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Mike Debunks Shottky Diode Receive Mod
- Thread starter KD8HMO
- Start date
Kinda' been there done that...
He covers a lot of stuff we've discussed here...
https://www.worldwidedx.com/threads/2sc2999-mod-analysis.161809/
Did pretty much confirm the Germanium versus Silicon debate BUT, the Schottky Vf reference is about the same - so...
Your point is???
If you think the debate is done, better look again.
You gonna' let China walk all over you for your choice?
They - the powers that be, have already marked, used and are currently marketing the Schottky Barrier Diode as a 1N60 device...
http://www.formosams.com/en/
But Microsemi has made a unique RF 1N60 replacement device using BKC's Sigma-Bond (before Merger) using Gold - PDF of it attached also...
So, Mike may have reinvented the wheel, but it is not gonna stop the ball that's Chinas' steamrolling over this...
He covers a lot of stuff we've discussed here...
https://www.worldwidedx.com/threads/2sc2999-mod-analysis.161809/
Did pretty much confirm the Germanium versus Silicon debate BUT, the Schottky Vf reference is about the same - so...
Your point is???
If you think the debate is done, better look again.
You gonna' let China walk all over you for your choice?
They - the powers that be, have already marked, used and are currently marketing the Schottky Barrier Diode as a 1N60 device...
http://www.formosams.com/en/
But Microsemi has made a unique RF 1N60 replacement device using BKC's Sigma-Bond (before Merger) using Gold - PDF of it attached also...
So, Mike may have reinvented the wheel, but it is not gonna stop the ball that's Chinas' steamrolling over this...
I have done the schottjy mod on a bunch of radios and I do think it made a difference. but of course those might have been borderline radios to start with and the mod corrected a misalignment in the radio. I have seen brand new right out of the box be off a very large amount 460 HZ on the pll. It would not even work on SSB.
Anything for people who can read? I do not have 2 hours to waste with something I could read in 5 minutes.
Mike
Mike
I tried to watch it and after 45 seconds all I heard was "Blah, blah, blah."
i watched most of that video.
I am neither defending nor doubting Mike or the mod itself.
I do the diodes only version of this to my old uniden radios and i notice a difference.
or at least i think i notice a difference.
If mike really wanted get all the data, he would have to do the same thing to the galaxy style radios, and the other old uniden chassis.
this video only shows the difference in the dual conversion MB8719 SSB chassis.
I can't imagine the data would be much different, but i would still be interested in knowing.
I posted a question to the video about whether or not he was re-aligning the radio between each parts change, but he probably hasn't seen it.
LC
I am neither defending nor doubting Mike or the mod itself.
I do the diodes only version of this to my old uniden radios and i notice a difference.
or at least i think i notice a difference.
If mike really wanted get all the data, he would have to do the same thing to the galaxy style radios, and the other old uniden chassis.
this video only shows the difference in the dual conversion MB8719 SSB chassis.
I can't imagine the data would be much different, but i would still be interested in knowing.
I posted a question to the video about whether or not he was re-aligning the radio between each parts change, but he probably hasn't seen it.
LC
I don't know if I have ever seen a Germanium diode. I have seen mostly standard silicone diodes that have a .6 volt forward voltage drop. Schottky diodes have a .2 forward voltage drop. Are they germanium? Maybe so.
The mod works because the diodes conduct and rectify more of the signal.
A gain of .4 forward voltage drop gets you more usable signal to work with.
The way I understand it how well it works varies quite a bit from one chassis to the next, it all depends on how crappy the diodes that the manufacturer used are.
He - Mike, made a comment about a "pop" or crackle that is heard ...
He also mentioned Tickler,
He's referring to this...
Cobra 142....
See the Blue arrow? That is your Tickler, note the value used...
Cobra 146GTL
Same for the 146 Which was more of a Uniden design than Cobra - but none-the-less look for that Tickler and note it's value and the circuit used...
Now, for what Mike mentioned...
Galaxy 3600 14 boards...
Look for the "BLUE" arrow - that part takes in 8 volts bias from the RX line, and shoves it into the AM detector - every radio that has an ANL/AM detector uses a Tickler as a means for passing "idle" current and when a signal propagates thru the IF chain, the Diode conducts readily. This sends audio signal and a current into the ANL as well as AGC sections.
