As I recall, you showed some alarmingly low signal levels as the
frequency went up.
If the si5351 can only give 8ma at dc, your notes suggest it gets
awfully small at 45mhz+SignalFreq
into the first mixer on the ubitx.

Though Gordon's right, there is some conduction through a schottky diode
even at 200mv or less.
Perhaps somehow the ubitx works well enough, but could do better if the
diode ring mixers were driven harder.

Jerry

On Tue, Oct 24, 2017 at 01:03 pm, Vince Vielhaber wrote:

I posted the RMS values of all four output modes yesterday. Do you
also want the P-P values?

There are many things that I don't know, and I sincerely thank all of you for the resource that is growing here in this group.

I am looking for some assistance troubleshooting a Bitx40.
Go easy on me, I have very little idea of what I am doing.

Let me tell you what I do know...
-This is my first HF radio, and my first kit build radio - what could possibly go wrong, right?
-I am running this radio from a 12v Battery. (12.4v -13.2v ish)
-100' of coax to an inverted V that has been tuned to the middle of the band.
-Receive works well.? I can regularly hear folks from the western half of North America, and frequently the east coast as well as others speaking Spanish (Mexico?? South America?)
-Transmit appears to not work.? I have not made any successful QSO's.
-I have a QRP dummy load (), and the voltage measured (between ground and VRMS pin is something like 0.57) (RF power = (0.57^2)/50= .0065 watts) when the mic is keyed.
-I have tested the voltages of all of the transistors and while not exactly the same, they are very close to the values published by?Randy, K7AGE
-I never saw the "Magic smoke"
-There are very few mods to this BitX40.? Allard's code, extra heat-sink one the raduino, and larger heat-sink on the board, extra capacitor on tuning pot, (there is one other capacitor that I added, but at the moment, I cannot precisely describe where I put it), external speaker/mic by BTech
-I don't have access to test equipment beyond a multi meter, small dummy load, and an antenna analyser.
-I have tried to measure Amps drawn, but I was likely doing something incorrectly as the values were not even close tho what is described in the BitX40 write up.
-Nothing gets hot when powered on, no visually obvious defects.
-I have listened (via WebSDR) to a frequency that I was transmitting on, and received nothing.? I'm not sure if I was too far away, or if I was really not transmitting.? I live far away from most everything so popping over to the next ham meeting is non-trivial.


So what can I test?? Are there any other troubleshooting guides out there?
Thanks for any ideas or suggestions that you might have.

WA7NJB

I'm going to have a look at the 2430A.

Current setup:
Tek 11402 Scope w/ 11A32 400MHz plugin
Tek P6121 10x probe - 1 meg termination in the scope
No bandwidth limiting

Adafruit si5351 board CLK2 terminated into 51 ohms.
Standalone Nano controlling it.
NOTE: CLK2 is also used for the following measurements.

There is a difference in output between 7.5MHz and 35.5MHz, but only about 15mv rms.

There's a bit of ringing on the square wave but that's probably in my setup.

Ok, with the above setup, at 11.020 MHz:

2ma setting: 190 mv rms.
4ma setting: 380 mv rms.
6ma setting: 560 mv rms.
8ma setting: 735 mv rms.

I posted the RMS values of all four output modes yesterday. Do you also want the P-P values?

Hmm, my analysis in post /g/BITX20/topic/6215251
might be full of beans.

The SiLabs document an619 shows that registers 16,17,18 can set drive
levels at clk0,clk1,clk2 to values of 2,4,6 or 8 ma.
With 8ma max into 50 ohms that's a 0.008*50 = 0.4v pk-pk square wave
across the 50 ohm load.
Farhan's ubitx has a 6db pad between the raduino and T1, so the primary
of T1 sees 0.4v/2 = 0.2v.
T1 has two windings driving the diodes, a step-up transformer, so the
diodes see a 0.4v pk-to-pk.
But a single schottky diode has a forward voltage of around 0.4v at
10ma, I have no idea how this
0.4v signal source can drive two schottky diodes in series.

But the ubitx apparently works.
What am I missing here?
I'll have to put a 50 ohm load on a si5351 someday, see just how much
drive the si5351 can give.

Might be best to include a buffer amp, if only to reduce all the
crosstalk you would get between si5351 channels
when asking it to deliver maximum drive.



On Mon, Oct 23, 2017 at 02:54 am, Gordon Gibby wrote:

think you're off a decimal point there.... 2 mA into 50 ohms is 1/5
of a milliwatt so it wold not be 3dBm....

------------------------------------------------------------------------
*From:* Kelly Jack <kellyjack1968@... *Sent:* Monday, October 23,
2017 5:30 AM
this page indicates that setting the drive at 2ma equates to 3dbm
into a 50ohms load.

