Topband: BCB Filter - final selection

[Jeff Blaine]

I don't know about the price end of it.  But Jim's comment about the 
alignment is true.

I fiddled around with some designs and then K8ZOA managed to talk me 
into back into the land of sanity.  Jack cooked up a version of his 
filter which put one of the notches on the head of our local BC station 
(I think it was on 1670).   I was -60dBc there and -1 dBc at 1.80.  
Unbelievable.  Then again, Jack was the master.

Still you don't need to spend much time in front of a VNA to appreciate 
the labor that can go into tweaking of some of these filters.

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com


On 4/17/20 7:01 PM, Jim Brown wrote:
> On 4/17/2020 4:19 PM, Roger Kennedy wrote:
>
> > $180 for a receiver filter?   That's absurd !
>
> That depends on the design criteria. I don't know how it is in your 
> part of the world, but folks here who design and build stuff like to 
> get paid a living wage. A filter that passes 160M but strongly 
> attenuates 1710 kHz (sidebands of 1700 kHz) is not a simple one. It 
> requires a very good design and precision components, careful 
> manufacturing, and precision alignment.
>
>> (By the way, if you now have stations broadcasting between 1.6 and 
>> 1.7 MHz,
>> how does anyone pick them up?  I don't know any broadcast radios that go
>> above 1.6 !)
>
> This is one of those frequency allocations that varies by region. In 
> NA, the AM band, stations are assigned carrier frequencies from 540 to 
> 1700 kHz, and radios sold here are programmed for that coverage. This 
> allocation has been in effect for several decades. By contrast, we 
> have no LF broadcasting.
>
> 73, Jim K9YC
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