The Ticker plays role in not just how the ANL works. It also affects how well the receiver works in general. It, that trickle power, is available all the time for the circuit to use and keep the difference of Signal versus Barrier the diode has, that difference low enough for the signals like whispers can pass thru the detector as well as stronger signals but prevent the forcing of carrier and any intelligence in it, that can get lost because it's clipped or "Barriered" off into and thru the "Barrier" the diode presents - which would have to be overcome without that tickler in place.
IN the RCI - Galaxy appraoch you can't have the best of both worlds without a sacrifice. Keeping the idle current low and starving the detector - so that when a signal is detected it is requiring a considerable amount of energy from the signal taken away from the circuit just to "Open" the diode into conduction. Which makes you hear a type of noise like shot noise or noise gating... The Galaxy RCI line is similar to those listed above, but they use the Tickler to work more like a noise gate due to the broadbanded response of the IF strip tends to bring in a lot of noise and artifacts - so that "R100" which will forward Bias the two Detector diodes D23 and D24 as well as affect the ANL diode at D26 - is the "best choice" for diode use else you have to mess more with AGC thresholds and the lack of bandwidth you will get when you try to adjust this - for the AGC will tend to "quiet or tamp down" the ambient noise when you adjust the tickler too low of ohmic resistance to obtain a even-level of operational noise quieting.
So the cost of the quenching needed to keep the noise down, they used Schottky instead of Germanium as they did with earlier DX model and SuperStar boards. Even the Noise Blanker section could use a Germanium upgrade.
Now I got my azz capped for a discussion of a simpler design back in the CB Tricks days...I didn't change my story then - nor do I now - for it keeps getting proven over and over again - read on...
Dealing with a Diode Bridge and resistors used across in parallel with the diodes in the bridge.
I called it "to soften" the noise for detection of near noise level to embedded in noise level signals - the human EAR can cognitively sort out the intelligence from the noise in the speaker when they are approaching receiver sensitivity at those levels.
To make the comment about the "pop" or crackle - Mike is addressing the issue of using Schottky versus the Germanium types.
There is also the effort of how quickly Germanium can recover versus Schottky - there is a considerable difference and the pinch off point is what differentiates between the two types as well as the frequency response and the required compensation network for proper AGC operation.
He also mentioned Tickler,
He's referring to this...
Cobra 142....
See the Blue arrow? That is your Tickler, note the value used...
Cobra 146GTL
Same for the 146 Which was more of a Uniden design than Cobra - but none-the-less look for that Tickler and note it's value and the circuit used...
Now, for what Mike mentioned...
Galaxy 3600 14 boards...
Look for the "BLUE" arrow - that part takes in 8 volts bias from the RX line, and shoves it into the AM detector - every radio that has an ANL/AM detector uses a Tickler as a means for passing "idle" current and when a signal propagates thru the IF chain, the Diode conducts readily. This sends audio signal and a current into the ANL as well as AGC sections.
The Ticker plays role in not just how the ANL works. It also affects how well the receiver works in general. It, that trickle power, is available all the time for the circuit to use and keep the difference of Signal versus Barrier the diode has, that difference low enough for the signals like whispers can pass thru the detector as well as stronger signals but prevent the forcing of carrier and any intelligence in it, that can get lost because it's clipped or "Barriered" off into and thru the "Barrier" the diode presents - which would have to be overcome without that tickler in place.
IN the RCI - Galaxy appraoch you can't have the best of both worlds without a sacrifice. Keeping the idle current low and starving the detector - so that when a signal is detected it is requiring a considerable amount of energy from the signal taken away from the circuit just to "Open" the diode into conduction. Which makes you hear a type of noise like shot noise or noise gating... The Galaxy RCI line is similar to those listed above, but they use the Tickler to work more like a noise gate due to the broadbanded response of the IF strip tends to bring in a lot of noise and artifacts - so that "R100" which will forward Bias the two Detector diodes D23 and D24 as well as affect the ANL diode at D26 - is the "best choice" for diode use else you have to mess more with AGC thresholds and the lack of bandwidth you will get when you try to adjust this - for the AGC will tend to "quiet or tamp down" the ambient noise when you adjust the tickler too low of ohmic resistance to obtain a even-level of operational noise quieting.
