Topband: 160 AM BCB filter

[Henry Pfizenmayer]

FWIW - I spent a few minutes looking at the filter and with 4 inductors I
could see in the picture - leading to a 9 th order Elliptic Cauer- Chebyshev
equal termination filter with ripple set to 0.03 db , min atten in stop band
of 40 db , and cutoff freq of 1.78 mhz  the highest zero is at 1.6997 mhz
(to kill 1.7 as he said ) . You can play between the cutoff freq and pass
band ripple and tweak the rejection zeros a bit which he apparently did to
kill the 1700 station -

with capacitor Q's of 1000 and inductor Q's of  300 - the filter loss at 1.8
is 0.82 db and at 2 is 0.23 db ( with "perfect elements " the losses are
0.026 and 0.02 db respectively)   - the loss gets progressively lower and
lower as you go up in the passband -- the return loss is better than 22.5 db
across from 1.8 to 28 mhz  - and the element  values are reasonable - cap
values from 7906 to 8176 pfd and inductors from 3.7 to 11 uhy .  So its
quite realizable. Loss at 1.8 might be a little high but you could lower the
pass band loss significantly if Fc was not set so close to 1.8 mhz (like 1.6
or so).


 Hank K7HP

> We'll see what he has to say about the filter.  Turns out he is WB5WPA
> in Allen, TX.  No bounce on his email, so we'll just have to wait until he
> replies.  I'll post any further info that I get.
>
> 73  John  W0UN