Questo è un documento “storico”. Circolava quando avevo in esercizio il mitico BBS Radioamatoriale IK0MHG-8, tra i primi ad operare a 9600 BPS in VHF.
Qui spiegavo come modificare il ricetrasmettitore Yaesu FT4700RH per collegarlo ai famosi TNC G3RUH/K9NG (come il famoso “Raschi”, di cui ne ho ancora uno).
Ecco qui (riporto con carattere Courier, visto che questo era un bollettino testuale), proviene dal sito di IK1WHN:
R:951025/1548Z @:IK0MHG.ILAZ.ITA.EU #:19852 [ARRL Roma ITALY] $:19852_IK0MHG From: IK0MHG@IK0MHG.ILAZ.ITA.EU To : IW6AOV@IK6XRE.#AP.IMAR.ITA.EU ---------- After asking @WW for someone running a YAESU FT4700RH @ 9600 BPS and waiting for weeks, I finally decided to shake my brain and find a way out. Here is how you get rid of your FT4700RH that you'd like to see running out those high speed bits from your K9NG/G3RUH modem. Follow my instructions step by step. 1) Disconnect your FT4700RH from your shack COMPLETELY. It contains sensi- tive digital ICs and working with connections may damage it. 2) Have a clean, wide and static-free surface. Discharge yourself from static electricity before doing the job, by touching an iron water pipe or heater tube. Heat a low voltage soldering iron or a ground connected wall-outlet-powered soldering iron. ASSUMPTION: the FT4700RH is a real DOUBLE RTX. You CAN NOT find any "magic point" where your "surgery" can carry a VHF/UHF 9600 connection: you have to decide. You will have to set up a VHF OR UHF modification. Or both: but in this case you'll have to carry out two different inputs and outputs to be switched by an external switch. 3) Grab one or two clean ash-trays to save the hardware you'll dismount while modifying the FT4700RH. 4) Assuming you are going to prepare the UHF portion to run 9600 BPS FSK I/O, open the speaker side of the RTX. Save the screws. Carefully disconnect the speaker and fan jack from the PCB. Then, unscrew the front panel and save its screws. Now you have to unscrews about a do- zen screws from the main PCB to be able to pull it outta the chassis. 5) Disconnect the flat connector from the fron panel and set the FP aside. 6) Carefully locate the fine screws over the power module (back side). Unscrew them and save the screws and the ground copper slide. You will have now to unscrew the screen of the power module and one more PCB screw. You'll save in total 2 male/female screws and two rectan- gular plates, plus the PCB screw, from the internal of the TX module. 7) Unscrew the output coax cable locking from the chassis and save the screws. Also save the half-circle aluminum plate over the external speaker connector. 9) VERY CAREFULLY, rotate the UHF PCB toward the front side. You have to gain access to the underside of the PCB. There, you'll find the TK10487 demodulator chip. 19) Have a thin copper wire ready and solder it VERY CAREFULLY to pin 11. The wire bust be long enough to reach an external connector. 20) Be aware that if this wire touches ground, you will no longer hear any signal from the UHF section; so carefully reposition the PCB into the chassis and reinsert all the screws by reading this DOC back- ward. Leave the new wire out of the PCB, externally accessible. This wire will carry the RECEIVER signal to the input of your mo- dem. 21) Locate the resistor inserted in the CTCSS smaller connector. It has one side connected to the leftmost pin and the other in a about- middle pin (pin 3). Carefully insert a copper rigid wire in the pin 3 of the connector. Leave the resistor installed. The wire you just installed will carry the OUTPUT signal from your modem directly to the VCO input, which is the best point. 22) Now at you chioice you can: A) disconnect e.g. the UP/DN contacts from the mike connector and use them as an high speed I/O wiring, or B) install an add-on connector, e.g. a standard stereo jack female plug to carry out these new connections. 23) Carefully check that no screws are left and close your equipment. 24) Fire up your modem and... enjoy high power and high-speed packeet. Note: - As you are acting directly on the VCO, this connections should also work at higher speed i.e. 19.2K FSK modems; - If you wish to modify the FT4700RH for VHF instead of UHF, well the modification is exactly the same. You just have to open the opposite side of the FT4700RH and act in the same way. E N J O Y !