Galaxy dx959 EPT069610Z help

[Stinkbait]

On the clairifier mod, Do you happen to know what the normal voltage range is to the x3 crystal? I will measure mine with a VTVM and do some experimenting to get a balanced 5kc slide without causing drift. I know it can be done properly, I'm assuming there has to a balance of voltage and reactance to increase and center the slide.

I still have a Washington with the infamous "Selman super diode" and original MB8719 in it. It got 10kc slide with only a part swap. and 26 to 30m with switches. I hate to part it out, maybe work on that later, it's buried in dust and I'm packed up to move to a new house for now.

 

[loosecannon]

stinkbait, the easiest way to increase slide would be to try different varactor diodes and see what their effects are.

as long as you have done the mod properly that is. it sounds like you have, and you seem to have gone further with it than i ever have.

i have unlocked the clarifiers in pretty much every DX959 that came through here, but i discouraged people from trying to get a bunch of slide out of them because these radios drift in stock form already. changing out components trying to get more slide will only increase the temperature based drift.

i have not tried it in this chassis, but the lower the load capacitance of the crystal used, the greater the effect the varactor diode has on it, therefore increasing the amount of slide.

the problem these days is that having a custom crystal made is next to impossible.
if you can find some place that still does that type of thing, it will be very expensive.

i suppose if someone were to be willing to buy 100+ of them, see it it works, and then sell them as an upgrade on ebay, it might be worth it, but that person is not me.

a load capacitance on the order of around 10pF would be my first blush guess.
i have no idea what that value is for the stock crystal.

good luck with it and please do post back with any results you achieve.
LC

 

[JoeDirt]

I have never seen a dual final galaxy 959 to do a full 45 watts. if you whistle or yell into the mic you might see a peak of about that. normally with a dual final radio you will see 12 to 18 watts when just talking.
here is a link to do the dual mosfet mod with all the holes filled in as you call it. a few will still be empty as a few parts are not needed. hope this puts you in the right direction. but you will not get 45 watts of talking power out of it. you will have a little more out put if you use the 13n10 mosfets and not the irf520 shown. the 13n10 uses all the same parts the 520 does.

http://www.cbtricks.com/miscellaneous/fet_papers/mosfet_conv/graphics/6900xxx_ssb_mosfet.pdf

It takes a lot of tuning to get more watts. I have one that does a clean perfect linear 60+ watts on a Bird pep meter. I built the radio 10 years ago.

However I notice more watts out of my single final radios driving the same amps...... Not worth the time, in my opinion.....

 

[Robb]

If it were my radio I wouldn't recommend extending the slide range. Never. If anything, I would want to decrease its range. Reason being that the more you make this particular radio with this chassis slide; then the more drift will occur in either cold or hot weather changes ('mobile environment'). It also allows for much easier adjustment of the clarifier in order to get an exact lock on who you are trying to dial in when slide is reduced.

To decrease it to +/- 1.2khz total slide (600hz from center in either direction) and decrease the radios weakness for drift can be done and will make it user friendly. Uniden radios really don't suffer from drift compared to Galaxy/Ranger chassis radios. But even they can suffer from drift if the freq slide is increased too much. Galaxy radios just get downright nasty when slide is increased. If you aren't aware of it now; then you will be acquainted with it if you proceed.

In addition, the more you make the radio slide; the less fine control you will have and then the harder it becomes to get an exact lock on the person you are trying to dial in. You will often overshoot and that will prove to be very frustrating. Frequency overshoot will also be increased at either end of the clarifier pot as well, compounding extra slide issues even further.

Exitthirteen (forum member) gave me some tips on how to make it more stable. One is to eliminate the capacitor (C130/20pf) that is in parallel with the varactor diode. Another is to keep R153 stock - or decrease its resistance slightly - for less slide. Do NOT jump R113, as this will increase slide and likewise increase drift. Changing out the varactor for a diode that has more slide will also just increase the amount of drift - too. Using a varactor diode out of a Uniden chassis would also make it more stable as well.

 

[Stinkbait]

If it were my radio I wouldn't recommend extending the slide range. Never. If anything, I would want to decrease its range. Reason being that the more you make this particular radio with this chassis slide; then the more drift will occur in either cold or hot weather changes ('mobile environment'). It also allows for much easier adjustment of the clarifier in order to get an exact lock on who you are trying to dial in.

To decrease it to +/- 1.2khz total slide (600hz from center in either direction) and decrease the radios weakness for drift can be done and will make it user friendly. Uniden radios really don't suffer from drift compared to Galaxy/Ranger chassis radios. But even they can suffer from drift if the freq slide is increased too much. Galaxy radios just get downright nasty when slide is increased. If you aren't aware of it now; then you will be acquainted with it if you proceed.

In addition, the more you make the radio slide; the less fine control you will have and then the harder it becomes to get an exact lock on the person you are trying to dial in. You will often overshoot and that will prove to be very frustrating. Frequency overshoot will also be increased at either end of the clarifier pot as well, compounding extra slide issues even further.