So the cost of the quenching needed to keep the noise down, they used Schottky instead of Germanium as they did with earlier DX model and SuperStar boards. Even the Noise Blanker section could use a Germanium upgrade.
Now I got my azz capped for a discussion of a simpler design back in the CB Tricks days...I didn't change my story then - nor do I now - for it keeps getting proven over and over again - read on...
Dealing with a Diode Bridge and resistors used across in parallel with the diodes in the bridge.
I called it "to soften" the noise for detection of near noise level to embedded in noise level signals - the human EAR can cognitively sort out the intelligence from the noise in the speaker when they are approaching receiver sensitivity at those levels.
To make the comment about the "pop" or crackle - Mike is addressing the issue of using Schottky versus the Germanium types.
There is also the effort of how quickly Germanium can recover versus Schottky - there is a considerable difference and the pinch off point is what differentiates between the two types as well as the frequency response and the required compensation network for proper AGC operation.
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I’m certainly not a tech. But I followed someone’s Shottky receive mod for dummies recipe on a 959 once and the noise reduction and receive improvement was significant.
Then I'll clarify.
Mike produced the vid in order to show that the older Gemanium diodes are the ones to keep in place.
Ok, I'm fine with that...
But what he does not tell you is this...
Germanium is a crystal lattice, and just like it's Silicon brethren - it's crystalline structure can "break" and or fracture diminishing the devices usefulness and shortened life span. Age, power surges and vibration take it's toll on those diodes and because of their design and "cat whisker" used as the point contact to make the junction - it's easily seen where the performance will degrade over time in mobile environments let alone anything a typical user will subject the radio to - no matter what
The radio has to complete two functions -
Derive audio from the signal...
Process the signal the audio is in - to obtain a gain factor to use as a feedback loop for the radios' Automatic Gain Control (AGC) which uses audio and the carrier together to form a feedback signal to control gain the radio has.
Use the incoming signal as a means to process the gain and maintain consistent volume while also attempting to reduce the noise the signal is embedded in.
Why am I telling you the above?
It's in how you approach the upgrade problem.
Galena, or Germanium - (at the age the radio was built - they could have used both types) has a performance that cannot be duplicated in a typical Silicon or Schottky diode design - it's simply not there. The overall performance of the part affects audio and it's inherent low- Forward Voltage Drop rating (V f) makes this an ideal part for Audio detection.
But, the drawbacks are it's sensitivity to the environment it will be used in. Shock, vibration, reverse current - power surges and power draw - all affect the lattice - rock, stuck in that glass capsule. It is a crystal, and they tend to "bend" or twist and heat up as power passes thru them. This action is strong enough to make the point contact itself "shift" and the diode is no longer as effective as it once was. The "rock" in that glass case is not pure - it's mined and refined from various ores (mostly Zinc and Lead)
In knowing the above, you can get a better idea that they have a limited variety of applications - they are rectifiers, yes, but not POWER rectifier devices. They work better in detection than in rectification.
So approach this problem knowing you have Audio to detect, and signal to process - and once you understand the difference between the two - Schottky can be used to replace the Germanium parts that are used in processing the signal, and leave Germanium for the Audio detection. Silicon Schottky as a power device provides the low-Forward Voltage drop like Germanium but handles the power and current issues better - versus keeping Germanium in the areas that you derive the audio from the signal - so it is not impacted by inherent noise issues commonly found in Silicon based Schottky designs.
So locate the diodes used in the radio, note their routes, find out-determine what signal is sent to where, audio to volume and ANL/Squelch, while another routes to and uses AGC functions and Feedback controls as well as power switching (Mode selector - Steering and high-speed switch functions) and let Schottky handle the power issues and let Germanium handle the Audio. (Detector - ANL)
Some of those older sets used Galena (lead sulfide - point contact) more than Germanium mineral but identified as Diodes'- so in some ways, the upgrade is needed - the parts are too old to recover any usefulness - best to remove them and use newer parts of better design.
Look over those parts, you may see something of a way to identify what they are by their banding...
See the "Green band" (D4) and then the "Double Blue" banded ones (D5 and D6).
