SUMMARY: DISABLE THE HW NOISEBLANKER ON THE MENU/RX PAGE NOT THE FRONT PANEL
TO AVOID OR CURE RX DISTORTION. IF YOU SEE OFF:H ON
THE DISPLAY YOU
IT IS NOT REALLY OUT OF THE CIRCUIT.
I made a remarkable discovery during SS this last weekend.
The noiseblanker in my Orion causes tremendous distortion, even when the
front panel is OFF during times when the band is full of strong signals.
How strong? Well I live at the repeater site, and my antennas are
therefore at almost 1200 feet above
Sacramento Valley. This makes up for my lack of skill as an operator,
but it also gives me line of site to
a number of KW stations, especially during SS. Typically I run 12-18 db
of attenuation on the RX and a
number of the California contest stations still run 30 over 9 here.
During the contest the band seems alive with crud. Since I got my Orion
about 3 years ago, I assumed
this crud was just bad transmitters being over driven in the excitement
of the contest etc.
As it happened I normally use the hardware noiseblanker here because it
works very well on the nearby
electric fence, but I leave it off when the fence is not an issue. The
front panel usually reads off:H
This is key, because apparently the noiseblanker isn't really biased off
when this is displayed.
I've relegated my 756 MK II as a bandscope to visually monitor band
openings. It works well for this
and I usually dont ever listen to the radio.
During SS the distortion was really killing me. Some of the
transmitters seemed so darn dirty, but it was
impossible for me to figure out exactly which one was causing the
problem though at times I could make out
the SS sent fast by a number of operators.
At one point I was taking a break and having some dinner, so I shut the
Orion down to let it cool off (more on my next posting on that subject)
and I decided to see how the 756 handled all the crud I was hearing on
the band. I turned up the audio. Suddenly I was shocked. I put the
foodbag down. There was no crud on the 756!
I turned the Orion back on and started looking at the RX menu, figuring
one of my super settings for the AGC must be causing a problem. (The
noiseblanker on the front panel read off:H). By accident, I disabled the
hadware noiseblanker on the RX Menu. Suddenly the Orion's audio
changed. I was a bit surprised by this
since it was supposedly OFF:H on the front panel. In the next 30
seconds I realized that the change was
due to the crud going away!
Suddenly the band was totally clear, and I mean clean. It was like a dream.
Suddenly I could run my 250 Hz roofing filter and hear QRP SS Stations
clearly. WOW is all I can say.
I don't think there is anything wrong specifically with my Orion. I
have not looked at the circuit they use for the noiseblanker, but I
suspect the front panel control signals generated by the CPU do not bias
the circuit off properly, and if you have a new in band strong signals
the distortion is incredible. Since the noiseblanker appears to be
connected before the RF Gain control (just from observation) backing
down the RF Gain never
helped during contests, the crud was still there.
In past contests, by accident, I probably had the HW Noiseblanker off
sometimes by accident, accounting for
some of my best Orion experiences. Now it will be off permanently until
it gets fixed.
Sorry for the long story, but if you have any RX trouble with your
Orion, go the to Menus/RX and disable the
hardware noiseblanker there. Even money the problem goes away - not
just on CW.
73,
Len
WT6G
(Clean Sweep, 89,600 score Nov 2008 ARRL SS)
[Imagine what a good operator up here could do]
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