[R-390] Filter Repair

[Garry Stoklas]

Even before this latest round of discussion on filter repair, I had thought 
about doing what Dave Curry had done; take a new, modern Rockwell Collins 
filter, and an impedence matching network and put the whole thing in the case of 
a bad, unrepairable R-390A filter. Their "low cost" product line has filters of 
.3, .5, 2.5, 5.8, 7.0 and 10.0 kHz @ 3 db bw. While these bandwidths don't match 
up with the R-390A 2,4,8,16, they might well be better than the aging filters 
that are failing. Their "low cost" filters are in a plastic case that is about 
1.25" long x .5" wide x .5" high including the pins so they and the matching 
network would fit nicely inside a R-390A filter case. They have lots of other 
badwidths that are closer or eqaul to the existing filters but they are not "low 
cost".

This discussion got me thinking so I called Rockwell Collins this morning to 
find out how much the filters are and where to get them. First, you can buy them 
directly from Collins, they'll even accept a credit/debit card over the phone, 
and they have no distributors. Second, the "low cost" line is still pretty 
expensive - $105.34 in 1 to 4 quantity, $86.69 5 - 9, $70.85 10 - 24, and $60.16 
25 - 49. These "low cost" ones are normally a stock item. The closet non-low 
cost on their filter list they have to a 4 kHz is 3.8 kHz that is also in the 
same platic package as the low cost line. Out of curiosity I asked the price of 
this filter and was flabbergasted by the 1 to 4 price of $329.05 each. No wonder 
the Dave Curry filters were expensive and he has stopped making them. Also, many 
of the other filters are in a metal package that are too big to fit inside a 
R-390A filter.

I have a Kenwood R-1000 that has the tiny Murata filters that I have found to 
not be all that good. I may buy one of the 2.5 or 5.8 filters to try in that 
radio to see what they can do. Will let the board know the results if I do.

Garry Stoklas