Now look here...
Ever try to find a 1N261, it isn't available readily - maybe in a reserved part bin, but not easily obtainable. So why not look more at the Markings and do some intuitive research.
Since they are Glass encapsulated, and look considerably different from the others, why not reconsider the banding for other reasons. Like perhaps the PIV ratings? Possible but let's not overthink this. Look at their place in the Schematic. More than likely they will handle current and power differently.
So, does it not make sense to utilize-allow Geranium, having a low Vf, diode to detect the Carrier and Audio - and let another - possibly Schottky - handle the S/RF and AGC? The D5 and D6 locations can use the Schottky as a power rated device - at least the Schottky can handle the Peak Inverse Voltage (PIV or Reverse Breakdown voltage) better and withstand that type of conduction condition. So install your Schottky's there, install your Germanium 1N60 or even 1N34 at D4.
What about the ANL diode D7? Well, that diode is a special one, but needs to be a low-noise type. Non-Schottky Silicon PN type that has a doping region but both Anode and Cathode ends are of the same material. See R27? Rated 560K ohm - or Blue - Green - Yellow? That resistor is this circuit designs "tickler" talked about above. So when you swap out the old diodes, remember the performance of them and the ANL diode are impacting the way this part of the radio will handle itself and the what it will do to the noise, the ANL circuit here - does. The Resistor may or may not need to be changed to restore performance.
The stronger the current flow thru the Tickler resistor (equates to lower ohmic resistance or impedance to the flow of power thru it) - the more D7 and D4 will attempt to conduct thru their junctions. Which then equates to the more NOISE you will hear in your receive.
Too high of a resistance value (larger ohmic value) then means the circuit will have less current available to flow thru it and power it (including the filter cap) so it will need to have a stronger signal pass thru this circuit in order to be detected. (That pop and clicking noise spoken about in the video)
Now, to help the "Tickler" (as Mike puts it) another filter cap is also used to SMOOTH out the rather choppy results that can happen in rectification of unequal signal (fluttering or even the carrier power itself) In keeping it in there, it can also provide a tonal filter to the ambient noise and hiss the internals of the radio generates. the circuit uses C31 (primary) a 0.001uF (!02) DISC cap and even C134 a 0.0068uF (682) ~ 0.0033uF (332) as additional capacitance to remove noise from the output side of the ANL diode and it's inherent "Shot noise" from the conduction and barrier performance issues.
So, the issue is not whether to use or not to use, but how they are used - when it comes to Schottky versus the Geranium. We can debate all day, but to each their own. I'm only trying to offer a direction to go or clarifying an approach as in, when it comes to fixing, upgrading or otherwise repairing the older sets using the newer technology available for them and where and how to apply it...
- It is not meant as a flame nor to incite riots and incur damages beyond anyones control.
- I'm only here posting this as a point of view.
- I'm using facts stated from sources already spoken about in the Vid as well as in the circuits mentioned.
- The post is meant to be considered as - For Educational Purposes Only
- Lighten up - I'm here to help.
Mike produced the vid in order to show that the older Gemanium diodes are the ones to keep in place.
Ok, I'm fine with that...
But what he does not tell you is this...
Germanium is a crystal lattice, and just like it's Silicon brethren - it's crystalline structure can "break" and or fracture diminishing the devices usefulness and shortened life span. Age, power surges and vibration take it's toll on those diodes and because of their design and "cat whisker" used as the point contact to make the junction - it's easily seen where the performance will degrade over time in mobile environments let alone anything a typical user will subject the radio to - no matter what
The radio has to complete two functions -
Derive audio from the signal...
Process the signal the audio is in - to obtain a gain factor to use as a feedback loop for the radios' Automatic Gain Control (AGC) which uses audio and the carrier together to form a feedback signal to control gain the radio has.
Use the incoming signal as a means to process the gain and maintain consistent volume while also attempting to reduce the noise the signal is embedded in.
Why am I telling you the above?
It's in how you approach the upgrade problem.
Galena, or Germanium - (at the age the radio was built - they could have used both types) has a performance that cannot be duplicated in a typical Silicon or Schottky diode design - it's simply not there. The overall performance of the part affects audio and it's inherent low- Forward Voltage Drop rating (V f) makes this an ideal part for Audio detection.
