[TenTec] "Low Note" 221 250Hz Filter Problem

[Dr. Gerald N. Johnson]

On Sun, 2007-03-04 at 12:42 -0700, Peter Hoon wrote:
> Jerry, K0CQ,
> 
> Nope, there is no jumper across the missing capacitor slot.  It is just
> plain missing.
> 
> Jerry, according to my translation from the handbook, the missing 102J
> small, blue, low voltage, polyester cap is indeed  .001 5% tolerance.

Looks right 10 plus 2 trailing zeroes.
> 
> Is my "translation" of 10J correct?
> 
> Unfortunately, don't have an exact replacement small .001 cap from my junk
> box to try.
> 
> Did find a ceramic .001, with a less precise tolerance to try.
> 
> Will go ahead and "tack solder" this cap in and test to see if the insertion
> loss problem improves, and report back.

If the value is critical (and at RF 1000 pf is not usually a critical
value, more for coupling or bypassing), it will change value for a while
as it cools from soldering. Many ceramics (especially the most compact)
can loose 85% of their C going from room temperature to boiling water
temperature. It comes back as they cool but can make a circuit fairly
temperature sensitive.
> 
> Any other ideas?
> 
> Thanks,
> 
> Peter
> VE1CHS
> 
Its hard to conceive that capacitor being missing for any good reason,
or that being present except to couple RF would have any effect. Its too
common a value to have been borrowed for some other project.

I'm sure you can order a 1000 pf 5% polyester from Mouser or Tentec
easily enough.