[Lowfer] Analog VS SDR LF comparison

[Douglas D. Williams]

You're welcome.

For what it's worth, I didn't purchase the equipment just in order to do
the comparison. It's more a case of, "Hey I have this equipment, why not do
a comparison?" ;-)

The only thing I really bought specifically for the comparison was the
splitter/combiner, and I probably would have purchased that anyway in order
to receive two different frequencies simultaneously and/or to have a
grabber running on one PC and still be able to hunt NDBs or somesuch on the
other.

-Doug

On Sat, Oct 6, 2012 at 8:37 PM, Lee <fccpart15 at earthlink.net> wrote:

> Thanks in advance for your hard work and investment of time and equipment
> into this very interesting subject/comparison.
> Lee
> KE6PCT
>
>
> -----Original Message-----
> >From: "Douglas D. Williams" <kb4oer at gmail.com>
> >Sent: Oct 6, 2012 1:17 PM
> >To: "Discussion of the Lowfer (US, European, &amp,
> >       UK) and MedFer bands" <lowfer at mailman.qth.net>
> >Subject: [Lowfer] Analog VS SDR LF comparison
> >
> >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.
> >
> >
> >Got it all hooked up today, and here are my initial results, after briefly
> >calibrating both receivers with WWVB.
> >
> >
> >This is afternoon copy of beacon MP, both receivers tuned to 137.780 kHz,
> >and the same version of ARGO running on each computer, with the settings
> as
> >close as I could get them.
> >
> >Beacon MP is approximately 464 miles from my QTH. Nice daytime signal.
> >
> >First, the R75+AMRAD converter:
> >
> >https://dl.dropbox.com/u/33457409/R75%26Winradio%20Comparison/R75MP1.jpg
> >
> >Second, the Winradio G33DDC:
> >
> >
> https://dl.dropbox.com/u/33457409/R75%26Winradio%20Comparison/WINRADMP1.jpg
> >
> >
> >In my opinion, there is essentially no difference in the two screen
> >captures.
> >
> >I will continue to do direct comparisons throughout the listening season,
> >at different frequencies (all 500 kHz or below).
> >
> >In a week or so, I am having the wooded portion of my land cleared out,
> >which will put my receive antenna much more in the clear and away from
> >trees.
> >
> >Once that happens, and the LF season really gets underway, I should be
> able
> >to do some really "weak signal" comparisons in the Part 15 Lowfer band.
> >
> >-Doug KB4OER
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