Exitthirteen (forum member) gave me some solid tips on how to make it more stable. One is to eliminate the capacitor (C130/20pf) that is in parallel with the varactor diode. Another is to keep R153 stock - or decrease its resistance slightly - for less slide. Do NOT jump R114, as this will increase slide and likewise increase drift. Changing out the varactor for a diode that has more slide will also just increase the amount of drift - too. Using a varactor diode out of a Uniden chassis would also make it more stable as well.

If it were my radio I wouldn't recommend extending the slide range. Never. If anything, I would want to decrease its range. Reason being that the more you make this particular radio with this chassis slide; then the more drift will occur in either cold or hot weather changes ('mobile environment'). It also allows for much easier adjustment of the clarifier in order to get an exact lock on who you are trying to dial in.

To decrease it to +/- 1.2khz total slide (600hz from center in either direction) and decrease the radios weakness for drift can be done and will make it user friendly. Uniden radios really don't suffer from drift compared to Galaxy/Ranger chassis radios. But even they can suffer from drift if the freq slide is increased too much. Galaxy radios just get downright nasty when slide is increased. If you aren't aware of it now; then you will be acquainted with it if you proceed.

In addition, the more you make the radio slide; the less fine control you will have and then the harder it becomes to get an exact lock on the person you are trying to dial in. You will often overshoot and that will prove to be very frustrating. Frequency overshoot will also be increased at either end of the clarifier pot as well, compounding extra slide issues even further.

Exitthirteen (forum member) gave me some solid tips on how to make it more stable. One is to eliminate the capacitor (C130/20pf) that is in parallel with the varactor diode. Another is to keep R153 stock - or decrease its resistance slightly - for less slide. Do NOT jump R114, as this will increase slide and likewise increase drift. Changing out the varactor for a diode that has more slide will also just increase the amount of drift - too. Using a varactor diode out of a Uniden chassis would also make it more stable as well.

Thank you for that. I'm on my mobile now but let me get back to my workstation and look at some prints.
,, then I can better comment. I do appreciate all the advice I can get before I open it up again.

 

[Stinkbait]

The varactors form vintage uniden chassis (Washington,148,142, ect) have been discontinued but cross to NTE612, so does the Ranger chassis but the NTE612 has a temp coefficient spec that is not even mentioned in the svc251 so he may be on to something there, I've got some on order. R114 and the fine tuning is not an issue because I have a 10k/10turn pot in place of the 1k factory part. A 1k to 5k ten turn might have been a better choice but I didn't have any. Those resistances are from 8v to ground and only give you a voltage range for the wiper to select from. without R114 the voltage drop across the pot would be the same as it's the only resister in the leg, making R153 the critical component. R153 was 12k, changed to 10k and maybe I need a VR here. I can see no reason to jumper D38 in the wiper leg, no one seems to know why is was ever done. It keeps ac off the 8v buss. C130 was explained to me by "nomadradio" earlier to be the safety net or minimum capacitance the crystal requires. Apparently 4pf(20pf is factory) has been used buy some to bring the up slide closer to the down slide for balance, but this can't be good for stability. Also c130 needs to be a ceramic U/T cap. U/T caps are Hi frequency and Temp compensating. I was thinking 10pf would be plenty. I never considered removing it but will consider it if you think that's a good idea. The drift problem is more than likely the quality of the crystal it's self and possibly the cheep L cans. I have always just dealt with drift it by adjusting the clairifier on side band, the AM side is wide enough that effects are minimal. Now that it's warmer weather I haven't noticed it alot.
All in all I am convinced that you are right , I don't need alot of slide, it was an old school method to get between channels, and I like the idea of the digital VFO kits like Lesscomm anyway. Butt I still think this radio will slide.

 

[loosecannon]

Stinkbait
I dont think a vr will be a good thing there. Might decrease stability.

Robb
I hope we can get some clarification on c130 because o thought it was the expressly to provide temp compensation and that removing it might increase slide but at the cost of stability.
Admittedly that's just an assumption and i never really looked into it.
LC

 

[Robb]

[QUOTE="loosecannon, post: 623732, member: 1368"
Robb
I hope we can get some clarification on c130 because o thought it was the expressly to provide temp compensation and that removing it might increase slide but at the cost of stability.
Admittedly that's just an assumption and i never really looked into it.
LC[/QUOTE]
I never tried it yet either. It was a tip provided by Exitthirteen awile back on a thread expressly dedicated to the drift problem of the Galaxy 959. All I did to my 959 was change out the varactor and re-tuned the PLL/VCO/Loop osc and put the radio back into service since it worked somewhat better than before.

From what I can gather, the varactor in parallel with C130 tells me that the more/less the voltage is applied to the varactor, it would up/drop the total capacitance into the Xtal. W/o that capacitor, it would throw the tuning of that Xtal's freq waaaay off, and make re-tuning the loop osc difficult if not impossible. But hey; what do I know? Maybe I misunderstood it, since I recollect that info from awhile back.Temp compensation? Yup; there are a few of them in that radio for that purpose.