But, the drawbacks are it's sensitivity to the environment it will be used in. Shock, vibration, reverse current - power surges and power draw - all affect the lattice - rock, stuck in that glass capsule. It is a crystal, and they tend to "bend" or twist and heat up as power passes thru them. This action is strong enough to make the point contact itself "shift" and the diode is no longer as effective as it once was. The "rock" in that glass case is not pure - it's mined and refined from various ores (mostly Zinc and Lead)
In knowing the above, you can get a better idea that they have a limited variety of applications - they are rectifiers, yes, but not POWER rectifier devices. They work better in detection than in rectification.
So approach this problem knowing you have Audio to detect, and signal to process - and once you understand the difference between the two - Schottky can be used to replace the Germanium parts that are used in processing the signal, and leave Germanium for the Audio detection. Silicon Schottky as a power device provides the low-Forward Voltage drop like Germanium but handles the power and current issues better - versus keeping Germanium in the areas that you derive the audio from the signal - so it is not impacted by inherent noise issues commonly found in Silicon based Schottky designs.
So locate the diodes used in the radio, note their routes, find out-determine what signal is sent to where, audio to volume and ANL/Squelch, while another routes to and uses AGC functions and Feedback controls as well as power switching (Mode selector - Steering and high-speed switch functions) and let Schottky handle the power issues and let Germanium handle the Audio. (Detector - ANL)
Some of those older sets used Galena (lead sulfide - point contact) more than Germanium mineral but identified as Diodes'- so in some ways, the upgrade is needed - the parts are too old to recover any usefulness - best to remove them and use newer parts of better design.
Look over those parts, you may see something of a way to identify what they are by their banding...
See the "Green band" (D4) and then the "Double Blue" banded ones (D5 and D6).
Now look here...
Ever try to find a 1N261, it isn't available readily - maybe in a reserved part bin, but not easily obtainable. So why not look more at the Markings and do some intuitive research.
Since they are Glass encapsulated, and look considerably different from the others, why not reconsider the banding for other reasons. Like perhaps the PIV ratings? Possible but let's not overthink this. Look at their place in the Schematic. More than likely they will handle current and power differently.
So, does it not make sense to utilize-allow Geranium, having a low Vf, diode to detect the Carrier and Audio - and let another - possibly Schottky - handle the S/RF and AGC? The D5 and D6 locations can use the Schottky as a power rated device - at least the Schottky can handle the Peak Inverse Voltage (PIV or Reverse Breakdown voltage) better and withstand that type of conduction condition. So install your Schottky's there, install your Germanium 1N60 or even 1N34 at D4.
What about the ANL diode D7? Well, that diode is a special one, but needs to be a low-noise type. Non-Schottky Silicon PN type that has a doping region but both Anode and Cathode ends are of the same material. See R27? Rated 560K ohm - or Blue - Green - Yellow? That resistor is this circuit designs "tickler" talked about above. So when you swap out the old diodes, remember the performance of them and the ANL diode are impacting the way this part of the radio will handle itself and the what it will do to the noise, the ANL circuit here - does. The Resistor may or may not need to be changed to restore performance.
The stronger the current flow thru the Tickler resistor (equates to lower ohmic resistance or impedance to the flow of power thru it) - the more D7 and D4 will attempt to conduct thru their junctions. Which then equates to the more NOISE you will hear in your receive.
Too high of a resistance value (larger ohmic value) then means the circuit will have less current available to flow thru it and power it (including the filter cap) so it will need to have a stronger signal pass thru this circuit in order to be detected. (That pop and clicking noise spoken about in the video)
Now, to help the "Tickler" (as Mike puts it) another filter cap is also used to SMOOTH out the rather choppy results that can happen in rectification of unequal signal (fluttering or even the carrier power itself) In keeping it in there, it can also provide a tonal filter to the ambient noise and hiss the internals of the radio generates. the circuit uses C31 (primary) a 0.001uF (!02) DISC cap and even C134 a 0.0068uF (682) ~ 0.0033uF (332) as additional capacitance to remove noise from the output side of the ANL diode and it's inherent "Shot noise" from the conduction and barrier performance issues.
