Chart fun: Blocky internal wifi antennae vs the Flat type

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doctor bloomquist · #1 Post by **doctor bloomquist** » Sun Aug 31, 2008 3:58 pm

Firstly thanks to all for the good advise upgrading my dad's T21 to internal wireless whilst keeping the LAN capability. All the bits arrived this weekend: Xircom PCMCIA flush fitting lan port, BG2200 card and antennas.

Unfortunately wires got crossed between myself and the Wifi card seller, who I used previously for my own T23's BG2200 card + antennas. Last time, I was sent chunky style antennas: great for the palm rest position but a very close call fitting the second in the LCD's ultraport cavity (using Ray's guide).

This time, I wanted 1 chunky antenna for the palmrest, and 1 of those flat ones for the ultraport.

Here's the chunky type http://tinyurl.com/6cl42h
And here's the flat type http://tinyurl.com/5ro8p5

Instead I was sent 2 of the flat type. In my ignorance, I ploughed on, and fit them in the same style as I did in the T23: 1 in the ultraport, 1 in the palmrest.

The signal is really *bad* compared to my T23. The antenna type is the only thing different between the two laptops.

Have a look at the Netstumbler charts, it's depressing viewing. Identical cards, drivers, settings (BG2200) same place on the desk, same antenna positioning, pretty much identical cases too.

T23's chart (2 chunky antennas)
http://img299.imageshack.us/my.php?imag ... aphal2.jpg

T21's chart (2 flat antennas)
http://img404.imageshack.us/my.php?imag ... apheh0.jpg

I'm going to send back the palmrest antenna for the chunky one I asked for in the first place, but my god what a waste of time and effort the flat antennas are. Don't touch them with a 10 foot pole!

sjthinkpader · #2 Post by **sjthinkpader** » Sun Aug 31, 2008 7:18 pm

Palm rest is not a good place for WiFi antennae. FCC rules require that antenna be placed at least 5 inches from your body.

I've place them on the top edge just to the side of the Ultraport in an A31. You should be able to place one on each side of the Ultraport in a T2x.

802.11n 3rd antenna

The 3rd green bar just above the yellow bar is signal strength from this antenna
Signal strength

Since T2x LCD cover has no metal lining, you can put them even behind the LCD.

#3 Post by **carbon_unit** » Sun Aug 31, 2008 7:58 pm

The T2x cover may not be made of metal but it blocks a lot of signal. That is why the T23's with wireless come with the "antenna windows" in them.

doctor bloomquist · #4 Post by **doctor bloomquist** » Sun Aug 31, 2008 8:13 pm

@ sjthinkpadder: I googled that FCC rule, and was only able to find the requirement of 5 centimetres or 2 inches, typo? The right edge of the palmrest is about 2 inches.

sjthinkpader · #5 Post by **sjthinkpader** » Sun Aug 31, 2008 9:39 pm

I am just going by recollection. In any case, palm rest area is not good for signal quality.

Signal pattern from a dipole antenna is in a donut shape. Best coupling is another dipole oriented the same. So if your access point antenna is pointed vertically, ideal client antenna orientation is also vertical. That is why one of the two antennae in the LCD cover is usually vertical.

On a new T61, there are antennae around all edges in the LCD cover, WiFi, Bluetooth, UWB, EVDO/HSDPA etc.

In A31 (also T23), the factory antennae are at the two vertical top edge. I added the 3rd antenna horizontally just right of the Ultraport on two machines.

In my T60 and T42, the factory antennae are at top horizontal left edge and vertical right edge near the top. I added the 3rd antennae about middle of the left vertical edge.

I have used the square rod shaped 2.4Ghz antennae from Hitachi Cable but only for BT cards.

ZAGNUT · #6 Post by **ZAGNUT** » Mon Sep 01, 2008 12:40 am

would i be correct in assuming that one side of that flat antenna is a ground plane? if so maybe you mounted one or both backwards?

dave

#7 Post by **RealBlackStuff** » Mon Sep 01, 2008 9:39 am

carbon_unit wrote:The T2x cover may not be made of metal but it blocks a lot of signal.

And the T in T2x stands for Titanium, the metal that is mixed in with the polymer out of which the lid is made.
This Titanium is another cause for poor reception from the lid, if you don't have the 'Sergeant Stripes'.

Davemci · #8 Post by **Davemci** » Mon Sep 01, 2008 4:02 pm

The t23 antennas are just a flat piece of metal and they actually contact the hinge supports that run along the side of the lid. The only difference I can see is the clear plastic windows on the side of the t23 lid. I've installed these on my t22 with just some minor trimming because the t23 lid is slightly thicker. The reception compared to the palm rest antenna (chunky) on my 600X is significant. I routed the wires on the lid exactly the same as they are on the T23 (per HMM). I'm willing to go so far as to say the plastic windows on the T23 add very little to the antenna's performance. Unlike the t23 lid which are hard to find the t23 antennas are available reasonably from several internet suppliers. YMMV

doctor bloomquist · #9 Post by **doctor bloomquist** » Mon Sep 01, 2008 4:03 pm

I sent the antenna off today for exchange.