<>

Well again, I didn't follow all of that, but if you put 8 mA into 50 ohms, you get .4 V peak; ?0.8 p-P

(Proof: ?use a halfway rectifier on your home outlet 120 V RMS, and you'll discover that you get somewhere around 160 V DC or more out of it. ? it's not 120 V peak to peak, it is 240 peak to peak!!)

Someone on this forum recently measured the voltages, out of some board or something. ?

I looked at the schematic of the micro bit X that was linked to here, and the RF signal seems to be in series with the transformer winding providing the Heterodyne signal, so the sum of the two could reach much higher levels than either alone at times.

Furthermore, I went and looked at the data sheet of a small signal Schottky diode here:

And there is significant conduction even at 200 mV. ? ?Sure, if you want 10 mA you'll need a little higher voltage, but you can get some signal out of those things at a lot lower voltage than that.

And of course, you already know the punchline, the thing does work!!

Sent from my iPhone

On Oct 24, 2017, at 2:14 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

Hmm, my analysis in post
might be full of beans.

The SiLabs document an619 shows that registers 16,17,18 can set drive levels at clk0,clk1,clk2 to values of 2,4,6 or 8 ma.
With 8ma max into 50 ohms that's a 0.008*50 = 0.4v pk-pk square wave across the 50 ohm load.
Farhan's ubitx has a 6db pad between the raduino and T1, so the primary of T1 sees 0.4v/2 = 0.2v.
T1 has two windings driving the diodes, a step-up transformer, so the diodes see a 0.4v pk-to-pk.
But a single schottky diode has a forward voltage of around 0.4v at 10ma, I have no idea how this
0.4v signal source can drive two schottky diodes in series. ?

But the ubitx apparently works.
What am I missing here?
I'll have to put a 50 ohm load on a si5351 someday, see just how much drive the si5351 can give.

Might be best to include a buffer amp, if only to reduce all the crosstalk you would get between si5351 channels
when asking it to deliver maximum drive.



On Mon, Oct 23, 2017 at 02:54 am, Gordon Gibby wrote:

think you're off a decimal point there.... 2 mA into 50 ohms is 1/5 of a milliwatt so it wold not be 3dBm....?

---

From:?Kelly Jack <kellyjack1968@... ? ?Sent: Monday, October 23, 2017 5:30 AM?

this page indicates that setting the drive at 2ma equates to 3dbm into a 50ohms load.

Hmm, my analysis in post
might be full of beans.

The SiLabs document an619 shows that registers 16,17,18 can set drive levels at clk0,clk1,clk2 to values of 2,4,6 or 8 ma.
With 8ma max into 50 ohms that's a 0.008*50 = 0.4v pk-pk square wave across the 50 ohm load.
Farhan's ubitx has a 6db pad between the raduino and T1, so the primary of T1 sees 0.4v/2 = 0.2v.
T1 has two windings driving the diodes, a step-up transformer, so the diodes see a 0.4v pk-to-pk.
But a single schottky diode has a forward voltage of around 0.4v at 10ma, I have no idea how this
0.4v signal source can drive two schottky diodes in series. ?

But the ubitx apparently works.
What am I missing here?
I'll have to put a 50 ohm load on a si5351 someday, see just how much drive the si5351 can give.

Might be best to include a buffer amp, if only to reduce all the crosstalk you would get between si5351 channels
when asking it to deliver maximum drive.



On Mon, Oct 23, 2017 at 02:54 am, Gordon Gibby wrote:

think you're off a decimal point there.... 2 mA into 50 ohms is 1/5 of a milliwatt so it wold not be 3dBm....?

---

From:?Kelly Jack <kellyjack1968@... ? ?Sent: Monday, October 23, 2017 5:30 AM?

this page indicates that setting the drive at 2ma equates to 3dbm into a 50ohms load.

think you're off a decimal point there.... 2 mA into 50 ohms is 1/5 of a milliwatt so it wold not be 3dBm....?

---

From:?Kelly Jack <kellyjack1968@... ? ?Sent: Monday, October 23, 2017 5:30 AM?

this page indicates that setting the drive at 2ma equates to 3dbm into a 50ohms load.

Q7 has mostly that 470 ohm emitter resistor to stop excessive reverse current, but probably survived.
I'm not really sure how Q7 (or any of the other transistor amps) would behave in the face of a reverse supply.

I heard you are working on an updated uBITX circuit, is this true? When will the drawings be available?

Well I got around to install a diode still no luck. I had some 1N914 which are supposed to be electrically the same. I ended up accidentally ripping one of the traces off that seems to lead to the relay. I drilled and installed diode. I installed annode to ptt1-2 (brown side). connected cathode side to c130. rarduino comes on. barely any noise came out of speaker even with antenna connected. then noticed c130 was smoking and melting into board. Does anybody know what capacitor I can switch that with?
Ps. If it sounds like I don't know what I'm doing it's because I don't but trying to look at the diagram and find the nearest point that it connects to solder to with the same polarity.