I have the same issues here. And the similar observation - filtering
before the preamp of some kind is needed.
Regarding Steve's solution below, an alternative is available from K8ZOA
Jack Smith. 9th order elliptical with pricing is about half the Array
offering.
http://www.cliftonlaboratories.com/z10023a_elliptic_high_pass_filter.htm
It's about -40 db at 1700 with a roll off starting just below 1800.
Order options include 50 or 75 ohm, SMA, F-type or UHF, and some case
varieties.
I have no horse in Jack's race. He's a first class RF enginner, builds
great stuff - and I'm a very satisfied customer hence the mention.
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
-----Original Message-----
From: wb6rse1@mac.com
Sent: Monday, February 11, 2013 5:30 PM
To: Top Band List List
Subject: Topband: W3NQN BCB Filter
This topic has been covered before on this list. I believe that my recent
experience is also worth reporting.
After over a decade of operating on 160m, I'd never experienced any
significant problems with BC carriers other than very weak carriers on
1810, 1820, 1830, 1840 kHz etc. The greater Los Angeles area is not at a
loss for high power BC stations. Several weeks ago a very loud and wide
signal appeared for the first time on 1840 kHz in addition to others every
10 kHz. These spurs were a bit weaker after sunset but still loud and
wide. Any legitimate 160m signal within about 3 kHz of these spurs could
not be copied. The spurs' modulation matched that of a broadcast station
six miles from my location. With the assistance of a local broadcast
signal compliance expert, signal strength measurements were made using
professional grade equipment close to the BC station's transmitting towers
as well as at my station. The spurious signals were just out of regulatory
specifications and the modulation was mushy. The station's engineer was
contacted. He advertised that he would perform some s
tandard maintenance. To date, nothing has changed.
All of the possible combinations of equipment at my station were tried in
an attempt to isolate and diagnose the problem. The result was that the
spurs appeared only with an external preamp in the path with a full size
receiving flag. This was observed with not just a single preamp but with a
second preamp of an entirely different design.
I inserted a W3NQN Receive Only BCB filter between the flag and each of
the two preamps, one at a time. The result in both cases was that the
spurs were reduced to very weak carriers daytime and to a just perceptible
level when the BC station switched to nighttime power (10 kW to 490
watts). Something has likely changed in the BC's station signal, causing
the preamps to become overloaded resulting in IMD problems.
http://www.arraysolutions.com/Products/BCB%20RF%20Filters.htm
This filter has an extremely sharp cut-off below 1700 kHz. I understand
that precision tolerance components are hand selected for custom assembly
of each filter to guarantee the specified response. W3NQN has started to
label his products "Design, Assembly and Testing by W3NQN."
These filters have a well deserved reputation. The BCB is superb.
73 - Steve WB6RSE
_________________
Topband Reflector
_________________
Topband Reflector
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