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
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
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.
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.
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