Cleaning my shack and I found my prototype 600 Hz roofing filter for the
original Orion. This was the first prototype of what later became the
Inrad #762 and eventually led Ten-Tec to redesign the front-end for Orion
II. This is a hand made unit with exposed crystals like original Orion
4-pole filters (photo in link below). It also has the distinction of being
the actual filter used by Rob Sherwood in his comments below, which were a
vast improvement over ARRL's initial results using the optional 500 Hz
filter (comparison below is to the stock 1 kHz 4-pole):
* >*
* > At 5, 10 and 20 kHz, there is no significant difference between the*
* > stock 1.0 kHz Ten-Tec filter and the Inrad filter.*
* > At 2 kHz spacing, the improvement is on the order of 6 to 7 dB.*
* > At 1 kHz spacing the improvement is closer to 10 dB.*
* > There is some strange hysteresis of a couple dB, as you change the
level*
* > around. The IMD does not act exactly as one would expect.*
* > I am guessing the digital AGC is doing strange things, causing the*
* > hysteresis.*
* >*
* > The insertion loss of filters #2 and #3 are identical to the Ten-Tec
1.0*
* > kHz filter.*
* >
*http://users.vnet.net/btippett/inrad_.htm (photo and more background)
Please reply direct...best offer over $50 ships Saturday by Priority Mail.
73, Bill W4ZV*
*
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