So, the issue is not whether to use or not to use, but how they are used - when it comes to Schottky versus the Geranium. We can debate all day, but to each their own. I'm only trying to offer a direction to go or clarifying an approach as in, when it comes to fixing, upgrading or otherwise repairing the older sets using the newer technology available for them and where and how to apply it...
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Good one Andy. But there is also one other important aspect of schottky diodes; they switch really fast. Tight. That is their real advantage. Dunno if someone else already said it . . .
And so there's is a problem, both of you noticed.
@Tallman (got it right this time YEA!) - Yes, but the specs are dated - note they say Max not TYP or MIN so these sheets are so old they aren't classified as an ISO standard, take them for what they are - just wanted to show the reader how "out-dated" all the info about Germanium versus Silicon is.
Now if you were to go back to those times you'd also notice the PIV is considerably LESS than the PIV of a Schottky in Silicon - another difference. The Reverse leakage current and why I mentioned the mined and refined - they are not as pure as their Si counterpart, nor was it needed, they only needed the "barrier" effect. They leak like a sieve and in some aspects are the reason for their "fans" to covet them - their "Warmth" they exhibit to the circuit - whether your Guitar gently weeps or fuzzy FM-ing done by your neighbors FT101 glowing brightly
To given them credit, the barrier threshold level comes at a price of PIV - so wildly swinging carriers and stodgy AGC action can actually DESTROY the diode from the power flowing thru in both Reverse leakage and in Forward drop. (Switching times are low but that adds another secondary aspect of their low-noise and low-distortion pinching off of the barrier) Again a ratings issue and although many would say just put in a Schottky, you're not obtaining the benefit of low-noise analog - you're missing 1/2 the story - you use the higher PIV, faster switching times in the PROCESSING side of the radio - not the Detector side.
@Robb - The "switching times" when dealing with AM carrier are kinda moot, you only need to extract the audio info off the carrier and whatever residual that is there is sent to the AGC and S/RF side or to ground whichever the case may be. This is where I referenced the audio sounds - comparably like a "Warmth" like Class A or tubes and the Phono RIAA EQ of older days. The emphasis of the vocal spectrum range lower bass and soprano tones - helps give an older radio chassis the warm sound many still appreciate. Germanium or Galena, has a built in hi-cut effect that you don't get from Silicon high-speed switching diodes. You don't need a high speed switch for audio - you'll need it for the radios power steering and mode selector power routing and circuit isolation they provide.
You folks can run your radios the way you want, but I'm only clarifying what Mike said, in light of the vid. We covered a lot of it in another thread yes, but Mike missed a couple of points that make this the argument and discussion it has become, that to ignore them you miss out on the benefits of both, if not applied properly. And that is due to the low loss barrier threshold (low forward voltage drop) both Germanium and Silicon provide, one provides a noise level when it transitions, functioning as a switch, the other has less noise but cannot handle high power applications .
Silicon - the high speed switch and PIV ratings of Schottky helps the S/RF and AGC begin conduction and their functions sooner. This allows Noise reduction and Abatement/Filtering circuits like NB and ANL to operate using the low barrier threshold. This approach lets' weaker signals pass and lowers noise levels thru more aggressive low level signal processing, being made possible by the detection of such and processing it while it's in the noise level - although weak, the low-barrier threshold enhances the ability of the radios' own gain functions so it can react to process it.
However, Germanium has the Audio effects that when used and (as Mike puts it) "Tickled" properly - they can make an otherwise harsh sounding operator into a warmer, full-bodied tone receiver that it can be enjoyed more for the reproduction of the other persons voice. - it just can't handle high-power processing demands nor does it have the switching times. It's low-power, low-barrier and it has a leaky junction which equates to poor PIV performance and unable to be used in Power Routing and High - Isolation their SI counterparts can provide.
I'm only pointing out that when you use the right mineral in the right spot in the radio - you can use Schottky as intended, Silicon for Power Steering and Control and Germanium as your Detector - just don't confuse them, or switch them around, for you may not like the results and you can possibly damage the radio in the process.
But most of all, this is for the purpose of enlightening you to the prospects of better communication thru the advances in technology and using the right parts where they should be and upgrade as possible- helps prolong the life of the equipment and the enjoyment of communication as a venture, venue or a hobby.
