R:991219/0844Z @:ZL3VML.#80.NZL.OC #:58373 [Chch-NZ] FBB7.00g $:25444G6CRV R:991217/1834Z @:ZL2BAU.#73.NZL.OC #:15656 [Blenheim] $:25444G6CRV R:991216/2214Z @:NX5V.#SETX.TX.USA.NA #:19295 FBB5.15c $:25444G6CRV R:991216/1734Z @:KE4HSB.#WKY.KY.USA.NA #:1634 [Benton, ky] FBB7.00g R:991216/1819Z @:KA6EYH.#CWA.WA.USA.NA #:14521 [CN96UJ] FBB7.00g23 R:991216/1726Z @:WB7AWL.#SWOR.OR.USA.NA #:64438 [Talent, OR] FBB7.00g R:991216/1826z @:N7OO.#SEAZ.AZ.USA.NA TNOS/U Z:85615 $:25444G6CRV R:991216/1821Z @:7M3TJZ.13.JNET1.JPN.AS #:46338 [Kunitachi/TOKYO] FBB R:991216/1811Z @:LZ1JW.#SOF.BGR.EU #:10369 [Sofia] FBB7.00g $:25444G6CRV R:991216/1810Z @:GB7CRV.#16.GBR.EU #:46177 [Heysham] LinFBB $:25444G6CRV R:991216/1810z @:G6CRV.GB7CRV.#16.GBR.EU [Heysham] TNOS/U $:25444G6CRV > > From: GW8FVI@GB7BAY.#55.GBR.EU > To : TNC@WW > > > Hello there, > > Do you know of a mod to make a Tiny2 tnc work at 2400 baud rate rather than > its 1200. I know the crystal has to be changed but thats as far as it goes. > So any help on this tnc would be welcome. > > Cheers Chris. > > GW8FVI/Sysop GB7BAY. > Hi Chris here are mods for the TNC2 and for the Tiny 2 :- TNC2 on 2400 Baud ================= - If you have a TNC with TCM-3105 chip, you can be qrv on 2400 bd and enjoy this speed after minor modifications to your TNC, you just have to replace some components and realigne your TNC. - Change the original Xtal (4.43 Mhz) to 6.5536 Mhz. It is easy to find this Xtal. - On the original Xtal you find 2 capacitors of 33 Pf,put a capacitor of 47 Pf parallel with ONE of the 2 33 Pf C's. - Change the HDLC baudrate (original 1200 baud) to 2400 baud, (the second strap of the first 6 inline). - Realigne your TNC as followed: - Use TAPR 1.1.7 or equal software. - install a jumper between pin 1 and pin 3 of the 5 pin DIN plug - Type "Cal" for Calibrate. - Type "D" for Diddle (2 tones are active). - Connect an osciloscoop on pin 8 of the TCM-3105. - Trim the 50Kohm potmeter for 50% duty cycle. - Type "Q" to quit the Calibrate function. - You can now operate 2400 baud AFSK,the tones are 1775 Hz & 3250 Hz. - Here are some "VERY IMPORTANT" points: 1) Our PTT regulations DO NOT allow us to use the 2400 Bd speed, but you can get a special authorization for 1 year. Please introduce a request to experiment the 2400 Bd (or even 4800 Bd and 9600 Bd) on UHF and SHF. Please introduce your request to RTT right NOW ! 2) We beg you to reduce your TXDELAY at the lowest possible value. For example if you loose the connection with a TXDELAY of 11 and got a good copy for 12, then use a TXDELAY of 15 (you have then a 30 % safety margin). In order to get full advantage of the speed increase, please reduce your TXDELAY. Lets compute the time for a AX.25 frame and lets compare it with the usual 300 ms TXDELAY : bytes bits time at 300 msec 2400Bd represents short frame (just "RR" for example) 19 152 63 ms 476 % long frame (256 bytes info frame) 276 2208 920 ms 32 % You see that the TXDELAY is really a WASTE of TIME, but it is necessary to be sure that the PLL of the transmitter is correctly locked and it is necessary to be sure that the squelch circuit of the receiver is open. (note that both time constants have been designed for "phone transmissions",but not for data !). - If you have a TNC with AM7910 chip, you can be qrv and enjoy this speed after minor modifications to your TNC, refter to the 2400 bd bulletin of ON7PC @ ON7RC. 73 Walter ON1AOT @ ON6AR PS: If you can not find the Xtal of 6.5536 just send me a message @ ON6AR. TNC2.2K4 *** EOF Modification of the Tiny-2 TNC to 2400 Baud. ============================================ Replace the 4.433Mhz xtal near the TCM3105 modem chip with a 7.3728Mhz xtal. Set the DIP switches for the Radio port to 2400 in order to clock the data to the modem chip at 2400 baud. With Paclen set to 255 and Max packets outstanding set to 7 a bit rate of about 10-15Kb/min is possible (optimum). This mod has been used in Germany for inter-node links and is reported to be very successful. Information supplied by John GI6IRL @ GB7TED. TINYBAUD.MOD *** EOF Dave Staniforth , Heysham Lancs UK. Internet: g6crv@lurpac.lancs.ac.uk dave@crvnet.demon.co.uk Amprnet: g6crv@g6crv.ampr.org AX25net: g6crv@gb7crv.#16.gbr.eu