<div dir="ltr">The frequency is around 300MHz and is known to within a couple of kHz - later models are a bit more stable, so perhaps within +/1 1kHz. Repetition is 1-2 seconds. So essentially a CW (morse) transmitter sending the word "e". Transmit power and aerial are not relevant to trying to improve the receiver - I'll take any improvement I can get! There is a test transmitter operating with a coverage of most of Christchurch - clearly heard at the Idris Rd clubrooms.<div>I don't want to put too many specifics in an open thread - anyone seriously interested can contact me and I will give them more specifics (after I have cleared it with the Wandersearch Trustees).</div><div>Trevor</div><div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, Mar 22, 2020 at 12:59 PM Mark Atherton <<a href="mailto:markaren1@xtra.co.nz">markaren1@xtra.co.nz</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div bgcolor="#FFFFFF">
<div>Some parameters please</div>
- max and min limit of carrier frequency, or Fnom <span style="color:rgb(60,64,67);font-family:arial,sans-serif;font-size:14px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:left;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial;float:none;display:inline">± Ftolerance<br>
</span>
<div>- repetition rate of the 100ms bursts ?
<div>- transmit power</div>
<div>- transmit antenna</div>
<div><br>
</div>
<div>Do you have a pendant in hand to take
apart ?<br>
</div>
<div><br>
</div>
<div>So unmodulated carrier, and no ident
modulation ?</div>
<div><br>
</div>
<div>- Mark<br>
</div>
</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div>On 22/03/2020 12:44 PM, Trevor Wignall
wrote:<br>
</div>
<blockquote type="cite">
<div dir="ltr">
<div>Hi all</div>
<div>As a Wandersearch responder (i.e. someone who goes out with
a directional receiver and tries to locate the small
transmitter pendants worn by people who tend to go wandering
e.g. dementia patients), I am looking at using a Software
Defined Radio (SDR) to receive these signals. However as the
signals are weak, I am looking for ways of extracting the
short transmitted pulses (around 100-200 milliseconds of
unmodulated carrier) from the background noise using narrow
band filtering. The problem is that the exact transmitter
frequency is not known due to tolerances, temperature changes
etc.</div>
<div>If anyone familiar with SDRs would like a challenge to
combat boredom, any help would be appreciated.</div>
<div>Trevor</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Sun, Mar 22, 2020 at
11:28 AM Mark Atherton <<a href="mailto:markaren1@xtra.co.nz" target="_blank">markaren1@xtra.co.nz</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">One more time, this go
includes the Robotics group in the to: list :)<br>
<br>
<br>
Greetings Robotters.<br>
<br>
<br>
This is more of a brain-dump than anything too coherent;
please <br>
contribute ideas as required.<br>
<br>
The next few weeks are going to be rather interesting to say
the least, <br>
and while some of us relish the thought of time alone,
others may be <br>
concerned about boredom creeping in.<br>
<br>
Spare time, does of course mean opportunity, and with a
little planning, <br>
things can be done, plates can be spun, and progress can be
made.<br>
<br>
Things that come to mind include the following:<br>
<br>
Develop. Something rattling around in your head for a while
and needs <br>
implementing, is it time to get out the soldering <br>
iron/keyboard/angle-grinder and get going on it ?<br>
<br>
Repair. Broken things tend to accumulate. Not sure how to
repair it - <br>
ask here, or find a specialist forum.<br>
<br>
Clear out. Sinking in it ? Round it up, and chuck it out.<br>
<br>
Document. Surrounded by lots of interesting complete
projects, but <br>
little published work ? Maybe it's time to open a hackaday
account, and <br>
start reporting your progress and projects to the world ?<br>
<br>
Learn. Stuff you are interested in ? Find a forum, an online
resource, <br>
youtube - get stuck in. Not sure what the question is ? Ask
here, we may <br>
know what you are trying to do and give some ideas about how
to find <br>
required resources.<br>
<br>
Educate. Time to give back ? Maybe find a forum who could do
with a <br>
mentor. Contribute.<br>
<br>
Stock up. Not sure how long the electronic component
suppliers are going <br>
to be open for, so maybe it's time to pay a visit to
Jaycar/South Island <br>
Components/Ecotech/Molten Media and load up with stuff while
they are <br>
open. They may have to close for a while, and an acute
widget shortage <br>
can be frustrating.<br>
<br>
Share. I hate that phrase, but in this context, you may have
stuff <br>
surplus which may be useful to others. Give to the other
givers first ?<br>
<br>
Scrounge. If you have a specific project in mind (not just
stocking up) <br>
put out a Request-For-Scrounge (RFS). You might be amazed
what stuff <br>
people have squirrelled away.<br>
<br>
As usual, lurkers, and regulars alike, please speak up about
projects, <br>
ideas etc. Please keep the subject line of messages updated
to track <br>
content.<br>
<br>
Things will return to some kind of normal over the next few
weeks, but <br>
busy hands, fingers and keyboards can alleviate the stress
of change.<br>
<br>
Comments, updates, and suggestions as usual are always
welcome.<br>
<br>
Keep safe.<br>
<br>
-Mark<br>
<br>
PS I have copied a few non-robot-group members who seem
relevant to this <br>
topic. Please sign up to be included in any of our
discussions via <br>
<a href="http://kiwibots.org" rel="noreferrer" target="_blank">kiwibots.org</a> or
directly at <br>
<a href="https://lists.ourshack.com/mailman/listinfo/chchrobotics" rel="noreferrer" target="_blank">https://lists.ourshack.com/mailman/listinfo/chchrobotics</a>
As a (nearly) <br>
French person once said "I will say this only once"<br>
<br>
<br>
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