Topband: W3NQN BCB Filter

[ZR]

A tuneable preselector such as an Ameco or Palomar may provide the needed 
front end selectivity. I used a Palomar I added a RF gain control to on the 
TS-940 before modifying the front end in the late 80's and it eliminated all 
the BC problems. Set the gain pot to a bit over unity gain.

Carl
KM1H


Subject: Re: Topband: W3NQN BCB Filter


>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 at 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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