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Author Topic: AX25 Packet over WIFI freqs?  (Read 2629 times)
N5PVL
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Posts: 210




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« on: June 02, 2010, 03:28:17 PM »

I am curious as to whether anybody has any experience running high speed AX25 Packet over the ham WIFI frequencies, utilizing regular WIFI equipment.

NO IP whatsoever, just AX25 Packet.

Would this be difficult to set up for? I'm interested in trying it out, but don't want to re-invent the wheel.


73 DE Charles Brabham, N5PVL

Prefer to use radio for your amateur radio communications? - Stop by at HamRadioNet.Org !

http://www.hamradionet.org
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AA4PB
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« Reply #1 on: June 03, 2010, 05:10:23 AM »

Regular WIFI equipment is set up for IP and its not going to accept an AX25 packet. These things are far more than a simple transceiver with a modulator/demodulator.
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W3JKS
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« Reply #2 on: June 03, 2010, 05:33:26 AM »

Charles -

You could run AX.25 serial streams using some of the lower-speed ISM-band modems which are commonly used for plant automation, RTUs, etc.  They will carry any kind of serial data, but they won't use the command streams within the AX.25 protocol.

Most Cisco routers will let you encapsulate X.25 over IP connections, but same type of issues --

73,
john W3JKS/AAT3BF/AAM3EDE/AAA9SL
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N5PVL
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« Reply #3 on: June 04, 2010, 02:32:42 PM »

AA4PB touched on one of the things I am wondering about.

I was wondering how difficult it may be to separate the Radio and modem sections of a WIFI device, so that an alternative modem's modulation ( or even analog voice ) could be transmitted and received over the resulting low-power 2.4gh transceiver.

What I specifically had in mind is the homebrew Slovenian 1MB Packet modem.


73 DE Charles Brabham, N5PVL

Prefer to use radio for your amateur radio communications? - Stop by at HamRadioNet.Org !

http://www.hamradionet.org
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AA4PB
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« Reply #4 on: June 05, 2010, 08:05:36 AM »

I was wondering how difficult it may be to separate the Radio and modem sections of a WIFI device, so that an alternative modem's modulation ( or even analog voice ) could be transmitted and received over the resulting low-power 2.4gh transceiver.


Because of the integration and propriety information I expect it would be rather difficult to do, Charles. The RF chips are designed form OFDM modulation (multiple parallel carriers with PSK type modulation).

The easiest way would probably be to do it at the digital level, decoding the arriving AX25 data and encapsulating the AX25 packet inside an IP packet so that it can be sent through the stock 802.11 devices. The whole 802.11 link would look like a digipeater to the AX25 networks. You'd have a AX25 to IP adapter at each end.

73, Bob
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W3JKS
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« Reply #5 on: June 12, 2010, 12:21:15 PM »

Charles --

OK, you want a screaming TNC -- don't forget the G3RUH on steroids made by the Baycom guys and gals in Deutchsland:  http://www.baycom.org/bayweb/tech/eppjnx/eppjnx.htm

Warning -- they are not inexpensive!  But they are designed around Flexnet, if memory services.

Unfortunately, they don't have I/Q in/out, which rules out the use of a lot of the newer low-powered 23cm/13cm-capable transceiver-on-a-chip solutions for the RF portion.

I'm talking to the folks at ViaSat about making their DVB-S2 modulator/demodulator chip available for low-quantity amateur radio use.  If I can talk them into it, we'd have a banging solution for both "packet" and Digital ATV -- the transport stream in DVB-S2 is bits, after all.  Whether they are IP-based or not isn't particularly relevent.

73,
john W3JKS/AAT3BF/AAM3EDE/AAA9SL
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KB1LKR
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« Reply #6 on: June 12, 2010, 08:23:38 PM »

You might look at interfacing to a bare 2.4 GHz (13cm) tranceiver such as an XBee Pro for short money. They also have 900 MHz (33 cm) modules. Not sure what's entailed in interfacing to them though, just that they're cheaply available for OEM wireless applications.

http://www.digi.com/products/wireless/point-multipoint/xbee-pro-series1-module.jsp

If you needed more power than 60mW you could add an external amp. You may also want a a larger connector such as an SMA vs. the tiny MMCX (or U.FL -- I forget).
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