I've searched through as many posts convering this topic as I could and did not come to an understanding. I hope i'm not re-asking an age old question that has already been answered.
The following speaks of your standard Saber. When I speaker cut the end of a UHF Public Safety shoulder mic and conectorized it for an external antenna I eventually found that it would not 'select' the universal connector's RF port unless 3.735V were applied to the OPTSEL Pin 7. From my understanding there should be 3.7V across Pin 7 and 13/14 (GND) for the RF port to be enabled.
http://www.repeater-builder.com/motorol ... 4c05-a.pdf
Model Specific Info from Batlabs says: "According to the schematic, there is a 20 kohm resistor from REG +5VDC tied to the OPT SEL pin. This means that in order to select one of the above modes, you will need to tie the OPT SEL pin to ground through a zener diode(s)(and with no connection the pin floats to 5V which is STD operation)."
Floats to 5V due to capacitor's charge?
The schematic I have for the test box has a 600pF cap and 2.5V zener (I think), in parallel with 7 & GND for it to work with external devices. What i'm wondering is it as simple replacing the zener with a 3.7V one, do they even make that rating? As well as, what about the 20k resistor, wouldn't that drop voltage too?
I'm not sure what component to place in the circuit at this point, limited engineering knowledge and all.
HELP?!
.Alex
Saber OPT SEL Design for External Antenna
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Saber OPT SEL Design for External Antenna
Last edited by alex on Sat Apr 05, 2014 8:10 am, edited 1 time in total.
Reason: Updated PDF URL at request of Repeater Builder.
Reason: Updated PDF URL at request of Repeater Builder.
Accually the resistor 'pulls up' the OPT SEL line to 5 volts with nothing connected to it. If I remember the zener diode is in the PS Mic head that drops or 'regulates' the voltage on the Sel line to opperate the PS SPKR/Mic. 2.5 volts according to the chart below.
And yes, they do make low power zener diodes in the voltages you need.
Heck a 59k ohm resistor would drop the voltage to the 3.74 volts needed.
The zener goes from the OPT SEL line to ground. The capacitor across the zener diode is for RF suppression.
* The OPT SEL pin follows the following table:
All Internal, STD Operation 5VDC
EXT MIC and SPKR, STD ANT 1.24VDC
EXT MIC, SPKR and ANT 2.5VDC
EXT ANT ONLY 3.74VDC
And yes, they do make low power zener diodes in the voltages you need.
Heck a 59k ohm resistor would drop the voltage to the 3.74 volts needed.
The zener goes from the OPT SEL line to ground. The capacitor across the zener diode is for RF suppression.
* The OPT SEL pin follows the following table:
All Internal, STD Operation 5VDC
EXT MIC and SPKR, STD ANT 1.24VDC
EXT MIC, SPKR and ANT 2.5VDC
EXT ANT ONLY 3.74VDC
Awesome, I think i'm getting there. The OPT SEL voltage selection is done in the mic or spkr/mic, can't re-use it since i'm using STD MIC/SPKR. And it's in the trash 
I'm looking to shrink wrap the component I need in with the antenna cable at the RF connector end.
Batlabs says a 20k resistor is in series from REG +5 to OPT SEL. Without anything connected there wouldn't be a circuit, no current, then would the OPT SEL pin read 5V still (Sensing REG 5V through a 20k resistor)? How does that work?
Using the 59k resistor it would go: REG 5V series to 20k to series 59k to series ground? How do you know the 59k in combination will drop 1.26V?
I looked through digikey.com's catalog and couldn't find a 1~2V zener, there are millions of components there, maybe I didn't see it. Then again there are a dozen values to sift through on zeners.
Since the +5 is already regulated, I wouldn't have to worry about diminishing battery voltage, I don't see any reason why not to use a resistor instead, besides to satisfy my curiosity of them zeners.
Thanks!
.Alex
I'm looking to shrink wrap the component I need in with the antenna cable at the RF connector end.Batlabs says a 20k resistor is in series from REG +5 to OPT SEL. Without anything connected there wouldn't be a circuit, no current, then would the OPT SEL pin read 5V still (Sensing REG 5V through a 20k resistor)? How does that work?