@Tallman (got it right this time YEA!) - Yes, but the specs are dated - note they say Max not TYP or MIN so these sheets are so old they aren't classified as an ISO standard, take them for what they are - just wanted to show the reader how "out-dated" all the info about Germanium versus Silicon is.
Now if you were to go back to those times you'd also notice the PIV is considerably LESS than the PIV of a Schottky in Silicon - another difference. The Reverse leakage current and why I mentioned the mined and refined - they are not as pure as their Si counterpart, nor was it needed, they only needed the "barrier" effect. They leak like a sieve and in some aspects are the reason for their "fans" to covet them - their "Warmth" they exhibit to the circuit - whether your Guitar gently weeps or fuzzy FM-ing done by your neighbors FT101 glowing brightly
To given them credit, the barrier threshold level comes at a price of PIV - so wildly swinging carriers and stodgy AGC action can actually DESTROY the diode from the power flowing thru in both Reverse leakage and in Forward drop. (Switching times are low but that adds another secondary aspect of their low-noise and low-distortion pinching off of the barrier) Again a ratings issue and although many would say just put in a Schottky, you're not obtaining the benefit of low-noise analog - you're missing 1/2 the story - you use the higher PIV, faster switching times in the PROCESSING side of the radio - not the Detector side.
@Robb - The "switching times" when dealing with AM carrier are kinda moot, you only need to extract the audio info off the carrier and whatever residual that is there is sent to the AGC and S/RF side or to ground whichever the case may be. This is where I referenced the audio sounds - comparably like a "Warmth" like Class A or tubes and the Phono RIAA EQ of older days. The emphasis of the vocal spectrum range lower bass and soprano tones - helps give an older radio chassis the warm sound many still appreciate. Germanium or Galena, has a built in hi-cut effect that you don't get from Silicon high-speed switching diodes. You don't need a high speed switch for audio - you'll need it for the radios power steering and mode selector power routing and circuit isolation they provide.
You folks can run your radios the way you want, but I'm only clarifying what Mike said, in light of the vid. We covered a lot of it in another thread yes, but Mike missed a couple of points that make this the argument and discussion it has become, that to ignore them you miss out on the benefits of both, if not applied properly. And that is due to the low loss barrier threshold (low forward voltage drop) both Germanium and Silicon provide, one provides a noise level when it transitions, functioning as a switch, the other has less noise but cannot handle high power applications .
Silicon - the high speed switch and PIV ratings of Schottky helps the S/RF and AGC begin conduction and their functions sooner. This allows Noise reduction and Abatement/Filtering circuits like NB and ANL to operate using the low barrier threshold. This approach lets' weaker signals pass and lowers noise levels thru more aggressive low level signal processing, being made possible by the detection of such and processing it while it's in the noise level - although weak, the low-barrier threshold enhances the ability of the radios' own gain functions so it can react to process it.
However, Germanium has the Audio effects that when used and (as Mike puts it) "Tickled" properly - they can make an otherwise harsh sounding operator into a warmer, full-bodied tone receiver that it can be enjoyed more for the reproduction of the other persons voice. - it just can't handle high-power processing demands nor does it have the switching times. It's low-power, low-barrier and it has a leaky junction which equates to poor PIV performance and unable to be used in Power Routing and High - Isolation their SI counterparts can provide.
I'm only pointing out that when you use the right mineral in the right spot in the radio - you can use Schottky as intended, Silicon for Power Steering and Control and Germanium as your Detector - just don't confuse them, or switch them around, for you may not like the results and you can possibly damage the radio in the process.
But most of all, this is for the purpose of enlightening you to the prospects of better communication thru the advances in technology and using the right parts where they should be and upgrade as possible- helps prolong the life of the equipment and the enjoyment of communication as a venture, venue or a hobby.
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Schottky diodes anyone? Shipped to you for $1;
https://www.ebay.ca/itm/CB-Receive-...h=item2141a8ab41:g:2sQAAOSwsN9XCzwv:rk:3:pf:0
https://www.ebay.ca/itm/CB-Receive-...h=item2141a8ab41:g:2sQAAOSwsN9XCzwv:rk:3:pf:0