Any thoughts on how to best shield u.fl connectors on NICs?
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
Signature · 2 lines
Ben Greear <[email protected]> Candela Technologies Inc http://www.candelatech.com
Quoted 10 lines · Ben Greear
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.
Quoted 7 lines
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,
Quoted 10 lines · Ben Greear
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.
Quoted 3 lines
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,
Signature · 5 lines
Julian Calaby Email: [email protected] Profile: http://www.google.com/profiles/julian.calaby/ .Plan: http://sites.google.com/site/juliancalaby/
Quoted 17 lines · Julian Calaby
Hi Ben,
Quoted 10 lines · Ben Greear
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.Quoted 3 lines
I am curious if anyone has any suggestions or experience with connecting u.fl NICs to
SMA cables in a highly shielded manner...
Quoted 7 lines
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
Quoted 3 lines
Thanks,
Signature · 2 lines
Ben Greear <[email protected]> Candela Technologies Inc http://www.candelatech.com
Hi Ben,
Quoted 37 lines · Ben Greear
Quoted 23 lines · Julian Calaby
Hi Ben,
Quoted 13 lines · Ben Greear
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.Quoted 3 lines
I am curious if anyone has any suggestions or experience with connecting u.fl NICs to
SMA cables in a highly shielded manner...Quoted 7 lines
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...
Quoted 5 lines
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:
I was expecting you to end up ripping the u.fl connectors off the NICs and replacing them with something better shielded.
Quoted 3 lines
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/
Quoted 8 lines · Julian Calaby
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
Quoted 11 lines · Adrian Chadd
Quoted 8 lines · Julian Calaby
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.
Quoted 1 line
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.
Quoted 2 lines
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
Signature · 2 lines
Ben Greear <[email protected]> Candela Technologies Inc http://www.candelatech.com
Hi Ben,
Quoted 9 lines · Ben Greear
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).
Quoted 6 lines
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,
Signature · 5 lines
Julian Calaby Email: [email protected] Profile: http://www.google.com/profiles/julian.calaby/ .Plan: http://sites.google.com/site/juliancalaby/
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
2012/10/29 Ben Greear <[email protected]>:
Quoted 17 lines
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
Quoted 8 lines
--
Ben Greear <[email protected]>
Candela Technologies Inc http://www.candelatech.com--
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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 ;-)
Signature · 3 lines
GPG ID: 0xEE878588 As you read this post global entropy rises. Have Fun ;-) Nick