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Tinny sounding electric miss on uBitx

Mike Lichtman
 

I was trying various electret mics with my uBitx today. Most of them sound very tinny lacking midrange and bass. 
This raises several questions: 1. is it me or do others find the transmitted sound is tinny when monitoring in another rcvr?
                                                 2. Short of an equalizer on the mic input what can be done? A cap, if so what value  .05 ? and where?
                                                 73 Mike KF6KXG

bill richardson
 

I had the same reports until I did the BFO adjustment. Mine is set at 11.996.100 for the best 

73 Bill


On Feb 10, 2018, at 11:17 PM, Mike Lichtman via Groups.Io <tchrme@...> wrote:

I was trying various electret mics with my uBitx today. Most of them sound very tinny lacking midrange and bass. 
This raises several questions: 1. is it me or do others find the transmitted sound is tinny when monitoring in another rcvr?
                                                 2. Short of an equalizer on the mic input what can be done? A cap, if so what value  .05 ? and where?
                                                 73 Mike KF6KXG

John Backo
 

Mike, Bill is probably right,

Check and adjust your BFO first. That is
almost always the reason for poor voice quality,
especially since others are using the more or
less the same setup and not reporting problems.

You will have to reload the software (maybe several times)
adjusting the BFO frequency until it sounds right. First,
use a frequency counter to find out what the present BFO
is. Record it so you can always reset it if the problem
turns out to be something different. Then find out what the
software says is your BFO and adjust it up or down by
500 Hz or so. Check the results and go from there...

It is relatively easy with a VFO, but using software makes
the job somewhat harder.

john
AD5YE.

John Backo
 

Oops -- I noticed you said "tinny when
monitoring in another receiver..."

That would rule out the BFO in YOUR receiver.

It could be the voice quality of your mic amplifier.
There have been various solutions posited for
that, including Kang's replacing resistors in
the amp. He also noticed a similar thing and
posited a larger solution. See his website
Small Wonder QRP for clues.

john
AD5YE

Jerry Gaffke
 

Transmit and receive are symetrical on the uBitx and Bitx40, uses the same bfo and IF filter.
Should have about the same audio characteristics on transmit as receive.

Assume the crystal filter has a passband from 11.998 to 11.996, the BFO is at 11.9955mhz
When transmitting, audio from the mike amp of 0 hz is at 11.9955mhz, audio that was 500hz is now 11.996mhz
and audio that was at 2500hz is now mixed with the BFO to create a signal at 11.998mhz.
Only stuff between 11.996 and 11.998 mhz will make it through the crystal filter.
So any audio from the mike between 500 and 2500 hz goes into the IF amp at frequencies between 11.996 and 11.998mhz.

On receive, the math is exactly the same.  The crystal filter only accepts incoming RF between 11.996 and 11.998,
when that RF is combined with our 11.9955mhz BFO we wind up with audio between 500 and 2500 hz.

Now if the BFO was at 11.9950 mhz but everything else was the same, the audio on transmit and receive
would be between 100 and 3000 hz, and perhaps sound a bit tinny.

Jerry, KE7ER


On Sun, Feb 11, 2018 at 02:49 pm, John Backo wrote:
Oops -- I noticed you said "tinny when
monitoring in another receiver..."

That would rule out the BFO in YOUR receiver.

It could be the voice quality of your mic amplifier.
There have been various solutions posited for
that, including Kang's replacing resistors in
the amp. He also noticed a similar thing and
posited a larger solution. See his website
Small Wonder QRP for clues.

Jerry Gaffke
 

<  would be between 100 and 3000 hz, and perhaps sound a bit tinny

Should be:
 >  would be between 1000 and 3000 hz, and perhaps sound a bit tinny


On Sun, Feb 11, 2018 at 03:39 pm, Jerry Gaffke wrote:
would be between 100 and 3000 hz, and perhaps sound a bit tinny.

Joe
 

I experienced similar tinny mic audio issues.  I had not realized the BFO affects both. 
After figuring out the BFO tx /rx relationship, I now just transmit and listen to my audio when transmitting.
While transmitting, I then tune the BFO 1199600 up or down until I hear the sound quality I desire.

Since I use the TFT Touch Control  display, the BFO is fully tune able from the touch display

Joe
VE1BWV



On Sun, Feb 11, 2018 at 7:41 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
<  would be between 100 and 3000 hz, and perhaps sound a bit tinny

Should be:
 >  would be between 1000 and 3000 hz, and perhaps sound a bit tinny

On Sun, Feb 11, 2018 at 03:39 pm, Jerry Gaffke wrote:
would be between 100 and 3000 hz, and perhaps sound a bit tinny.


Mike Lichtman
 

Bill and the group,
Thank you. I did the BFO adjustment and what a great improvement. I am located in Glendale, CA just north of Los Angeles near the Rose Bowl. My
first contact was to Tucson, AZ and then to Utah. My signal reports were 5-5 and 5-9 with good audio. And that’s with mediocre propagation.
Made my day. Now I am waiting for the case I ordered to arrive. One mod I am making is a panel mounted pushbutton that parallels the key jack to have a signal
for tuning when using SSB. I generally have been putting out about 9 watts on 40m. 73 Mike KF6KXG

Mike Lichtman
 

John,
Both the receive and transmit audio (monitored on another rcvr) were tinny. Maybe my original question wasn’t clear. Adjusting the BFO solved the problem. Thank you for your response. 73 Mike KF6KXG

Jack Zielke
 

I know this is an old thread, but I wanted to say thank you to everyone involved.  My BFO was set to 11.995.250.  If I went 1 kHz away people were loud by tinny.  If I went on frequency, they were soft but sounded right.  I set it to 11.996.100 and everything sounds wonderful!

