It appears hard to get well-shielded u.fl (IPEX) to SMA pigtails, and all of the
modern ath9k NICs I've seen use u.fl connectors on the NIC.
I have found a vendor that will do double-shielded 1.32mm cable, and I have some of those
on order, but the way u.fl connectors are made it seems there is always a bit of un-shielded
cable where the connector is crimped onto the cable.
I am curious if anyone has any suggestions or experience with connecting u.fl NICs to
SMA cables in a highly shielded manner...
Thanks,
Ben
--
Ben Greear <[email protected]>
Candela Technologies Inc http://www.candelatech.com
Well, we have metal shield boxes to put cards and APs in, with
extender PCI/cardbus/ and PCIe/expresscard holes as needed.
I don't know who makes them but I'm sure they're out there.
You can then cable up boxes to other boxes, via attenuators and
splitters/mixers/etc.
Adrian
On 10/30/2012 10:16 PM, Adrian Chadd wrote:
> On 30 October 2012 16:45, Julian Calaby <[email protected]> wrote:
>
>> That's a good point, all the NICs I've looked at closely (e.g. the
>> rt2500usb cards on my desk at the moment) have an antenna or u.fl
>> connector with some passive components around it and usually the
>> antenna trace runs exposed on the board for a couple of millimetres
>> before it disappears under the shielding around the RF chip. I'll
>> check my collection at home tonight, but I'm pretty sure that all the
>> PCI cards have a couple of cm of exposed antenna trace between the SMA
>> connector and the RF shield.
>
> I've even seen ${COMMERCIAL} kit do this internally.
From what I can tell, the WPEA-127n has a 1cm or so unshielded
run from the u.fl mounts to the RF chip logic. I'm guessing this
acts as a mini-antenna, and maybe it was done that way on purpose,
but it's all guessing at this point.
>
> Ben, what are you worried about in particular?
Two things come to mind:
First, I'd like to put 2+ NICs close together in the same chassis.
Would be nice if they were as isolated from each other as possible
so that each NIC could work independently of the other (once I can
get to SMA connectors, there are > 90db shielded cable options,
but of course it could just go to antenna where it all mixes again
anyway).
Second: If one wants to use an attenuator and coax cables to connect
AP and Station systems together, the AP and Station need to NOT also
be transmitting through the air. Anything I can do to keep that
over-the-air communication minimal should help.
Truth is, I'm not sure how much it really matters, but after a few weeks
of poking at cabling and such, I've gotten kind of curious :)
Thanks,
Ben
--
Ben Greear <[email protected]>
Candela Technologies Inc http://www.candelatech.com
On 10/30/2012 03:22 PM, Julian Calaby wrote:
> Hi Ben,
>
> On Tue, Oct 30, 2012 at 4:06 AM, Ben Greear <[email protected]> wrote:
>> It appears hard to get well-shielded u.fl (IPEX) to SMA pigtails, and all of
>> the
>> modern ath9k NICs I've seen use u.fl connectors on the NIC.
>>
>> I have found a vendor that will do double-shielded 1.32mm cable, and I have
>> some of those
>> on order, but the way u.fl connectors are made it seems there is always a
>> bit of un-shielded
>> cable where the connector is crimped onto the cable.
>>
>> I am curious if anyone has any suggestions or experience with connecting
>> u.fl NICs to
>> SMA cables in a highly shielded manner...
>
> I have an awful feeling that it's simply not going to happen - I would
> guess from what you've described that the u.fl connector is designed
> to be cheap, small and easy and not really designed for "real" work
> like what you're doing with it. I'm guessing that the signal leakage
> through the connector is probably not a problem for the manufacturers
> as they're always shielded inside a computer case - i.e. it complies
> with the FCC rules.
I think it must be able to leak quite a bit before the FCC cares... Standard
single-shielded pigtails are quite noisy, nevermind the connectors...
