[amsat-bb] Re: searching advice on low hpass filter for 146 MHz

[i8cvs]

Hi, KA1RRW

I was looking at the passband filter DCI 145-2H with center frequency of 145
MHz but it has a flat responce 4 MHz large from 143 to 147 MHz (see the
skirts diagram) so that it canno't attenuate the very strong POCSAG signal
that HB9BNK has at 147.300 MHz
In addition I have not seen any notch added in all models for 2 meters band.
Do you know if DCI can add a notch to a selected frequency upon customer
request ?
For example 145.900 MHz center pass-band frequency and a notch at
147.300 MHz ? It would be a very good soluction for Werner HB9BNK

73" de

i8CVS Domenico

----- Original Message -----
From: "MM" <ka1rrw at yahoo.com>
To: "HB9BNK''Werner Kullmann" <hb9bnk at uska.ch>; <amsat-bb at amsat.org>; "Dee"
<morsesat at optonline.net>
Sent: Monday, May 09, 2011 8:12 PM
Subject: [amsat-bb] Re: searching advice on low hpass filter for 146 MHz




http://www.dci.ca/?Section=Products&SubSection=Amateur

You can buy a custom low pass filter for 2-meters from DCI.

Marex had DCI custom build a 2-meter filter for simular usage on Mir.
The filter passed 144.000 - 146.000, and had a notch added for 143.xxx.
The filter worked great.
It reduced most noise out side of the band and it blocked out a 50 watt
transmitter located about 10 meters away.



--- On Wed, 4/27/11, Dee <morsesat at optonline.net> wrote:

> From: Dee <morsesat at optonline.net>
> Subject: [amsat-bb] Re: searching advice on low hpass filter for 146 MHz
> To: "'Werner Kullmann, HB9BNK'" <hb9bnk at uska.ch>, amsat-bb at amsat.org
> Date: Wednesday, April 27, 2011, 10:25 AM
> Werner,
> Since you are using a very good rig and adding a great
> preamp, to hear what
> you are after and expense involved might be as simple as
> adjusting the gain
> (SP2000 indicates it is adjustable and already has a
> helical front end) so
> as to stop this interference. Doing this simple thing
> might correct
> everything--Let us know if it works. I adjusted the
> gain of my preamp to
> stop similar type intermod.
> 73,
> Dee, NB2F
>
> -----Original Message-----
> From: amsat-bb-bounces at amsat.org
> [mailto:amsat-bb-bounces at amsat.org]
> On
> Behalf Of Werner Kullmann, HB9BNK
> Sent: Wednesday, April 27, 2011 9:42 AM
> To: amsat-bb at amsat.org
> Subject: [amsat-bb] searching advice on low hpass filter
> for 146 MHz
>
> To improve the reception of the sats on 145.9xx MHz
> with my little yagi, I
> recently acquired a SSB-preamplifier SP-2000. To my dismay,
> the reception on
> my IC910H was intermittend heavily distorted.
>
> After a while I found, that a nearby located commercial
> transmitter (POCSAG)
> emitting bursts on 147.300 is so strong, that the frontend
> of the IC910H (or
> its AGC) practically quites the receiver on 145.900.
> When the bursts stop,
> reception resumes.
> Difficult to qso.
>
> I have experimented with a large cavity filter and found,
> that the impact of
> the bursts can be reduced, so that normal satellite work is
> possible again.
>
> Now I am looking for advice on how to build a steep low
> pass filter,
> eliminating everything above 146 MHz, to be mounted before
> the preamp on the
> mast. The filter must however be capable to accept the rf
> power, if I work
> in V/U mode.
>
> Thank you for any ideas !
>
> Werner, HB9BNK
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> _______________________________________________
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