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'[EE]: RF xcvr no groundplane'
2003\05\09@141903 by Charles Craft

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I've got some small RF xcvr modules with integrated antenna but no ground plane. The modules are designed to be added to a larger circuit board that would have the ground plane.

Hams have told me in the past that running a xcvr into no load is a bad thing. What about running these without the groundplane for testing? I assume the output power will be greatly reduced but I need to get started on some software development before the larger boards are done. Will running them without a groundplane to react against fry things?

thanks
chuckc

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2003\05\09@142946 by Dave VanHorn

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>
>Hams have told me in the past that running a xcvr into no load is a bad
>thing.

Not normally.  You aren't running much power, and you do afterall have a load.
OLD designs used to be sensitive like this, but I've not seen anything in
the last 10 years or so.

>What about running these without the groundplane for testing? I assume the
>output power will be greatly reduced but I need to get started on some
>software development before the larger boards are done. Will running them
>without a groundplane to react against fry things?

Very doubtful.
If you're really worried, solder a 100 ohm resistor across the antenna lead.
That will cost you some power, but your SWR will be less than 2/1 (Assuming
50 ohm source, and ANY antenna)

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2003\05\09@144406 by Charles Craft

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I didn't give you the whole story but it sounds encouraging so far. :-)

It's 868 Mhz and the antenna is punched out of aluminum and soldered to the module. Think I'll just give it a shot.

thanks
chuckc


>What about running these without the groundplane for testing? I assume
the
>output power will be greatly reduced but I need to get started on some
>software development before the larger boards are done. Will running them
>without a groundplane to react against fry things?

Very doubtful.
If you're really worried, solder a 100 ohm resistor across the antenna
lead.
That will cost you some power, but your SWR will be less than 2/1
(Assuming
50 ohm source, and ANY antenna)

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2003\05\09@150834 by Dave VanHorn

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At 02:56 PM 5/9/2003 -0500, Charles Craft wrote:
>I didn't give you the whole story but it sounds encouraging so far. :-)
>
>It's 868 Mhz and the antenna is punched out of aluminum and soldered to
>the module. Think I'll just give it a shot.

You can run a 3dB pad in the line somewhere, just three SMD resistors, and
that will give a 50 ohm load to the TX, and buffer you from just about
anything at the antenna.
Costs 3dB of course.. Nothing's free, especially with antennas!

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2003\05\09@224217 by John Ferrell

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A quarter wave is about 3.25 inches at that frequency. Add a couple of
pieces of wire this length at the connection provided for thr the ground
plane.
Don't be surprised if it out performs the ground plane...


John Ferrell
6241 Phillippi Rd
Julian NC 27283
Phone: (336)685-9606
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Dixie Competition Products
NSRCA 479 AMA 4190  W8CCW
"My Competition is Not My Enemy"

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