1. BITX20@groups.io
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Re: Aircraft headset speaker impedance and ubitx #ubitx

pat griffin
 

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

From: BITX20@groups.io <BITX20@groups.io> on behalf of adrien.grelet@... <adrien.grelet@...>
Sent: Saturday, August 24, 2019 8:21 AM
To: BITX20@groups.io <BITX20@groups.io>
Subject: [BITX20] Aircraft headset speaker impedance and ubitx #ubitx #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: Aircraft headset speaker impedance and ubitx #ubitx

Adrien F4IJA
 

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

Ian Reeve
 

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.

From: BITX20@groups.io <BITX20@groups.io> on behalf of adrien.grelet@... <adrien.grelet@...>
Sent: Saturday, August 24, 2019 3:52:15 PM
To: BITX20@groups.io <BITX20@groups.io>
Subject: Re: [BITX20] Aircraft headset speaker impedance and ubitx #ubitx #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 F4IJA
 

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

Ian Reeve
 

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?

From: BITX20@groups.io <BITX20@groups.io> on behalf of adrien.grelet@... <adrien.grelet@...>
Sent: Saturday, August 24, 2019 4:09:39 PM
To: BITX20@groups.io <BITX20@groups.io>
Subject: Re: [BITX20] Aircraft headset speaker impedance and ubitx #ubitx #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

Mark - N7EKU
 

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

Ian Reeve
 

Agreed typical measurement for a dynamic mic but not electret.

From: BITX20@groups.io <BITX20@groups.io> on behalf of Mark - N7EKU <n7eku@...>
Sent: Saturday, August 24, 2019 4:36:31 PM
To: BITX20@groups.io <BITX20@groups.io>
Subject: Re: [BITX20] Aircraft headset speaker impedance and ubitx #ubitx #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: Audio pre-amplifier for microphone?

Tom, wb6b
 

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

Tom, wb6b
 

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: Bitx40 very loud, high-pitched, low frequency noise

John Norris
 

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.

On Sat 24 Aug, 2019, 1:42 AM Ian Reeve, <ian.radioworkshop@...> wrote:
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.

From: BITX20@groups.io <BITX20@groups.io> on behalf of Woody <woody@...>
Sent: Friday, August 23, 2019 8:58:25 PM
To: BITX20@groups.io <BITX20@groups.io>
Subject: Re: [BITX20] Bitx40 very loud, high-pitched, low frequency noise
 
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

Adrien F4IJA
 

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

Woody
 

On 8/24/2019 16:34, John Norris wrote:
My BITX40 shrieks if I get my cellphone too close to it.
Not too surprised after I discovered a similar issue.   My high frequency hearing isn't very good so I built an active high pass filter (741 ICs) / amp (LM386s). Worked great but had a problem.  Intermittent loud clicking and screeching.   After a lot of troubleshooting, discovered that if my cell phone was within 2', it was bad.   Moved the phone away a bit and the problem disappeared.
Woody - KZ4AK

--
Re: Wired up Bitx40 and it doesn't work!

KM6HFR <mark3575@...>
 

Thanks!

Mark

On Aug 24, 2019, at 2:58 AM, Raj vu2zap <rajendrakumargg@...> wrote:

That 0.49v means you have the power supply reversed.

At 24-08-19, you wrote:
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@...

Current v5 ubitx fixes adequate?

Tech Guy
 

Is the current product’s spurs much better than v4? Any new features or just signal improvement?
Re: Current v5 ubitx fixes adequate?

Evan Hand
 

Per the ARRL September QST the uBitx v5 passes FCC requirements.  The prior versions did not.

Other than cleaning up the signal, there are only differences, not necessarily improvements in the calibration procedure.  Calibration now requires a dummy load, or else you would be transmitting on 10MHz, out of band for the US. 

I do feel like I can now build the 70 watt linear for the rig that I was hesitant to do so with the prior versions.  After that will go back and work on the 2 v4 rigs that I have to get them up to speed and setup for digital.

Really fun rig, and a good platform to learn on.

The above is my opinion, others may differ and are entitled to their own.

73
Evan
AC9TU
Re: Current v5 ubitx fixes adequate?

Curt
 

Primary focus is lower spurious.  I myself have not seen a complete set of SSB spurious, but it is said to be in the neighborhood of compliance.  It uses a wider SSB filter, not really an improvement in my thinking but this was done to move away from some internal spurious leakage.  Functionality is unchanged.  I am a v4 owner - its a fun rig - I have all but the high frequency SSB spurious corrected. 

73 Curt
Re: Current v5 ubitx fixes adequate?

Curt
 

I am suspicious the arrl lab evaluated harmonics but did not know to look for ssb mixer spurious. No evidence that they did.

Curt
Re: Current v5 ubitx fixes adequate? Is there a thread about v4 fixes?

Tech Guy
 

Is there a place that lists v4 fixes for improved compliance?
Qrp kits dds with bitx 40

Tech Guy
 

I have an early bitx 40 without the radino dds. Has anyone used the dds from qrp kits? I have something  that I stuck together on an experimenter board but it doesn’t have enough drive for the mixer I think. I used a dds from ebay with a nano.
Re: Qrp kits dds with bitx 40

RICHARD
 

The QRP LABS dds works great. I think it is 3 volts p/p out The only problem is the software is not open source.

 

K6KWQ

 

Sent from Mail for Windows 10

 

From: BITX20@groups.io <BITX20@groups.io> on behalf of Tech Guy <tech48055@...>
Sent: Saturday, August 24, 2019 4:00:21 PM
To: BITX20@groups.io <BITX20@groups.io>
Subject: [BITX20] Qrp kits dds with bitx 40
 
I have an early bitx 40 without the radino dds. Has anyone used the dds from qrp kits? I have something  that I stuck together on an experimenter board but it doesn’t have enough drive for the mixer I think. I used a dds from ebay with a nano.