19-07-1998 FT-726 AUDIO Modifications Hello my name is Juan, this text talk about the mods for transceivers of Ham Radio... I hope you interest this... If you need mods for others tranceivers, ask me.... BE CAREFUL! Procede at your own risk. Dont forget that transmitting outside the amateur band is not allowed so please consult your local athorities for a special permit. THANKS EA5SP.EA5FDS.EAV.ESP.EU.WW Subject: FT-726 AUDIO MODIFICATIONS Further improvement in FT-726 audio quality can be achieved by a simple modification to the product detector. The product detector seems to be overloaded by the input IF signal, the 6dB attennuator described here will improve the RX-quality The circuit is proposed by LA8AK, and tested by LA7BI (Egil); ----------------- 1K --------------- to pin 5, Q13;uPC1037 I I I I T11 I output 1K link I I I -------------------------- I I C67 47nF( .047) I I --- pcb/ground the two resistors (1000 ohms) are easily mounted below the PCB Break the pcb between the coil and IC pin 5, mount the resistor, and connect the other resistor from the capacitor to IC pin 5 The audio quality should be much improved, and you should at least be capable of understanding somebody who does not exactly speak the same language as you. Englishmen should now be able to read foreigners who speak english, although it is well known that foreigners from different countries who use english understand each other, but the englishmen often do not understand them. This modification is read 296 times. top of page

19-07-1998 TAPR PSK mods for the FT-726R Throughput improvement for the FT726R - Tapr PSK modem On the Lo-19 and Ao-16 digipeaters I was only averaging 1 in 5 UI frames returned. Viewing my PSK signal on a scope at the FM varactor driver (Q08) on the Sat Unit revealed a very distorted and jittery audio waveform. Replacing the Tapr's obsolete 4030 (U21) with a 4070 gave me a steady but still distorted wave. My throughput was now 1 in 3; better but not good. Modifying Tapr's low pass output filter (as suggested by G3RUH for his PSK modem) and a change in the Tapr's attenuator and alignment has given me almost 100% throughput. TAPR Attenuator mod: Remove R5 (22K) by putting a jumper on JP7. Replace R6 (5K trim pot) with a 100K trim pot. Be careful when unsoldering as those small trace pads come off very easily. TAPR filter mod: Replace R7 (22K) with a 47K resistor and C8 (.047 mf) with a .01 mf disk capacitor. FT726R mod: Find plug J04 on the Satellite Unit (front left corner). Buy an equivalent plug and header pins and solder them together with short bare wire, attaching the center conductor of RG174U coax to pin 2 and the shield to pin 1 of the adapter. Then plug the Yaesu's plug onto the adaptor's header pins, and the adaptor's plug onto the Sat Unit board's male header pins. You could solder the cable directly to the board or connector, but this way the board's original condition is retained. Alignment: The waveform out of the TAPR (ungrounded end of JP8) will now be a somewhat rounded sawtooth. Adjust the 100K pot (R6) to mid range. Set the FT726R's Mic Gain to the first "tick" (8 O'clock). Attach your scope to the RG174U coax and slowly increase the Tapr's output (R6). You will see the PSK's distorted waveform smooth out and grow to become more like a sine wave. Around .6 v pp it will be at it's best. As you continue to increase the PSK output distortions will reappear as the FT- 726R's FM limiter clips the signal. Back off the audio until you get the least distorted wave shape. It will be almost a sine wave. When you set your transmit power lever, back off so your ALC is not active. Assuming you have all your software switches and parameters set properly you should now have greatly improved throughput. Let me know how this works for you or if you improved your throughput in other ways so we can write it up. This modification is read 535 times. top of page

19-07-1998 Sensitivity for FT726, 50-54, 144-148,430-440 MHz Empfindlichkeit FT470 MHz ľV 50 0,25 51 0,26 52 0,27 53 0,28 54 0,33 144 0,22 145 0,23 146 0,23 147 0,23 148 0,25 430 0,2 431 0,18 432 0,18 433 0,18 434 0,18 435 0,18 436 0,18 437 0,18 438 0,18 439 0,19 440 0,28 Messung wie folgt: Signalgenerator (Marconi 2022) an Antennenbuchse. Am Lautsprecherausgang der Funke wird die NF-Spannung (FM-Rauschen) ohne Signal auf 100mV eingestellt. Dann wird das unmodulierte HF-Signal im Pegel soweit erhöht, bis das Rauschen um 20dB zurückgegangen ist. Vorteil dieser Methode: Sie ist äußerst einfach durchzuführen. Allerdings können mit dieser Methode die Propagandadaten der Prospekte nicht erreicht werden weil hier ohne Modulation und ohne CCITT-Filter gemessen wird. Zum Vergleich mit anderen Funken geht dies aber hervorragend und der Empfindlichkeitsverlauf über die Bandbreite läßt sich sehr schön darstellen wenn man die Meßwerte in z.B. Excel graphisch auswertet. Bemerkung:Auf 70cm ist das Gerät außerordentlich empfindlich. 73 de DD0BI @ PI8AWT This modification is read 830 times. top of page

