[Lowfer] Analog VS SDR LF comparison

[Douglas D. Williams]

Minor update.

The KIWA splitter, being a passive unit, introduces a 6dB attenuation to
both output ports. Is this a problem? Most likely not, given the band noise
at VLF/LF, and the gain at the output of the Clifton Labs Z1501D active
antenna.

Regardless of that logic, I decided to obtain and introduce into the entire
system a 20 dB preamp, and for that purpose I chose a special order model
by Advanced Receiver Research (our own Jay Rusgrove):

http://www.advancedreceiver.com/

Since that will likely produce a signal level that will drive the
input Winradio SDR input into clipping, I managed to bid and win on eBay a
50 ohm, 0-50 dB step attenuator (1 dB steps) by JFW Industries, INC.

My plan is to place the 20 dB preamp after the 500 kHz low pass filter,
then to the step attenuator, then the KIWA splitter, then etc. etc.

It will likely be a haywire mess on my workbench, with all the patch
cords, and I am happy with that.

-Doug KB4OER









On Sat, Oct 6, 2012 at 4:17 PM, Douglas D. Williams <kb4oer at gmail.com>wrote:

> Well, as I mentioned to this group a few weeks ago, I planned to do a
> series of comparisons between an analog receiver and an SDR at VLF/LF
> frequencies, using the same antenna.
>
> In order to receive the same signal simultaneously on both receivers with
> the same antenna, I would need some sort of "splitter". KIWA Electronics
> manufactures two models:
>
> http://www.kiwa.com/LFCombiner
>
> Neither one completely covered the frequency range I am interested in,
> which is 5kHz to 500+kHz, so I commissioned a "special order" model, which
> I received today. BTW, I would like to take this opportunity to thank Craig
> Seigenthaler at KIWA for his help in this. In addition to the custom
> splitter/combiner, I own one of their 500kHz low pass filters, and can
> recommend their products without reservation. They are built like a Sherman
> tank.
>
> The antenna that will be used in this comparison is a custom Clifton
> Laboratories Z1501D active whip, located about 50' from my house with the
> base up 20' from ground. The "custom" part is I asked Jack at Clifton Labs
> to lower the bottom range of the active antenna from 20kHz to below 8kHz,
> which he did with flying colors (all the way to about 3kHz).
>
> The setup is as follows:
>
> Output from the Clifton Labs indoor DC coupler goes first to the KIWA
> 500kHz low pass filter, then to the KIWA splitter. Output "A" goes to an
> AMRAD LF converter custom built by Todd Roberts with an OCXO for stability,
> then to an Icom R75 with the OCXO option, as well as a 500Hz and a 250Hz
> crystal filter. Output "B" goes directly into a Winradio Excalibur Pro
> G33DDC receiver.
>
> At first, I was going to run two instances of Argo on the same PC, one for
> each receiver, but I ultimately decided to connect the two receivers into
> two separate PCs.
>



>  *[SNIP]*
>