Homebrew wifi antenna coax adapters
 

For some strange reason, wifi connectors are not compatible with normal
SMA coax connectors. The center pin is a male in an otherwise female
connector. And visa versa.

But you probably have accumulated a few wifi "rubber duck" antennas.
Inside the plastic "duck" is just some thin teflon coax cable and a
dipole antenna with a 1/4 wave shroud around the coax and 1/4 wave
exposed center conductor. It's easy to separate the plastic duck off
the antenna, just bend it at the joint just above the elbow and it
should just pop off. Being teflon, you don't have to worry about
melting it with the soldering iron. This coax looks to be 50 ohm
impedance. Get a BNC connector and attach it like you would to coax of
this thin type. To deal with the extra thin coax, I used a small
solderable metal washer to give the shield clamping connector pieces
(the funny looking washers) something to grab when you tighten the
threaded on the outside bushing you tighten into the connector. As the
connectors I had were meant for fatter coax. Don't forget to place the
washers and such on the coax before you solder the washer to the coax
shield.

As a test, I inserted two such adapters into the feedline for my wifi
antenna, and looked at the wifi utility software window that reports
signal strength, and saw no desernable extra signal loss (less than a
dB). (I scrapped out a bad wifi booster module to get its reverse SMA
connectors to get the mate for the antenna side connector)

Once you have built this adapter, you can then use regular good quality
coax cable with BNC connectors (or N or other connector good for
microwave work) to connect a homebrew wifi antenna to the wifi computer
card. There's also a ham band that shares part of the wifi band, so we
could conceivably run high gain high power ham to ham using wifi based
equipment.

Homebrew wifi antenna coax adapters
 

In article .net,
robert casey wrote:

For some strange reason, wifi connectors are not compatible with normal
SMA coax connectors. The center pin is a male in an otherwise female
connector. And visa versa.

The "strange" reason is that the FCC requires it.

Part 15 devices, such as 802.11 cards, are supposed to be tested for
compliance and certificated by their manufacturer as a system (radio
and antenna together). Replacing the manufacturer-tested antenna with
a different one (higher gain, or perhaps different impedance) changes
the system's behavior, in a way which means that the tests done by the
manufacturer for Part 15 certification are no longer valid.

The FCC's position is that making such un-tested changes automatically
voids the Part 15 certification of the device, and it's no longer
technically legal to transmit using the modified device.

In order to (try to) deter people from making such arbitrary changes,
the FCC requires that makers of Part 15 radio cards with detachable
antennas use only connectors which are either proprietary, or are "not
generally available". Most manufacturers seem to have settled on
RP-SMA or RP-TNC connector for this purpose.

I've only heard of a very small number of cases (fingers-of-one-hand)
in which the FCC has cited someone for running non-certificated WiFi
equipment... and in the only case I can remember clearly, a
non-certificated amplifier was being used to push about 5 watts out
through an omnidirectional antenna, which is rather more than the
FCC's Part 15 ERP rules for WiFi will allow.

In practice, people using simple, commercially-provided "gain"
antennas with their commercial access points are probably safe
(especially if they buy the AP and antenna from the same vendor, as a
package which has been tested as a system). If you're concerned about
the potential legal risks, though, consult with a knowledgeable lawyer
(I'm not one).

There's also a ham band that shares part of the wifi band, so we
could conceivably run high gain high power ham to ham using wifi based
equipment.

This does seem to be legal, as long as you're licensed, limit your
hopped-up transmissions to the small part of the WiFi band which
intersects the ham 13 cm band, and honor the ham-radio usage rules in
re ID'ing properly, no encryption for the purpose of concealing or
obscuring the transmission (which probably means no SSL), and no use
for purposes in which you have a significant financial interest.

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Homebrew wifi antenna coax adapters
 

"robert casey" wrote in message
link.net...
For some strange reason, wifi connectors are not compatible with normal
SMA coax connectors. The center pin is a male in an otherwise female
connector. And visa versa.

... Being teflon, you don't have to worry about melting it with the
soldering iron. ...