Jack
KG4GJY

Timothy Fidler
 

Jack it is not a problem - it's  FEATURE ! But if you were setting this up on a system which has to swap USB/LSB between 40 m and 20m, which yours will since you are uBitx ..  I suggest you need to check it  works on USB after you have done the cludge ie on 20m as it is clear to me you are talking LSB operation and thusly 40 or 80 for your fix.. I kind of see probos ahead,  unless the firmware is incredibly smart.  


Let's face it though at the price it sells for the Cohn filter sets are not going to all be exactly on 12.0000 Mhz.  If you talk nicely to Leon at Ozqrp and offer him what he wants for matching and ship him say 12 HC 49U full hght xtals for matching you might be able to correct the problem.  But you need to get an indep and traceable calibration frequ counter on the BFO and get a second opinion as to if it is the BFO or the xtal filter set... just my tuppence worth....

Timothy E. Fidler : Engineer BE Mech(1) Auckland , NDT specialist AINDT UT /RT3 , MT2 
Telephone Whangarei   022  691 8405
e: Engstr@...



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Sent:
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Subject:
Re: [BITX20] Tinny sounding electric miss on uBitx


I know this is an old thread, but I wanted to say thank you to everyone involved.  My BFO was set to 11.995.250.  If I went 1 kHz away people were loud by tinny.  If I went on frequency, they were soft but sounded right.  I set it to 11.996.100 and everything sounds wonderful!

Jack
KG4GJY

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Timothy Fidler
 

Sorry . brain fade.. invert the answer. Jack clearly had to set the BFO way Low to select USB so it would pass the Cohn filter which appears to have its passband low on 12.0000 but the issue still remains.. does the uBitx work correctly on a frequency that uses LSB such as 40m. I would guess not unless the firmware was utterly bullet proof Mil Spec. Re comment on LEon.. He may refuse the work as he deals only with 10 Meg IFs on the kits he sells. AND you would need to put the squeeze on someone you know with a a Hot air chip removal station for  SMD to remove all the affected crystals if the kit refuses to work properly on both sides of the IF. sometimes you may have to put up with something with limited functionality than the worst case outcome....

ajparent1/KB1GMX <kb1gmx@...>
 

OK, we have a lot of misunderstanding here...  uBitx.

If the master osc is not set on frequency everything else is likely to be off frequency and work poorly.

The filter is ladder filter (not a Cohn) and like all ladderfilters due to the parallel caps are loaded to
the lower frequency.  so technically it is a filter of about 2.1Khz with a center frequency a of
11.9989mhz built with nominal 12mhz crystals.   From here out we call it a 12mhz filter as 
11.99989 is just longer! ;)

Also the default startup setting for the software uncalibrated is 11.995 (at least 1khz too low).

The IF filter 12mhz has a roughly 2.1khz pass band with the upper edge just below 12mhz
and the bottom ends around 11.997ish  Small errors in BFO placement (100hz) is enough to
impact audio quality both RX and TX.   FYI OSC-0 is the BFO.   In mine the magic number was
11.996750mhz.  NOTE: the BFO is not changed to change sideband.

ubitx changes sideband by flipping oscillator 1 between 33mhz and 57mhz with a small correction
for the 45mhz filter that is not at 45mhz but about 5-10khz lower.    If the calibration is off or not
done correctly these oscillators will be off for the 45mhz filter and sensitivity will suffer (if far enough off).

Now if the 25mhz crystal on the Raduino board is off and generally they will be its the master
oscillator for the whole game.  So the first thing is to get the "calibration" dialed in so when the
MPU/software commands xxx frequency you actually get it and the other two oscillators are also
where they should be.

Changing out the crystals in the filter can improve the filter but not likely solve the "tinny sound"
as that set will likely have a different offset for the BFO.   FYI changing the parallel capacitors 
will also move the filter center frequency and the bandwidth requiring BFO change.  
They are not SMT they are conventional leaded HC49U parts and easily desoldered without
art or rework station.

If the BFO is right the low end should cut off at about 200hz and the high end around 2300hz.
That will not be tinny.

For an FYI: I included a image of the filter pass band while testing a personal mod to get 
to a wider band width (2.7khz) for better fidelity.  The ripples on the top of the pass band
are about 1.5db and not at all bad.  Even widened up the upper edge is barely 12mhz
(11.999985ish mhz).  Best sideband setting is 11.996685mhz for that filter.

Allison

Timothy Fidler
 

Arggh an assumption re-arranged  makes an Ass out of you and me.!!!. I thought Ashar F would have gone done the merry conventional way with pulling the BFO to get sb flip  ..


so next time you want Space shuttle Field joints and O rings re-designed  AP .. you know where NOT to go.

Every single photo  I have seen of uBitx or ubitx40 seems to have half height xtals on it so either AJP got a premium build or TEF needs better specs or a bit of both.    :-).  

ajparent1/KB1GMX <kb1gmx@...>
 

Tim, your the go to then as you know know why its important. ;)

Yes the BITX (20/40/17...) are similar but not the same as uBitx.

The biggest change is the second conversion as that opens up
a few ways to alternately do things like change sideband.

Allison

ajparent1/KB1GMX <kb1gmx@...>
 

Its possible someone got standard HC49... not the shorter 49u like mine.  it actually does make a
difference as the quartz inside has a different cut.

Premium build, no.  It has all the bugs.

Allison

Timothy Fidler
 

More than a different cut... the 49S  nb S has a beam hogging mode of oscillation and the HC49U (13mm h) has a diaphragm mode. I thin we both speak Anglisky but 
there is a slight confusion here on the size designators : and the industry she don't help none : See https://www.golledge.com/products/hc49-leaded-crystal-with-industry-standard-package/c-26/p-239