoff between HF and VHF operation is 40MHz but gqrx out of the box only understands the coverage of the RTL-SDR, so 27MHz to 1700MHz or so. The trick is either to tune 40MHz up, or set an LNB Offset of -40MHz, the latter resulting in the correct frequency being displayed. One does need to remember to set the LNB Offset back to zero when changing to VHF, but hey.

So now I need to have a play in Gnu Radio and see if I can fiddle up a few decent receivers. However it does need a decent aerial. The wideband scanner whip I have sat by the PC does little other than pick up QRM. Unfortunately my ‘active’ aerial is in the workshop and the Linux desktop isn’t, well not yet anyway.

CPU load is not excessive with gqrx on my i5 based desktop, the 4 cores average 20% overall with the waterfall and FFT displays running.

It will be interesting to see how well gqrx and this SDR plays on a Raspberry Pi Mk3. More on that when I find a spare HDMI TV to plug the Pi into…

 

Haltron CV8067

I just added a CV8067 to the site. This is one of a number of Haltron valves I have noticed recently on eBay where the valve just carries the CV number. All those I have noticed are in the CV8xxx range.

Now K1001 does permit this but specifically when it is “impractical, on account of physical limitations” – see here¬†(pdf) section 4.1.4. It is hard to see how a valve such as this example could not carry the full CV information. On on a subminiature valve, but not here.

The valve came in a Haltron box with no markings, and a label attached giving the CV and NSN numbers.

Looking at the valve the printing is slightly different too, as if the original Haltron marking is the original and the CV number added later. There is no obvious evidence of the civilian part number being removed, but of course it may just have been cleaned off sufficiently well as to leave no trace.

CV1475-78

Another little sequence completed – I now have all four magnetrons from CV1475 to CV1478. These are four frequency variants and successors to CV69A-D.

I have CV69A and D too, so now need CV69B and CV69C to complete that set.

There are two other sets of four – CV1479-82 which I have already and are CV76A-D (I have CV76B and C, so need A and D, and CV1483 to 87 which are CV99A-D. I am missing CV1483, and CV99B and D.

 

Gnu radio

Not really valve related (ok, not in the least valve related!) but after a lot of messing about I finally got Gnu radio to work last night on Ubuntu 16.04. I say finally because it was the end of a lot of messing about off and on, and in no way the fault of Gnu radio.

First, some background. I’ve been using Ubuntu since version 7 I think. I settled on it because it was easy to install on the old and dodgy hardware I had at the time – other distro’s would not even install. My current PC had 12.02 LTS – I use the LTS versions as they have, well, Long Term Support. I had an older Gnu radio package set up and working but it later broke and I’d no idea why. Anyway, I had no time to fix thing back then.

I got back to it later but never fixed it, so I installed the then latest Ubuntu 14.04 LTS. No matter what I did I could not get the software to work. As it was nearly time for the 16.04 release I left it.

I installed 16.04 LTS a couple of days ago but again Gnu radio failed. The software would install via apt-get but gave errors when running. The script (below) failed to complete. Again, no time to fiddle.

Last night I wiped the PC and installed a clean Ubuntu 16.04 LTS and this fixed things. The excellent script (below) ran and set everything up. I had to fiddle with the USB settings and blacklist a kernel module but this is all documented. Finally, I got a basic FM radio working to prove the installation is ok.

So, although upgrading Ubuntu is generally OK for mundane stuff, it is clearly a tad off for actually getting the system up to grade. A clean install is a far better option, and indeed is recommended. Having more than one physical disk makes this a lot easier as one can copy anything needed to the other disk, or have home volumes on that other disk, and trash the o/s disk for each clean upgrade.

This script (http://gnuradio.org/redmine/projects/gnuradio/wiki/InstallingGRFromSource#Using-the-build-gnuradio-script) is really useful and does all thew work for you.

The morale – don’t be lazy! Now for the interesting stuff…

 

CV1931 update

For some time I had a CV1931 on the website, the example being a 6H6 metal double diode, though not 6H6 marked. Today I got a glass CV1931, also marked 6H6GT. I never checked before but the metal one is clearly incorrectly marked.

The CV Register has three CVs in a  series: CV1929 / 6H6G, CV1930 / 6H6 and CV1931 / 6H6GT. This makes sense.

For now I’ve left the page as-was but added the glass valve.

 

Removed valves

I have been trimming the collection for some time now and disposing of valves which helps maintain this virtual museum and also reduces the amount of storage space needed. It also helped me finally focus on what I want to collect, rather than just anything and everything.

But someone mentioned to me a whole back that people may still want to see these. As the main pages only display what I actually own, once removed a valve’s web page is removed too.

So I have been making PDFs of the more unusual valves as I remove them and these are now held at http://vacuumtube.info/oldvalves/ – it is simply an automatically generated list of PDF documents, each one of which is basically the valve page saved as a PDF via Safari.

Update – about this WordPress

I have been using WordPress recently to drive parts of the website and also to record new exhibits and so on. However, this has the drawback that every time the home page was called it would also call WordPress. Although this is common practice there is really no need for the simple text entries involved. I have now written scripts and modified the database to handle this without needing WordPress.

The content in here remains valid for now but will be removed once I am sure it has all been copied across correctly. After that, I will probably keep this here as a general blog, which is, after all what WordPress is good at.

The German collection

My thinning of the German collection is under way with some having gone onto my disposals page and others onto eBay or into a crate ready for the next local sale in November. This section of the collection can be seen here. Not all of the valves will go, the two Gema valves and the RD4Ma for example will most likely be staying here.