[Patrick Turner]

Andre Jute wrote....

10,000kmpa is a bit ambitious at 68. I still ride the hills, but nowhere near 10K; but then I was never a roadie, so I didn't aspire to the big round numbers.

Andre Jute

Well, the 10km++ a year was until about 2 months ago. I have genetically very poor knees, courtesy of my dear departed mother, who was, like me, a plodder, and who never rode a bike or ran anywhere. She prefered to look good on a horse at Centennial Park aged 25, super hot, but alas, no possible suitors noticed her there. Later she drove, and walked and swam, but in very limited amounts. I inherited her terrible knees combined with my dad's genes.. He set a NSW schoolboy running record for the Mile in about 1926. He had a terrible temper I am glad not to have inherited, so ppl tell me.
In 1994, a surgeon told me I needed new knee joints but also that I was too young then. OK, I struggle on after giving up the building trade. I thought I might learn a bit about hi-fi sound gear - a journey of wonderment.
In 2005, I could hardly stand up for longer than 5 minutes, and I needed pain drugs.
But the surgeon gave me an arthroscopy to tidy&clean both knees, and next day I found I had no pain, and a whole new life began with more confidence. In 2006, I got back on bike, and since then I've ridden about 100,000km, and I had a very fine time with a local ride group. Well, in June last year, while going up a very steep short hill, I felt something "give" and sure enough I'd hurt a knee. Well, maybe you'd expect that; it was an Irish hill, O'Conlon Crescent, and where **** which could happen, and it did happen.
Next doc, a young jerk said he wouldn't do an arthroscopy, and offered only two joints, about $30k, plus all other costs, and he said I'd be begging him for the knees soon enough. That was 15mths ago, no begging, but knees have same symptoms as in 2005, and scan reports fill 2 pages. No more bike because pain has returned, but now chasing the doc who did me in 2005, appointment is Feb, and maybe in 10 mths I get another arthroscopy, keep me going for maybe 5 more years. By then, other things probably will take me out. I need mobility because I live alone and the bicycle was the finest wheelchair I ever used.....

Meanwhile, there is a FABULOUS Thai restaurant which opened 3 years ago just nearby, and its my home away from my house, which I've never managed to make into a real home. Being gregarious at 68 is mainly a useless quality because most old ppl my age don't or can't or won't be friendly, and the few younger folks who turn up loathe all ppl over 35. Good cafe's have limitations.

But I tinker with all sorts of stuff, with more time now because I ain't spending 10 hours a week riding around, and I retired from working 50hrs a week on old junk for less net wages than the dole. Wonderment can only be stretched so far.

I get distracted, and this last month investigated the Gilbert Cell - using tubes, very good for DSB without carrier, but hopeless for normnal AM.
I then discovered AM using an LTP with bjts, and modulating with emitter current change, its the SS version of what HP did in about 1955 with their Fantabulous HP606A RF signal gene - I have one, and it works fine - and it uses all tubes and has a balanced oscillator, and balanced LTP RF amp with cathode modulation with 6B4. This piece of gear has 2 lots of tuned LC tanks on a rotating turret switch to get 6 x F ranges between 50kHz and 65MHz, with ability for 100% modulation and envelope THD 1% at 95% mod depth. My efforts so far with untuned circuits and bjts is 100kHz to 4MHz, with about 5% THD at 2MHz.
HP used NFB to remove envelope THD with internal detector signal compared with AF input signal. I've done that in an SE oscillator in about 2005, good, but nowhere near as good as HP.
But, to apply about 20dB FB around the circuit where modulated carrier is involved, and without tunes circuits, the darn thing just oscillates with parasitics no matter what theoretical cures I think up and apply. Remarkably, there isn't much online which where others have had success.
But I've learnt, and some ideas just will not work, and to get my pathetic attempts with bjts to work anywhere near as well as tubes in HP, I'd have to use tuned RF circuits which have the magical quality of supressing parasitic oscillations, because the LC can only work at ONE F, not several, or allow broadband noise to occur.

I think electronics with soldering iron and old things is better than doing crosswords because those only prod memory, making stuff to work prods problem solving AND memory. Both need constant prodding, to delay insanity for as long as possible.

Keep well, try to stay sane,
Patrick Turner.