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<div dir="ltr" data-setdir="false">Hi Bob</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">I covered this topic at my Def Con talk on the Care and Feeding of SDR's.</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">A bit harder to get these days, but Radio Shack and several others sell an</div><div dir="ltr" data-setdir="false">FM Band Notch filter In with the rest of the TV accessories. Very little</div><div dir="ltr" data-setdir="false">loss outside 80-120 MHz.</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">These days if you put up a broad band antenna in a urban area, about</div><div dir="ltr" data-setdir="false">2/3rds of the RF energy it picks up will be in the FM Broadcast band.</div><div dir="ltr" data-setdir="false">(Quite a bit of local variation in that 2/3rd's)</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">Amazing how many guys though they could eliminate the FM band overload</div><div dir="ltr" data-setdir="false">but just telling the SDR to ignore 88-108 MHz in the software.</div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false">73 Kent WA5VJB<br></div><div dir="ltr" data-setdir="false"><br></div><div dir="ltr" data-setdir="false"><br></div><div><br></div>
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On Sunday, November 1, 2020, 10:20:36 AM CST, Robert McGwier via Ground-Station <ground-station@lists.openresearch.institute> wrote:
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<div><div id="ydpf498f8f3yiv6518006172"><div><div>A single strong FM transmitter anywhere near will collapse the front end. A FM bandstop filter also degrades 2 meter low end and has insertion loss that harms the sensitivity further. <div><br clear="none"></div><div>RTLSDR is great but you get what you pay for </div><div><br clear="none"></div><div>Bob</div><div><br clear="none"></div></div><br clear="none"><div class="ydpf498f8f3yiv6518006172yqt1607146043" id="ydpf498f8f3yiv6518006172yqt41479"><div class="ydpf498f8f3yiv6518006172gmail_quote"><div class="ydpf498f8f3yiv6518006172gmail_attr" dir="ltr">On Sat, Oct 31, 2020, 2:10 PM Phil Karn via Ground-Station <ground-station@lists.openresearch.institute> wrote:<br clear="none"></div><blockquote class="ydpf498f8f3yiv6518006172gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><br clear="none">
On 10/31/20 11:10 AM, Douglas Quagliana wrote:<br clear="none">
> Hi Phil,<br clear="none">
> Please let me know when the code is available. I would like to try<br clear="none">
> getting it to run off an RTLSDR dongle and try to have it identify the<br clear="none">
> callsigns of the repeaters that it receives. <br clear="none">
> 73,<br clear="none">
> Douglas KA2UPW/5<br clear="none">
><br clear="none">
In principle I could use the RTL-SDR, but I haven't actually used it<br clear="none">
myself yet. It has a rather low dynamic range, so strong local repeaters<br clear="none">
could blank weaker signals on other channels within its bandwidth.<br clear="none">
Getting the most out it will probably require a lot of work on a good AGC.<br clear="none">
<br clear="none">
My favorite SDR used to be the AMSAT-UK Funcube dongle, but it has a<br clear="none">
very limited bandwidth (192 kHz). I'm now using the Airspy R2, which has<br clear="none">
a 10 MHz bandwidth and 12-bit sampling. This is enough to easily cover<br clear="none">
the entire 2m band. It can cover most of the 440-450 segment, but the<br clear="none">
actual coverage of SDR is a little less than 10 MHz because of<br clear="none">
anti-alias filtering ahead of the A/D. But it can easily cover the 5 MHz<br clear="none">
half of whatever segment used in your local area for repeater outputs<br clear="none">
(i.e., either 440-445 or 445-450).<br clear="none">
<br clear="none">
Phil<br clear="none">
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