Just be careful when working with teflon. NASA rules require that thermal
stripping of teflon wire be done in a hood because the fumes are poisonous.

73,
Bob AD3K

Homebrew wifi antenna coax adapters
 

"robert casey" wrote in message
link.net...
For some strange reason, wifi connectors are not compatible with normal
SMA coax connectors. The center pin is a male in an otherwise female
connector. And visa versa.

But you probably have accumulated a few wifi "rubber duck" antennas.
Inside the plastic "duck" is just some thin teflon coax cable and a dipole
antenna with a 1/4 wave shroud around the coax and 1/4 wave exposed center
conductor. It's easy to separate the plastic duck off the antenna, just
bend it at the joint just above the elbow and it should just pop off.
Being teflon, you don't have to worry about melting it with the soldering
iron. This coax looks to be 50 ohm impedance. Get a BNC connector and
attach it like you would to coax of this thin type. To deal with the
extra thin coax, I used a small solderable metal washer to give the shield
clamping connector pieces (the funny looking washers) something to grab
when you tighten the threaded on the outside bushing you tighten into the
connector. As the connectors I had were meant for fatter coax. Don't
forget to place the washers and such on the coax before you solder the
washer to the coax shield.

As a test, I inserted two such adapters into the feedline for my wifi
antenna, and looked at the wifi utility software window that reports
signal strength, and saw no desernable extra signal loss (less than a dB).
(I scrapped out a bad wifi booster module to get its reverse SMA
connectors to get the mate for the antenna side connector)

Once you have built this adapter, you can then use regular good quality
coax cable with BNC connectors (or N or other connector good for microwave
work) to connect a homebrew wifi antenna to the wifi computer card.
There's also a ham band that shares part of the wifi band, so we could
conceivably run high gain high power ham to ham using wifi based
equipment.

Hi Robert

I'd like to know more about how well your extended range WiFi performs.
What type of antenna seems to be the most effective?
Why did you decide to not use a reverse SMA adapter like ShowMeCables
sells for about $5.00?
How do you measure "signal loss" to within a dB?

Jerry

Homebrew wifi antenna coax adapters
 

On Thu, 02 Aug 2007 10:58:32 -0400, Bob Spooner wrote:

Just be careful when working with teflon. NASA rules require that
thermal stripping of teflon wire be done in a hood because the fumes are
poisonous.

Watermellons are dangerous too. If you feed one to a lab rat too
quickly, it will explode! So be extra careful when eating watermellons.

The average Joe_User, thermally stripping teflon coax at his work bench,
is not in any more danger than he is when breathing the solder fumes and
flux smoke of any other job. If it were his 9to5 job, that would be a
completely different story...

--Teh

Homebrew wifi antenna coax adapters
 

I'd like to know more about how well your extended range WiFi performs.
What type of antenna seems to be the most effective?
Why did you decide to not use a reverse SMA adapter like ShowMeCables
sells for about $5.00?
How do you measure "signal loss" to within a dB?

I'm taking the word of the wifi utility program, which appears to be
reasonably believable. Didn't know about ShowMeCables.

Homebrew wifi antenna coax adapters
 

non-certificated amplifier was being used to push about 5 watts out
through an omnidirectional antenna, which is rather more than the
FCC's Part 15 ERP rules for WiFi will allow.

That's like a 2m repeater being an alligator, unless that setup had a
good preamp on receive.

In practice, people using simple, commercially-provided "gain"
antennas with their commercial access points are probably safe
(especially if they buy the AP and antenna from the same vendor, as a
package which has been tested as a system).

That's basically what I have, except I needed a longer coax cable
between the wifi board in the computer to the directional antenna from
Hawking. And nobody around here sells the damm extension cables
anymore. But that won't stop a ham....

There's also a ham band that shares part of the wifi band, so we
could conceivably run high gain high power ham to ham using wifi based
equipment.


