Topics

Bitx40 - receiver works great, but do not transmit #bitx40help

Ivan Ilyichev
 

I have a trouble with BITX40 kit from HFSignals.
Receiver work great - i hear a lot of stations all over the world. But there are no transmission when pressing PTT.
I check currencies al described in instruction (both main board power and PA power connected):
In receive mode current is 136 mA
When press PTT - 330 mA
If saying HAAAAALO to microphone when PTT pressed - the current still 330 mA and not changed.
I try to adjust PA as described in instrunction - connect ammeter directly to PA power line. First step is adjust VR1 to PA currency 100 mA. It is ok. Second step - saying HAAAALO  microphone - fail, PA currency still 100 mA and not changes. I try to change value of VR136 - PA currency changes a little.
Also i try to check microphone amplifier - i connect external LM386 amp board to negative pin of C122 capacitor. When pushing PTT and saying anything do microphone -  hear me from external amplifier, it means that mic amp works ok.
At the next step i connect an external continuous wave oscillator worked at 7.100 Mhz to input of PA - left pin of C132. The PA currency raise to 1 A and there is a CW output in antenna. It means that PA works.
At the next i connect continuous wave oscillator worked at 7.100 Mhz to to the right end of C43. The PA currency raise to more than 1 A and there is a CW output in antenna. It means that preamp Q4 also works.
I have no ideas what to check more with my equipment - i have no oscilloscope, have only digital multimeter, frequency meter (up to 70 Mhz), and a continuous wave oscillator (up to 70 Mhz).

Vic WA4THR
 

Take a look at the voltages around Q13. That is a weak point as it can fail even if the rig is powered off in the presence of a nearby signal and you may see the base and emitter are at the same voltage. Mine had failed there and had very similar symptoms. replacing it with a conventional transistor restored operation and power out.

=Vic=

KC9SGV <kc9sgv@...>
 

Is your 12 V station power from a wall wart transformer ?
Try a higher amperage rated transformer or a car battery.

Bernie,
KC9SGV


On Feb 11, 2018, at 7:50 AM, Ivan Ilyichev <ilyichev.ivan@...> wrote:

I have a trouble with BITX40 kit from HFSignals.
Receiver work great - i hear a lot of stations all over the world. But there are no transmission when pressing PTT.
I check currencies al described in instruction (both main board power and PA power connected):
In receive mode current is 136 mA
When press PTT - 330 mA
If saying HAAAAALO to microphone when PTT pressed - the current still 330 mA and not changed.
I try to adjust PA as described in instrunction - connect ammeter directly to PA power line. First step is adjust VR1 to PA currency 100 mA. It is ok. Second step - saying HAAAALO  microphone - fail, PA currency still 100 mA and not changes. I try to change value of VR136 - PA currency changes a little.
Also i try to check microphone amplifier - i connect external LM386 amp board to negative pin of C122 capacitor. When pushing PTT and saying anything do microphone -  hear me from external amplifier, it means that mic amp works ok.
At the next step i connect an external continuous wave oscillator worked at 7.100 Mhz to input of PA - left pin of C132. The PA currency raise to 1 A and there is a CW output in antenna. It means that PA works.
At the next i connect continuous wave oscillator worked at 7.100 Mhz to to the right end of C43. The PA currency raise to more than 1 A and there is a CW output in antenna. It means that preamp Q4 also works.
I have no ideas what to check more with my equipment - i have no oscilloscope, have only digital multimeter, frequency meter (up to 70 Mhz), and a continuous wave oscillator (up to 70 Mhz).

Ivan Ilyichev
 

Thank you for answers.
I measure voltages around Q13 and Q14 when transmitting:
Q13: collector 11.77 v, base 3.73 v, emmitter 3.07 v
Q14: collector 12.02 v, base 1.09 v, emmitter 0.41 v
Power of transceiver comes from 7A-h lead-acid battery that produces up to 20 amps currency.
I describe in first message that PA works - if give him continuous wave to input in amplificate it well. I guess that problems somewhere in IF part but i do not know, how to check it with my equipment.

Ivan Ilyichev
 

I forgotten to write in a first message. This transceiver board was NEVER transmit, only receive.