 

[Stinkbait]

At this point that sounds like a good idea to me too. The radios is working good atm, dead key 2 swings 12 on am max, voice compressor schottky diode receive and NB enhance. Speech processor and echo. Some drift on cold days but seem to like the hot car. This and the channel mod is all that's left then I start another project.

 

[Stinkbait]

It's from an eBay estate sale, I only got less than $200 invested in it, not counting labor and the parts I already had. Think I'll name it "Minnow Bucket".

 

[Stinkbait]

I found this crystal at Digikey
HC-49US ECS-153-20-4
Frequency Stability ±50 ppm (Stock Galaxy ±100ppm)
Tolerance ±30 ppm (Stock Galaxy ±50ppm)
Load Capacitance 20 pF (Stock Galaxy 15 to 50pf)
ESR 40 Ohms (Stock Galaxy 25 ohms)
price $.69 cents LINK---> digikey

Would this not be a more stable and tighter crystal than the stock one?

 

[nomadradio]

What you'll find is that not all crystals will 'slide' the same way in the same circuit. A stable crystal is better, but the oscillator circuit will also affect the crystal's drift performance.

Never learned how to predict that kind of performance from reading the published specs.

But it's cheap. Worth trying, at least.

73

 

[Handy Andy]

Greetings!

When you put that 4pF in, you just lost MOST of the slide that Varactor could provide - so your 1kHz of slide result...(Caps act like series in that scenario)

Don't try to put all the 10K to entire voltage buss range from 8V+ all the way down to ground - you'll wind up damaging the radio - you can lose the Varactor if you don't keep it biased by the clarifier in that circuit...

Glad you changed it back...

R114 needs to have some resistance (Try 1K) to help keep the POTS own voltage towards the Varactor - higher, to keep the Varactor in reversed biased condition...so you have some capacitance.

The 10uF - "dampens" down the jittery wiper output on the stock clarifier control - if you use the 10-turn super slide - then the cap can be brought to as low as a 0.1uF Polarized to help with the noise level present on any potentiometers substrate as it's wiper arm is scraped along the internal composition.

The 47K is simply the inputs' impedance loading - the circuit is so capacitive - the highly resistive effort places very little loading in power levels - just voltage - the 47K just keeps that "real world" event of body capacitance and noise levels out of the circuit as much as possible.

Varactors are not linear devices, they act more logarithmic - meaning they have their best capacitive change in a narrow range of voltage - so you know - you will lose linearity (equal levels of slide) if you don't provide or compensate for this.

Your 10K effort is admirable - and you're seeing the "linearity" issue already - like a Cobra 148 or even a TRC453 - they "swamp" the pots output line to ground with a 6.8K to as much as 22K - but get the slider range you want without going to the extremes.

If 10K won't take you there in frequency stability and range - get R114 back in and try that again - see what that Varactor can develop in the working window of voltage to capacitive charge change to obtain the best range of slide for your needs. You may not get it all but keep it simple...

With dual final scenario - the 2030 versus IRF520 - 6 of one, 1/2 dozen of another .

It's a lot of power to throw at an amp - so if you run a 5 pill you may "overdrive the input" with those duals - but if you have a 4 pill - you'll need the dualies to drive it.

But again why switch finals if the 2030 seems ok? IRF 520 may work - and yes they do but you're spending dollars just to get a few more pennies in change...

Get the thing to do some of the stuff you want first then re-evaluate the setup, and as you step back - you can work on a different approach as you need.

Don't put the cart before the horse...

Regards!
:+> Andy <+:

 

[Stinkbait]

Good stuff, Thanks for input. Say I put a 10pf/UJ at C131, 1k at R144 to keep pot from bottoming out, leave R153 at 10k, and go to a higher range variactor, say NTE614(33pf) or inlist a 612 (near cross to stock but has temp comp), I have both of these in the parts bin . Leave everything else alone, re-tune and test.
I've already sold the the 500w amp, it only got 250bird anyway. Will find me a better one somewhere. I'm moving atm, and my shop is packed up but I'm collecting parts and will try out some of the tips I have been getting. Thanks everybody, a goldmine of knowledge on these pages.

 

[Grouchy Ham]

I have never seen a dual final galaxy 959 to do a full 45 watts. if you whistle or yell into the mic you might see a peak of about that. normally with a dual final radio you will see 12 to 18 watts when just talking.
here is a link to do the dual mosfet mod with all the holes filled in as you call it. a few will still be empty as a few parts are not needed. hope this puts you in the right direction. but you will not get 45 watts of talking power out of it. you will have a little more out put if you use the 13n10 mosfets and not the irf520 shown. the 13n10 uses all the same parts the 520 does.

http://www.cbtricks.com/miscellaneous/fet_papers/mosfet_conv/graphics/6900xxx_ssb_mosfet.pdf

Thanks for this info. Should work great on this Texas Ranger TR-966 I bought with a dead 2SC1969. I've been searching for this.