#10 Post by **carbon_unit** » Mon Sep 01, 2008 4:49 pm

Davemci wrote:[snip] I've installed these on my t22 with just some minor trimming because the t23 lid is slightly thicker. [snip]

Actually only the wireless T23 lid is wider. The regular T23 lid is the same as the other T2x lids.

ZAGNUT · #11 Post by **ZAGNUT** » Mon Sep 01, 2008 5:03 pm

maybe off topic but somehow relevant are the antennas used on 2.4GHz radio control equipment in model airplanes. on the transmitter a wifi modem antenna is usually used but on the receivers there is just a pair of coax cables with 31mm of the braided shield stripped off the end. 31mm is 1/4 wave if you do the math. proper installation means mounting the antennas at 90° to each other for best diversity. power is normally 100mW at the most and range is well over a mile or two line of site.

dave

sjthinkpader · #12 Post by **sjthinkpader** » Mon Sep 01, 2008 6:07 pm

These hobby radio control devices has FCC IDs on both ends?

doctor bloomquist · #13 Post by **doctor bloomquist** » Mon Sep 01, 2008 6:15 pm

ZAGNUT wrote:maybe off topic but somehow relevant are the antennas used on 2.4GHz radio control equipment in model airplanes. on the transmitter a wifi modem antenna is usually used but on the receivers there is just a pair of coax cables with 31mm of the braided shield stripped off the end. 31mm is 1/4 wave if you do the math. proper installation means mounting the antennas at 90° to each other for best diversity. power is normally 100mW at the most and range is well over a mile or two line of site.

dave

Thanks for nothing Zagnut I rigged up the thinkpad with those airplane antennas and the [censored] thing shot straight up into the sky. If anyone has one of those remote control things can you try and bring it down, I think it was heading due east before it went behind some clouds.

jronald · #14 Post by **jronald** » Mon Sep 01, 2008 7:11 pm

If it gets this far.....
My 7 year old has numerous control sets, Ill bet between he and I we can get it landed!

Ron

ZAGNUT · #15 Post by **ZAGNUT** » Tue Sep 02, 2008 5:23 pm

sjthinkpader wrote:These hobby radio control devices has FCC IDs on both ends?

yes. bi-directional communication is usually only done at a much lower power level for the purpose of "binding" a receiver to a transmitter but there is at least one brand that constantly sends acks back to the transmitter and is based on the zigbee protocol. most use off the shelf modules and are either DSSS or FHSS.

dave

JBUK · #16 Post by **JBUK** » Thu Sep 04, 2008 3:49 pm

I use the flat type antennas and get good results when placed at the top of the LCD. Check out my posts here : http://forum.thinkpads.com/viewtopic.ph ... highlight=

The signal recieved any where under the top cover around the keyboard is too weak to be useable in my experience.

doctor bloomquist · #17 Post by **doctor bloomquist** » Thu Sep 04, 2008 4:50 pm

I really hope someone can help me out with this because as of now I'm baffled by this one. To recap, trying to fit internal wifi in a T21.

Remember I sent back the flat antenna I put under the palmrest, to swap for a chunky one? Well the chunky one came today. As soon as I got it out the envelope, the wire came off the antenna section, only the tiniest blob of solder had been holding it on. I soldered the antenna block back to the wire, and checked it with a multimeter, no resistance from the socket end to the antenna block.

BUT and this is a big round but... even with the antenna dangling on the table & plugged into the PCI card, reception is still about 22dbm poorer than my T23, in the same position on the desk, same card, same antenna type inside its case ( I unplugged the auxiliary antenna to compare like with like).

I then put the laptops back to back, and plugged the T23's antenna into the T21's wifi card (there's about an inch of wire loose in the T23's mini PCI bay) The reception with this precarious setup is great; 'Excellent' in the xp connection properties and the same SNR value as the T23.

So on the T21, I get better reception from an antenna that's buried in the T23's case than one that's loose on the desk.

Can anyone think of what's on earth is going wrong here? Am I just jinxed or something? I soldered the wire to the antenna block in the same place it came off.

ps hey jbuk I actually read that post way back when I was searching for install methods for my T23! But honestly I'm really happy with reception from the palmrest in my T23, next to the battery like in rays guide.

JBUK · #18 Post by **JBUK** » Fri Sep 05, 2008 3:07 am

Two thoughts here :

As both the PCI outputs are the same and the card itself selects ths stronger signal, swap the antenna wires around on the PCI card. Maybe one of the outputs is bad.

Put the T21 pci card in the T23 and vice versa, see if the results change. This will tell you if both of the cards are working at the same sensitivity.

doctor bloomquist · #19 Post by **doctor bloomquist** » Fri Sep 05, 2008 10:22 am

Ok:
(both the cards are BG2200 with same settings)

With the T21 card in the T21, using only the antenna that's loose on the desk: 'low' signal

With the T23 card in the T23, using only its palmrest antenna: 'excellent' signal.

With the T23 card in the T21, using only the antenna loose on the desk: 'low'signal

STOP PRESS **************************

It was the antenna and it was all my fault! I had soldered both the internal bit of the wire and the external bit, now it's just as good as the T23.

What a palaver!

Chart fun: Blocky internal wifi antennae vs the Flat type

Chart fun: Blocky internal wifi antennae vs the Flat type

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