19-07-1998 FT-726R Improvement Remove the 2mtr module , remove the top cover of the module,,, It the PA module end of the unit you will find Q01, it is a Mos-Fet a 3SK74L2X. Replace this with a BF982,,, the leads are slightly thicker than the original, so a 1MM drill is required to open the holes on the PCB. The LONG LEAD of the BF982 should be fitted facing away from the PA Module. When the Fet is fitted a very small length of wire should be fitted from the Source lead (The lead facing into the center of the board) to the surrounding groundplane. This should be it, but if you really want to be a perfectionist tune up on T01, T02 and T03 ONLY!! Finally, Box up and enjoy the low noise, improved signal reception. This modification is read 1128 times. top of page

19-07-1998 FT-726 mods for 9.6kbps FSK RX data connection RX signal is drawed from the junction R44-DO4(1S188) with 10K ohm resistor. It must be connected to RX in of G3RUH modem TX data injection You must inject both TX unit and Satellite unit if you need full duplex operation ( example for uosat4/5 ). The TX data injection point is DO5(FC-53)-C27 in TX unit and DO6(Fc-53)-C25 in SAT unit. You may be able to direct connect from TXD out of G3RUH modem as DC decoupling is in the modem board. You need selection SW for TXD injection to select sinplex/full duplex operation. This modification is read 1370 times. top of page

19-07-1998 Mods for ft726r to do 9600 From James Miller G3RUH: Inject your modem TXaudio directly to the transmitter varactor in the SAT unit via J04 pin 2. Remove the main lid; remove the SAT unit lid. Locate J04 which is a 3 wire connector in the front left-hand corner. Unplug J04, and inject your audio on pin 2, ground on pin 1, using a screened cable. This is of course assuming you are using a G3RUH or K9NG 9600 baud FSK modems. The receive side needs to come straight from the discriminator which I haven't had a chance to locate yet. Perhaps if someone else has the necessary hook up information for the receive side, they could post it here. This modification is read 1610 times. top of page

18-11-1999 Hang AGC for FT-726R Author: Chuck - KD9JQ - kd9jq@mc.net This modification is read 1866 times. top of page

18-11-1999 TX module RF Delay for FT-726R Author: Chuck - KD9JQ - kd9jq@mc.net This modification is read 2122 times. top of page

24-09-2000 Expansion mod for the Yaesu FT-726 Author: Dennis - us49ca@hotmail.com This mod is for the expansion of the RX/TX on 2 Meters. After this mod the transceiver will work from 143.500 to 148.499 Take off the transceivers top cover, than u will see the 144 and 430 units. Take out the 144 unit and open it up. There are two boards in the unit and you need to work on the board that has two connectors attached to it. On this board you need to locate diodes numbered D19 up to D26 they're in a corner located all together. How they are lined up in your transceiver right now is different in every transceiver 'cause there are about 6 different units. For out of band functioning make sure D19, D23, D24, D25 are connected by either a Diode or a wire those are the ones necessary for the mod. D20, D21, D22, D26 Need to be open and Unconnected. If your set made 12,5 khz steps before, it will now make 5 or 10 Khz steps. I have tried to restore it on my set but closing the other Diode openings only results in the set not working properly meaning the 144 or 430 unit does'nt signal or work anymore......... Important however is, the fact that the set needs to be resetted to make the set work out of band....... when the top is still of the transceiver and all the cables are re-connected, find a little switch on the top left side of the front of the radio (on the circuit board behind the meters) this switch is for the memory battery and control backup. Switch it to "off" and turn the set on the display should now read 147. Mhz. Now switch the little switch back to the "on" position and reassemble your radio. (The switch positions are also to be seen on the top cover next to rubber cap.) There is no real expansion for the 430 unit the only one there is, this will only make it work from 440 to 450 instead of 430/440. Open this 430 unit and make sure D18, D19, D21, D22, D23 are closed and the rest should be open. But in europe there is nothing interesting there so why modify it ??? Good luck with this mod and be careful when transmitting out of band. Released September 16th 2000 Dion US49CA/19DC49 us49ca@hotmail.com This modification is read 2470 times. top of page