I'd like to install a higher gain antenna to this wifi adapter.
I'm looking for advice on the proper place to attach a 50 ohm
antenna ( or coax ).

amdx wrote:

I'd like to install a higher gain antenna to this wifi adapter.
I'm looking for advice on the proper place to attach a 50 ohm
antenna ( or coax ).


Can you make out which chip they used and find the datasheet? Often they
have an LC matching network and the L can be some piece of trace. The
datasheets are usually quite elaborate on how to connect variuous loads.

--
Regards, Joerg

http://www.analogconsultants.com

amdx wrote:
I'd like to install a higher gain antenna to this wifi adapter.
I'm looking for advice on the proper place to attach a 50 ohm
antenna ( or coax ).

I think you have come to a similar one that I would have
come to, except that I would scratch off the solder mask,
around the large hole and attach the shield at several
points around it.

"Joerg" wrote in message
...
amdx wrote:

I'd like to install a higher gain antenna to this wifi adapter.
I'm looking for advice on the proper place to attach a 50 ohm
antenna ( or coax ).

Can you make out which chip they used and find the datasheet? Often they
have an LC matching network and the L can be some piece of trace. The
datasheets are usually quite elaborate on how to connect variuous loads.

--
Regards, Joerg

Thanks Jorge,
The chip is covered by a shield and even if the data sheet said put a 1nh
inductor
in series, I'd have to say that's smaller than anything I can plan for.
I'm just hoping to connect a higher gain antenna. The board kind of looks
like
they had thoughts about a coax connection.
Mike

"John Popelish" wrote in message
...
amdx wrote:
I'd like to install a higher gain antenna to this wifi adapter.
I'm looking for advice on the proper place to attach a 50 ohm
antenna ( or coax ).

I think you have come to a similar one that I would have come to, except
that I would scratch off the solder mask, around the large hole and attach
the shield at several points around it.

That sounds good to me. I'll give it a try when I get an antenna figured
out.
That part I suggested I would remove, I don't know what it is,
it measures 0 ohms in circuit.
Thanks, Mike

amdx wrote:
"John Popelish" wrote in message
...
amdx wrote:
I'd like to install a higher gain antenna to this wifi adapter.
I'm looking for advice on the proper place to attach a 50 ohm
antenna ( or coax ).
I think you have come to a similar one that I would have come to, except
that I would scratch off the solder mask, around the large hole and attach
the shield at several points around it.

That sounds good to me. I'll give it a try when I get an antenna figured
out.
That part I suggested I would remove, I don't know what it is,
it measures 0 ohms in circuit.

It may just be a jumper to connect the antenna after board
testing with equipment connected to the large hole. Or it
may be a capacitor or inductor. The far side is shorted to
ground through the antenna structure, and the upstream side
may also have an inductor or other low resistance path to
ground, in parallel with your resistance measurement.

I agree that you should remove it, but save it, in case your
antenna doesn't work well.

amdx wrote:

"Joerg" wrote in message
...

amdx wrote:


I'd like to install a higher gain antenna to this wifi adapter.
I'm looking for advice on the proper place to attach a 50 ohm
antenna ( or coax ).

Can you make out which chip they used and find the datasheet? Often they
have an LC matching network and the L can be some piece of trace. The
datasheets are usually quite elaborate on how to connect variuous loads.

--
Regards, Joerg


Thanks Jorge,
The chip is covered by a shield and even if the data sheet said put a 1nh
inductor
in series, I'd have to say that's smaller than anything I can plan for.
I'm just hoping to connect a higher gain antenna. The board kind of looks
like
they had thoughts about a coax connection.


Yes, but many of those chips are not made to drive 50ohms without a
matching network. The ones I had dealt with a long time ago had
complementary outputs of 100ohms each. So you were allowed to attached a
symmetrical antenna directly (as long as EMC rules were followed) but
for 50ohm connections these two outputs had to be combined and that
required a 180 degree phase turner for oneof them. I don't remember what
the datasheet said about frying an output over the long run if loaded
with 50ohms but there might have been a warning. IOW there is a chance
of it all working just fine for a few weeks and then bzzzt ... poof.

--
Regards, Joerg

http://www.analogconsultants.com

"John Popelish" wrote in message
. ..
amdx wrote:
"John Popelish" wrote in message
...
amdx wrote:
I'd like to install a higher gain antenna to this wifi adapter.
I'm looking for advice on the proper place to attach a 50 ohm
antenna ( or coax ).
I think you have come to a similar one that I would have come to, except
that I would scratch off the solder mask, around the large hole and
attach the shield at several points around it.

That sounds good to me. I'll give it a try when I get an antenna figured
out.
That part I suggested I would remove, I don't know what it is,
it measures 0 ohms in circuit.

It may just be a jumper to connect the antenna after board testing with
equipment connected to the large hole. Or it may be a capacitor or
inductor. The far side is shorted to ground through the antenna
structure, and the upstream side may also have an inductor or other low
resistance path to ground, in parallel with your resistance measurement.

I agree that you should remove it, but save it, in case your antenna
doesn't work well.

Well, I removed it, it's tiny maybe .05" x .03". I carefully opened
a small container, tipped my hand and the part disappeared somewhere on
the bench. Ok, so that just means the new antenna has to work :-).
I proceeded to connect this gigantic RG58 to the pcb. The late night
preliminary tests show dramatic improvement over the horn antenna
that was my first attempt. See comparision numbers below.
Horn antenna signal strength -72dbm to -74dbm
Biquad antenna signal strength -50dbm to -52dbm
That's a major improvement, a quick check of the neighboehood
signals showed higher levels and two new signals I haven't seen before.
I'll test it in it's final position today, but it sure looks good.

Notes; On the Horn antenna I cut a slot a 1/4 wavelength form the closed
end
and inserted the wifi adapter ( dongle). this was about an 8 db signal
improvement.
For the biquad I disconnected the internal antenna and connected a 6" coax
that went to the antenna. I built the antenna pretty much following this
site.
http://martybugs.net/wireless/biquad/
I used 1/4" copper tube, removed the jacket the length of the copper tube
and tinned the shield for a tight fit in the tube.
Mike