I've been measuring the IF response of my boatanchors. All meet specs
except my Racal on the 8 and 13 kHz settings.
Measured by tuning my synthesizer fed into the antenna input on the set's
RF meter I find them much too narrow. There are small bumps in the response,
about 10 dB down from the peak in the center, right where I expect, b ut
the overall curves are too narrow, see picture in red.
https://www.vintage-radio.net/forum/...1&d=1512589439
I have checked the alignment as described in the manual and the followed
the instructions exactly. The 1 and 3 kHz curves are quite as described. The
response through the 2 100kHz IF stages appears not right. There is no
picture of it, but the description of having two peaks 9 kHz apart
cannot be achieved. Its clear that a right broad curve there with real peaks
rather than shoulders as I observe would make the overall response right.
I checked all the resistors and capacitors in the IF cans with two good
meters, and all are now spot on. Several were wrong but replacement did not
fix the problem. There are of course no coil adjustments in the two IF
stages and L81, just caps.
Does anybody have any ideas?
Now, all this matters not at all for actual use of course, as listening on our
broadcast band in the US this response, at 13k setting is just perfect to
undo our theoretical 75 kHz preemphasis (same as FM), and on SW ... who
cares? There are no music stations with 20 kHz channel width on SW. I do
have two BCB music stations,one Spanish and one "Gospel Rock". The Spanish
one is quite listenable, while the other one is set for one of the most hideous
of Mr. Orban's creations.