electronics

[ericmark]

If I knew were you lived I may know where clubs are, some are very small and some are huge, often they meet in Pubs, some times even have aerials in the pub and transmit from them.

I started in the Falklands as a VP8, then to UK and GW7 call, and then Hong Kong with a VR2 call, and I was a member of HARTS the Hong Kong amateur transmitting society, there would be around 150 in the meeting, and we would then go for a meal, not all, but around 80 and we would descend on a restaurant and ask if they had tables for 80, and normally they did, can you imagine that happening in the UK? We would sit at large round tables with turntables in the centre designed to take the food of course, around 15 to 20 to a table, and it was a bowl or rice then a power supply, some chicken then a hand held radio.

At that time I was into packet radio just before the Chinese took over Hong Kong. I was still using an Amiga computer.

 

[EddieM]

The local one is in Cleveleys.

 

[ericmark]

Oh don't know anyone there now sorry, but while in the Falklands my dad had a heart attack, I would contact a local Fred using 2 meter who came from Cleveleys who would talk to a Cleveleys radio ham using 20 meters and Morse code who would ring my sister and give me daily reports on how my dad was. Clearly very nice guys.

 

[Burnerman]

Really interesting stuff, Eric
I never got as far as the RAE but I do have morse at 12 wpm, and cut my teeth on ex military kit and the bible was Practical Wireless, or Camms Comic. Heathkit ruled!
Happy days, learnt lots.
John

 

[ericmark]

I don't play any more, kept up my licence, son didn't he passed RAE at 14 then dropped it.

 

[mattylad]

TBH radio is old hat now, when I have mad contacts on the other side of the world my kids have said "so what dad, I talk to someone from there every day"... which is via the net and when playing games lol.
There is so much interference at home now that going mobile is the only way (apart from echolink) to make a contact on HF.

If you have not re registered your license for many years then it may have been removed and reissued - best check on the status of it at https://ofcom.force.com/licensingcomlogin

 

[EddieM]

Thank you all, really, we are however conflagrating this with a different thread of mine. But honestly, no matter.

 

[EddieM]

This electronics malarky is making my head hurt a bit. I know from my childhood I always found it a bit of a mystery, nonetheless I shall plough on and read more about it. I'm afraid I didn't find the book that John recommended very good (and it's just GCSE!)

 

[Burnerman]

This is the one, Eddie - please be aware I've been retired for 10 years now but still a good publication.
https://www.amazon.co.uk/Collins-GC...d+technology+textbook&qid=1604780375&sr=8-210
John

 

[EddieM]

This is the one, Eddie - please be aware I've been retired for 10 years now but still a good publication.
https://www.amazon.co.uk/Collins-GC...d+technology+textbook&qid=1604780375&sr=8-210
John

I know, it's the one I bought!

It's a bit confusing and doesn't explain things too well for me, though I have to admit I've never had much of a flair for electronics.

 

[Burnerman]

Ah, apologies Eddie, I misread your post.
Sorry you weren’t too happy with that book, the guy Mick Horsley has contributed to many CDT books and was well respected at the time. There are others in the series.
Pity you didn’t have a better teecha when you were at school!
John

 

[EddieM]

Ah, apologies Eddie, I misread your post.
Sorry you weren’t too happy with that book, the guy Mick Horsley has contributed to many CDT books and was well respected at the time. There are others in the series.
Pity you didn’t have a better teecha when you were at school!
John

Didn't do any electronics at school. I'll post a couple of examples that I think are unclear tomorrow.

 

[EddieM]

These are the bits I didn't think we're explained well.



Now I understand it (I think) but the diagram just says 2V voltage drop, there is no explanation that this is the LED's operating (forward) voltage.

Then a few pages later, we have



Which shows a (typical?) 2V LED 9V supply with a 560Ω resistor, which is different from the 1st image and too high?

 

[Burnerman]

If I recall, we understood that all LED’s lost 2v and the resistor was used to limit the current to the diode to around 20mA...that’s all that was required for GCSE at the time (dealing with 15 yr olds).
Maybe others can comment?
John

 

[Gasguru]

That's a badly written book...

Zener/Avalanche diodes are reversed biased ie. connected the other way round in normal operation
LEDs are often driven at currents much higher than their continuous ratings..
Really poor annotation of the diagram
The calculation is written badly...
etc..

There must be far better books or just use the web.
LED voltage drop varies considerably with the LED colour...