开云体育

The only problem with the audio amp on the v3 boards was that
they had a run of bad TDA2822 clone chips.
The TDA2822's with a "WX" marking may (or may not) fail when powered from 12v,
if you catch it before it blows you can add a voltage regulator to feed it only 6v or so and it will be fine.
As far as I know, nobody ever had other than the "WX" marked parts fail.
If a WX does fail, I'd suggest you replace it with an NJM2073D (identical pinout and function), costs about $1 US.
Other TDA2822's from hfsignals (mostly marked "FCI") work fine with no mods required.

The v4 boards replaced the TDA2822's with an 2n3904/2n3906 push-pull pair.
But that suffers from low volume and often lots of crossover distortion.

Lots of little LM386 amplifier modules out there for $1 US if you don't want to mess with chips,
should work fine as a replacement of the final audio amp on either v3 or v4.
???
Wire the input to that module from VOL-M on the uBitx volume control pot and feed the LM386 12v.
You'll want the 1uF (or so) cap between LM386 pins 1 and 8 to boost the gain up from 20dB to 40dB.
Should wind up with something very much like the LM386 audio amp on the Bitx40.

Jerry, KE7ER

On Tue, Jan 22, 2019 at 07:41 PM, Evan Hand wrote:

The ADC is 8 bits, so same as the RTL-SDR.

Maybe the SDRPlay with the 12 bit ADC?? The dual receiver version was $270.? Might be a good compromise, as well as with an automatic switch (MFJ makes one) you could have a pan adapter display to use with the uBitx.? Since I already have that function in my IC-7300 not a selling point for me.

On Tue, Jan 22, 2019 at 07:22 PM, Evan Hand wrote:

Dave,
Do you know the ADC specs for your scope?? It could be a dynamic range of the input again.? 8 bits are fine when there is a voltage divider to scale the input so that it fits on the screen.? The FFT would be limited by that range in detecting small signal variation that are required for the FFT to be very accurate.? Same problem as the input to the RTL-SDR.

Maybe someone has a better explanation, or way to test for the harmonics

I did ask some of the members at my club, and to my surprise they are using the RF Explorer as their SA.? Was looking for a way to verify if I had the spurs or not.

I keep thinking about that $700 Rigol, maybe could try it, and if it does detect the spurs then could look at a white noise generator for the filter testing in place of the tracking generator function. Just adds an extra step in verifying the input prior to measuring the output.? If that doesn't work, still might be able to recover some of the cost by selling used and then buy the $1200-$1300 devices.


73
Evan
AC9TU

On Tue, Jan 22, 2019 at 06:43 PM, Jerry Gaffke wrote:

21.5mhz is the third harmonic of 7.15mhz, we can expect some trouble there,
though -20dBc is worse than I recall seeing on measurements posted here for other uBitx's.
Moving to the axicom relays might help this considerably, or any of the other mods
proposed for fixing the ubitx board layout issues in the transmit low pass filters.
Or could just add an external low pass filter between rig and antenna
when operating on 40 meters to fix this.

I'd guess you are transmitting in CW mode, which may be driving the final too hard.
You might try reducing the drive to the final at RV1, see if that helps.
Make a mark first so you can remember how it had been set originally.

Jerry


On Tue, Jan 22, 2019 at 05:43 PM, Dave Space wrote:

So I remeasured my ubitx this time with my oscilloscope FFT.? Not sure how accurate those are?

It shows a lot less spurs but does still show a spur only -20db down when transmitting at 7.150MHZ somewhere around 21.5MHZ or so (I didn't zoom in too far so plus or minus ~500khz .? (I tested connected to the scope through coax -40db attenuator).

It tends to confirm of the rtl-sdr which saw one about -30db down or so.? I didn't notice the large amount of IMD within 750khz range as I did with the RTL-SDR though there was a lot of noise (might have to up the averaging to see if I can filter that out).

