Date   
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

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.

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

Curt
 

V3 and v4 need reduced leakage through LPF relays. Either add a pc board hosting added relays or switch the relays to axicom. Our club kitted a relay board designed by Gordon Gibby, but no one is yet selling it.

That leaves spurs associated with the mixer from 45 MHz to RF. Shielded inductors said to help, and additional 45 MHz filtering. This issue impacts 21 MHz and higher only.

No clear consensus nor kitting on these.

Curt

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

 

Either add a pc board hosting added relays or switch the relays to axicom.

Or do Allison's relay mod as described in the wiki.  No need to buy new parts if you don't want to.  Also the Axicom swap relies on the relay having better specifications (which may change with production or if you end up with conterfeit parts) while Allison's mod relies on better isolation of the signal paths and a better switching scheme (like you get with the v5 and probably like is done in the accessory relay board).

73,


Mark.

Apartment antenna question for uBitx #ubitx

ashok.das81@...
 

Dear all,

I live on the top floor of a 3 story apartment. I do not have any other space for antenna except the rooftop. To set up a dipole antenna I made a plan i have attached below. I will use common PVC insulated household electrical wire approx 3-4 sqmm dia, for antenna. I will use a uBitx transceiver and tx power will not be much (Maximum that uBitx support). I am requesting you to suggest/advice me how this antenna will perform and also advise me to make balun/matching transformer/antenna tuner for this antenna. Thick black wire is coax and thick blue wire is antenna.

Regards
Ashok

Re: Aircraft headset speaker impedance and ubitx #ubitx

Adrien F4IJA
 

OK I've the confirmation here : https://sennheiserusa.happyfox.com/kb/article/51-pj068-microphone-plug/

The 6.35mm jack is well for the headset. 

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

Evan Hand
 

Tech Guy,

Here is a link to the issues as per the designer Ashhar Farhan:
https://groups.io/g/BITX20/topic/spurs_harmonics_whew/28982939?p=Created,,,20,1,0,0::recentpostdate%2Fsticky,,,20,2,0,28982939

I am still trying to find the thread that Ashhar presented the attached hand sketch for the Spurs fixes: (Note: there are some discrepancies in the text vs the schematic)

The longest thread also delves into the issues of how to measure the emissions without spending >$800 for test equipment.
https://groups.io/g/BITX20/topic/29340928#64194

Lastly, I would look at the differences between the v5 and v4 board for the transmitter circuits to see what was done.  As mentioned by Curt and Mark, the best solution for the harmonics is to either add a daughter board for the LPFs, or cut and rewire the traces on the board to reduce the blow back.  This will not address the spurs above 14mhz, that was only solved by the LPF between the IF and the final mixer (going from audio to PA).  The v5 board also changed the 2n3904 out for that IF stage to BFR93Ws to overcome low gain at 90mhz.

Of note is that the entire spurs and harmonic issues came about by an effort to make the output consistent across all of the bands.  It was during that effort that showed that there was a potential issue.

As far as I know the answer to your question is that there are multiple lists, including one at ubitx.net.  For me, I have reached the conclusion that you will need test equipment that can measure the 2 known issues of spurs and harmonics to verify that the v3 and v4 boards are clean enough to feed into a linear amp, but are probably low enough to not be an issue running bare foot on 12 vdc power to the PA.  This is of course for the US.  For most of the rest of the world, the board as supplied meets their requirements.

Truthfully, the lessons learned has been the most fun of the v4 board fix.  Since I have gotten the v5 board, have not really used it, as I am not really that much into operating, more into the technical solves.

FWIW, Above are my observations and opinions, others may be different.  Please do your own research before you make any choices based on them.  The search function on the board are hard to use (at least for me), however there is information here that is worth the digging.

73
Evan
AC9TU