Using the 59k resistor it would go: REG 5V series to 20k to series 59k to series ground? How do you know the 59k in combination will drop 1.26V?
I looked through digikey.com's catalog and couldn't find a 1~2V zener, there are millions of components there, maybe I didn't see it. Then again there are a dozen values to sift through on zeners.
Since the +5 is already regulated, I wouldn't have to worry about diminishing battery voltage, I don't see any reason why not to use a resistor instead, besides to satisfy my curiosity of them zeners.
Thanks!
.Alex
The proper way to do it is with the zeners. Then a current limit resistor
of any reasonable value will work and not be critical in value.
Also be aware that the voltage is read at boot up and options cannot
be just installed at will and expected to work. The only time the
voltage is read and the port configured is within the first second or so
following power aplication, then the config is selected for the duration
of the power on. The only exception to this is upon inserting in
an SVA (convertacom). That unit sends its own signal down the data
bus that makes the option select code in the radio firmware re-run and
it senses that a SVA is there and it configures the port on the fly.
Hope that info may be helpful. Phrawg
of any reasonable value will work and not be critical in value.
Also be aware that the voltage is read at boot up and options cannot
be just installed at will and expected to work. The only time the
voltage is read and the port configured is within the first second or so
following power aplication, then the config is selected for the duration
of the power on. The only exception to this is upon inserting in
an SVA (convertacom). That unit sends its own signal down the data
bus that makes the option select code in the radio firmware re-run and
it senses that a SVA is there and it configures the port on the fly.
Hope that info may be helpful. Phrawg
BBbzzzzz... ZAP.. GULP !!! ahhhh GOOD fly !
While a resistor will 'pull' down to the 3.74 V, the zener 'clamps' the voltage at 3.74 V and is THE most reliable method of maintaining the voltage required, the ancillary components are used as Phrawg states; as RF supression to keep stray signals from remaining on control connections and possibly falsing the controller at some point.
I've played and modeled around in ORCAD/PSPICE for the greater portion of the day and couldn't come up with an schematic answer. I measured ~26k ohms through OPT SEL and ground (Probably the 20k resistor Batlabs says is there and then other non-sense) and +5VDC between OPT SEL and ground. Also, GND (Pin 13/14 to case) was ~0.
My major dilemma wasn't that I couldn't regulate voltage with a Zener setup but it was that I couldn't put it back into the OPT SEL which was acting at my source. As well as, when I only strung a zener across OPT SEL and GND it would still read +5V no matter what, at least on my computer it did.
pharwg:
I'm pretty sure I understand what you mean about the current limiting resistor, it's a crucial piece in the standard voltage regulator circuit.
The limiting resistor 'sets up' the zener and allows all excess voltage to be dropped through it. Where the regulated voltage is tapped off in parallel. http://wiki.4hv.org/index.php/Voltage_Regulator
I've confirmed I CAN attach my shoulder SPKR/MIC at will, regardless of power state and it'll work. It OPT Sel's 2.5VDC.
AEC:
Understand usage of RF suppression caps and such but, they are ancilliary (hopefully) components set in place once the voltage is regulated. I'll have to tacke that beast later.
What will a Zener do if it is the only component in series with source VDC? Drop all or only up to its rated breakdown value, if so, doesn't that go against Kirchoff's law? Obviously, if you read off a meter in parallel you'll get the source voltage.
Will:
Thanks for suppling part info and turning me onto Mouser, hadn't heard of them before. Check out these schematics and see what you think. First one is a zener from OPT SEL to GND which will read 5V, second is of my dilemma stated above and third is of how I understand Batlabs' info on how it is setup, doesn't seem right.
I also took apart a standard SPKR MIC and found that Motorola uses a LM285Z 1.2, microvoltage regulator? Seems to be a IC Regulator. Eitherway, I'm still stuck and terribly confused.
