Well, shoot just as the conversation starts to condense into something can write about...
We are looking at drift, and finding a better method to use for those whom can't wait or are in an environment that doesn't work well for the typical methods...
One aspect was encasing the entire XCO in a shield - and in older radios - that was THE go-to for it.
Another was the oven method, you warm up the innards of the radio - in conjunction with the above - you got things to work well within a limited, but still a waiting, period of time until you can use the radio in a roundtable.
I was simply trying to show that many a good clarifier circuit gets ruined by poor mods- because as I fix the radios that come across my desk, I find in the Clarifier replacement column - they're replaced because the end user had a mod done to the circuit to maximize slide or several attempts at mods to make the Coarse and Fine track as one to help them tune others in. Another problem was due to the mod itself damaging the substrate or the pot to make it unusable because the user modded it in a way it popped like a fuse and in some instances - took out parts of the VCO circuit too - at least a foil trace or two.
If you filter out just my messages in this thread, I wasn't bashing the temperature effects or even downplaying them - I'm learning right along with the rest of you. I'm looking for options...I have several but I need the rest of those jumping into the thread - don't add so much foam to it - that we can't see the efforts others are making.
With that being said...
How To Build A Better Mouse....
1.
The Mayhem, The Animal - The Beast...
For Clarity here's how - or what I do - for someone when they want to unlock the Galaxy Clarifier - I'm using 98 for this - I can show this also on a 949 as needed...my own stock radio...
But because more documentation is available for the 98 - this is shown Graphically to help others with older style radios - work alongside as you may want to investigate these as I go...
Since there has been issues before - I will add that the graphics contained have logos and originations and sources for their specific design and all copyrights are held by the respective companies ...
- used for Educational Purposes Only
First though...
ss
Schematically...
What the front panel looks like ...
2. Select the Right Cheese...
When the conversion is complete - there is little if any retuning that is necessary - for the Diodes, R113 and all parts are kept intact, the only thing that has changed in this, is a constant source from the 8 volt PLL power supply is used.
The mod listed above unlocks BOTH Fine and Coarse and ties both together to use for VCO to track SSB modes and AM FM and any mode in-between. RX and TX are sourced to a single power supply reference.
The cheese is in the use of two diodes and this is how I found out about the COMPENSATION the diodes can provide was by accident. D68 and D38 are the two I'm referring to in this.
The drift the galaxy would have - and after this conversion - still does occur - is slightly different - but still inherited by the design and parts used. So we don't have all our ducks in a row yet.
What I want you to pay attention to is the Voltage Divider design - for it isn't all the way up to source rail voltage or all the way down to ground buss - it floats - not towards the ground buss, more in the upper range of voltage but not all the way to the top.
A lot of people, techs or otherwise have always complained that the Galaxy radios have this "drift" problem - it's from the design itself - it's not all to blame on thermal though - it's the sheer range of tuning both the Fine and Coarse provide the person when it comes to tuning in to someone.
To blame it on thermal would be fantastic for then we'd have a fighting chance to force the maker to re-design the radio to suit the user needs better and save us from having to face the music from the customer for the makers bad design in the first place.
I reduce some of the drift by the use of the resistor and diode in series - limits slide but the user is able to recover the channel center and use the "detent" on both controls to obtain it - faster.
3. Use Your Mouse Like You Own It...
One thing I do see, that many others are either not paying attention for or not offering any recourse to fix is when the user transmits - it Warbles - or it's frequency is not steady. This is a separate problem dealing with load variation - the power supply and the voltage regulation on it, and from it, is not the best. Although some improvement can be made in current handling by upgrading the 473 to a greater capacity transistor - it does not offer much more than extra capacity. There is another problem and that deals with the sensitivity of the Varactor to changes in voltage from the supply.
Again the upgrading of the transistor is a good option but to reduce the effects of loading - we still have the problem of a large window of adjustment or range to tune and we have it straight across the 8 volt rail.
The mod shown above is a simple one an uses R113 as a BUFFER from the voltage supply. This helps to reduce the loading off the rail into the clarifier - but little else only other options are increase the R113 value to limit slide even further or abandon the dual concentric and settle for single range carbon composition potentiometer - with todays radios, not an option.
So limit power supply drains by reducing the sags (dropout events) by keeping limiters in place and operating normally by setting AM power, ALC, AMC and FM Power and deviation levels to operate like stock.
I guess what I'm trying to say here is there are little factors that many would not tend to think as problems until the radio is heavily modded and or limiters removed - then do we notice the failures and shortcomings in the system.
So while everyone blames drift on thermal - there are a lot of other mitigating factors that tend to cause more problems even for radios that are warmed up and on frequency - including poorly managed regulation and or heavy modulation conversions that affect the power supply and it's ability to keep up with demand.
I can also show you other methods I dabbled in for offsetting Clarifier drift by using diodes ACROSS a resistive shunt.
How that method works is by knowing how much of a voltage variance is happening when the radio is cold to when it warms up - anyone whom has used a 2950 and 2970 knows the RIT Clarifier tune WHEN COLD is not equal to the frequency displayed nor is the expected frequency of the VCO is exact to the display even if the RIT had been kept center slot - even correctly tuned AFTER it had been warned up to room temperature. This is due to the loop issue I discussed earlier - the tech can do some initial measurements of voltage using warmed up equipment on that cold radio - to see a profile of the voltage rise or fall on the wiper line or the line that goes to the XVCO VCO from the RIT and TX from PLL feed into - the line is from the voltage divider of the source line and the ground buss, again a drift that can be compensated for by using a diode across a resistor - use a simple formula to obtain the voltage drop needed when cold and sub in accordingly. The tech or user can use a FIXED resistor to provide a known drop and the diode or series of diodes (some PLL and RIT differences can get to as high as two volts from one side or another requiring the inherent voltage drop across the resistor paralleled with the set of diodes) to obtain the compensation thru the voltage drop changes the diodes provide across the fixed resistance.
So that is another thread for later. The whole effort here is to show that although thermal seems to be the paramount importance for the Drift problem, I've seen other issues of drift that are not seeming to be covered here, which is part of this problem - it's not going away so we have to face it.
:+> Andy <+:
