Moderator: JR Moderator
This modification will allow the DX959 & DX949 to exhibit the RF output and swing of the Galaxy DX-series 10-meter radios. The board was always capable of this type of output; it was simply choked off by the design engineers in order to meet FCC 11-meter specifications.
The first thing you need to do is turn up VR14 which is the AM high power variable. If you?ve already done the modulation improvements, you should be able to dead key about 8-10 watts and swing around 15 watts. 18 watts is probably the best you?ll get (using a peak-reading Bird wattmeter). Now, perform the following modifications:
Remove C218 (3pf) and discard.
Change C216 (470pf) to a 1000pf (100V mylar-type)
Remove C210 (470pf) and discard.
Remove C199 (560pf) and reinstall it in the C210 spot.
Don't try to get a 10 watt deadkey out of single mosfet. It'll do it, but the general consensus is that it'll fry, and you'll never get 100% modulation doing 10 swinging 15.
Have a tech do a dual mosfet, or avoid the headaches and just get a small kicker. RM Italy makes some tiny amps you can get for 45-50$ shipped, it'll cost you the same as getting a second mosfet, and put out the same or more, depending on what you get. (KL-40, KL-60)
I run my radio into a 2x6 box. I would just like to have more swing to drive the top end a bit more. I am not sure what the max input is into the type of box though. Its a 2 (1446) x 6 (2879)
that will raise the swing and the avg. power quite a bit...and your amp
will love it too.
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The problem with the Galaxy DX 959 is not so much the output power, it is the fact that they come from the factory out of alignment and drastically off frequency. The power increase can be done by just putting in the right pair of driver/ final combination.
I have used the 2SC 2166 and a 2SC 2029. The driver used (2SC 2166) was tested out of a batch of 2166's that I had, I chose the one with the highest gain; I used an beta tester. The 2029 I knew from experience had a high gain from working on the original 29 GTL. After that it was a question of adjusting the modulation and carrier. I have gotten 7 watts dead key (a waste of energy) and a peak of 24 watts. This would put you just over 100% modulation if you talked directly into the mic. On sideband it came close to 26 watts peak.
Spreading the toroidal, and the other fixed coils are okay to achieve maximum output, but I recommend not to remove any capacitors. Removing the capacitors may give your radio a few extra watts, but you may interfere with the output impedance of the radio which is 50 ohms. That means your antenna will have to be cut to match the radio. For the maximum amount of energy to be transferred the input and output impedance must be the same. Your radio may see a high SWR on another person's antenna. Be careful when adding or taking out capacitors in the tank and output circuit.
The alignment can be found on my Web site. Go to Radio List and click on the DX 959 or DX 2547 for the picture, then click on the picture for description, under one of the pictures is the alignment. The picture of the inside of the DX 959 has a link on the description page to the alignment procedure. I guarantee your radio needs one. I haven't come across one in a hundred that came anywhere close to being properly aligned. It could not be used on SSB (On AM you would not notice).
Once properly worked on it is not a bad SSB radio. You will never get a true peak output of more than 24 watts. For 35 watts you need dual finals. For the cost of doing the upgrade it is not worth it, but if you like to experiment then I say go for it. The only way we can learn is by trying and experimenting. If you enjoy doing; even better.
Good luck with your radio. It is a capable of a lot more than what it does. Why do you thing that it comes with a variable Talk- Back?
Rick, The CB Doctor
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I just removed one resistor and replaced it with a zener diode.
It is the next resistor in line after the VR for am high power.
I think it's the r249 but I'm not positive about that #.
I found it was hiding under a ceramic disc capacitor
right beside the VR for am high power. I made sure the cathode end was
toward the right with the radio facing me. Some mods call for lifting
one leg of the resistor and adding a 1n4001 diode in line with the cathode end
facing the right, but I've found that with just removing the resistor and replacing it
with the zener diode adds much more swing.
The one I set up had a real low dead key, but still would swing about 20 on my meter.
I refuse to cut any audio limiter, but it may do more if you did that.
I don't recommend removing any audio limiters....especially in a side band radio,
because it will eventually burn up the audio IC....which is kinda expensive to
How does this sound for a simple mod to achieve max swing under any dead key?
That would give me about another 5-7 watts from a 2 watt dead key which I would be happy with
I'd have to look at the board to know.
I'd try anything once just to see what happens.
but the r264 does sound familiar. So many of those radios have the same
components, just have different numbers.
The mod that calls for lifting one leg and adding a 1n4001 in line with
the resistor is good, but I like to just remove the resistor and replace it with
a 12 volt zener diode. Seems to get just a hair more swing with a lower dead key.
I've done the same mod on hundreds...maybe thousands of galaxy "clones"
with the same results. I don't try to remember the numbers, I just follow the trace
from the AM high power VR to the next resistor and do my thing.
Good luck with it.
always be on the right with the cathode end towards the right.
If you use the .....I think it is R264, you may have trouble finding it.
It is hiding under a ceramic disc capicitor directly to the right of the VR
for AM high power. The diode itself usually covers the number, so it is hard to see
until you have lifted the right leg and moved the resistor. Then you should see
the number for the resistor. I think they deliberately try to hide it to discourage
people from doing this particular mod....they are trying to make it look like they
want people to comply with fcc regulations.
If you are just adding the diode in series with the resistor, it is best to try to
twist the legs together, then solder the twist and trim the excess. With that mod,
it is best to use a 1N4001 silicon protection diode.
Try that mod first, and you should see some increase in audio no matter how low
you set the dead key. You may be satisfied with the results.
