Galaxy 959 AGC improvement

[wyatt knight]

I found this mod listed on several places on the net including this one [Please login or register to view this link]. Is there any improvement to be had on a otherwise properly functioning radio? Both of my Galaxy's have had the recieve mod done to them and have been checked and are on frequency. If modifying the AGC circuit would give an improvement, how can I tell if it needs to be monkeyed with? Maybe somebody can enlighten me. Thanks in advance.

['Doc]

What 'AGC' does is keep a signal at a sort of constant level. Typically that means it reduces the strength of a signal so that it doesn't exceed a 'normal' range, don't have to adjust the volume control to make it easy to listen to, or over load the audio section of the radio (that's not an exact description, but you get the general idea). The usual adjustment range as far as signal 'strength' is concerned variable, but it typically chosen for the best 'average'. I'd leave that part alone if you are generally an 'average' person with 'average' ears. The other adjustment common with 'AGC' is the 'speed' it reacts. The 'best' setting for that depends on the mode of the signal being received. For the usual AM signal, a "slow" 'AGC' is nice since the average signal strength, the amount of change between high and low portions of that signal isn't much. So, it sort of 'smooths' things out till is sounds 'normal', no blaring sort of. A SSB signal has quite a bit of change between the high points and the low points (no sound at all at the low points so no signal being received). SSB benefits from a faster AGC, the signal get's 'leveled out' faster. Something between 'fast' and 'slow' will typically handle either. You could 'tailor' it to your taste, but typically, it's going to be 'good enough' how it's set. Best thing I can think of is to listen to a radio with adjustable AGC, see which you prefer for the different modes and go from there.Manufacturers tend to pick the 'best' setting to start with, so unless it's really aggravating, leave it alone. Wanna see what the differences are? Why not, have at it.
- 'Doc

[wyatt knight]

Thanks Doc, I appreciate the comment. I'm actualy satisfied with my 959's and don't think they need any more tweaking. They recieve well and have good transmit ability. I was just wondering for myself and the benefit of others if there was a telltale indication that the AGC circuit is in need of modification.

[TheCBDoctor]

Thanks Doc, I appreciate the comment. I'm actualy satisfied with my 959's and don't think they need any more tweaking. They recieve well and have good transmit ability. I was just wondering for myself and the benefit of others if there was a telltale indication that the AGC circuit is in need of modification.

Hi wyatt knight,

The circuit that controls the AGC and the squelch threshold is IC-!. IC-1 is a quad operational amplifier. It is set up for the best operation between performance and practicality. The circuit is fine just as it was engineered. I agree with 'Doc.....leave it alone.

If you can put up with the drifting due to temperature change on SSB, then I would say it is a good radio for the money. You may find that it needs an alignment to operate properly on SSB. I have yet to take one out of the box that didn't an alignment. You won't notice drifting or the alignment problem on AM.

[Please login or register to view this link] Photos

[Please login or register to view this link] Alignment procedure.


Respectfully,

[wyatt knight]

I have two and they have been checked by a local tech here and he said they were spot-on. I bought my first one in 2002 and my last one I bought was made in 2007 and I bought it last year , around November, and after "peaking" them myself and adding echo boards to them, I am very happy with them. I am thinking of opening them back up though to lower my dead-key to where I can turn the RF power down to two watts for running an amp. The one I have set-up as a base has a 3 1/2 watt DK swinging to 18 bare-foot, giving me 100 watt DK swinging to around 200 with the amp on low.

[wyatt knight]

Opened up my "base" 959 and turned the dead-key down, and two watts wasn't far enough. I ended up with .8 watts giving me a 20 watt DK swinging to around 150 with a loud audio. On high I get a 40 watt DK swinging to the same 150 watts. On sideband I get 250 watts on low to 300 watts on high. The help and the advice available here is priceless.

[TheCBDoctor]

Opened up my "base" 959 and turned the dead-key down, and two watts wasn't far enough. I ended up with .8 watts giving me a 20 watt DK swinging to around 150 with a loud audio. On high I get a 40 watt DK swinging to the same 150 watts. On sideband I get 250 watts on low to 300 watts on high. The help and the advice available here is priceless.

Hi wyatt knight

You realize with a dead key of .8 watts and a 20 watt peak output that you no longer have an AM modulated carrier. You are in fact running a dual sideband suppressed carrier operation. Granted that carrier is a waste of energy and efficiency, but you do need some carrier in order for a distant station to lock onto your signal. The result is stations close by will say you sound loud and proud. Distant stations will say you sound fuzzy or that you sound like you are on sideband. I believe you already know this.

As for getting 3 DX-959 that required no alignment, I have yet to get one out of the nearly 1,000 that I have received out of the box that worked on SSB. Am will never be noticed, but every sideband operator that has brought me their DX-959 or DX-2547 needed a serious alignment. You must be the lucky operator that had an adult tune the radio from the factory using calibrated equipment. I found that the older models that used transistor Finals were much better. They have gone down hill since then.

The up side is the radio will not kill your dog like the dog food that China exported to the USA a few years back. I stay away from Chinese and Malaysian crap.

Just my personal observation and 2 cents,

Respectfully as always,

[wyatt knight]

The .8 DK is with the variable RF turned down and it swings to 6 from there. With the RF power knob turned back up, I get 4 watts swinging to 12 watts. That's with the amp off and barefoot, I keep the RF knob turned up when the amp is off. When I turn the amp on, I DK 20 watts swinging to 120 with amp on low, and with the high setting, I get 40 watts DK swinging to 150. The transistors in the amp I have are two, 568BLYCF's. I haven't been able to find any info on them so far but as far as output goes, they are performing along the lines of what I have read on the MRF 455 and the SD1446 pills. I may go ahead and turn my RF back up to where I can adjust from 1.5 DK for running the amp, and 4 watts or so for running barefoot. Any thoughts are appreciated and welcomed. This could be it's own thread as it has gotten away from the original post.

[wyatt knight]

I forgot to mention, I have two 959's and they were checked by two different shops. I had talked to each shop about getting them aligned and asked how much for the service. At each shop, they benched them at no charge and told me that they were fine. Now they may be off as I don't know anything about the test equipment they use. These radios were bought several years apart, one being made in 2002, and having a 1969 final, and the other one has the IRF-520 final. All I know is they work for me as I have them now and I've been pleased with them. I'm just trying to not burn up my amp with too much DK.