But anyway...I was thinking something like this (but with different
gender u.fl side) and some sort of physical attachment option to keep
it on the NIC might be interesting:
http://www.pimfg.com/Product-Detail/000-SMA-UFL
For all I know, the NIC itself may leak worse than the u.fl pigtail connector,
however...
Thanks,
Ben
>
> Thanks,
>
--
Ben Greear <[email protected]>
Candela Technologies Inc http://www.candelatech.com
On 10/29/2012 10:06 AM, Ben Greear wrote:
> It appears hard to get well-shielded u.fl (IPEX) to SMA pigtails, and
> all of the
> modern ath9k NICs I've seen use u.fl connectors on the NIC.
>
> I have found a vendor that will do double-shielded 1.32mm cable, and I
> have some of those
> on order, but the way u.fl connectors are made it seems there is always
> a bit of un-shielded
> cable where the connector is crimped onto the cable.
>
> I am curious if anyone has any suggestions or experience with connecting
> u.fl NICs to
> SMA cables in a highly shielded manner...
>
> Thanks,
> Ben
>
If you find a solution for this I would be interested in hearing as well.
Thanks.
Hi Ben,
On Wed, Oct 31, 2012 at 4:28 PM, Ben Greear <[email protected]> wrote:
> Two things come to mind:
>
> First, I'd like to put 2+ NICs close together in the same chassis.
> Would be nice if they were as isolated from each other as possible
> so that each NIC could work independently of the other (once I can
> get to SMA connectors, there are > 90db shielded cable options,
> but of course it could just go to antenna where it all mixes again
> anyway).
>
> Second: If one wants to use an attenuator and coax cables to connect
> AP and Station systems together, the AP and Station need to NOT also
> be transmitting through the air. Anything I can do to keep that
> over-the-air communication minimal should help.
>
> Truth is, I'm not sure how much it really matters, but after a few weeks
To be quite honest, if I were doing this, I'd be making a custom
chassis that had shielded partitions to house the NICs and probably
use something like this to get signal to the NICs:
https://encrypted.google.com/search?q=pcie+extension+cable
But this would be getting towards the construction of some serious
test equipment.
What are you trying to achieve here?
Thanks,
--
Julian Calaby
Email: [email protected]
Profile: http://www.google.com/profiles/julian.calaby/
.Plan: http://sites.google.com/site/juliancalaby/
Hi Ben,
On Tue, Oct 30, 2012 at 4:06 AM, Ben Greear <[email protected]> wrote:
> It appears hard to get well-shielded u.fl (IPEX) to SMA pigtails, and all of
> the
> modern ath9k NICs I've seen use u.fl connectors on the NIC.
>
> I have found a vendor that will do double-shielded 1.32mm cable, and I have
> some of those
> on order, but the way u.fl connectors are made it seems there is always a
> bit of un-shielded
> cable where the connector is crimped onto the cable.
>
> I am curious if anyone has any suggestions or experience with connecting
> u.fl NICs to
> SMA cables in a highly shielded manner...
I have an awful feeling that it's simply not going to happen - I would
guess from what you've described that the u.fl connector is designed
to be cheap, small and easy and not really designed for "real" work
like what you're doing with it. I'm guessing that the signal leakage
through the connector is probably not a problem for the manufacturers
as they're always shielded inside a computer case - i.e. it complies
with the FCC rules.
Thanks,
--
Julian Calaby
Email: [email protected]
Profile: http://www.google.com/profiles/julian.calaby/
.Plan: http://sites.google.com/site/juliancalaby/
On 30 October 2012 16:45, Julian Calaby <[email protected]> wrote:
> That's a good point, all the NICs I've looked at closely (e.g. the
> rt2500usb cards on my desk at the moment) have an antenna or u.fl
> connector with some passive components around it and usually the
> antenna trace runs exposed on the board for a couple of millimetres
> before it disappears under the shielding around the RF chip. I'll
> check my collection at home tonight, but I'm pretty sure that all the
> PCI cards have a couple of cm of exposed antenna trace between the SMA
> connector and the RF shield.
