Re: Aircraft headset speaker impedance and ubitx
#ubitx
Thanks everyone for your answers. I've well measured something opened on the 5mm jack connector. So maybe it's the mic.?
So it seems that :
6.35mm jack is for headset and is about 60 ohms
5mm jack is for mic and acts like an open circuit.?
Does anybody with that kind of aircraft headset could confirm that the mic is well on 5mm jack and headset is 6.35mm jack??
If yes I guess that kind of headset could work. I'll give it a try.?
|
Re: Bitx40 very loud, high-pitched, low frequency noise
My BITX40 shrieks if I get my cellphone too close to it.
On Saturday, August 24, 2019, 03:20:36 AM UTC, Ashhar Farhan <farhanbox@...> wrote:
I think it could even be an issue with the way the LM386 is wired up. The power supply to the audio amp is via a 100 ohms resistor. So, when something loud gets into the audio input, it would draw more current and the voltage across that resistor will increase, in turn decreasing the dc voltage to the LM386. The dip in the dc voltage would dip the gain of the LM386, decreasing the current... The cycle would repeat causing oscillations. But that would lead to motor boating : butbutbutbutbrrrrrr.. kind of a sound.
I think that your comment about even on battery there is faint noise and it is near your PC is significant.Some pc's give out lots of hash or wine and I wonder if moving the uBITX? further away may silence that last bit of noise.I am surprised that the capacitor
combination on the output does not help,that has always worked for me as I proved by my test last evening on a randomly picked switch mode wall wart.? Anyways it's progress in the right direction,keep the leads short and you will minimise pickup.A ferrite
ring or two on the cables won't do any harm,the best quality power supplies usually have fitted on the DC lead to keep switching noise away from the DC output.
On 8/23/2019 19:39, Gordon Gibby wrote:
> You may decide that you want to build a real low pass filter, with an
> inductor etc., similar to what people had to use in the past to get
> rid of alternator whine
--
...Or a new / different power supply.
--
It would be interesting to examine the supply output with an oscilloscope.
W00DY
--
|
Re: Aircraft headset speaker impedance and ubitx
#ubitx
Hi,
Because the earphones are directly over your ears, would it be possible that you don't need as much power to drive them, and 600 ohms would provide sufficient power to possibility supply more volume than needed? Likely the audio output of the amplifier is not bothered by driving 600 ohms vs 8 ohms.?
Another question. Would the impedance of the earphones be higher for AC (the audio) than DC, as measured by an ohmmeter? That would be the case for a transformer and the earphones seem to be a transformer like device when the magnet is moving in the coil, when driven by audio.?
It is possible that earphones are not very efficient and the DC and AC impedance are nearly the same.
Tom, wb6b
|
Re: Audio pre-amplifier for microphone?
On Fri, Aug 23, 2019 at 10:55 PM, Voitto Vataja wrote:
How to connect this to uBITX?
It looks like you hook the "output" to the mic pin of the uBitx and the phantom power on the uBitx mic pin will power it. Tom, wb6b
|
Re: Aircraft headset speaker impedance and ubitx
#ubitx
Agreed typical measurement for a dynamic mic but not electret.
toggle quoted message
Show quoted text
Hi,
The 600 ohms sounds more like a spec for the mic.? Perhaps it is a dynamic one, where 600 ohms would be quite typical.
73,
Mark.
|
Re: Aircraft headset speaker impedance and ubitx
#ubitx
Hi,
The 600 ohms sounds more like a spec for the mic.? Perhaps it is a dynamic one, where 600 ohms would be quite typical.
73,
Mark.
|
Re: Aircraft headset speaker impedance and ubitx
#ubitx
I would say your deduction is correct as regards the Jack plugs. The one where you measure the 63 ohms is the headset,the mic if electret should measure as a open circuit.Does each Jack plug just have two connections,the tip and sleeve?
toggle quoted message
Show quoted text
I've tested the headset and the resistance which is not really the impedance seems to be 63 ohms on the 6.35 mm jack. I guess the 6.35mm jack is for speakers and the 5mm for the mic.
Could you please confirm that??
|
Re: Aircraft headset speaker impedance and ubitx
#ubitx
I've tested the headset and the resistance which is not really the impedance seems to be 63 ohms on the 6.35 mm jack. I guess the 6.35mm jack is for speakers and the 5mm for the mic.
Could you please confirm that??
|
Re: Aircraft headset speaker impedance and ubitx
#ubitx
I see no reason why the electret mic should not be satisfactory but I have my doubts on the 600 oh impedance head phones.The uBITX requires 8 ohms to around 32 ohms to match most earphones.I suspect that you would get very little output into 600 ohms.
toggle quoted message
Show quoted text
Thank for letting me know. I'll try to measure my actual headset speaker impedance to be sure of that.?
|
Re: Aircraft headset speaker impedance and ubitx
#ubitx
Thank for letting me know. I'll try to measure my actual headset speaker impedance to be sure of that.?
|
Re: Aircraft headset speaker impedance and ubitx
#ubitx
Adrien,
I have used aviation headsets a good bit with the ubitx and others and the speakers are usually 10-15 ohms. The 600 ohm will likely not work very well without a little audio step down transformer.? On the other had, the electret mic might work very well.
73,
Pat
Pat Griffin AA4PG
http://www.cahabatechnology.com/aa4pg.html
toggle quoted message
Show quoted text
Hi everyone!?
I've ordered yesterday my ubitx and I'm thinking upon the boxing and peripherals to add.?