M Garza <mgarza896@...>
 

I would say that Q13 is bad.  
Here is a document that shows approximate voltages to compare (Thanks Randy!).

Marco - KG5PRT 

On Feb 11, 2018 8:56 AM, "Ivan Ilyichev" <ilyichev.ivan@...> wrote:
Thank you for answers.
I measure voltages around Q13 and Q14 when transmitting:
Q13: collector 11.77 v, base 3.73 v, emmitter 3.07 v
Q14: collector 12.02 v, base 1.09 v, emmitter 0.41 v
Power of transceiver comes from 7A-h lead-acid battery that produces up to 20 amps currency.
I describe in first message that PA works - if give him continuous wave to input in amplificate it well. I guess that problems somewhere in IF part but i do not know, how to check it with my equipment.

M Garza <mgarza896@...>
 

Also consider adding the protection diodes discussed an this page.  It will protect Q13 from high power transmitters that will cause Q13 to fail.

On Feb 11, 2018 10:00 AM, "M Garza" <mgarza896@...> wrote:
I would say that Q13 is bad.  
Here is a document that shows approximate voltages to compare (Thanks Randy!).

Marco - KG5PRT 

On Feb 11, 2018 8:56 AM, "Ivan Ilyichev" <ilyichev.ivan@...> wrote:
Thank you for answers.
I measure voltages around Q13 and Q14 when transmitting:
Q13: collector 11.77 v, base 3.73 v, emmitter 3.07 v
Q14: collector 12.02 v, base 1.09 v, emmitter 0.41 v
Power of transceiver comes from 7A-h lead-acid battery that produces up to 20 amps currency.
I describe in first message that PA works - if give him continuous wave to input in amplificate it well. I guess that problems somewhere in IF part but i do not know, how to check it with my equipment.

Ivan Ilyichev
 

I use a 13.5 , 2 amp power source instead of 12 volts lead-acid battery, like in shown voltages chart.
Remeasured voltages are:
Q13: collector 13.34 v, base 4.21 v, emmitter 3.57 v
As i see they are practically the same as in voltage chart.

M Garza <mgarza896@...>
 

Ivan,
You are correct.  Q 13 seems fine.  Since you tested the PA, we need to work backwards in the circuit.  Looking at the schematic, Q4 is next, when transmitting.  Check the voltages on Q4.  If fine, check Q5, then Q6.  I think this covers the TX chain.
Look at the chart and test the transistors that have voltages during transmit.  You should find one, not correct and that will be where your problem lies.

Good luck,
Marco - KG5PRT 

On Feb 11, 2018 11:04 AM, "Ivan Ilyichev" <ilyichev.ivan@...> wrote:
I use a 13.5 , 2 amp power source instead of 12 volts lead-acid battery, like in shown voltages chart.
Remeasured voltages are:
Q13: collector 13.34 v, base 4.21 v, emmitter 3.57 v
As i see they are practically the same as in voltage chart.

Ivan Ilyichev
 

I was rechecking everything and find my own mistake. I reverse of polarity of connecting RADUINO VFO to main board. Very strange, but receiver works find with this connection. But transmission was not work. Now circuit current is correct, try to help someone to listen for me.

Ivan Ilyichev
 

I check current of transceiver. Whole transceiver in transmission mode, when speaking - 0.85 - 0.9 amp , PA only in transmission mode, when speaking -0.55 - 0.6 amp. This is in top position of RV136 resistor, in lower positions current is lower. Is this current too small or not? Maybe i burn something like Q9 when connected VFO incorrect.

M Garza <mgarza896@...>
 

are you still able to receive?
does it transmit now?
current doesn't always go to 1 amp.  That can be adjusted by RV136.  This is the drive level.
how much output power are you seeing?

Marco - KG5PRT

On Sun, Feb 11, 2018 at 12:39 PM, Ivan Ilyichev <ilyichev.ivan@...> wrote:
I check current of transceiver. Whole transceiver in transmission mode, when speaking - 0.85 - 0.9 amp , PA only in transmission mode, when speaking -0.55 - 0.6 amp. This is in top position of RV136 resistor, in lower positions current is lower. Is this current too small or not? Maybe i burn something like Q9 when connected VFO incorrect.


