[TenTec] Ten Tec Eagle noise blanker

[Rick at dj0ip.de]

John,

The Eagle's NB is indeed an analog one, and yes, it does distort the radio's
audio signal;  ALL NB (by design) must do that.
They reduce noise by cutting out part of the frequency spectrum, which
ultimately distorts the audio.

I won't make any kind of claim that analog NBs are better than DSP NBs,
because I'm sure that is just a question of the combination of DSP chip(s)
and the firmware.  However the Eagle's Analog NBs better than most modern
radios using DSP NBs.

It is always bad to generalize because there are many differences or
exceptions, but I will do it below:

The reason the NB often lowers the dynamic range is simple.
On radios with a high dynamic range, the signal usually go straight into a
narrow 1st IF filter.
However it is difficult/impossible to limit pulse noise with a narrow filter
in front of it.
So they have a wider filter in the NB and thus strong signals can overdrive
the circuitry within.

The reason the OM5/6/6+ had the broad simple xtal filter in its front end
was to enable use of a NB.
The INRAD replacement filter for this improved dynamic range significantly,
at the cost of the NB.  The NB is no longer effective when the INRAD roofing
filter is in place.

Normally we would only use the NB in a mobile environment, where we have a
small antenna anyway, so this does not create a problem.
However now days with all the noise we have in our homes, people are turning
on the NB when using larger antennas and then it can be a problem.

As I said, it's hard to generalize.
Rob Sherwood always scrutinizes the NB carefully in his tests.
If you really want to know, you should read his individual tests, don't just
look at the table of RX performance.

You will find most of his reviews/tests in full length on my web site, here:
http://www.dj0ip.de/sherwood-forest/sherwood-xcvr-tests/ 

73
Rick, DJ0IP



-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of John Geiger
Sent: 14 November 2017 20:01
To: Discussion of Ten-Tec Equipment <tentec at contesting.com>
Subject: [TenTec] Ten Tec Eagle noise blanker

>From the Ten Tec Manual, it appears that the noise blanker for the Eagle is
not a DSP one, but an analog, hardware one, is that correct?

I have seen a couple of You tube videos which show that the NB is very good
at taking out RFI noise, but does the NB distort the received signal, or
lower the receiver's dynamic range like many noise blankers do?

73 John AF5CC
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