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
I believe DCI makes a 144-146 bandpass filter.
73s John AA5JG
----- Original Message ----- From: "Werner Kullmann, HB9BNK" hb9bnk@uska.ch To: amsat-bb@amsat.org Sent: Wednesday, April 27, 2011 1:41 PM 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 _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
The DCI filters are VERY good but are designed, as standard, to provide a bandpass between 144-148MHz!
I guess a special version that is either much narrower, or is setup for 142-146MHz, might give maybe 20dB of attenuation ...maybe this plus your cavity as a suck out notch/rejecter after preamp would be a winning combination?
good luck
Graham
G3VZV
----- Original Message ----- From: "John Geiger" aa5jg@fidmail.com To: "Werner Kullmann, HB9BNK" hb9bnk@uska.ch; amsat-bb@amsat.org Sent: Wednesday, April 27, 2011 3:04 PM Subject: [amsat-bb] Re: searching advice on low hpass filter for 146 MHz
I believe DCI makes a 144-146 bandpass filter.
73s John AA5JG
----- Original Message ----- From: "Werner Kullmann, HB9BNK" hb9bnk@uska.ch To: amsat-bb@amsat.org Sent: Wednesday, April 27, 2011 1:41 PM 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 _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Werner Kullmann, HB9BNK Sent: Wednesday, April 27, 2011 9:42 AM To: amsat-bb@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 _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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@optonline.net wrote:
From: Dee morsesat@optonline.net Subject: [amsat-bb] Re: searching advice on low hpass filter for 146 MHz To: "'Werner Kullmann, HB9BNK'" hb9bnk@uska.ch, amsat-bb@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@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Werner Kullmann, HB9BNK Sent: Wednesday, April 27, 2011 9:42 AM To: amsat-bb@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 _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
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@yahoo.com To: "HB9BNK''Werner Kullmann" hb9bnk@uska.ch; amsat-bb@amsat.org; "Dee" morsesat@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@optonline.net wrote:
From: Dee morsesat@optonline.net Subject: [amsat-bb] Re: searching advice on low hpass filter for 146 MHz To: "'Werner Kullmann, HB9BNK'" hb9bnk@uska.ch, amsat-bb@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@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Werner Kullmann, HB9BNK Sent: Wednesday, April 27, 2011 9:42 AM To: amsat-bb@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 _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
_______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
It does not hurt to aks. DCI has been very responsive to our Space Station projects. I can assume that there are many european stations that could use a 2-meter pass band filter designed for just 144.0 - 146.0.
A notch can be added, but that of course will cost extra.
On a side Note: Once a month or so, ISS crews will turn on the 143.xxx backup transmitter for a few orbits. The FM 10k Dev, transmitter will send a carrier for all of the ground stations to lock on to and test with. If you are trying to work the 2-meter station on ISS While the 143.xxx transmitter is active, the ham reciever will be deaf! You may still have some down link beacon packets from the Digipeater, but it will not be able to hear you. The DCI filter project for ISS was rejected as not required. PS Ham Voice contacts are also affected while 143.xxx is active.
Miles WF1F
--- On Mon, 5/9/11, i8cvs domenico.i8cvs@tin.it wrote:
From: i8cvs domenico.i8cvs@tin.it Subject: Re: [amsat-bb] Re: searching advice on low hpass filter for 146 MHz To: "MM" ka1rrw@yahoo.com, "HB9BNK''Werner Kullmann" hb9bnk@uska.ch, "Amsat - BBs" amsat-bb@amsat.org, "Dee" morsesat@optonline.net Date: Monday, May 9, 2011, 4:47 PM 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@yahoo.com To: "HB9BNK''Werner Kullmann" hb9bnk@uska.ch; amsat-bb@amsat.org; "Dee" morsesat@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@optonline.net wrote:
From: Dee morsesat@optonline.net Subject: [amsat-bb] Re: searching advice on low hpass
filter for 146 MHz
To: "'Werner Kullmann, HB9BNK'" hb9bnk@uska.ch,
amsat-bb@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@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Werner Kullmann, HB9BNK Sent: Wednesday, April 27, 2011 9:42 AM To: amsat-bb@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 _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the
amateur
satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the
amateur
satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Thank you all for your valuable informations. Yesterday, I carried the IC910H into the garden and attached a Arrow Antenna directly to it. Then I listened to AO-7 and FO-29 pointing the Arrow roughly into the right direction. The result was amazing: I guess, I have not heard such good signals since quite a while !
So, it is clear, that I must first fix my installation - I have obviously a problem, which reduces my 'hearing' and I must have become used to the bad situation over time.
Then, as some of you suggested, I may have to reduce the preamp gain drastically and can probably go without them.
This will take some time. I will document my findings and inform you afterwards.
Thanks a lot and 73 Werner, HB9BNK
----- Original Message ----- From: "Werner Kullmann, HB9BNK" hb9bnk@uska.ch To: amsat-bb@amsat.org Sent: Wednesday, April 27, 2011 3:41 PM 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
Hi Werner , HB9BNK
Few years ago I was suffering the same problem and I fixed it using cavity filters as passband filters and notch filters normally used in the FM repeaters.
In addition I built high dinamic range Norton type preamplifiers and high intercept point 2 meters converters using double balanced mixers.
At the end of the above succesfull experimentation I writes a few technical articles covering the above matter published into the italian Radio Rivista magazine of ARI that you can request as photocopy at no cost to:
ARI Via Domenico Scarlatti, 31 20124 Milano Italy. TEL 02 6692894 and FAX 02 67078923
Obviously the text is in italian but you will understand the drawings the pictures and the schematic diagrams.
Radio Rivista march 1994 pagg 30 to 33 " " april " " 38 to 41 " " may " " 27 to 32 " " june " " 37 to 41 " " august " " 29 to 33
If you are looking on how to build a steep low pass filter, eliminating everything above 146 MHz, to be mounted before the preamp on the mast and the filter must be capable to accept the rf power because you work in V/U mode I believe that a low pass filter with the capability to pass 145.900 MHz and reject with high attenuation 147.300 MHz is impossible to be built.
I have in my hand one of the best professional tubular filter capable of 500 watt built by the French manufacturer STTA model FL.24.A . it is 21 cm long and 22 mm in diameter including N connectors.
I have measured it with my spectrum analyser HP 8555A and tracking generator HP 8444A and the results are the following:
Frequency (MHz) Insertion Loss (dB)
144 0.3 160 0.4 180 > 50
As you can realize even if the tubular filter rejects by more than 50 dB a 180 MHz signal from a 144 MHz signal it reject nothing between 144 MHz to 160 MHz and so in your case only a big passband cavity filter tuned to 145.900 MHz plus another cavity filter tuned as a notch to 147.200 MHz can do the job othervise you must remove the SP-2000 preamplifier wich in your situation is responsible to generate gain compression and intermodulation distorsion.
Best 73" de
i8CVS Domenico
participants (6)
-
Dee -
Graham Shirville -
i8cvs -
John Geiger -
MM -
Werner Kullmann, HB9BNK