Ivan Ilyichev
 

Marco,
Thank you for your answers. I still able to receive, and it looks like sensetivity of the receiver goes up now. But i have no tools to measure it. I adjust RV136 to the top (as drawn in a circit) position, the current of whole transceiver when transmitting is 0.9 amp. Also i have no tools to measure output power. I try to lease measuring tools and see power output.

M Garza <mgarza896@...>
 

Since you do not have a watt meter, and you have a multimeter, you could build a rf probe.  You can see the rf voltage and calculate the wattage.
Here is a link to one you can build.  It is very easy:

Good luck
Marco - KG5PRT 

On Feb 11, 2018 2:00 PM, "Ivan Ilyichev" <ilyichev.ivan@...> wrote:
Marco,
Thank you for your answers. I still able to receive, and it looks like sensetivity of the receiver goes up now. But i have no tools to measure it. I adjust RV136 to the top (as drawn in a circit) position, the current of whole transceiver when transmitting is 0.9 amp. Also i have no tools to measure output power. I try to lease measuring tools and see power output.

Jerry Gaffke
 

Good advice, build a diode RF probe.
A germanium diode such as the 1n34a or 1n60 works well, but they are expensive now and hard to get.
A schottky diode (such as the Bat54s used on the Bitx40 diode mixers) works reasonably well.
A standard silicon diode such as a 1n4148 might be good enough for measuring fairly high RF power nodes 
such as at the antenna port of a working transmitter, but definitely will not see the expected RF voltage at the base of Q13.
The issue here is the forward voltage drop for small currents, perhaps 0.3v for the Schottky and 0.6v for the 1n4148.

The germanium diodes will be less than the Schottky but dependent on temperature.
The datasheet punts, and says 1 volt max at 5ma, should be good down to 100mv or so with the currents involved in an RF probe at 10megaohms:
    http://www.nteinc.com/specs/original/1N34A.pdf
    https://electronics.stackexchange.com/questions/223813/the-classic-1n34a-ge-diode-has-a-vf-of-1v-how-could-a-diode-with-such-a-high

N5ESE tries to explain the probe, but only goes so far.
That RF probe design assumes a voltmeter with an input resistance of 10megaohms,
some DVM's will have an input resistance that is considerably less.
So don't count on that probe reading RMS voltages accurately until somehow calibrated.
As the RF voltages approach the forward voltage drop across the diode it will become less and less accurate,
though can still be surprisingly useful (perhaps with a calibration chart) down to a few tens of millivolts if you have the right diode.
Also, N5ESE fails to mention that the capacitance between the probes into the DVM is an integral part of the design,
that capacitance along with his 4.7megaohm resistor forms a low pass filter so that the meter sees DC instead of rectified RF.


We should have a spare Bat54s plus cap and resistor into an analog Nano pin, 
so we can all have a common way of measuring RF voltages when debugging.
With different diodes and different voltmeters, we will all get different results and cannot usefully compare our measurements.

Jerry, KE7ER



On Sun, Feb 11, 2018 at 01:14 pm, M Garza wrote:
Since you do not have a watt meter, and you have a multimeter, you could build a rf probe.  You can see the rf voltage and calculate the wattage.
Here is a link to one you can build.  It is very easy:
 

Joe Puma
 

I’m waiting for this to come in the mail 

image1.png



On Feb 11, 2018, at 5:08 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

Good advice, build a diode RF probe.
A germanium diode such as the 1n34a or 1n60 works well, but they are expensive now and hard to get.
A schottky diode (such as the Bat54s used on the Bitx40 diode mixers) works reasonably well.
A standard silicon diode such as a 1n4148 might be good enough for measuring fairly high RF power nodes 
such as at the antenna port of a working transmitter, but definitely will not see the expected RF voltage at the base of Q13.
The issue here is the forward voltage drop for small currents, perhaps 0.3v for the Schottky and 0.6v for the 1n4148.