I already have a great quality tourism aircraft headset with mic and was thinking about using it with the ubitx to have comfortable equipment for my ears.
But the impedance of the speakers is 600 ohms. I've red that the IC audio output is for something about 8 ohms. So what should be the behavior with 600 ohms? Does it will work in your opinion or best : did someone already test it?
Thank you for your kind answers.
73
Adrien F4IJA
|
Re: Kit box paint removal
Hi,
I would take a small "pocket screwdriver" and file it down to a sharp chisel tip.? Then go around the hole and make a circle cut the size of the bolt head or standoff.? Finally, chip/chisel off the paint going from the outer circle towards the hole.? It should do a neat job in the end and not be too hard.
73,
Mark.
|
Aircraft headset speaker impedance and ubitx
#ubitx
Hi everyone!?
I've ordered yesterday my ubitx and I'm thinking upon the boxing and peripherals to add.?
I already have a great quality tourism aircraft headset with mic and was thinking about using it with the ubitx to have comfortable equipment for my ears.
But the impedance of the speakers is 600 ohms. I've red that the IC audio output is for something about 8 ohms. So what should be the behavior with 600 ohms? Does it will work in your opinion or best : did someone already test it?
Thank you for your kind answers.
73
Adrien F4IJA
|
Re: Kit box paint removal
I used a drammel to make bare the areas that needed to be grounded;; also the tops of the 4 lugs where the board is connected..? ?
|
Re: raduino crystal question
Thank you Gordon. ?Helps my understanding of crystals and Bitx adjustments. David J. Wilcox K8WPE¡¯s iPad
toggle quoted message
Show quoted text
On Aug 23, 2019, at 3:31 PM, Gordon Gibby < ggibby@...> wrote:
Crystals are specified by their manufacturer to oscillate to correct frequency when placed in a circuit that has a certain amount of parallel capacitance, which is a property of the circuit, not the capacitance per se of the crystal
If you need a few extra picofarads of capacitance and your circuit to meet the manufacturers requirement, that is easily added with a small capacitor. ?
The reason that the bitx series tends to oscillate ?just a little bit higher than where it should¡¯ve, is because there apparently isn¡¯t enough capacitance in parallel¡ª which makes the crystal oscillator be a little higher than expected?
You can easily fix that in the source code of the software by just changing the designated frequency of the Crystal to match where it actually oscillates, and then all of your adjustments should be simple from then on ? ? A good communications receiver
will allow you to measure the actual oscillation frequency. ?Dip a ?wire near the raduino and you¡¯ll pick up a ?signal
Even easier is to command the read you a note to go to the specified frequency of the Crystal, and then measure the amplified output! ? That¡¯s a very loud signal!
Add 10-20 picofarads in parallel with the capacitor and you may find that you get it exactly on frequency without doing any software at all
These are wonderful things to learn in?
ham radio
Thanks KE7ER thats helps a lot.
|
Re: Wired up Bitx40 and it doesn't work!
That 0.49v means you have the power supply reversed.
At 24-08-19, you wrote:
toggle quoted message
Show quoted text
I finally got around to wiring
up my bitx40 QRP radio and when I applied 12v, 2.0 amps from my bench
power supply, nothing happens with the bitx40... the bench power supply
supply voltage drops down from 12v to 0.49 V, but nothing happening on
the Bitx40 display and no sound from the speaker.? I checked the
inline fuse and it is working and it did not pop...?
Any suggestions are greatly appreciated.
--
73,
Mark / WU6R
mark.wheeler3575@...
|
Re: Audio pre-amplifier for microphone?
How to connect this to uBITX?
Vote oh3jve
|
Re: Bitx40 very loud, high-pitched, low frequency noise
I think it could even be an issue with the way the LM386 is wired up. The power supply to the audio amp is via a 100 ohms resistor. So, when something loud gets into the audio input, it would draw more current and the voltage across that resistor will increase, in turn decreasing the dc voltage to the LM386. The dip in the dc voltage would dip the gain of the LM386, decreasing the current... The cycle would repeat causing oscillations. But that would lead to motor boating : butbutbutbutbrrrrrr.. kind of a sound.
I think that your comment about even on battery there is faint noise and it is near your PC is significant.Some pc's give out lots of hash or wine and I wonder if moving the uBITX? further away may silence that last bit of noise.I am surprised that the capacitor
combination on the output does not help,that has always worked for me as I proved by my test last evening on a randomly picked switch mode wall wart.? Anyways it's progress in the right direction,keep the leads short and you will minimise pickup.A ferrite
ring or two on the cables won't do any harm,the best quality power supplies usually have fitted on the DC lead to keep switching noise away from the DC output.
On 8/23/2019 19:39, Gordon Gibby wrote:
> You may decide that you want to build a real low pass filter, with an
> inductor etc., similar to what people had to use in the past to get
> rid of alternator whine
--
...Or a new / different power supply.
--
It would be interesting to examine the supply output with an oscilloscope.
W00DY
--
|
Re: Audio pre-amplifier for microphone?
Once again, very good art work from ND6T. --KB5PWL, Donald
|
Re: Audio pre-amplifier for microphone?
On Fri, Aug 23, 2019 at 04:50 PM, Don, ND6T wrote:
common-base amplifier
It is great to be reminded that there are other configurations than the knee-jerk choice of common emitter. Because the impedance of the microphone is low and you are basically trying to raise the voltage, not so much the current, this works just like the ever popular common grid arrangement of vacuum tube days of the (not completely) past. Tom, wb6b
|
David Wilcox K8WPE
Raj vu2zap