[Lowfer] Question about SDR Dongle with Win-XP
Andy - KU4XR
ku4xr at yahoo.com
Mon Oct 8 19:59:59 EDT 2018
Hi Clint:
Thanks for the info.. That's a lot to think on.. The Softrock, or possibly better, a KIWIlooks like a better way to go over the RTL dongles... It might be time to consider thechange to Linux as you mention for these old dinosaurs.. The still work just as they
were designed to do, and I hate to " throw them away "...
73 for now:
Andy - KU4XR
On Monday, October 8, 2018, 1:04:59 PM EDT, Clint Turner <turner at ussc.com> wrote:
Hi Andy,
There are several "moderately-priced" options:
While one of those $20 RTL-SDR dongles may look attractive - and will
(more ore less) work for LF (if you get one that does "direct" input
such as the "RTL-SDR.com" sells - AND if you remove the DC power
insertion jumper as noted in their documentation) the "only 8 bits" of
A/D conversion is a huge factor.
There are those (more expensive) with built-in "up-converters" (e.g.
they take LF/HF signals and convert them up to >100MHz) rather than
using the "direct" mode: Even though they may have 1ppm TCXOs in them,
you'll likely see a bit of drift on very narrow-band signals. Whether
or not this mixer is good down to LF/MF - or even capable of the dynamic
range of the device itself depends largely on how well-engineered it
was. (I personally avoid the up-converter if it's reasonable to do so.)
While I am (sort of) able to get away with this sort of thing on the
"AM-160-120M" receiver on the Northern Utah WebSDR, this is possible
only with with (what is possibly over-the-top) levels of filtering
coupled with judicious amounts of amplification (see:
http://ka7oei.blogspot.com/2018/02/managing-hf-signal-dynamics-on-rtl-sdr.html
)
The upshot is that these dongles are "marginally usable" for anything
other than the VHF/UHF frequencies for which they were designed - but
there are a few things that *may* make them usable - particularly in
light of their very low cost:
- Use a band-pass filter only for the frequency of interest. (Usually a
good practice no matter what).
- Carefully set the RF input level so that they will "clip" (maximum
A/D) only occasionally under "strong signal conditions".
- Even more important is to set the level so that under "quiet"
conditions that you are always "tickling" the bottom 2-3 bits:
Under-driving (too-low signal) is arguably more deleterious than
mild/moderate overdriving.
- To do the above, the software needs to have some way of monitoring the
raw A/D levels as it may not be difficult to find the "sweet spot" - or
even know if you are over/under driving without it. I don't know if the
available RTL-SDR dongle programs for Windows even have this capability.
As for which will work with XP: You may need to dig around and find
some old drivers as the current crop of drivers from "Zadig" do *NOT*
support XP.
* * *
Another option that will probably yield */far superior/* results
(because of much better RF circuitry and the use of an A/D converter - a
sound card - with 16 bit depth) would be to use an "Softrock" type
receiver. Ones that I would recommend are those from "fivedash.com" and
there are two to consider:
- The "LF/MF" version of the Softrock Ensemble II. As a kit it's in the
$70 range and a pre-built is already available This is a self-contained
receiver with switchable band-pass filters that can cover from
130kHz-3MHz - provided that you use a 192 kHz sound card (the local
oscillator, as designed, doesn't really go much below 200 kHz unless one
added another divide-by-two and reconfigured the USB interface chip to
account for that - both of which are easily done, but not well
documented. I use this for monitoring the range for monitoring the
range that includes the 2200 and 1750 meter bands and it works well.
- A modified "Softrock II Lite" receiver, available as a kit for around
$20. If your PC already has a half-decent sound card (which will
probably be only 48 or 96 kHz sampling rate) this may be the most
economical option. The Northern Utah WebSDR uses this for its 630 meter
band receiver (a receiver for covering 2200-1750 is available, but
pending some infrastructure work to allow the installation of an antenna
that will work <250 kHz) and I have documented how this may be done, here:
http://websdr1.utahsdr.org/info/rx_equipment.html#lf_mf_receiver
This shows the revised input filtering and modifications for these
receivers to work at 630 and also 2200-1750 meters, including revised
band-pass filters that are specifically designed for 2200-1750 and also
630 meter use, being optimized for use with a 96kHz sound card - needed
if you plan to cover 2200+1750 meters. (A lowly 48kHz sound card is
find for 630 meters.)
Not shown in the diagram - but described elsewhere on the above page -
is how these are interfaced with the $18 "SoftRock" kit (from QRP labs)
as the local oscillators: The QRP labs kit can produce up to 3 LO
signals, so just one of these will produce the two LOs needed for
2200-1750+630 meter coverage.
The /second/ option (the modified Softrock II Lite) is almost
hardware-agnostic: As long as you can find some sort of program that
will run on your computer and do the audio processing, you will be
fine: Older version of programs like HDSDR, etc. work and I've used
them in the past on XP machines.
* * *
If you have old hardware kicking around, one should not completely
ignore the possibility of using them with a "ham radio" version of Linux
(free!) that will do everything you need, and be more "lightweight" in
its processor and memory requirements. There are some "live boot" (e.g.
run from a DVD or thumb drive - no need to install to try them out, you
can install later) "ham radio" distros out there with which one can
test, but it would require a bit of a learning curve. There are a
number of programs in these Linux distros that will work with both
dongle and sound-card based systems.
I hope that this helps.
73,
Clint
KA7OEI
On 10/7/2018 4:29 PM, Andy - KU4XR via Lowfer wrote:
> Greetings all:
>
> The quickest way to obtain information ... ask those who ARE ... I have a couple of windows XP machines that
> I would like to possibly put back into service as a " Remote Receiver " setup using a Dongle and software..
> As always, I am budget oriented, so, which Dongles, and which Software will work with Windows XP ??
>
> Thanks for information, and 73:
>
> Andy - KU4XR
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