Well John the comments that follow are entirely subjective.
The results are as you might expect when you change a 2-pole 15 kHz wide
roofing filter with a 6-pole 4 or 5 kHz wide filter. However, there are still
some images of the primary strong signal getting through. I found that an image
of the test signal (S9 +30 dB - that's over 1,500 uV and huge by any standard)
appeared within 2.5 kHz of a primary signal (sub-receiver in CW with a 900 Hz
bandwidth and a 600 Hz filter in the 1000 Hz slot, and firmware 1.373b5). Some
additional images appeared at 2.5 kHz intervals above and below this "phantom"
signal. Both the modified and unmodified sub-receiver suffer from these
self-generated signals at 2.5 kHz intervals. In both the un-modified and
modified rig the signals decrease in strength as you tune off the primary
frequency. In the modified rig the number of images is significantly reduced.
I don't know the source of the 2.5 kHz mixed signal BUT it is definitely not
present in the Orion's main receiver. Since these phantom signals occur at such
precise intervals my thought is that the 2.5 kHz source is likely generated
somewhere in the sub-receiver's digital circuitry.
I'll leave the tracking down of this source to others.
Bottom line, I think it has improved the sub-receiver without any noticeable
side effects.. Has it eliminated all the problems? Short answer - no!
73,
Rick
VE7TK
Website: http://www3.telus.net/ve7tk
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Re: [TenTec] InRad 902 Filter For Orion Sub-Receiver
John Oglesby
Sat, 12 Dec 2009 21:39:28 -0500
Rick - What was the difference in sub-receiver performance when you
installed the filter? I assume you were trying to improve the strong
signal performance - did it help? Any side effects?
John
N9RE
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