[1000mp] Collins Filter and DSP

[Hans Remeeus]

Hello Ian,

I agree with you.

However it is rather difficult to compare the Main Rx with the Sub Rx,
because the Main has three IF's, while the Sub has two IF's.

Nevertheless the Yeasu YF-115C has very wide skirts, while the Inrad 400 Hz
has very steep skirts. A noticable difference between these two filters!

The YF-115C (or equivalent from Inrad) is good enough for the Sub Rx. IMHO
it is even a very good choice for the Sub Rx, in the way you will use the
Sub Rx...


73, Hans Remeeus.
Ham Radio: PA1HR
www.remeeus.nl

Communication is about people, the rest is technology.


----- Original Message -----
From: "Ian White, G3SEK" <G3SEK@ifwtech.co.uk>
To: <1000mp@mailman.qth.net>
Sent: Wednesday, January 28, 2004 9:45 PM
Subject: Re: [1000mp] Collins Filter and DSP


>
> I found the same. Compared with the two cascaded 500Hz filters in the
> main RX, the single Collins 500Hz filter in the sub-RX sounded waaay too
> broad. The skirts just didn't drop away fast enough. Some off-tune
> signals were so strong, I sometimes had to check that the sub-RX hadn't
> flipped back to the SSB filter.
>
> The Inrad 721 500Hz filter made an amazing difference in the sub-RX.
> When signals are outside the passband, they're pretty much gone.
> Comparing the data for the two filters shows why: signals that are 600Hz
> off-tune are 30dB stronger through the skirts of the Collins filter than
> they are through the skirts of the Inrad.... and that's a lot.
>
> If you think about the extra cost of the Inrad filter, and then factor
> in the relatively small amount of time you actually use the sub-RX, you
> could conclude that putting an Inrad in there is terrible value for
> money. Well, maybe... but it certainly makes a big difference!
>
> Final point: the Collins 500Hz filter sounds great when it's cascaded
> behind the stock Yaesu 500Hz filter at 8.2MHz, and the combined skirt
> performance is very acceptable. Of all the available CW filter
> combinations in my (old-style) MP, those two are my favorite to listen
> to.
>