Another one of those filter questions

[Alan. G4GNX]

I purchased a 400Hz 8 pole (Inrad) filter and installed it in my K3 yesterday.
There were no markings on the box and some obscure numbers on a small label on the side of the filter case, but there was no offset figure.
The Cady book mentions that for 8 pole filters an offset is unnecessary, so I presume this is correct?
It also mentions adding a small gain figure of 1 or 2, what do others normally do for a CW filter?

73,

Alan. G4GNX
 
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[Mike K2MK]

Hi Alan,

The information is in the manual but you sometimes have to search for these things.

On page 46, the crystal filter setup page, it states that you should enter a gain of 1-2 db for the 400 Hz filter. I have a 400 Hz filter and I have entered 2 db.

I searched the PDF version of the K3 manual for offset and found on page 79 that it states that all 8 pole filters have zero offset. A note to this effect should have probably been added to page 46.

73,
Mike K2MK

<quote author="G4GNX">
I purchased a 400Hz 8 pole (Inrad) filter and installed it in my K3 yesterday.
There were no markings on the box and some obscure numbers on a small label on the side of the filter case, but there was no offset figure.
The Cady book mentions that for 8 pole filters an offset is unnecessary, so I presume this is correct?
It also mentions adding a small gain figure of 1 or 2, what do others normally do for a CW filter?

73,
Alan. G4GNX

[Vic Rosenthal]

You are correct that the offset is zero for 8-pole filters.

What I do is adjust the filter gains so that there will be no change in
signal strength when switching filters. You can do this by ear if you
turn off the AGC, or you can use the K3's DBV function if you are a
perfectionist.

I found -- and you may get very different results -- that the following
gain values were about right for my filter complement:

2.8 kHz  0 dB
1.0 kHz  1 dB
400 Hz   5 dB
200 Hz   6 dB

73,
Vic, 4X6GP/K2VCO
Rehovot, Israel
http://www.qsl.net/k2vco/

On 16 Jul 2015 11:19, G4GNX wrote:

> I purchased a 400Hz 8 pole (Inrad) filter and installed it in my K3 yesterday.
> There were no markings on the box and some obscure numbers on a small label on the side of the filter case, but there was no offset figure.
> The Cady book mentions that for 8 pole filters an offset is unnecessary, so I presume this is correct?
> It also mentions adding a small gain figure of 1 or 2, what do others normally do for a CW filter?
>
> 73,
>
> Alan. G4GNX
>
> ______________________________________________________________
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>
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[Alan. G4GNX]

Thanks for all the replies guys, much appreciated.

I will do a quick "by ear" setup for the time being and a more scientific
setup with instruments, when I have a little more time.

73,

Alan. G4GNX

-----Original Message-----
From: Vic Rosenthal 4X6GP/K2VCO
Sent: Thursday, July 16, 2015 2:02 PM
To: [hidden email]
Subject: Re: [Elecraft] Another one of those filter questions

You are correct that the offset is zero for 8-pole filters.

What I do is adjust the filter gains so that there will be no change in
signal strength when switching filters. You can do this by ear if you
turn off the AGC, or you can use the K3's DBV function if you are a
perfectionist.

I found -- and you may get very different results -- that the following
gain values were about right for my filter complement:

2.8 kHz  0 dB
1.0 kHz  1 dB
400 Hz   5 dB
200 Hz   6 dB

73,
Vic, 4X6GP/K2VCO
Rehovot, Israel
http://www.qsl.net/k2vco/

On 16 Jul 2015 11:19, G4GNX wrote:

> I purchased a 400Hz 8 pole (Inrad) filter and installed it in my K3
> yesterday.
> There were no markings on the box and some obscure numbers on a small
> label on the side of the filter case, but there was no offset figure.
> The Cady book mentions that for 8 pole filters an offset is unnecessary,
> so I presume this is correct?
> It also mentions adding a small gain figure of 1 or 2, what do others
> normally do for a CW filter?
>
> 73,
>
> Alan. G4GNX
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

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[Petr, OK1RP/M0SIS]

Hi Alan,

in my opinion it is very important to do what Vic mentioned over here at least. Otherwise You will notice big attenuation when You will switching thru the BW down to 400/250Hz filters. As I do not like to get attenuation during weak signals hunting when going down in BW I did it the same as Vic mentioned and it is working nice for me specialy when I am spending most of the time on 150Hz BW on LB.

In my case I found the 400Hz/4dB and 250Hz/5dB as good solution.

73 - Petr, OK1RP