Re-[R-390] Low sensitivity on 7-8 Mhz band

[Flowertime01 at wmconnect.com]

Fellows,

Once you get past the bad crystals, oxide in crystal sockets,
alignment of oscillator deck, and just old tubes there are a couple more
things to look at.

A bad slug will get you on the top end of an octave.
The top of .5 - .999, Top of 1.00 - 2.999 ---- 4.0 - 7.999

Look for a chipped slug.
You may not see any thing with an eye ball inspection.

Swap a pair of RF octave slug racks and then realign both octaves.

If the problem moves over or goes away you can think is a slug.

Some times moving a slug over to a lower frequency will let it worj there when
if will not work in the higher frequency band.

Try to align the octive band high frequency first and low frequency last.

If the slug has lost some of its purmability it will not track the full 
frequency range.
On the low end with the slug in the coil, you gan get enough slug centered in 
the coil
to peak up the low end frequency.

On the high end, too much of the poor slug is out of the coil and there is 
not enough cap to track the alignment. Then the whole octive is out of tracking 
alignment.

Every cap in the Rf deck should have two peaks, at the alignment point. A 
clue that there is more than enough cap to reach a good alignment. On both sides 
of max cap value is a peak alignment value. If you have a cap that only has 
one peak you may be at the edge of OK or you may not have enough trim cap to 
reach best alignment point.

Its a  tinker and find experience with your receiver to get a good feel for 
where the slugs and caps should be.

Start on the top frequency of the octave and play with both the slugs and 
caps to find
a place where the cap has two peaks. Adjust the slug a little and dial the 
cap around one turn and watch the meter.

You can likely swap some of the slugs racks around and get a better adjustment
to bring a weak octave back up to good performance.

Just watch what you are doing. Find and fix the other real problems before 
you try and cure every thing with a spline wrench and a slug adjustment.

Roger AI4NI