I've even seen ${COMMERCIAL} kit do this internally.
Ben, what are you worried about in particular?
Adrian
Hi Ben,
On Wed, Oct 31, 2012 at 9:34 AM, Ben Greear <[email protected]> wrote:
> On 10/30/2012 03:22 PM, Julian Calaby wrote:
>>
>> Hi Ben,
>>
>> On Tue, Oct 30, 2012 at 4:06 AM, Ben Greear <[email protected]>
>> wrote:
>>>
>>> It appears hard to get well-shielded u.fl (IPEX) to SMA pigtails, and all
>>> of
>>> the
>>> modern ath9k NICs I've seen use u.fl connectors on the NIC.
>>>
>>> I have found a vendor that will do double-shielded 1.32mm cable, and I
>>> have
>>> some of those
>>> on order, but the way u.fl connectors are made it seems there is always a
>>> bit of un-shielded
>>> cable where the connector is crimped onto the cable.
>>>
>>> I am curious if anyone has any suggestions or experience with connecting
>>> u.fl NICs to
>>> SMA cables in a highly shielded manner...
>>
>>
>> I have an awful feeling that it's simply not going to happen - I would
>> guess from what you've described that the u.fl connector is designed
>> to be cheap, small and easy and not really designed for "real" work
>> like what you're doing with it. I'm guessing that the signal leakage
>> through the connector is probably not a problem for the manufacturers
>> as they're always shielded inside a computer case - i.e. it complies
>> with the FCC rules.
>
>
> I think it must be able to leak quite a bit before the FCC cares...
> Standard
> single-shielded pigtails are quite noisy, nevermind the connectors...
>
> But anyway...I was thinking something like this (but with different
> gender u.fl side) and some sort of physical attachment option to keep
> it on the NIC might be interesting:
>
> http://www.pimfg.com/Product-Detail/000-SMA-UFL
I was expecting you to end up ripping the u.fl connectors off the NICs
and replacing them with something better shielded.
> For all I know, the NIC itself may leak worse than the u.fl pigtail
> connector,
> however...
That's a good point, all the NICs I've looked at closely (e.g. the
rt2500usb cards on my desk at the moment) have an antenna or u.fl
connector with some passive components around it and usually the
antenna trace runs exposed on the board for a couple of millimetres
before it disappears under the shielding around the RF chip. I'll
check my collection at home tonight, but I'm pretty sure that all the
PCI cards have a couple of cm of exposed antenna trace between the SMA
connector and the RF shield.
Thanks,
--
Julian Calaby
Email: [email protected]
Profile: http://www.google.com/profiles/julian.calaby/
.Plan: http://sites.google.com/site/juliancalaby/
2012/10/29 Ben Greear <[email protected]>:
> It appears hard to get well-shielded u.fl (IPEX) to SMA pigtails, and all of
> the
> modern ath9k NICs I've seen use u.fl connectors on the NIC.
>
> I have found a vendor that will do double-shielded 1.32mm cable, and I have
> some of those
> on order, but the way u.fl connectors are made it seems there is always a
> bit of un-shielded
> cable where the connector is crimped onto the cable.
>
> I am curious if anyone has any suggestions or experience with connecting
> u.fl NICs to
> SMA cables in a highly shielded manner...
>
> Thanks,
> Ben
>
> --
> Ben Greear <[email protected]>
> Candela Technologies Inc http://www.candelatech.com
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-wireless" in
> the body of a message to [email protected]
> More majordomo info at http://vger.kernel.org/majordomo-info.html
Hello Ben ;-)
I've used a setup like this on the lab I work at to do some mac/phy
experiments and spectrum analyzer measurements on ath5k cards
card -> ufl-sma pigtail -> sma -> rf cable -> nmale -> attenuator <-
nmale <- rf cable <- sma <- pigtail <- card
This was done on 2 pair of cards for both tx and rx antenas (using the
debug mode on ath5k that does tx on one antenna and rx on the other
one). Then the attenuator of the tx path of link a was connected
together with the attenuator of the rx path of link b. The idea was to
mix one link's rx path with the other link's tx path to see at what
channel distance we could get the cards to sense non-idle channel and
cause one of the two links to lose packets etc.