This does seem to be legal, as long as you're licensed, limit your
hopped-up transmissions to the small part of the WiFi band which
intersects the ham 13 cm band, and honor the ham-radio usage rules in
re ID'ing properly, no encryption for the purpose of concealing or
obscuring the transmission (which probably means no SSL), and no use
for purposes in which you have a significant financial interest.

I haven't checked, but if you have all security features disabled (WEP
and such) and name your computer wifi setup (peer to peer mode) with
your callsign, that might be all you need to do for ID, as wifi is a
widely recognized RF standard, like packet radio.

Also no pecuniary interest material, and no indecent material.

Homebrew wifi antenna coax adapters
 

"robert casey" wrote in message
link.net...


I'd like to know more about how well your extended range WiFi performs.
What type of antenna seems to be the most effective?
Why did you decide to not use a reverse SMA adapter like ShowMeCables
sells for about $5.00?
How do you measure "signal loss" to within a dB?

I'm taking the word of the wifi utility program, which appears to be
reasonably believable. Didn't know about ShowMeCables.

Hi Robert

I have been looking for "software" that provides read-out to show WiFi
signal strength. Can you tell me more about your "wifi utility program"?

I noticed that you intend to use a coax cable to connect the WiFi antenna
to the Computer. Would it be difficult for you to locate the Router or
access point at the antenna so the coax will be shorter?

Jerry

Homebrew wifi antenna coax adapters
 

I have been looking for "software" that provides read-out to show
WiFi signal strength. Can you tell me more about your "wifi utility
program"?


There's "Net Stumbler" that will give you a time/signal strength graph.
It's what the wifi card reports.
Did a google search,found it at
http://www.netstumbler.com/downloads/


I noticed that you intend to use a coax cable to connect the WiFi
antenna to the Computer. Would it be difficult for you to locate the
Router or access point at the antenna so the coax will be shorter?

That would actually be the better way to go, as there'd be less loss in
the coax. But I'd have to change a lot of things in the physical layout
of my shack...

Homebrew wifi antenna coax adapters
 

Tehrasha Darkon wrote:
On Thu, 02 Aug 2007 10:58:32 -0400, Bob Spooner wrote:

Just be careful when working with teflon. NASA rules require that
thermal stripping of teflon wire be done in a hood because the fumes are
poisonous.

Watermellons are dangerous too. If you feed one to a lab rat too
quickly, it will explode! So be extra careful when eating watermellons.


You might want to read this one:

http://www.mikeholt.com/documents/mo...EP2003MSDS.pdf


I'll take the watermelon over teflon fumes any day.


- 73 de Mike KB3EIA -

Homebrew wifi antenna coax adapters
 

Michael Coslo wrote:

You might want to read this one:

http://www.mikeholt.com/documents/mo...EP2003MSDS.pdf


I'll take the watermelon over teflon fumes any day.

Although not unheard of, FEP is less commonly found in cables than PTFE.
Do you have a link for the PTFE hazard sheet?

Both are Teflon, which is a DuPont trade name for a variety of related
materials.

Roy Lewallen, W7EL

Homebrew wifi antenna coax adapters
 

Roy Lewallen wrote in
:

Michael Coslo wrote:

You might want to read this one:

http://www.mikeholt.com/documents/mo...FEP2003MSDS.pd
f


I'll take the watermelon over teflon fumes any day.

Although not unheard of, FEP is less commonly found in cables than
PTFE. Do you have a link for the PTFE hazard sheet?

Both are Teflon, which is a DuPont trade name for a variety of related
materials.


http://msds.dupont.com/msds/pdfs/EN/...2f80006d37.pdf

for the Delrin PFTE. It looks like very similar effects. It is something
that this very stable chemical undergoes such a transformation when very
hot.

What bothered me a little bit was that this stuff is used in fireworks.

- 73 de Mike KB3EIA -

Homebrew wifi antenna coax adapters
 

Thanks for the additional link.