If you want to see even more swing from a very low dead key, remove the
resistor and diode and replace it with a 12 volt zener, and also have the cathode
end toward the right. That mod also works well with a 1N4048 glass diode.
The radio will be loud, but not over modulated because the carrier will still rise
naturally with the modulation. It will technichly be over modulated on a meter, but
will sound clear. Some people also remove the audio limiter, but I don't recommend
that....especially on a side band radio, because it will not sound as good.
On side band, it will be very distorted with the audio limiter removed.
Also, the audio limiter is there to help protect the audio intergrated circuit
from burning up or getting weak from overmodulation. That is a rather
expensive chip, and not as easy to replace since it has multiple legs that
are very close together, and could easily get 2 or more legs interconnected.
Use the VR for am modulation to increase audio....you can even turn it fully
for maximum pep without damaging the radio's circuitry, and still have control
in the modulation section to protect the other chips.
I think you'll be very happy with the end results. What makes it even easier,
is the fact that you don't even have to re-tune....it's already tuned from the factory,
and usually balanced well on all channels. Just set the high and low power where you desire,
and let it swing !!!
I've seen some sites that say the radio won't match well with an amplifier if you do this mod,
but I've never seen an amp that doesn't like the low dead key and high swing. There are a few
amps out there that need more dead key to keep the relays from chattering, and a few that
need a very low dead key....say 1 watt or less (like a super star 550) .
Good luck, and have fun with the loud and proud radio.
Will the zener diode still allow the radio to swing properly with say up to a 4 watt dead key?
Would I be ok to just pick up a 1 watt 12 volt zener diode pack from radio shack?
How do I identify what side is the cathode size of the zener diode? I can look it up but just thought I would ask.
I really appreciate all of your help. Thank you so much I cant wait for this thing to really swing. I bet my box will love the increased swing as compared to what i have now. Right now with my dead key set I see about 10-12 watts swing peak as I am talking.
Im totally happy. I was going to do the zener diode but RS was out of stock on them so i tried this one. You cant even tell I soldered there either which I was proud of!
Anyways before I could not slap my 20 watt meter. Actually I couldnt swing more than 18 watts even with the mic gain all the way up. Now with my radio all tuned back in sounding good I bang out the 20 watt section everytime. This may not be very accurate because of my meter but I dont care about the number. All I know is it swings way more than before on the same meter and setup. I also notice my power stays peaked on my meter much more as I talk and it peaks at 1400 from a 200 watt dead key.
Now I need to finish my bigger power supply. I am droping this one to 13.5 volts under drive and with my new power supply I will have a 30 amp bigger transformer setup so it should hold voltage a bit better. Either way in my neck of the woods im one of the LOUDEST out there! haha
If my memory serves me correctly, their's are grey with a black stripe.
A 1N4048 will work too. They are clear (glass) with a red or black stripe.
The cathode is marked with a banded stripe....usually a black stripe.
The 1N4001 silicon protection diodes that most sites recomend to put
in series with the resistor is usually black with a grey stripe.
Just be sure that stripe is to the right with the radio facing you !!!
It will let the radio swing to full potential no matter where you put the dead key.
On the 959, I usually see about 18-20 watts pep after I do the mod.
I'm pretty sure it's the R264, but I won't swear to it, that I remove and replace
with the diode. I know it's right beside (to the right with the radio facing you) the
VR for AM high power, and usually it's hiding under a ceramic disc cap.
Your amp will love it !!!
You can use the VRs for AM high power and AM low power to set your power
wherever you want. I set every one differently depending on what they want.
Some will have a very low dead key on low (say less than 1 watt) but won't go over
a 2 or 3 watt dead key with the power on high, and will still swing about 18 or 20
no matter where the dead key is set. That way they can talk through their boxes well on low,
but be able to "raise the wave" when conditions get rough and tough, without over-driving
Some I set at a 2 or 3 watt dead key on low, but about a 8 watt dead key on high.
That way they can have the best of both worlds. They can talk barefoot on high, but be
able to turn the dead key down to drive a box.
Some people want 1/4 watt dead key or less, some want 3 or 4 watts, some want more.
It all depends on their preference and their application. But they will still swing to full potential
no matter where the dead key is set. Just dont let the dead key go over 8 or 9 watts.
That will strain the radios final. The finals are supposed to be rated for about a 13 watt dead key,
but that is pushing it to the max, and you may not be able to get 100% modulation if the
radio's dead key is to high.
If you see much more than 18 or 20 watts swing, your meter is lying to you.
I always use a non radiating dummy load when I am setting up
a radio. Mine is a military type dummy load that can handle up to
5000 watts for at least 15 minutes constant. Most "paint can" type dummy
loads can take 1500 watts for only a few minutes. If you do your peaking and
testing on an antenna, it will be radiating (others will hear you) and you will
most likely get somewhat false readings just because of SWR, image reflection,
magnetic wave, distorted internal harmonics and other factors.
I'm just now noticing that you've already done the mod last night.
Sorry I was so slow with my response, but I've been busy working on radios for
some of the local mud ducks around here.
I hope you put that 1N4001 in series with the resistor. If you replaced the resistor
with that diode, it may not last long.
If you want to see even more swing, try the mod that I recommended sometime.
Let them all know that Hanky Panky helped you. Some of them may even know me.
I am world famous for the radios I've repaired. Well.... as far as Barbados anyway.
I'm around Shelbyville, IN and I usually talk local on channel 4. (27.005) when I have
time to just chat.
Stop in and wave a hand if you ever hear me, I may even be able to get it back to you.
I only run about 300 watts around here....I like my neighbors and they like me.
If I try to run more than that, my phone will start ringing !!!
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