[Lowfer] Daylight SIW in EN90xn

Sat Nov 15 11:00:38 EST 2014

Jay:  OK, Thanks for the "heads up."  I'll stick with <50K attachments until 
I figure on the mechanics of dropbox....

On the processing end, going from a 16 bit internal sound card to the 24bit 
external sound card, the Asus Xonar U7, made a significant improvement on 
both ARGO captures and WSPR2 SNRs.  The U7 requires a newer Win7 machine, 
which in this case is a Acer V5 netbook-size machine.

On the antenna-receiver end, new 10mh range CM chokes were made for the two 
RG6QS transmission lines that run to each end of my LF EWE antenna over the 
summer.  They are
wound with Belden 9221M 75 ohm  cable and are a few to several feet away 
from the antenna matching transformers to minimize coupling. RG6 line 
lengths
are about 175 and 200 feet long to reach the SW and NE ends of the EWE 
antenna. I added a dual grounding block and a pair of ground rods about 
midway
 on the RG6 runs where they separate to go to the two ends of the antenna. 
The RG6 cables then run parallel to each other on the ground to the shack.
 At the shack end, I'm using an opposing phase coaxial >10mh range CM choke 
in a 5 inch steel junction box (mag shield) with ground-isolated BNC 
connectors.
It's on a high permeability 3 inch toriod found at a hamfest.

 The BNC shields are tied together at in the box (but not grounded to the 
box), which does a fair job of attenuating the surface wave signal from 50Kw
KDKA station 4.5 miles away. The effect is noticeable with an O scope across 
the two BNC shields when they are open vs tied together.
Other side of the opposing phase CM choke goes to isolated ground BNC 
connectors. One end is terminated in either 75 ohms or
a 175 ohm variable potentiometer for EWE directivity selection, the other 
end feeds a 75:50 ohm isolation transformer on a type 75 core to the AM BC 
LPF and MF/LF converter.

I went through all the above to stay away from grounding the RG6 lines near 
the house so as to minimize the ground-probe antenna noise coupling effect 
between the
LF antenna ground and my AC service ground---which is quite noisy....

The improvement in noise level reduction from the above effort was several 
dB  across the LF/MF band according to ARGO waterfall background levels.

One other improvement was to frequency scale your 500kHz preselector design 
to the 3.0 ~ 3.5 MHz range to match my RX converter range. It helps
the so-so Yeasu FT-817/FT-847 receivers here which are woefully lacking of 
roofing filters. I have it tweaked for 3.475 Mhz. A bit of a patience test 
to get the
return loss well matched for bidirectional use.  I used my MFJ analyzer, a 
handful of stick attenuators for isolation, and my HP141T. I used the MFJ 
analyzer to tune for the best match
 and monitored the signal throughput throuhg the filter on the HP141T while 
reversing the filter ports after each trimmer tuning iteration.  I think I 
quit when I got to 16~17 dB of bidirectional return loss and 5~6 dB of 
insertion loss...

Thanks for all the LF/MF preamp & filter info on your web site. It was a 
good learning experience to build them....

73 Mike wa3tts

----- Original Message ----- 
From: <jrusgrove at comcast.net>
To: "Discussion of the Lowfer (US, European, & UK) and MedFer bands" 
<lowfer at mailman.qth.net>
Sent: Saturday, November 15, 2014 7:29 AM
Subject: Re: [Lowfer] Daylight SIW in EN90xn

> Mike
>
> No problem ... just reporting what I found. Probably any 'service' that 
> lets one view a pix without all of the 'overhead' will work just fine.
>
> I've been noticing your improving captures. Curious what station 
> improvements made the biggest difference.
>
> Jay
>
>
> ----- Original Message ----- 
> From: "Michael Sapp" <wa3tts at verizon.net>
> To: "Discussion of the Lowfer (US, European, & UK) and MedFer bands" 
> <lowfer at mailman.qth.net>
> Sent: Friday, November 14, 2014 11:00 PM
> Subject: Re: [Lowfer] Daylight SIW in EN90xn
>
>
>> Jay: Somewhat confounding. No other real options for the photobucket 
>> links.
>> I sent myself an e-mail with all of them to test
>> and the "Direct" link was the only one that AdBlock showed no hits on.
>> Sorry to cause issues. I will look for a better alternative....
>>
>> I can send you the jpg via e-mail it you want to take a look at it, it's
>> 236kb....
>>
>> So far this fall sason I'm hearing better from summer upgrades to system,
>> but still a few orders of magnitude shy of your pristine online grabber
>> views...
>>
>> 73, Mike wa3tts
>>
>> ----- Original Message ----- 
>> From: <jrusgrove at comcast.net>
>> Sent: Friday, November 14, 2014 10:03 PM
>>
>>> Mike
>>>
>>> FYI ... not a direct link here ... all the Photobucket 'overhead' is 
>>> there
>>> ... slow load ;~( .
>>>
>>> Jay
>>
>
>
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