If you maintain a sane channel distance (more than 2 channels) you
won't have any problems, if you want to transmit closer or even on the
same channel then no matter what you do you'll always have some
interference, even the angle of the ufl connector matters. I suggest
you go for mmcx connectors and pcmcia cards (that are fully shielded)
and even there there is still leakage at some point (you can measure
it with a spectrum analyzer) that might affect your measurements. It
worked for us (here is a related paper btw
http://www.eu-mesh.eu/files/publications/RWS2008.pdf)
The closer you can get to a "shielded" approach with a mini-pci card
is a card with mmcx connectors and shielding around them like this one
http://www.ubnt.com/sr7115
Then use high quality mmcx pigtails and cables (e.g. check out
http://www.fab-corp.com/) and keep them to some distance from each
other and "stacked" (see photos below).
If you have multiple cards on the same box and want a highly shielded
environment you also have to worry about IF leakage and you can't get
rid of this one by maintaining channel distance. Most of the
mini-pci(-e) cards should have shielding around the RF chip but only
from one side of the card, leaving the back side exposed. Wraping them
with foil etc will result heat problems and increased thermal noise so
it's not an option. Again I suggest you go with pcmcia cards or
expresscards.
As for the antenna trace from the chip to the ufl port if it's length
is not a multiple of the half-wavelength of the channel you are at you
don't need to worry much about it.
Finaly I suggest you go for 5Ghz, not only because there are few APs
out there that operate on 5Ghz but also because of the band's
propagation properties etc.
Now does it all matter ?
In my opinion unless you want to do some highly acurate lab
measurements for academic usage, it doesn't. In practice even on
highly congested environments you can get your links to work just fine
if you design them propertly, you don't have to go extreme on
shielding. Here are a few examles of some of our outdoor setups on
awmn (all on 5Ghz)...
Example 1:
3 mini-pci cards very close together
http://info.awmn.net/album.php?albumid=68&attachmentid=29795
and another 3 (and many more :P)
http://info.awmn.net/album.php?albumid=68&attachmentid=29812
on this rooftop
http://info.awmn.net/album.php?albumid=68&attachmentid=29802
Example 2 (this one is one of our "stable" bases):
Again 3 cards very close together
http://info.awmn.net/album.php?albumid=37&attachmentid=25537
on a tower mast on top of mount Parnitha, together with cell phone
towers and tv broadcast antennas (some of them are actually very close
to our IF btw)
http://info.awmn.net/album.php?albumid=37&attachmentid=25415
that goes like this in the winter :P
http://info.awmn.net/album.php?albumid=22&attachmentid=24869
In my experience you should focus on these factors for start:
a) Your antenna (you might notice we use handmade antennas using
offset dishes or dish antennas to reduce front-to-back ratio, very few
grid antennas, mostly used for backup 2.4 links)
b) Minimize rf cable length (you 'll notice that most boxes are
mounted right behind the antenna, that's because you 'll get more
interference from the rf cables than your pigtails and the dielectric
inside the cables is more vulnerable to moisture etc)
c) Channel and band selection (go for 5Ghz, use non overlaping
channels and in case of too-many antennas like the first example,
chose carefuly which box will operate on which channel, maintain a
distance between them and make sure the antennas look on oposite
directions).
d) Make sure your cards are not back to back since the back sides are
not shielded (you'll notice they are "stacked").
Good luck and have fun ;-)
--
GPG ID: 0xEE878588
As you read this post global entropy rises. Have Fun ;-)
Nick