I had the problem of stripping some very fine PTFE insulated wire some
years ago, and had to search a bit to find a stripper to do it. It was
fairly expensive, and was a lot like a conventional wire stripper except
that the insulation was cut by means of a couple of blades which
momentarily heated to red hot temperature when they came together over
the wire. I'm sure I breathed some of the resulting fumes, with no ill
effects. I wonder how much exposure is necessary in order to produce the
symptoms listed in the hazard sheet.

In any case, I doubt that many amateurs use a thermal stripper for PTFE.
I do fairly routinely heat PTFE insulated semi-rigid coaxial cable to
around 350 C (700 F) when soldering it. That results in extrusion of
PTFE from the tube, but no obvious fumes. And so far none of the
symptoms listed in the hazard sheet.

I'd think that a Teflon coated frying pan could easily reach 300 - 400
C. What's the function of PTFE in fireworks?

Roy Lewallen, W7EL

Mike Coslo wrote:
Roy Lewallen wrote in
:

Michael Coslo wrote:
You might want to read this one:

http://www.mikeholt.com/documents/mo...FEP2003MSDS.pd
f


I'll take the watermelon over teflon fumes any day.
Although not unheard of, FEP is less commonly found in cables than
PTFE. Do you have a link for the PTFE hazard sheet?

Both are Teflon, which is a DuPont trade name for a variety of related
materials.


http://msds.dupont.com/msds/pdfs/EN/...2f80006d37.pdf

for the Delrin PFTE. It looks like very similar effects. It is something
that this very stable chemical undergoes such a transformation when very
hot.

What bothered me a little bit was that this stuff is used in fireworks.

- 73 de Mike KB3EIA -

Homebrew wifi antenna coax adapters
 

Roy Lewallen wrote in
:

Thanks for the additional link.

I had the problem of stripping some very fine PTFE insulated wire some
years ago, and had to search a bit to find a stripper to do it. It was
fairly expensive, and was a lot like a conventional wire stripper
except that the insulation was cut by means of a couple of blades
which momentarily heated to red hot temperature when they came
together over the wire. I'm sure I breathed some of the resulting
fumes, with no ill effects. I wonder how much exposure is necessary in
order to produce the symptoms listed in the hazard sheet.

In any case, I doubt that many amateurs use a thermal stripper for
PTFE.

I used to use a type that had jaws that clamped down on the wire from
the front, and after heating up you would just pull and the insulation
would come off. They were kind of nice because you just didn't nick a
wire ever with them.

I could even use a regular pair of strippers, although they would leave
a little nib of insulation that I had to trim off with a nippper.

While I suspect that the thermal strippers are probably safe, I have to
say that the fumes given off were pretty unpleasant.

I do fairly routinely heat PTFE insulated semi-rigid coaxial cable
to
around 350 C (700 F) when soldering it. That results in extrusion of
PTFE from the tube, but no obvious fumes. And so far none of the
symptoms listed in the hazard sheet.

400 C is the apparant magic temp. Below that it is pretty inert.


I'd think that a Teflon coated frying pan could easily reach 300 - 400
C.

There has been accounts of Teflon pans overheating and causing harm to
pet birds. I've looked at some of the evidence, and although some of the
people are kooks, I think that a badly overheated pan will release HF
gas.


What's the function of PTFE in fireworks?

It is used as an oxidizer.

Homebrew wifi antenna coax adapters
 

For some strange reason, wifi connectors are not compatible with normal
SMA coax connectors. The center pin is a male in an otherwise female
connector. And visa versa.

Reverse SMA connectors and thin coax are both available cheaply, why go to
the bother of destroying an antenna.

It is also possible to get the female pin from a line SMA socket to fit into
an SMA plug, if you have not a reverse SMA plug.

Jeff

Homebrew wifi antenna coax adapters
 

"Jerry Martes" wrote in
news:7dtsi.6380$2c6.1122@trnddc01:




Hi Robert

I have been looking for "software" that provides read-out
to show WiFi
signal strength. Can you tell me more about your "wifi
utility program"?
google 'network stumbler' , it's freeware or actually "BEG"-ware
but it works most the time.
I here there's a few WalMart craptastic USB dongles that will
not work with it but thats a rare synptom.