GAXLAXY DX959 MODULATION BOOST NEEDED

[EmptyPockets1013]

So I’m new to tuning radios and working on my own stuff. I have way more than enough equipment to do, o-scope,spectrum analyzer, RF communication tester (CMU200), and an Signal generator. I’m still trying to learn the tricks to tune some on my own radios which are the popular ones, particularly my DX959. I have one with bipolar finals and one with mosfets, both same to get the same reports that my radio sounds good/clear. Although I hear it could use more modulation that I’m a little low. I have the mod VR tuned to where I have a nice wave form on the scope with the mic gain knob set at about 3 o’clock just I can give it a little more when needed. The little extra put the wave into the start of flat topping. What do I need to do to get a little modulation but keep the wave form perfect on the scope? The MOSFET radio is running about 8-10 rms and 26-30 peak, which I have seen guys get more out of these. I know the really good techs have been years learning all the little tricks to get a loud proud and very clean radio, I just need some guidance please. Thanks 73’s

 

[sp5it]

Turn micgain to the max, adjust mod VR to 95% modulation.
Solved.
Mike

 

[EmptyPockets1013]

That’s what everyone says….. do that and look at the signal with an O-Scope, it has a very nasty clipped positive peak on this particular radio. I’m not doing a Golden screwdriver tune on my radio using proper test equipment you can actually see what the waveform does when adjusting the VR’s.

 

[sp5it]

If it is clipped, so turn ccw mod VR inside until it will be clean and round.
With AMC working properly you can put as much audio as you want on input and you will never see flat-toping.
if you can't achieve that with mod VR it means it's not working as it should.
Mike

p.s. One more thing is driver and final transistor bias. I would check that too if it works in AB class.

 

[Shadetree Mechanic]

Don't try to get every last watt out of it, the RM 203 goes great with these if you want more power. Keying 20w and swinging to 100w will get you loud. I did some mods to an 86v, let me see if I can find the thread.

Found it, you will have to read through it to get the good stuff. The mods might be slightly different but should be close enough to figure out for the 959.

Galaxy DX86V mods

I just picked up a DX86v. The previous owner had the dimmer switch changed to a roger beep. I want to change it back to stock so the dimmer works. I traced the wires and they plug into the board at J10 RB. I assume that means roger beep. This radio isn’t supposed to have a roger beep but I’m...

www.worldwidedx.com

 

[EmptyPockets1013]

I have it paired with a Texas Star DX350 low drive which is working well.

 

[Dr_DX]

install one of these:

1-10x MAX4466 Electret Microphone Preamplifier Module SSM2167 Voice Compression | eBay

Using max4466 microphone amplifier + ssm2167 voice compression amplifier design. 1/2/5/10PCS MAX4466 Electret Microphone Amplifier Board. 1: Compressing the dynamic range of the microphone signal reduces the level of peak signals and increases gain for low-level signals.

www.ebay.com

in front of or behind the mic gain. * Make sure and use a blocking cap on the input.

You can also replace R264 (5.6K above VR14) with a 914 diode or 240K resistor. Keep mic gain at 3 o'clock and re-align. Then adjust VR13 & VR16 for your preferred wave form on the scope.

Good Luck!

 

[Dr_DX]

Looks like this one will work with a Dynamic mic

SSM2167 Microphone Preamplifier Board Preamp COMP Compression Module DC 3V-5V | eBay

1 x SSM2167 Microphone Preamplifier Board. This preamplifier includes a built-in compression and noise gate, For this function,it is better than just using an op amp in the preamplifier circuit. The noise gate attenuates the signal level below a certain threshold, in order to amplify only the...

www.ebay.com

 

[Shadetree Mechanic]

In the 86v thread, there is an audio mod to increase the gain of the internal microphone amplifier to make a regular mic like a power mic. Works great with the Astatic 636. The modulation limiter mod reduces the clamping action of the limiter and will do over 100% and still be clean on the scope. Icing on the cake is the adjustment of L8 to quiet the receive.

 

[Shadetree Mechanic]

Not modulation, but an interesting mod. I have not tried it yet.

Galaxy 959 Frequency Counter Sixth Digit mod

Here is a video I found about a mod to see the sixth digit on the five digit counter. Might try it on mine.

www.worldwidedx.com