On Tue, Jan 22, 2019 at 05:43 PM, Dave Space wrote:

So I remeasured my ubitx this time with my oscilloscope FFT.? Not sure how accurate those are?

It shows a lot less spurs but does still show a spur only -20db down when transmitting at 7.150MHZ somewhere around 21.5MHZ or so (I didn't zoom in too far so plus or minus ~500khz .? (I tested connected to the scope through coax -40db attenuator).

It tends to confirm of the rtl-sdr which saw one about -30db down or so.? I didn't notice the large amount of IMD within 750khz range as I did with the RTL-SDR though there was a lot of noise (might have to up the averaging to see if I can filter that out).

On Tue, Jan 22, 2019 at 02:24 PM, Curt wrote:

Andy

See if you have sidetone when using cw. If you don't have a key, you still need that external 4.7k resistor anyway. Then put a short across the key input to listen for sidetone audio. If none, possibly the audio amp ic is defective, a common v3 malady I am told. Also you can inject audio into its input to see if this is the issue.

If this is the problem, I would be so tempted to not repair it, but use another audio amp board. V3 folk can chime in, or search here for v3 audio.

Curt

On Tue, 1/22/19, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

Subject: Re: [BITX20] ubitx 40 Connecdtion
To: [email protected]
Date: Tuesday, January 22, 2019, 7:08 PM

Bob,

I think you have it figured out.
The 5 pin cable goes on the end of the 16 pin
connector that's nearest the 7805 regulator.

They only build one version of
the raduino, one that plugs into a uBitx.
So
all raduinos now have the 16 right angle header pins on the
bottom.
Back when hfsignals only sold the
Bitx40, it had a 5 pin connector on the end near the 7805
regulator,
leaving 11 unused holes in that
row of 16.

Another change
is that the Nano is socketed, so easy to swap out if you
blow an IO cell.
However, if you buy a
replacement Nano, be sure to get one that does not yet have
the?
header pins soldered in place, because
they must be installed on the "wrong" side of the
board.

The only other
change to the raduino is that they all come with uBitx
firmware (I believe).
You will likely have
to flash it with Bitx40 firmware.

There have been no board layout changes to the
raduino
since it first came out in late
2016.

Jerry, KE7ER



On Tue, Jan 22, 2019 at 03:40 PM, Bob Lunsford
wrote:

Just got the BITX40 today. I had the uBitx
before and sold it to
a man who wanted to
run digital. It was a dream to put together,
no problem whatsoever.

But the picture on the wire-up page for the
BITX40 does not
show the same thing for the
Raduino that I got today. I do not
want to
assume too much but it seems the 5-pin connector
plugs into the 16-pin connector but it's
not clear if it's to be
put in on one or
the other end. The 16-pin connector is
labeled P3. Off to one end of the board is U3
which is a
3-pin regulator, it seems. I
think I know where the 5-pin
connector goes
but want to make sure...

Bob — KK5R

On Tue, Jan 22, 2019 at 03:40 PM, Bob Lunsford wrote:

Just got the BITX40 today. I had the uBitx before and sold it to
a man who wanted to run digital. It was a dream to put together,
no problem whatsoever.

But the picture on the wire-up page for the BITX40 does not
show the same thing for the Raduino that I got today. I do not
want to assume too much but it seems the 5-pin connector
plugs into the 16-pin connector but it's not clear if it's to be
put in on one or the other end. The 16-pin connector is
labeled P3. Off to one end of the board is U3 which is a
3-pin regulator, it seems. I think I know where the 5-pin
connector goes but want to make sure...

Bob — KK5R

On Tue, 1/22/19, Doug W <dougwilner@...> wrote:

Subject: Re: [BITX20] ubitx 40 Connecdtion
To: [email protected]
Date: Tuesday, January 22, 2019, 6:12 PM

Bob,
?BITX and BITX40 are different radios.? Which
do you have?
--
www.bitxmap.com