DK2GZ wrote:
>I am very pleased with the 500HZ TT filter, sure I know the IMD performance
should be better with the 600 HZ Inrad(Sherwood test), but I like the bigger
att of the 500 HZ TT filter and the RX is less noisey than with the 600
Inrad.
You may have a defective 500 Hz filter (high insertion loss). It
typically has about 6 dB insertion loss versus the 250 Hz filter's 12
dB loss. Both are followed by a 12 dB amplification stage which makes
the 500 Hz position have 6 dB TOO MUCH gain. The 12 dB amplifier is
almost a perfect match for the 250 Hz filter's insertion loss. If
your 500 Hz position is showing less signal than the 250 Hz position,
it is definitely defective. If you like "quiet", Orion's attenuator
is a better way to do this than using a defective filter.
Regarding the IMD problems of the 500 Hz position, I am not
sure what is causing this. It could be the additional amplifier
stage or it could simply be the construction of the 500 Hz filter.
Whatever causes it, there is a real problem with it as measured by
ARRL, Sherwood and YT1NT. The stock 1000 Hz filter has much better
IMD performance than the 500 Hz and the Inrad #762 substantially
improves upon the 1000 Hz filter.
"At 5, 10 and 20 kHz, there is no significant (IMD) 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."
Robert Sherwood NC0B, Sherwood Engineering
http://users.vnet.net/btippett/inrad_.htm
73, Bill W4ZV
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