I've got the 6kHz Collins filter in my 7030....................skirt
selectivity is improved. Still, most of the time, I use the wide ceramic
filter for program listening.
If you do choose to purchase the mechanical filter, get it directly from
Rockwell Filter Products Division, in Costa Mese, Ca.
The direct price in single lot quantities is about 86 dollars vs. the
aftermarket price from other vendors.

Pete

"Mark S. Holden" wrote in message
...
WeLoveSpam wrote:

You will have to be more specific about what you mean about better.



Ok, how would the audio sound different ? warmer, etc ? What is so good
about
Collins mechanical filters, they seem to have a reputation for being
good.

Mike


Collins has a reputation for quality.

But more important than the name on the label is the shape factor.

Some people like mechanical filters for their sound - others prefer
crystal ones for the shape factor.

A graph of the pass band of a filter looks like a bell shaped curve.
With steeper skirts, (or a better shape factor) the sides of the bell
will look more vertical like an upside down "U". With less desirable
filters the shape of the skirts will be wider at the bottom. (Like an
upside down "\_/")

Narrower filters are less prone to picking up junk from a station
broadcasting on a frequency close to the one you want to listen to.

Wider filters (within reason) give better sound fidelity.

If your filters have a good shape factor, you can go a bit wider on the
filter to get improved fidelity without adjacent channels stepping on
what you want.

I use Filtronetics crystal filters in my 7030+. One is marked 3.24khz
and reads in the radio as 2.9khz. The other is 6.8khz and reads 6.1khz.
I'm told they have a shape factor of 1.33 - which is great. I'm sure
part of the reason they're as good as they are is they were intended for
the Racal 6790/GM, and Uncle Sam buys the best.

They sound beautiful, and I use them almost all the time.

Here is a completed auction for a 3.24khz filter identical to the ones I
use. (I was not the seller)

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3082943902

I have a few spares, new in sealed packaging. I'd let one go for less
than this auction closed for if you contact me directly.

It is physically large, so it would be a good idea to discuss how I did
it, and make sure you're comfortable with it before taking it on. It's
a one evening project and doesn't require damaging the case for the
radio. I could send you digital photos of how I did it.

I don't have any spares of the wider one.

Regards,

Mark