21-08-2012, 09:55 AM
Many thanks to Joe for tidying up my scan of the original article and for uploading it to the forum.
Mark H mentioned quite correctly that by now some of the carbon composition resistors used for substitution and in the bridge will doubtless have drifted high, so out of curiousity, I've tested the resistors and caps, with the following results:
Resistors:
Should be: %age over or under
10k - is 11.1k = +11%
33k - is 36.2k = +9.7%
100k - is 114k = +14%
330k - is 330k = 0
1M - is 1.111k = +11%
3M3 - is 3M15 = - 4.5%
Caps:
100pF - is 85pF = - 15%
1nF - is 795pF = -21%
3nF - is 3N36 = +12%
10nF - is 10.75nF = +7.5%
30nF - is 31.7nF = +5.6%
300nF - is 330nF = +10%
iuF - is 1.02nF = +2%
5uF - is 6.28uF = +12%
25uF - is 32uF = +27%
100uF - is 340uF = +240%!
I guess that after 30 years, bearing in mind that some may even have been NOS items rather than brand new when it was made, and weren't close tolerance types, nor were they selected on test, it's what we might expect to have happened over time . The whole point of test gear is for it to be accurate, so were I building such a project now, then I'd carefully select and components used as 'standards' to make sure they're close tolerance ones.
Interestingly, the oscillator frequencies are virtually bang on 1kHZ and 1 MHz. The 465kHz is 463KHz, and could be made spot on by melting the wax and tweaking the coil. It tends to confirm that with most IFTs using close tolerance stable silver mica or polystyrene caps, unless the 'phantom twiddler' has been at it, most IFTs in radios won't have altered much since they left the factory.
Oh well, it kept me occupied for a good few hours building it, and that's what I've enjoyed doing since a schoolboy in the mid 1950s. As I've passed through life I've come to realise there's little correlation between money expended and enjoyment derived. I guess in part that comes from having grown up in the 'make due and mend' and 'cut your suit according to your cloth' mentality. The only debt we've even had was our mortgage - never taken out a loan, never not paid off our credit card each month, never been overdrawn, never hankered after anything we can't afford.
Rambled and dribbled Yorkie.
Mark H mentioned quite correctly that by now some of the carbon composition resistors used for substitution and in the bridge will doubtless have drifted high, so out of curiousity, I've tested the resistors and caps, with the following results:
Resistors:
Should be: %age over or under
10k - is 11.1k = +11%
33k - is 36.2k = +9.7%
100k - is 114k = +14%
330k - is 330k = 0
1M - is 1.111k = +11%
3M3 - is 3M15 = - 4.5%
Caps:
100pF - is 85pF = - 15%
1nF - is 795pF = -21%
3nF - is 3N36 = +12%
10nF - is 10.75nF = +7.5%
30nF - is 31.7nF = +5.6%
300nF - is 330nF = +10%
iuF - is 1.02nF = +2%
5uF - is 6.28uF = +12%
25uF - is 32uF = +27%
100uF - is 340uF = +240%!
I guess that after 30 years, bearing in mind that some may even have been NOS items rather than brand new when it was made, and weren't close tolerance types, nor were they selected on test, it's what we might expect to have happened over time . The whole point of test gear is for it to be accurate, so were I building such a project now, then I'd carefully select and components used as 'standards' to make sure they're close tolerance ones.
Interestingly, the oscillator frequencies are virtually bang on 1kHZ and 1 MHz. The 465kHz is 463KHz, and could be made spot on by melting the wax and tweaking the coil. It tends to confirm that with most IFTs using close tolerance stable silver mica or polystyrene caps, unless the 'phantom twiddler' has been at it, most IFTs in radios won't have altered much since they left the factory.
Oh well, it kept me occupied for a good few hours building it, and that's what I've enjoyed doing since a schoolboy in the mid 1950s. As I've passed through life I've come to realise there's little correlation between money expended and enjoyment derived. I guess in part that comes from having grown up in the 'make due and mend' and 'cut your suit according to your cloth' mentality. The only debt we've even had was our mortgage - never taken out a loan, never not paid off our credit card each month, never been overdrawn, never hankered after anything we can't afford.
Rambled and dribbled Yorkie.
Regards, David.
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
BVWS Member.
G-QRP Club Member 1339.
'I'm in my own little world, but I'm happy, and they know me here'
