[chbot] Planning for the next few weeks - SDR Experts?

Sun Mar 22 00:22:26 GMT 2020

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.
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).
Trevor

On Sun, Mar 22, 2020 at 12:59 PM Mark Atherton <markaren1 at xtra.co.nz> wrote:

> Some parameters please
> - max and min limit of carrier frequency, or Fnom ± Ftolerance
> - repetition rate of the 100ms bursts ?
> - transmit power
> - transmit antenna
>
> Do you have a pendant in hand to take apart ?
>
> So unmodulated carrier, and no ident modulation ?
>
> - Mark
>
>
>
> On 22/03/2020 12:44 PM, Trevor Wignall wrote:
>
> Hi all
> 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.
> If anyone familiar with SDRs would like a challenge to combat boredom, any
> help would be appreciated.
> Trevor
>
> On Sun, Mar 22, 2020 at 11:28 AM Mark Atherton <markaren1 at xtra.co.nz>
> wrote:
>
>> One more time, this go includes the Robotics group in the to: list :)
>>
>>
>> Greetings Robotters.
>>
>>
>> This is more of a brain-dump than anything too coherent; please
>> contribute ideas as required.
>>
>> The next few weeks are going to be rather interesting to say the least,
>> and while some of us relish the thought of time alone, others may be
>> concerned about boredom creeping in.
>>
>> Spare time, does of course mean opportunity, and with a little planning,
>> things can be done, plates can be spun, and progress can be made.
>>
>> Things that come to mind include the following:
>>
>> Develop. Something rattling around in your head for a while and needs
>> implementing, is it time to get out the soldering
>> iron/keyboard/angle-grinder and get going on it ?
>>
>> Repair. Broken things tend to accumulate. Not sure how to repair it -
>> ask here, or find a specialist forum.
>>
>> Clear out. Sinking in it ? Round it up, and chuck it out.
>>
>> Document. Surrounded by lots of interesting complete projects, but
>> little published work ? Maybe it's time to open a hackaday account, and
>> start reporting your progress and projects to the world ?
>>
>> Learn. Stuff you are interested in ? Find a forum, an online resource,
>> youtube - get stuck in. Not sure what the question is ? Ask here, we may
>> know what you are trying to do and give some ideas about how to find
>> required resources.
>>
>> Educate. Time to give back ? Maybe find a forum who could do with a
>> mentor. Contribute.
>>
>> Stock up. Not sure how long the electronic component suppliers are going
>> to be open for, so maybe it's time to pay a visit to Jaycar/South Island
>> Components/Ecotech/Molten Media and load up with stuff while they are
>> open. They may have to close for a while, and an acute widget shortage
>> can be frustrating.
>>
>> Share. I hate that phrase, but in this context, you may have stuff
>> surplus which may be useful to others. Give to the other givers first ?
>>
>> Scrounge. If you have a specific project in mind (not just stocking up)
>> put out a Request-For-Scrounge (RFS). You might be amazed what stuff
>> people have squirrelled away.
>>
>> As usual, lurkers, and regulars alike, please speak up about projects,
>> ideas etc. Please keep the subject line of messages updated to track
>> content.
>>
>> Things will return to some kind of normal over the next few weeks, but
>> busy hands, fingers and keyboards can alleviate the stress of change.
>>
>> Comments, updates, and suggestions as usual are always welcome.
>>
>> Keep safe.
>>
>> -Mark
>>
>> PS I have copied a few non-robot-group members who seem relevant to this
>> topic. Please sign up to be included in any of our discussions via
>> kiwibots.org or directly at
>> https://lists.ourshack.com/mailman/listinfo/chchrobotics As a (nearly)
>> French person once said "I will say this only once"
>>
>>
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