> I am on 1.823.5 calling CQ and working stations. A station
> shows up
> at 1.823.8 and another at 1.823.2, both with S9+20 db
> signals, and
> calling CQ. What current radio, and with which roofing
> filter(s) can
> handle this situation best?
Well, if you have a stock Yaesu and have not corrected the
noise blanker you are in for problems.
http://www.w8ji.com/ft-1000_noise_blanker_mod.htm
> I currently use a FT1000D with 4 kHz INRAD roofing
> filter, together
> with 250, 500, and 2000 Hz filters. But I have no idea how
> this
> compares with some of the more modern radios under the
> above stated
> operating conditions.
The 4kHz Inrad may actually make the situation described
above a bit worse, and at best will not make it better. The
roofing filter will make things significantly better when
one or both of the undesired signals falls outside the
passband of the roofing filter...but won't do anything good
for anything close. The added gain will almost certainly
hurt, because the first mixer in the Yaesu has much better
performance than later stages before the narrow filters.
Anything we do in the Yaesu to increase gain in front of the
narrow filters will generally decrease close-spaced IM
performance. We never really want to increase gain before
the selectivity once we are above the antenna noise floor.
The worse Yaesu's I have measured show an almost one for one
decrease in close spaced IM dynamic range as gain in front
of the 8MHz IF is increased, and the best only show a small
deterioration. This varies from radio to radio, not just
model to model.
I've had quite a few radios here. Second to the modified
Drakes I actually prefer the FT1000MK V with corrected noise
blanker for receiving. I'm sure other people have other
preferences.
73 Tom
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband
|