[Lowfer] Analog VS SDR LF comparison

[Douglas D. Williams]

After several hours of experimenting, I have decided that my current
receive system needs no additional gain.

In fact, increased gain is introducing spurious signals into my receive
chain.

Like Jay pointed out to me, if I can hear band noise with my current
system, no more gain is needed.

"Nuff said" about that.

I hope to use the preamp to experiment with a tuned ferrite loop this
season.

More experimentation is needed on my end, IMO, regarding the signal to
noise ratio in relation to active antenna base height.

Currently, I have my active antenna base height at 20' above ground level
(on top of a hill).

Once my "jungle" property is cleared (hopefully this month) we shall see if
that produces a better signal to noise ratio. If not, I am prepared to
increase the height of the base of the active antenna to 30' or more, even
though that greatly increases my worries about direct lightning strikes.

Doug - KB4OER









On Fri, Oct 12, 2012 at 4:17 PM, Douglas D. Williams <kb4oer at gmail.com>wrote:

> Got it all hooked up just now. I have an octopus of patch cables all over
> my desk/workbench, but my wife doesn't care, so that's that.
>
> The AAR Preamp definitely does the job. First thing I noticed was
> daytime QRN levels on 180kHz went from not registering on the S-Meter to
> S7(ish). No big effect on the R75, but, as I suspected, this drove the SDR
> into "ADC Clipping". Fortunately, I purchased the handy-dandy 0-50dB step
> attenuator. 10dB of attenuation later, and all is well. Will probably have
> to dial it down a bit more at night.
>
> Thanks Jay. Always nice to have some extra gain when needed, and the step
> attenuator give me precise control over just how much gain.
>
> -Doug KB4OER
>
> On Tue, Oct 9, 2012 at 7:07 PM, Douglas D. Williams <kb4oer at gmail.com>wrote:
>
>> 10 kHz - 20 MHz
>>
>> I hope Jay does not mind me linking this.
>>
>> (And since he has published the schematic on his own web page, I feel
>> safe.)
>>
>>
>> D.
>>
>>
>>
>>
>> On Tue, Oct 9, 2012 at 6:48 PM, K2ORS <k2ors at verizon.net> wrote:
>>
>>> Doug,
>>>    What frequency range did you get with the custom ARR preamp?
>>> tnx & 73 Warren
>>>
>>> ----- Original Message -----
>>> From: "Douglas D. Williams" <kb4oer at gmail.com>
>>> To: "Discussion of the Lowfer (US, European, &amp, UK) and MedFer bands"
>>> <lowfer at mailman.qth.net>
>>> Sent: Tuesday, October 09, 2012 6:37 PM
>>> Subject: Re: [Lowfer] Analog VS SDR LF comparison
>>>
>>>
>>> > 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
>>>
>>