Cheers,
Alex
My major dilemma wasn't that I couldn't regulate voltage with a Zener setup but it was that I couldn't put it back into the OPT SEL which was acting at my source. As well as, when I only strung a zener across OPT SEL and GND it would still read +5V no matter what, at least on my computer it did.
pharwg:
I'm pretty sure I understand what you mean about the current limiting resistor, it's a crucial piece in the standard voltage regulator circuit.
The limiting resistor 'sets up' the zener and allows all excess voltage to be dropped through it. Where the regulated voltage is tapped off in parallel. http://wiki.4hv.org/index.php/Voltage_Regulator
I've confirmed I CAN attach my shoulder SPKR/MIC at will, regardless of power state and it'll work. It OPT Sel's 2.5VDC.
AEC:
Understand usage of RF suppression caps and such but, they are ancilliary (hopefully) components set in place once the voltage is regulated. I'll have to tacke that beast later.
What will a Zener do if it is the only component in series with source VDC? Drop all or only up to its rated breakdown value, if so, doesn't that go against Kirchoff's law? Obviously, if you read off a meter in parallel you'll get the source voltage.
Will:
Thanks for suppling part info and turning me onto Mouser, hadn't heard of them before. Check out these schematics and see what you think. First one is a zener from OPT SEL to GND which will read 5V, second is of my dilemma stated above and third is of how I understand Batlabs' info on how it is setup, doesn't seem right.
I also took apart a standard SPKR MIC and found that Motorola uses a LM285Z 1.2, microvoltage regulator? Seems to be a IC Regulator. Eitherway, I'm still stuck and terribly confused.
Cheers,
Alex
In the lower left hand diagram it shows the resistor IN the radio and is correct. The lead from pin 7 to ground is NOT there. The micro processor senses the voltage at the end of the resistor at the OP SEL pin 7.
5 volts no connection
3.6 volts for accessory ext operation.
0 volts for PTT, TX
DO NOT try to feed a voltage into the radio.
Now you just need to put the Zener diode, cathode to the OP SEL and anode to the ground pin. If the zener is rated at 3.6 volts, the 20 k resistor drops the voltage or more correctly the zener diode clamps it to the rated zener voltage.
I wish I had that program a long time ago when I was in the engeneering department. but my lab is still the engineering 'LAB'!!!!
5 volts no connection
3.6 volts for accessory ext operation.
0 volts for PTT, TX
DO NOT try to feed a voltage into the radio.
Now you just need to put the Zener diode, cathode to the OP SEL and anode to the ground pin. If the zener is rated at 3.6 volts, the 20 k resistor drops the voltage or more correctly the zener diode clamps it to the rated zener voltage.
I wish I had that program a long time ago when I was in the engeneering department. but my lab is still the engineering 'LAB'!!!!
Don't forget that you are attempting to 'fool' the radio by using external components that the radio's microprocessor is not 'seeing' in circuit, and therefore, unable to control and regulate the operation of your control line on OPT-SEL.
Remember the return(ground) path of the Zener circuit as well.
A better method might be to open the mic, and the accy connector and take readings on the connections as the mic is attached and measure the voltage at those points, then detach the mic and take another reading and note the difference in control voltages, you may need a scope to measure subtle changes.
You are using an external cure to an internal problem, and the radio is defying your actions with an attempt to reinvent the wheel(of sorts), as well as externally trigger an action that is internally controlled.
The micro is not recognizing your attempts, as the OPT-SEL line is 'already' preset and adding more circuits to the presets will probably not lead to a cure, but to more questions as to 'how' the 'task' is performed.
The mic values are 'known' by the radio, like the ohmic value of the mic , the speaker plus the wiring of same, this provides a set of somewhat 'preset' values, not to mention the voltage/current use by those items while in circuit as these will have an effect on the accy. port connection you are trying to deal with.
Remember the return(ground) path of the Zener circuit as well.
A better method might be to open the mic, and the accy connector and take readings on the connections as the mic is attached and measure the voltage at those points, then detach the mic and take another reading and note the difference in control voltages, you may need a scope to measure subtle changes.
