Re: Broadcast band Interference Filter for Cricket 80A


Jeff Peters <k9jp.radio@...>
 

Hello Curt,

Is it easy to replace any of the parts (caps. or inductors) on your built filter?  I guess, I would have picked a design frequency of 1.8 or 1.9 Mhz and then the knee might have moved to 2.0 or 2.5 MHz.  If my guess is correct, then you should have nearly the same output with or without the filter.

Hope this might help.

72/73 Jeff K9JP

On Tue, Feb 27, 2018 at 6:04 PM, Curt <rhulett1@...> wrote:
I built a Hi Pass filter with two inductors and three capacitors.  I ended up wih 1000pF/1.6uH/560pF/1.6uH/1000 pF.  According to Elsie, the knee is at 3.1 mHz.  At 3.58 loss is 0.3 dB.

Tested with a dummy load, the Cricket failed.  Output without the filter was 600 mW, with the filter was 200mW.  Trying the filter on an NE4040, output without was 900 mW, with was 800 mW.  Testing on an SST-20, without was 2W, with was 1.9W.

Not understanding how the loss on 20M and 40M is 5-10% but on 80M is 67%. 

What have others experienced using a simple high pass filter for BCI reduction on a Cricket.  What was the architecture?  What was the power loss?

72, Curt KB5JO (Cricket #5) Chirp Chirp




--
Not all of me will die - - - The good I do for others will live on forever.  <><

Join main@4SQRP.groups.io to automatically receive all group messages.