wrt54 antennas
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Posted by on July 22, 2008, 2:41 pm
Please log in for more thread options WRT54 wireless routers. I had heard that one is for TX and the other for RX but my router seems to work equally well with either antenna disconnected. I cant tell a difference in performance unless I take them both off. Jimmie | |||||||||||||||||||||||||||||||
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Posted by Jeff Liebermann on July 22, 2008, 3:53 pm
Please log in for more thread options No. The antennas area identical. However, the two ports are slightly different. One is designated as "main" while the other is "aux". The router will normally favor the "main" antenna and only switch to the "aux" if the diversity receive algorithm determins that the "aux" antenna has a better signal. Unfortunately, I can't recall which is antenna is main or aux, or for that matter, which antenna is considered "left" or "right". Sigh. Looking at the inside photos at: <http://www.linksysinfo.org/forums/showthread.php?t=47124>
I would *GUESS*(tm) that the antenna port with the long coax cable
running across the board would be the "aux". >I had heard that one is for TX and the other
>for RX but my router seems to work equally well with either antenna >disconnected. I cant tell a difference in performance unless I take >them both off. Some routers will only transmit on one antenna (i.e 2-wire). Routers that have two antennas invariably use diversity receive and sorta "scan" between the two antennas in receive. I vaguely recall that the WRT54 transmits on the same antenna that it receives. However, you should be able to tell the difference with only one antenna attached. If you remove the antenna from the "main" port, the stupid firmware will continue to favor the "main" port, even though there's no antenna or signal. If you ping the router, you'll probably find that the first ping will be lost using just the "aux" antenna. That's not the case using only the main antenna. If you insist on using only one antennna (a good idea if you're attaching external antennas), some alternative firmwares have a means of disarming the diversity switch system and just using one antenna. Start reading here: <http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a008019f646.shtml>
especially the part about the golf course and using two different
types of antennas. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 | |||||||||||||||||||||||||||||||
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Posted by on July 22, 2008, 6:27 pm
Please log in for more thread options > On Tue, 22 Jul 2008 11:41:51 -0700 (PDT), jimmi...@gmail.com wrote:
> >IS there a distinction between the two antenna connectiond on the
> >WRT54 wireless routers. >
y
> No. =A0The antennas area identical. =A0However, the two ports are slightl= > different. =A0One is designated as "main" while the other is "aux". =A0Th=
e
> router will normally favor the "main" antenna and only switch to the
> "aux" if the diversity receive algorithm determins that the "aux" > antenna has a better signal. > > Unfortunately, I can't recall which is antenna is main or aux, or for > that matter, which antenna is considered "left" or "right". =A0Sigh. > Looking at the inside photos at: > <http://www.linksysinfo.org/forums/showthread.php?t=3D47124> > I would *GUESS*(tm) that the antenna port with the long coax cable > running across the board would be the "aux". > > >I had heard that one is for TX and the other
> >for RX but my router seems to work equally well with either antenna > >disconnected. I cant tell a difference in performance unless I take > >them both off. >
> Some routers will only transmit on one antenna (i.e 2-wire). =A0Routers > that have two antennas invariably use diversity receive and sorta > "scan" between the two antennas in receive. =A0I vaguely recall that the > WRT54 transmits on the same antenna that it receives. > > However, you should be able to tell the difference with only one > antenna attached. =A0If you remove the antenna from the "main" port, the > stupid firmware will continue to favor the "main" port, even though > there's no antenna or signal. =A0If you ping the router, you'll probably > find that the first ping will be lost using just the "aux" antenna. > That's not the case using only the main antenna. > > If you insist on using only one antennna (a good idea if you're > attaching external antennas), some alternative firmwares have a means > of disarming the diversity switch system and just using one antenna. > > Start reading here: > <http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note091...= > > especially the part about the golf course and using two different > types of antennas. > > -- > Jeff Liebermann =A0 =A0 je...