You are using an external cure to an internal problem, and the radio is defying your actions with an attempt to reinvent the wheel(of sorts), as well as externally trigger an action that is internally controlled.
The micro is not recognizing your attempts, as the OPT-SEL line is 'already' preset and adding more circuits to the presets will probably not lead to a cure, but to more questions as to 'how' the 'task' is performed.
The mic values are 'known' by the radio, like the ohmic value of the mic , the speaker plus the wiring of same, this provides a set of somewhat 'preset' values, not to mention the voltage/current use by those items while in circuit as these will have an effect on the accy. port connection you are trying to deal with.
Hmmmm Interesting on the hot attach of a speaker mic.
Very well could be some firmware changes since the last time
I tried that sense hot addition of the device. Last time I tried
was many years ago and it would not work so I assumed it to still
be the case. Im gonna check that one out. Thanks. Phrawg
Very well could be some firmware changes since the last time
I tried that sense hot addition of the device. Last time I tried
was many years ago and it would not work so I assumed it to still
be the case. Im gonna check that one out. Thanks. Phrawg
BBbzzzzz... ZAP.. GULP !!! ahhhh GOOD fly !
Will:
Okay, back at it. I changed up a few things and found that I can't measure voltage across an 'open' circuit on the computer. On the first circuit, what will be the voltage reading across a meter set at the two probe points there? Will it sense 5v? Otherwise my real world will disagree
On the second circuit, all looks well the zener does clamp down to 2.2v (even running simulation up to 30v), I think I need to choose a different rating since I can't move or change up the 20k resistor.
Which engineering department? If someone was so inclined to pirate a copy the program, I'd expect that there be a copy available
AEC:
The reoccurring theme in your response is that i'm attempting to trigger 'states' inside the radio externally, where they would normally be done elsewhere. This isn't the case i'm afraid, crazy Motorola has engineered a standard where the peripheral device must adapt voltage in accordance with its capabilities. Each device has a circuit in it to do this (more thought out, I admit) and I am attempting to create one. This can be recognized by looking in a SPKR/MIC and seeing the clamping/regulating circuit using a zener IC or peer through the manual in the first link listed above.
I have tried to reverse engineer the MIC but, it became annoyingly tedious. I'll have to grab another PS Mic from work where my test equipment is located. Once I have the circuit inputted into PSPICE, I can simulate to pico seconds if i'd prefer.
phrawg:
No worries, just trying to keep the information in-line. Who can keep up with the updates?!
Okay, back at it. I changed up a few things and found that I can't measure voltage across an 'open' circuit on the computer. On the first circuit, what will be the voltage reading across a meter set at the two probe points there? Will it sense 5v? Otherwise my real world will disagree
On the second circuit, all looks well the zener does clamp down to 2.2v (even running simulation up to 30v), I think I need to choose a different rating since I can't move or change up the 20k resistor.
Which engineering department? If someone was so inclined to pirate a copy the program, I'd expect that there be a copy available
AEC:
The reoccurring theme in your response is that i'm attempting to trigger 'states' inside the radio externally, where they would normally be done elsewhere. This isn't the case i'm afraid, crazy Motorola has engineered a standard where the peripheral device must adapt voltage in accordance with its capabilities. Each device has a circuit in it to do this (more thought out, I admit) and I am attempting to create one. This can be recognized by looking in a SPKR/MIC and seeing the clamping/regulating circuit using a zener IC or peer through the manual in the first link listed above.
I have tried to reverse engineer the MIC but, it became annoyingly tedious. I'll have to grab another PS Mic from work where my test equipment is located. Once I have the circuit inputted into PSPICE, I can simulate to pico seconds if i'd prefer.
phrawg:
No worries, just trying to keep the information in-line. Who can keep up with the updates?!
I have found this to be much more difficult without the saber's schematic in hand. I'm pushing the 'I believe' button on the 20k resistor (although I measure 26k) and assume +5 would be sensed at the universal connector's pins while setup in the second to last circuit of mine.
