I suggest you consider AFC. Not enough demand for that wide a filter.
Won't work for packets, or at least would require a long TXD making packet communicatiosn inefficient.
As to rarity, only one filter in the whole world is needed and that is on the uplink receiver. This lets eveyrone on the ground use conventional rigs without mods, and with minimal doppler uplink tracking.
Too many simple satellites are being built without considering the need for a wider bandwidth receiver on the uplink. The difficulties of such an approach for users is very obvious on the ISS cross band repeater, which is using a stock amateur transceiver with a 12 KHz wide receiver on the uplink, which makes even 5 KHz step tuning on the uplink be out-of-bandwidth splatter half the time.
This is not a complaint at all. The ISS team is to be congratulated for making the most of what they were able to get up there. It just takes more skill by users on the ground...
It is good to see this new UK project planning on a wider uplink RX filter.
Bob, Wb4APR
Bob, My point is that filter is not easily found in a 455 KHz center frequency. ECS, Inc. makes 30 KHz wide filters in 10.7 , 21.4 and 45 MHz center frequencies in 2 and 4 pole. They are available from Digi-Key. 455 KHz is reserved for narrow band applications. A post data filter will reduce the wide band noise by limiting the data rate to the incoming data rate. This works well as long as there are no other signals within the IF pass band of the receiver. For digital signals Hi and Low comparators would give you a fast response for AFC and would not require excessive preamble.
Art, KC6UQH
-----Original Message----- From: Bob Bruninga [mailto:bruninga@usna.edu] Sent: Wednesday, December 31, 2008 7:43 AM To: kc6uqh@cox.net; 'Anthony Monteiro'; G0MRF@aol.com; amsat-bb@amsat.org Subject: Re: [amsat-bb] Re: FM receiver filters
I suggest you consider AFC. Not enough demand for that wide a filter.
Won't work for packets, or at least would require a long TXD making packet communicatiosn inefficient.
As to rarity, only one filter in the whole world is needed and that is on the uplink receiver. This lets eveyrone on the ground use conventional rigs without mods, and with minimal doppler uplink tracking.
Too many simple satellites are being built without considering the need for a wider bandwidth receiver on the uplink. The difficulties of such an approach for users is very obvious on the ISS cross band repeater, which is using a stock amateur transceiver with a 12 KHz wide receiver on the uplink, which makes even 5 KHz step tuning on the uplink be out-of-bandwidth splatter half the time.
This is not a complaint at all. The ISS team is to be congratulated for making the most of what they were able to get up there. It just takes more skill by users on the ground...
It is good to see this new UK project planning on a wider uplink RX filter.
Bob, Wb4APR
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You might find an old Motorola TU-540W filter around a two-way radio shop. Those were used in equipment when the deviation was +/- 15 kHz and when the deviation was dropped to +/- 5 kHz the filters were replaced with the TU-540S. They are for a 455 kHz i.f.
Glen, K9STH
Website: http://k9sth.com
--- On Wed, 12/31/08, Art McBride kc6uqh@cox.net wrote:
From: Art McBride kc6uqh@cox.net
My point is that filter is not easily found in a 455 KHz center frequency. ECS, Inc. makes 30 KHz wide filters in 10.7 , 21.4 and 45 MHz center frequencies in 2 and 4 pole. They are available from Digi-Key. 455 KHz is reserved for narrow band applications.
participants (3)
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Art McBride -
Bob Bruninga -
Glen Zook