by Russell E. Clift,  AB7IF


Tired of having to drill holes in your Ranger for a new mod?

Try this. The SWR and Roger Beep functions are open collector outputs pulled to ground by the CPU when the specific function is activated. There are a few more, such as NB and ANL (3 steps), and a voltage function from the Dimmer that can also be used for various mods. Keep in mind that the transistors are not power devices, if you wish to control some circuit needing a larger current sink use a fire train, ie., another device which will handle the load. For example, you can use the SWR or Roger Beep for talkback from the front panel by removing the wire from the connector on the mainboard and simply soldering it to the cathode of D78. Do not cut or remove D78, just connect the wire from the function used to the side opposite the band. Do not connect to the banded side! The green wire from CN607 to the mainboard plug is roger beep, right behind the mike plug 3 inches, a 6 pin connector; black (ground on one end, green (the RB signal control line we want) on the other end. If you use SWR function, go to plug from CN608, just behind antenna output, two coax wires with a common ground. The hot opposite the shield is the one you want to use for a transistor low, activated when SWR is lit on the LCD display. I use both functions because I also have auto squelch, that mod next. Don't forget to open D115 to clean up the audio quality of your talkback. Do not replace the zener D115 with a cap. or resistor or whatever like you have seen out there, just leave it open. A few hundred picofarads here may slightly improve sound but it also affects recieve and PA audio, and I like the recieve sound of my Ranger so I leave the D115 circuit open. If you love SSB like I do but also like the chicken radio talkback with connex, but hate the distorted (lack of carrier for AM detection which is how TB works on Ranger and Galaxy radios) TB on SSB and drilling holes in your new radio, you will love this idea.

Now for autosquelch. Look at the 3 pin connector from the squelch control, up front just to the right of center. Wires are violet, grey, and white. Look on bottom, center pin is grounded. Cut foil to unground. Look to unused pad just beside 3 pin conn., you will see it goes to 22k to ground. Jumper center pin to this point. Now at this point you will connect the wire (green) from the CPU board to roger beep (you removed it from the 6 pin conn. to RB) to this junction of center pin to 22k to ground. You now have auto squelch by activating the no longer functioning rober beep. The problem is: with RB lit you have normal squelch, with RB out you have auto squelch. So, to invert this like I did (I like things to be on with indicator not vice versa), connect the green wire to the base of a 2N3904 transistor. Connect the base to the 10k going to 8 volts. Connect the emmiter to ground, collector to the center pin on the 3 pin squelch pot. connector. Now you have autosquelch on when RB is lit, and talkback on (previous mod) when SWR is lit. COOL!
You can make the autosquelch looser by lowering the value of the 22k R315, to make it tighter just raise the squelch control when autosquelch is on. You can also play with R71 (47k in some and 39k in others), but it is better just to alter R315 (22k) if need be.

For better AM recieve change the detector diodes D34,35 to a better quality SK9975, or use ECG or NTE 583 (germanium only here, no silicon). While you can reduce the reciever sensitivity to help overload by changing R78 from 2.2k to 6.8k, I don't think it is a good idea if you are into long distance communication.
For front end overload the going mod is to change R49 (100k) to 33k. The problem here is it also severely degrades extreme weak signal reception. So to fix this just tap the hot end of R49 (the other end is ground) with a 100k trimmer pot in series with a 1k (to protect the quad op amp's output from damage if you turn the pot all the way down by accident) for a variable trimmer adjustment for overload protection, set the pot for best effect (other end of your pot is grounded to parallel the 100k R49). Now for the cool part. If you have no use for switchable talkback then use the signal described earlier (SWR or RB) for the ground end of the trimmer pot (or fixed value if you go that way). Now you can at the touch of the SWR or RB button control front end overload and restore weak DX recieve by pressing the button again. WAY COOL!

For power limit removal just solder the base of TR32 to ground, looking at the foil side you will see the base lead is closest to the wall, next to a handy close point to ground. Note that some people just clip TR32. I add this info for completeness, this limiter clip or the base resistor to it are always clipped when I see one come in for repair, but keep in mind that doing this limiter removal to the Ranger of any Galaxy radio is hard on the circuitry and can cause problems as well as part failures.

For faster scan and function speeds replace X601 (a 4 MHZ ceramic resonator) with an 8MHZ crystal, but remember speeding up the CPU makes it run hotter, and going to fast will make it prone to locking up.
If the load capacitance of your crystal to too far off, the circuit may not oscillate, play with the values for R630 (1M), and C612,613 (33pf).
For a little more power replace C270 (to base driver), C261,262 (base of finals) with 1000 pf, or just parallel the 560 pf's there already with about 330 pf; retune radio output stage for best power. While changing the regulator transistor Q51 (2SB754) to a higher power unit such as a 2SB688 (never use the junk ECG 37) may seem a good idea, the collector to emmiter "on" resistance is critical, or the unit will overheat. So if you sub this part away from 2SB754 pay attention to this fact!

For you 2970 owners another choice exists. Use the RB or SWR signal to turn the power amplifier on and off. Locate the 2 pin plug going to the linear unit. one wire is the hot 8 volts for transmit. Connect this to the emmiter of a PNP 2N3906, tie the emmiter through 4.7k to the base. Connect the base through 10k to your chosen open collector output either RB or SWR. Connect the collector to the wire going to the linear. Now when you push the front button you will allow or not allow the transmit 8 volts to activate the relay inside the linear unit. More Cool! No holes in the covers and selectable high or low power!

Russell Clift AB7IF Copyright 2001 Russell E. Clift