I will have to play with which zener to place. Remembering from a few days ago that 20k resistor dropped too much voltage to even consider clamping anything above 2.2v. Hmm.
Gotta put this on hold, will come back when time allows. Fingering a GR300 that won't key partner radio. Seems as though Will is resident expert on that too!
Thanks for all the help guys!
KG6YFX
I will have to play with which zener to place. Remembering from a few days ago that 20k resistor dropped too much voltage to even consider clamping anything above 2.2v. Hmm.
Gotta put this on hold, will come back when time allows. Fingering a GR300 that won't key partner radio. Seems as though Will is resident expert on that too!
Thanks for all the help guys!
KG6YFX
From the schematics:
OPT-SEL (8) feeds into a 68 ohm resistor that is set with the option select table.
These are the levels according to connected accessories:
1. All internal standard options.................5 VDC
2. Ext. Mic/spkr, standard antenna............ 1.24 VDC
3. Ext. mic/spkr & antenna....................... 2.5 VDC
4. Ext. antenna only................................. 3.74 VDC
OPT-SEL (7) feeds directly to pin 62 of U400(micro).
(4)(accy. conn) feeds VR800(to gnd) and C32(.039uF) to pin 22 of U102 audio IC with R111 tapped between R45 and R9(2Kohms)which derives 5VDC from pin 12 of U201(transmit 5V) line.
Pin 22 C32 tie point R111
U102-------| |------*----------vvvv---->to point between R45/R9
|
|
|-------------------<----(4)ext. mic/DVP clk.
I sure hope this garbled mess shows properly.....I don't have the 'good stuff' to display the schematics correctly.
The '*' is the tie point between C32 and R111 where (4) connects.
OPT-SEL (8) feeds into a 68 ohm resistor that is set with the option select table.
These are the levels according to connected accessories:
1. All internal standard options.................5 VDC
2. Ext. Mic/spkr, standard antenna............ 1.24 VDC
3. Ext. mic/spkr & antenna....................... 2.5 VDC
4. Ext. antenna only................................. 3.74 VDC
OPT-SEL (7) feeds directly to pin 62 of U400(micro).
(4)(accy. conn) feeds VR800(to gnd) and C32(.039uF) to pin 22 of U102 audio IC with R111 tapped between R45 and R9(2Kohms)which derives 5VDC from pin 12 of U201(transmit 5V) line.
Pin 22 C32 tie point R111
U102-------| |------*----------vvvv---->to point between R45/R9
|
|
|-------------------<----(4)ext. mic/DVP clk.
I sure hope this garbled mess shows properly.....I don't have the 'good stuff' to display the schematics correctly.
The '*' is the tie point between C32 and R111 where (4) connects.
My god AEC, it has taken me awhile to absorb your last post and my brain hurts... I did ask for it though
I'm not sure on a few of your notations.
You've got a U201 and 202, Pin 12 and 22, is that right or a typo? No biggie just wanna make sure if they are the same.
Is this right? U400 -> 68 ohm -> Pin 7 (universal connector)? Or directly to U400?
Then you lose me, i'm not sure where that schematic you drew is located in all of this jazz, does ( 4 ) mean "4. Ext Ant Only"? Or Pin 4 Ext Mic, if so i'm not totally sure is plays a role in the selection process.
Any chance of scanning and post/emailing? Eitherway I have a few zeners in hand and will eventually get them plugged in.
Cheers
I'm not sure on a few of your notations.
You've got a U201 and 202, Pin 12 and 22, is that right or a typo? No biggie just wanna make sure if they are the same.
Is this right? U400 -> 68 ohm -> Pin 7 (universal connector)? Or directly to U400?
Then you lose me, i'm not sure where that schematic you drew is located in all of this jazz, does ( 4 ) mean "4. Ext Ant Only"? Or Pin 4 Ext Mic, if so i'm not totally sure is plays a role in the selection process.
Any chance of scanning and post/emailing? Eitherway I have a few zeners in hand and will eventually get them plugged in.
Cheers
Got three zener diodes plugged in and this is what came about.
