[TenTec] NS (ten tec) filter variations?

[Clark Savage Turner]

I'm now curious.  I have had lots of Ten Tec rigs and various filter 
combinations in my shack.  I have some INRAD's.   I went for them 
because I had really disliked the model 219 (having tried several) 
because they seemed lossier than I would like and their center frequency 
was a bit high for my ears.  I have always been happy with the model 217 
at 500 Hz.

One day, Ten Tec responded to all our carping and moaning about the 700 
Hz center frequency.  They talked to NS and got us a 250 Hz filter 
centered at 500 Hz tone.  Nice, I decided to try one, without much hope 
after my other experience.  Well, the model 221 that I got is the nicest 
CW filter, for many occasions, that I have ever used.  I have all the 
INRAD equivalents, they are nice and all, but not as "quiet" as the 
221.  It just cuts background noise like no other crystal filter I've 
heard.  My ears are happy with that filter.

I now have an OMNI C that I use a lot.  I wanted a model 220 SSB filter 
for the 1.8 slot (the 1.8's are too narrow for me, want to buy mine?) 
and I found someone (Lynn) offering a model 220 and 219 reasonably.  I 
picked them up.  I put in the 219 to test it, not expecting much (per my 
usual experience) but found it to be really wonderful.  It "seems" to be 
less lossy than most (the equalization in the OMNI C keeps the S meter 
about equivalent to the reading with the wider filtering) and sharp 
center (not the usual noticeable ripple...my ears measure it, not 
expensive equipment, so this is just my gut talking...)

To make a long story short, this model 219 filter just cuts through QRM 
and quiets the background without lots of loss.  It sounds good, even if 
a bit high for my tastes.  I like it better than my 217.

Anyone ever look at the variation in NS filters?  I don't have a 
scientific way to measure my observations, but I wonder if others have 
seen this.  Now, it may be explained by something other than variations 
in NS filters as sold by Ten Tec: does crystal aging come into play in 
20 years?  These filters can be that old.  Caps can age, too, so I 
suspect the ripple can show up in older filters that have aged poorly.  
I don't know the answers.  Anyone have ideas?

I now love my 219 filter.  I have a 219 and a 217 filter for sale.

Clark
WA3JPG