@cruzio.com > 150 Felker St #D =A0 =A0http://www.LearnByDestroying.com > Santa Cruz CA 95060http://802.11junk.com > Skype: JeffLiebermann =A0 =A0 AE6KS =A0 =A0831-336-2558 Thanks Jeff, I am guessing that the traces on the board may form a type of diplexer. If this is the case leaving one antenna disconnected and the port unterminated would defeat the operation of the diplexer. In this case one antenna connected to one port would work as well as connecting it to the other. This would explain my experience of having the unit work equally well with 1 antenna on either port. Having 1 or 2 antennas woud probably make little difference if ther is not a multipath issue Jimmie.. | |||||||||||||||||||||||||||||||
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Posted by Jeff Liebermann on July 23, 2008, 12:58 am
Please log in for more thread options On Tue, 22 Jul 2008 15:27:51 -0700 (PDT), jimmie68@gmail.com wrote:
>Thanks Jeff, I am guessing that the traces on the board may form a
>type of diplexer. Nope. It's a diversity switch. If you look carefully, there's a 6 lead chip sitting at the junction of the two i/o ports. The chip does the switching. >If this is the case leaving one antenna disconnected
>and the port unterminated would defeat the operation of the diplexer. >In this case one antenna connected to one port would work as well as >connecting it to the other. Not exactly. The port with the long coax cable (aux) has a bit of extra loss in the cable and exhibits perhaps 0.5dB more loss. Not worth worrying about unless you're trying to squeeze every last dB out of the system. >This would explain my experience of having
>the unit work equally well with 1 antenna on either port. Having 1 or >2 antennas woud probably make little difference if ther is not a >multipath issue Read the Cisco article. The problem is when you have two different types of antennas. It's quite possible that the wrong antenna will hear the signal first. The diversity algorithm doesn't continuously test for the best signal. If it hears something on the FIRST antenna that hears a signal, it could easily just sit there forever. The only justification for switching antennas is if there is a signal loss, or a rather high bit error rate. If you're planning to use just one antenna, you should disable the diversity switch in firmware. -- Jeff Liebermann jeffl@cruzio.com 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 | |||||||||||||||||||||||||||||||
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Posted by on July 26, 2008, 2:02 pm
Please log in for more thread options > On Tue, 22 Jul 2008 15:27:51 -0700 (PDT), jimmi...@gmail.com wrote:
> >Thanks Jeff, I am guessing that the traces on the board may form a
> >type of diplexer. >
> Nope. =A0It's a diversity switch. =A0If you look carefully, there's a 6 > lead chip sitting at the junction of the two i/o ports. =A0The chip does > the switching. > > >If this is the case leaving one antenna disconnected
> >and the port unterminated would defeat the operation of the diplexer. > >In this case one =A0antenna connected to one port would work as well as > >connecting it to the other. >
> Not exactly. =A0The port with the long coax cable (aux) has a bit of > extra loss in the cable and exhibits perhaps 0.5dB more loss. =A0Not > worth worrying about unless you're trying to squeeze every last dB out > of the system. > > >This would explain my experience of having
> >the unit work equally well with 1 antenna on either port. Having 1 or > >2 antennas woud probably make little difference if ther is not a > >multipath issue >
> Read the Cisco article. =A0The problem is when you have two different > types of antennas. =A0It's quite possible that the wrong antenna will > hear the signal first. =A0The diversity algorithm doesn't continuously > test for the best signal. =A0If it hears something on the FIRST antenna > that hears a signal, it could easily just sit there forever. =A0The only > justification for switching antennas is if there is a signal loss, or > a rather high bit error rate. =A0If you're planning to use just one > antenna, you should disable the diversity switch in firmware. > > -- > Jeff Liebermann =A0 =A0 je...@cruzio.com > 150 Felker St #D =A0 =A0http://www.LearnByDestroying.com > Santa Cruz CA 95060http://802.11junk.com > Skype: JeffLiebermann =A0 =A0 AE6KS =A0 =A0831-336-2558 Interesing, this has got me wondering how hard it would be to alter the software to use the the switch as a T/R switch. My thought is to use one antenna for Rx with an antenna mounted LNA. I think I need to check in with the guys over at DD-WRT. Jimmie | |||||||||||||||||||||||||||||||
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>WRT54 wireless routers.