The diode was between pin 7 and the rf ground pin 13/14 twisted carefully at the end of the cable.
1N4730A (3.9 breakdown voltage) measured 2.02v across 7 - 13/14
1N4729A (3.6 breakdown voltage, 1w) measured 1.58v across 7 - 13/14
1N747A (3.6 breakdown voltage, .5w) measured 0.04v across 7 - 13/14
My dioide figures may be off, google to doublecheck.
Bear in mind I wasn't able to test if RF was coming out of the external port or not, but there isn't 3.74v on OPT SEL. Looks like I should just increase the diode until it measures 3.7 ish. Any guesses? This feels like a kick in the balls.
I would model this in my computer but, this stupid complicated program is beyond me at this time. Other 3.6 (high wattage rating I believe) clamp just fine.
If this weren't my only HT, it would be across the hall in my neighbor's living room.
.Alex
The diode was between pin 7 and the rf ground pin 13/14 twisted carefully at the end of the cable.
1N4730A (3.9 breakdown voltage) measured 2.02v across 7 - 13/14
1N4729A (3.6 breakdown voltage, 1w) measured 1.58v across 7 - 13/14
1N747A (3.6 breakdown voltage, .5w) measured 0.04v across 7 - 13/14
My dioide figures may be off, google to doublecheck.
Bear in mind I wasn't able to test if RF was coming out of the external port or not, but there isn't 3.74v on OPT SEL. Looks like I should just increase the diode until it measures 3.7 ish. Any guesses? This feels like a kick in the balls.
I would model this in my computer but, this stupid complicated program is beyond me at this time. Other 3.6 (high wattage rating I believe) clamp just fine.
If this weren't my only HT, it would be across the hall in my neighbor's living room.
.Alex
Figured I'd report back that none of the 3 diodes listed above enabled the external antenna port.
Looks like the Saber service manual is finally cancelled, fugg.
I suppose I could do some easter egg'n zener action, but would rather someone just tell me what to put there.
I'll settle for a comment or suggestion though.
Looks like the Saber service manual is finally cancelled, fugg.
I suppose I could do some easter egg'n zener action, but would rather someone just tell me what to put there.
I'll settle for a comment or suggestion though.
You guys are overly complicating things. You don't need to analyze things in OR-CAD or P-spice etc.
I have built 3, 900 MHz, wireless speaker mics for my VHF sabers and all I did was a simple resistive voltage divider with no problems at all.
I even modified a Bendix King LAA style speaker mic to use on my UHF and VHF sabers as they were free-bees and I liked the hi/low volume switch on them, I also used the voltage divider and passed on using the zener method.
I don't have my schematics at hand right now but as I remember the Opt select line has a well regulated 5 volts or something like that. Just select the V divider output for the desired voltage according to the option desired and use large > 10K resistors and the current draw will be negligible.
Just turn your radio OFF and attach the desired adapter to your Saber and then turn the radio ON and it recognizes the accessory device. Turn it OFF and remove the adapter to operate in regular mode.
As simple as that. I got away with 5 % resistors without any problems.
No RF tripping either on any of the modified accessories.
Resistors are cheap compared to hard to get or series connected zeners also.
Mike
I have built 3, 900 MHz, wireless speaker mics for my VHF sabers and all I did was a simple resistive voltage divider with no problems at all.
I even modified a Bendix King LAA style speaker mic to use on my UHF and VHF sabers as they were free-bees and I liked the hi/low volume switch on them, I also used the voltage divider and passed on using the zener method.
I don't have my schematics at hand right now but as I remember the Opt select line has a well regulated 5 volts or something like that. Just select the V divider output for the desired voltage according to the option desired and use large > 10K resistors and the current draw will be negligible.
Just turn your radio OFF and attach the desired adapter to your Saber and then turn the radio ON and it recognizes the accessory device. Turn it OFF and remove the adapter to operate in regular mode.
As simple as that. I got away with 5 % resistors without any problems.
No RF tripping either on any of the modified accessories.
Resistors are cheap compared to hard to get or series connected zeners also.
Mike