Can u pls explain for the stupid ppl (me) where is the solder pints for the antenna and where is the antenna in the Axim...
Make a close comparison among pictures published by Ziele at current thread and full set of internal pictures published here and here. You will probably find the answer yourself. Antenna seems to be that long piece of metal facing outside the PDA.
Originally Posted by Kolyan
... also i was thinking by the looks of the wire that was used, it was well shielded so do u think that, this is true necessary
Well we are not going to enter a discussion of "Transmission Lines" and "Propigation" theories, so the short answer is: yes, it is necessary.
The only problem I see from adding an external antenna while while keeping internal antenna working is we get what is called in "Antennas Theory" an "antenna array". The result of this a a directional pattern diagram.
In brief, if you have just one dipole antenna, you get an omni-hemisphere pattern. When you add a second dipole you get two broad lobes with some directive gain.
Home TV antennas are the most tipical dipole array to get directive gain.
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The only problem I see from adding an external antenna while while keeping internal antenna working is we get what is called in "Antennas Theory" an "antenna array". The result of this a a directional pattern diagram.
In brief, if you have just one dipole antenna, you get an omni-hemisphere pattern. When you add a second dipole you get two broad lobes with some directive gain.
Home TV antennas are the most tipical dipole array to get directive gain.
Correct.
Also, by connecting an external antenna in parallel with the internal antenna, you will create an impedance mismatch on the output of the RF amplifier module. This increases the VSWR (voltage standing wave ratio) which is an indication of how much RF energy will be reflected from the antenna circuit back into the amplifier, causing reduced output and possible damage to the RF output.
Ideally, you need to disconnect the internal antenna when you connect the external one. When you're dealing with RF energy in the microwave region, you need to be careful how you match the components.
If you look carefully at the PCB, you will notice a small round connector just below the internal WiFi and BT antennas. Those are the manufacturing RF test points. They are actually switches that disconnect the internal antennas when the board is connected to the manufacturing test equipment.
My original thought on an external antenna was to design small RF transformer that would sit on top of the case just above the internal WiFi antenna. That way you would not have to open the case. This would be similar to the way that cellphone antennas on cars are coupled through the windshield.
I have attached a photo of the WiFi antenna area showing the test connector. You will see there is an impedance matching circuit that consists of a coupling capacitor, an inductor and an RF stub (the part of the WiFi antenna between ground and the spot where the trace connects to it from the capacitor). Even the length of the trace between the capacitor and the antenna affects the impadance at 2.4GHz. Connecting your external antenna to this point will screw up the matching and might cause problems, so please be aware of this.
If you want to connect to the input of the connector, you will need to add a coupling capacitor of about 100pF (picofarad). The best way is to use an electronic switching circuit that uses biased PIN diodes to switch between the two antennas. Unfortunately, that is out of the scope for 99.99% of most forum members here.
I had some old cell phone with external antenna connector.
Maybe they internally have required switching and coupling components.
Any RF device (Cellphone, WiFi, etc) that has both internal and external antennas are designed with the proper switching/matching circuitry to accomodate them.
Yes, as hardware hackers, we can and do add to and make modifications to our 'toys' thus killing any FCC/IC/IDA/(your regulatory agency here) approval for the PDA.
One thing that an unbalanced/mis-matched output can do is to create an increase in spurious radiated signals (RF noise) that can interfere with other communication devices. As an Amateur Radio operator, I need to be very careful when I design/build/modify/operate any radio devices as I could lose my license, even though it's not on any Amateur band.
These are rather stupid quedtiosn, I guess, but.....
would this have any effect on the BT range?
also, aside from difficulty wiring to the side of the case, if there is already an input for an external antenna, y couldn't it be used? also is there aany way to add the dardware to regulate the mismatch on the antenna instead of mucking around further in the axim?
For a car, or such, could one simply mount some kind of amplifier to the roof using the normal axim signal? (i.e. like how a bt headset transmits to a phone and then the phone relays it from the bt input to the cellular output)
((for those wondering, I do not feel comfortable messing with the mainboard and a soddering iron... nor do I know much about rf theory or electricity... so I appoligize for the stupid questions))
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These are rather stupid quedtiosn, I guess, but.....
would this have any effect on the BT range?
also, aside from difficulty wiring to the side of the case, if there is already an input for an external antenna, y couldn't it be used? also is there aany way to add the dardware to regulate the mismatch on the antenna instead of mucking around further in the axim?
For a car, or such, could one simply mount some kind of amplifier to the roof using the normal axim signal? (i.e. like how a bt headset transmits to a phone and then the phone relays it from the bt input to the cellular output)
((for those wondering, I do not feel comfortable messing with the mainboard and a soddering iron... nor do I know much about rf theory or electricity... so I appoligize for the stupid questions))
No questions are stupid if you aren't familar with the technology.
1. BT range is not affected.
2. As I stated above, even if there was room for a switching circuit, it's not something a weekend hacker could do. I've worked in the industry for 30+ years, so for me it would be 'fun' as I know how not to kill my PDA. It boils down to experience. Also, the connector is for automated assembly line testing. We don't know what the impedance of the test system was. Just placing a piece of coax and external connector on that could cause more problems.
3.You're talking about a repeater. Yeah, that's one solution but really expensive.
I'd still like to try and model the antenna idea I have. I need to talk to one of the RF engineers I work with to see how feasable that is.
Dell axim x50v with external wifi antenna connector ;) Looks like brand new.
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Ziele, good work. The modification looks clean, like factory OEM.
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My original thought on an external antenna was to design small RF transformer that would sit on top of the case just above the internal WiFi antenna. That way you would not have to open the case. This would be similar to the way that cellphone antennas on cars are coupled through the windshield.
Snap! I tried this using an old dell laptop antenna coupled to a hi-gain wifi stick.
After a lot of fiddling I managed a consistant 2dB improvement :( Not enought to be worth playing with.
Ideally, you need to disconnect the internal antenna when you connect the external one. When you're dealing with RF energy in the microwave region, you need to be careful how you match the components.
So can you disconnect the internal antenna without damaging the rest of the device?
Are there two antennas, one for BT and one for WIiFi, or is just one pulling double duty? I am a little confused.
So can you disconnect the internal antenna without damaging the rest of the device?
Are there two antennas, one for BT and one for WIiFi, or is just one pulling double duty? I am a little confused.
You can remove internal antenna, but I would not try to turn on WIFI without external antenna, it would be the worst decoupling you could build. I do not know if internal circuit is prepared for that.
I have no idea about BT antenna, it could be the same but I do not think so.
Does anyone located BT antenna?
So can you disconnect the internal antenna without damaging the rest of the device?
Are there two antennas, one for BT and one for WIiFi, or is just one pulling double duty? I am a little confused.
No, you need to have a WiFi antenna (internal or external but not both) connected to the unit or you risk damaging the RF amplifier chip due to a high VSWR.
Yes - two antennas. Look at the pictures referenced in the posts above.
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