Saturday, 30 April 2011

First Swallow of the Summer, etc

THIRTY-odd years ago, early in my professional career I moved up to Central Scotland from Yorkshire, where I remained for about six years.   In the late Spring of the first year I was there I noted the date on which I spotted the first swallow of the summer, it happened to be May 1st, and thereafter May 1st has been the "yardstick" with me for spotting these harbingers of the coming Summer.  For some reason I'd never taken any notice of this phenomenon before.

Having subsequently back to South of the Border, some hundred miles to the south, I usually reckon to see swallows two or three days before that particular date, but unusually this year, it is now April 30th, and no swallows have yet come to my attention (I am not saying they aren't hereabouts!). However, unusually this morning the first house martins I've seen were swooping around the front of my QTH.  Usually swallows are to be seen before the martins in my experience.

TS-180S Repair - Part 2

It is now time to report on the progress with my ailing TS-180S.   Until yesterday evening there wasn't much to report save that I had come to a couple of conclusions.

Firstly, the radio definitely has a problem with the PLL circuitry.   That's enough to make one feel that this could be a long haul!   PLL circuits can be difficult to diagnose and fix, as they only work when the loop is closed, and a fault anywhere in that loop could potentially stop the PLL from working.  This radio has a quite early implementation of the "PLL derived PreMix System" which became popular in era immediately prior to the adoption of full synthesis and continuous coverage.  Trio improved the circuitry for their very popular TS-120 model, but I am left to struggle with their earlier attempt.  The PLL circuitry doesn't lock very well, and when it does lock, for a 100kHz change in VFO frequency, the actual het. frequency derived in the PLL Premix system only changes by 60kHz.

The TS-180S PLL Board
 The second conclusion I came to after probing around the circuitry with a spectrum analyser was that the high gain Wide Band Amplifier between the VCO stages and the prescaler/divider was producing a lot of garbage.

I'd previously checked out the condition of the two electrolytic capacitors in this part of the board on my ESR tester, and they suprisingly appeared to be absolutely fine.

With this knowledge I began to ponder how I might break into the loop and possibly inject test signals from a stable source, (ie replace the WBA with a signal generator and see how things behave), but before doing that I decided I would check the DC conditions around the five transistor WBA.   These checks showed that the first transistor in the chain (Q14) appeared to be short circuit in all directions.  Hah!  That is clearly not going to help!

The 8-40MHz Wide Band Amplifier - things are just a bit tight in there!

Anyhow, the faulty transistor was extracted with no little difficulty, tested, and yes, it is completely dud.

Unfortunately I don't appear to have anything close to it in my spares, so it will have to be an EBay search for something suitable.   The original transistor type is 2SC1907 which has a very high fT (>1GHz), so any old gash BC182 just won't cut it on this occasion!  According to the data sheet the 2SC1907 was designed for UHF TV local oscillator applications.

To be continued ...

Sunday, 24 April 2011

Band I TV and Radio Meteors - the End is Nigh!

I have blogged a couple of times already about the disappearance of VHF analogue TV in Band I, today I came across a little more information about the demise of the few remaining sources available to we "Meteor Reflection Enthusiasts".

It seems the Ostrava (Czech Republic) transmitter on channel R1 (49.76MHz) will close on 30th November 2011, and the Lousa (Portugal) transmitter on channel E3 (55.25MHz) will close on 26th April 2012, in almost exactly a year's time.

Spectrum Lab Capture of Metor Burst

Quite what, if any signals will be found for displaying meteor reflections once these disappear, I know not, but in the meantime I have resolved to make some audio recordings so that the use of the audio software I use (R_Meteor, SpectrumLaboratory, etc) can be demonstrated should anyone show any interest!

R_Meteor Capture of above SpecLab event

Amateur signals such as beacons are too low in power to fill the gap.   Maybe some QRO beacons are required?   Not very "green", though!

Friday, 22 April 2011

Wrestling with PHP, MySQL and Simple Machines Forum ...

Like a lot of busy folk, I've been looking forward for some time to the few days off work around the Easter / May Day holiday period (enhanced (in length at any rate) by Royal Shenanigans of course) to allow my poor old brain to cool down and to start functioning again.

So it was I returned to tackle a little problem I had set myself a few months ago, to install a Simple Machines Forum on my own web server, with the principle objective of using said forum as a tool to help our local Repeater Group operate.

I'm not an IT professional, but as I understand it, a Simple Machines Forum is some nifty code written largely in PHP, XHTML with some neat CSS, and which is in turn a "front end" to an SQL database.  I hope I've got that right, but that's how I've got it figured in my head at any rate.

Conventionally, people wanting to install SMF applications (which are free!) usually upload the said files to a web server provided elsewhere, and apart from tweaking the forum to look feel and operate like you want, that's more or less it.   Not that I am belittling such things, as they do take quite a bit of tweaking, it seems.

Of course this just isn't good enough here in the G4FUI shack, as I am running the repeater group web site in question on my own PC so the operation is a wee bit trickier.

You have to install PHP (free), MySQL (also free!),  configure Apache (the web server I use) to talk to PHP, and you have to configure PHP in turn to connect to the SQL service so that SMF can build a database and shuffle data in and out of it on demand.

It all sounds a bit geeky, doesn't it?   Well that is precisely how I found it.

Luckily there is a lot of helpful information out there on the web, and after a bit of "Googling" I found some advice which seemed to be pretty well aimed at my own requirements.    As a side note, whilst I was browsing through the various troubleshooting suggestions I couldn't help but notice the lack of hostility and aloofness which I have found on some of the equivalent Linux pages.   Maybe I'm imagining it?

The first serious attempt to get all this working was a month or so ago, and that ended in failure, so the project was "parked" until the Easter break.

The second attempt was much more successful.   Careful reading of the online advice revealed a little trick with a command line box.  This didn't produce a working system but it did produce an error message which was a bit of a giveaway "unable to find ..." followed by a file name which looked sort of  familiar.

The file in question had featured in one of the configuration files (php.ini) I had carefully edited a while ago, and if I'd only spelled the name of the file correctly my system would have been up and running a month or so ago!

D'oh!  Just one little letter makes such a big difference!