[Lowfer] WWVB clock on 60 kHz

[Michael Sapp]

Garry: Try a high order low pass filter in the 250 to 300 kHz cutoff range 
to quell the AM beasts. I use a 9th order Butterworth 300kHz LPF that 
suppresses AMBC energy and much of the (very detectible) spur emissions from 
(very) local broadcasters. I think it has something like 70dB attenuation at 
750 kHz. That is what I use to be able to copy SIW all day long at the 
watering hole or XND in daylight on 137 kHz.   I have nearby 50KW stations 
here at  1020 and 1080, as well as 5KW stations at 730, 970, 1320, and 
1410 --- all within 5 miles of my QTH --- makes LF/MF a bit of a challenge.

https://www.dropbox.com/s/xepc43gxpjhgnqc/300kbtw3.jpg?dl=0

https://www.dropbox.com/s/u6oud6xt0uen00l/IMG_4214.JPG?dl=0

All type 61 toriod cores for high Q as per W7ZOI and W1VD recommend

I've been wanting to build some other higher order Butterworth LPFs but 
other projects keep getting in the way. I think the AADE will go 15th order, 
I have a few designs tucked away for a rainy weekend to tryout. The return 
loss on the Butterworth LPFs are great and nominal insertion loss below 
cutoff...

BTW hearing SIW wspr15 this afternoon and evening, using the above filter 
before the receive converter and split IF for 1750m and 2200m wspr...

12 spots:
Timestamp Call MHz SNR Drift Grid Pwr Reporter RGrid km az
 2017-02-06 01:45   K3SIW   0.185184   -35   0   EN51   0.001   WA3TTS\2 
EN90xn   762   95
 2017-02-06 01:30   K3SIW   0.185184   -36   0   EN51   0.001   WA3TTS\2 
EN90xn   762   95
 2017-02-06 00:45   K3SIW   0.185184   -35   0   EN51   0.001   WA3TTS\2 
EN90xn   762   95
 2017-02-05 23:15   K3SIW   0.185184   -38   0   EN51   0.001   WA3TTS\2 
EN90xn   762   95
 2017-02-05 23:00   K3SIW   0.185184   -36   0   EN51   0.001   WA3TTS\2 
EN90xn   762   95
 2017-02-05 22:45   K3SIW   0.185184   -38   0   EN51   0.001   WA3TTS\2 
EN90xn   762   95
 2017-02-05 22:30   K3SIW   0.185184   -36   0   EN51   0.001   WA3TTS\2 
EN90xn   762   95
 2017-02-05 22:00   K3SIW   0.185184   -37   0   EN51   0.001   WA3TTS\2 
EN90xn   762   95
 2017-02-05 21:45   K3SIW   0.185184   -36   0   EN51   0.001   WA3TTS\2 
EN90xn   762   95
 2017-02-05 21:30   K3SIW   0.185184   -35   0   EN51   0.001   WA3TTS\2 
EN90xn   762   95
 2017-02-05 21:15   K3SIW   0.185184   -34   0   EN51   0.001   WA3TTS\2 
EN90xn   762   95
 2017-02-05 21:00   K3SIW   0.185184   -34   0   EN51   0.001   WA3TTS\2 
EN90xn   762   9

73 Mike wa3tts

----- Original Message ----- 
From: "Garry" <k3siw at sbcglobal.net>
To: <lowfer at mailman.qth.net>
Sent: Sunday, February 05, 2017 10:58 PM
Subject: [Lowfer] WWVB clock on 60 kHz


> Of course WWVB is pounding in on 60 kHz, but around Chicago there's a
> big problem decoding it with an e-probe. That isn't because of the 60-Hz
> picket fence present here - that's weak compared to WWVB. Rather it's
> because high-powered AM broadcast stations WGN on 720 kHz and WBBM on
> 780 kHz mask the signalling with second-order IM. To get around that I
> have to use a loop and aim it at roughly 15 deg (the AM broadcast
> stations are at roughly 105 deg) to null the IM.
> -- 
> Garry, K3SIW, EN52ta, Elgin, IL
>


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