Ahh - The glory days of EA and the Serviceman... My favourite story was of the time "he" was called to fix an old mantle rad= io - a cabinet AM model with valves. He pulled it away from the wall to fin= d a shrivelled, mouldy sausage pushed in behind. "That's right" said The Ow= ner. "I remember - if you touch that wire the reception was much better so = we stuck the sausage there." Apocryphal and one I have heard elsewhere but first read in the Serviceman = about 1969... That reminds me - I was in my local electronics hobbyist store recently and= spotted a new electronics print magazine. Rare to= see in this digital era! The usual Arduino/Raspi projects expected these d= ays but also a smattering theory (Bresenham and transistors in the current = issue). Online as well of course but PRINT! I wish them success! Stephen -----Original Message----- From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On Behalf Of= alan.b.pearce@stfc.ac.uk Sent: Tuesday, 5 December 2017 10:51 AM To: piclist@mit.edu Subject: RE: [EE] Bypass capacitor really required? > It's not the same as a purely digital example but I once designed a=20 > board that used a direct digital synthesizer (DDS) to generate the refer= ence for a PLL in a microwave synthesizer. .... > >> I saw one instance of a product in production using an Atmel AVR,=20 >> where there is a single pin which is an ADC AREF input only rather=20 >> than a fully implemented I/O pin. .... These two stories remind me of a story that appeared in Electronics Austral= ia "Serviceman who tells" feature. This was a column written by someone who= se identity was concealed by the editor, but ran a typical one man radio/TV= service business in a suburb of Sydney, Australia. This particular story w= as related to him by another serviceman who ran a similar business in an ar= ea that had a number of residential tower blocks in his 'catchment area'. T= his particular story concerned a customer whose TV would periodically not r= eceive a certain TV channel, even though they were line of site to the tran= smitter. Said customer was some way up one of the tower blocks, and despite= some visits to the abode the problem was not diagnosed. Eventually custome= r was told to call him immediately the problem recurred and he would come a= round promptly. In due time said phone call happened, so serviceman goes to= the home and sure enough the channel concerned was just visible in the sno= w that was typ! ical of a very weak signal in the days of analogue TV. No matter what he d= id to the set to attempt to repair the problem produced any improvement, so= after some time he ends up standing in customers lounge pondering what the= cause of this strange loss of channel was - it was one specific channel, a= ll the other channels were as strong a signal as they had ever had. His eye= s are wandering around the apartment as he was thinking, and he realised th= at son was playing with his train set on the floor - and the loop of track = was about right size for a dipole at the VHF frequency of the channel conce= rned. A moments stoppage of the train and breaking a track joint soon resto= red the picture on the channel of interest. Another story from the same source concerned a colour TV that would give on= ly B&W pictures on a certain channel. This was eventually tracked down to t= he 300 ohm ribbon from the terminals on the back of the cabinet to the tune= r being secured with a piece of wire looped around a suitable point and the= n had the ends twisted to secure the ribbon cable conveniently out of the w= ay. The loop combined with the twisted ends combined to make a tuned circui= t at the colour burst carrier frequency on this particular channel which ac= ted as a trap preventing the colour burst from reaching the tuner. A quick = trim of the amount of twisted portion (which were fairly long) produced col= our pictures. -- http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/chang= e your membership options at http://mailman.mit.edu/mailman/listinfo/piclis= t --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .