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'[EE] Aerial for data link'
2006\10\08@183405 by Jinx

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I've a 433MHz RF link with Keymark modules, PIC-PIC, and
have questions about the aerial. Supply is 4.5V (3 x AAA alkaline).
Data is simple Manchester on/off modulation

Transmitter, 212kB (NB, they say 3V supply but actually 2-5V)

http://www.jaycar.co.nz/products_uploaded/ZW3100(mod).pdf

Receiver, 779kB

http://www.jaycar.co.nz/products_uploaded/ZW3102(mod).pdf

At present it's what the datasheet suggests. I have a 173mm length
of 22B&S (0.63mm) enamelled wire as a 1/4 wave at both ends.
This works fine up to at least 100m line-of-sight

1) how important is wire diameter

2) how is aerial material

3) what pros / cons are there for 1/2 or 1/1 wave or even 2/1

TIA

2006\10\08@192550 by Richard Prosser

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On 09/10/06, Jinx <spam_OUTjoecolquittTakeThisOuTspamclear.net.nz> wrote:
{Quote hidden}

> -

2006\10\08@220308 by Jinx

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Thanks for the tips Richard. For this product I need
something that's just cheap and reliable. Directional
would be nice, as there could be several of these things
in an area, but the data coding *should* take care of
that. A couple of quick tests indicate it does. Expected
transmission range is going to be generally under 50m

For a longer range application (will need to be done at
some stage, perhaps up to 500m) I'll look at more tailored
aerials to get the best out of the power available, maybe
even try a more powerful transmitter if necessary

2006\10\08@222533 by Richard Prosser

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Great.
One type that may be worh looking at in the longer term is the
J-pole.  Omnidirectional but has useful gain over a 1/4 wave, doesn't
require a ground plane and has a reasonably low radiation angle. Can
be made using old-style TV ribbon & placed inside PVC pipe for
external protection if required (although the lengths need to modified
slightly).

Again - examples can be found with Google.

But you'd probably need some sort of test gear to get it optomised for
your frequency

Richard P.

On 09/10/06, Jinx <.....joecolquittKILLspamspam@spam@clear.net.nz> wrote:
{Quote hidden}

> -

2006\10\08@223917 by Jinx

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> One type that may be worh looking at in the longer term is the
> J-pole.  Omnidirectional but has useful gain over a 1/4 wave

Nice one

http://en.wikipedia.org/wiki/J-pole

linking to

http://www.hamuniverse.com/slimjim.html

2006\10\08@232935 by Dennis Crawley

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Jinx <joecolquittspamKILLspamclear.net.nz> wrote:
> Thanks for the tips Richard. For this product I need
> something that's just cheap and reliable. Directional
> would be nice, as there could be several of these things
> in an area, but the data coding *should* take care of
> that. A couple of quick tests indicate it does. Expected
> transmission range is going to be generally under 50m
>
> For a longer range application (will need to be done at
> some stage, perhaps up to 500m) I'll look at more tailored
> aerials to get the best out of the power available, maybe
> even try a more powerful transmitter if necessary


Hi Jinx,
For directivity, use a yagui, with a parabolic plane as reflector, builded
with 1,5mm bronze wire,(separation of elements < 1/16 lamda),... mount the
receptor near the antenna.

For a omnidirectional:
Choose rigid wire or little coper tube (1/4 lamda < 17cm).
Mount the receiver in a sealed metal box and use a BNC to connect the
anntena for the experiment.
Then build a pi tank.
Make the transmitter send a continous 0xAA at the desierd baudrate.
Try to See the 0xAA with a scope on the RSSI pin,... or linear pin.
Adjust the pi tank until the pulses have a good shape. Vary the cap values.

Regards,
Dennis.

ps: What happened with your friend? Is she still listening that noise?




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2006\10\09@010950 by Jinx

face picon face
> For directivity, use a yagui, with a parabolic plane as reflector

Thanks for the info Dennis

> ps: What happened with your friend? Is she still listening
> that noise?

Yes, and things are moving along. Not quite ready to let you
all know what the outcome, still a couple of government types
to talk to yet

2006\10\10@050824 by Jinx

face picon face
> ps: What happened with your friend? Is she still listening that noise?

Today she reported meeting with a researcher from the
Albany campus of Massey University

Amongst the things they discussed were

http://en.wikipedia.org/wiki/The_Hum

http://www.igzab.de/Ausland/English/english.html

including the Kokomo hum (2800kB)

http://www.igzab.de/data/KokomoHumFinalReport.pdf

RF measurements around a complainant's property (292kB)

http://www.igzab.de/data/KokomoHumReportAppendixB.pdf

No word back yet from The Men From The Ministry

She's found also, after investigating, that several comms
towers have gone up in her neighbourhood in the past few
recent years, ones she hadn't even realised were there

2006\10\11@091615 by Jinx

face picon face
> ps: What happened with your friend? Is she still listening that noise?

Latest development -

The researchers have gone public and made the national radio news

http://www.newstalkzb.co.nz/newsdetail1.asp?storyID=105395

It looks like it may have some legs

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