The germanium diodes will be less than the Schottky but dependent on temperature.
The datasheet punts, and says 1 volt max at 5ma, should be good down to 100mv or so with the currents involved in an RF probe at 10megaohms:
    http://www.nteinc.com/specs/original/1N34A.pdf
    https://electronics.stackexchange.com/questions/223813/the-classic-1n34a-ge-diode-has-a-vf-of-1v-how-could-a-diode-with-such-a-high

N5ESE tries to explain the probe, but only goes so far.
That RF probe design assumes a voltmeter with an input resistance of 10megaohms,
some DVM's will have an input resistance that is considerably less.
So don't count on that probe reading RMS voltages accurately until somehow calibrated.
As the RF voltages approach the forward voltage drop across the diode it will become less and less accurate,
though can still be surprisingly useful (perhaps with a calibration chart) down to a few tens of millivolts if you have the right diode.
Also, N5ESE fails to mention that the capacitance between the probes into the DVM is an integral part of the design,
that capacitance along with his 4.7megaohm resistor forms a low pass filter so that the meter sees DC instead of rectified RF.


We should have a spare Bat54s plus cap and resistor into an analog Nano pin, 
so we can all have a common way of measuring RF voltages when debugging.
With different diodes and different voltmeters, we will all get different results and cannot usefully compare our measurements.

Jerry, KE7ER



On Sun, Feb 11, 2018 at 01:14 pm, M Garza wrote:
Since you do not have a watt meter, and you have a multimeter, you could build a rf probe.  You can see the rf voltage and calculate the wattage.
Here is a link to one you can build.  It is very easy:
 

Jerry Gaffke
 

That's looks great if you want a high impedance probe for your oscilloscope or spectrum analyzer.
RF goes in, bigger RF at the same frequency goes out

But that is not a suitable RF probe for a DVM, where you want RF in, and a DC voltage out
that represents how strong the RF in was.

There are some similar AD8307 probes available on Ebay that I previously pointed to 
in response to one of your posts, they look much more suitable though I have not tried them.

Jerry, KE7ER


On Sun, Feb 11, 2018 at 02:45 pm, Joe Puma wrote:
I’m waiting for this to come in the mail: RF Active Probe 0.1-1.5GHz  analyzer oscilloscope

Joe Puma
 

Hmmm I didnt know this lol. I wanted to measure something with a RF millivolt meter that measures 8v?   So I saw that it can output a signal greater then 8v so I thought it had the range I was looking for. 

And now that you mention it I was reading my technical manual incorrectly and the voltage I was looking for is actually DC volts

image1.jpeg

I guess I will order the one that you linked me to because It’s the RF millivolts that I want to check on my radio at various test point Locations. 

And I guess I can check those DC voltages myself with my DVM now :) 

Joe
KD2NFC 


On Feb 11, 2018, at 6:28 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:

That's looks great if you want a high impedance probe for your oscilloscope or spectrum analyzer.
RF goes in, bigger RF at the same frequency goes out

But that is not a suitable RF probe for a DVM, where you want RF in, and a DC voltage out
that represents how strong the RF in was.

There are some similar AD8307 probes available on Ebay that I previously pointed to 
in response to one of your posts, they look much more suitable though I have not tried them.

Jerry, KE7ER


On Sun, Feb 11, 2018 at 02:45 pm, Joe Puma wrote:
I’m waiting for this to come in the mail: RF Active Probe 0.1-1.5GHz  analyzer oscilloscope

Jack, W8TEE
 

taydaelectronics.com has the 1N34a for $.24. Combine with some other stuff you need/want to cut down on shipping costs.

Jack, W8TEE



From: Jerry Gaffke via Groups.Io <jgaffke@...>
To: BITX20@groups.io
Sent: Sunday, February 11, 2018 5:08 PM
Subject: Re: [BITX20] Bitx40 - receiver works great, but do not transmit #bitx40help

Good advice, build a diode RF probe.
A germanium diode such as the 1n34a or 1n60 works well, but they are expensive now and hard to get.
A schottky diode (such as the Bat54s used on the Bitx40 diode mixers) works reasonably well.
A standard silicon diode such as a 1n4148 might be good enough for measuring fairly high RF power nodes 
such as at the antenna port of a working transmitter, but definitely will not see the expected RF voltage at the base of Q13.
The issue here is the forward voltage drop for small currents, perhaps 0.3v for the Schottky and 0.6v for the 1n4148.

The germanium diodes will be less than the Schottky but dependent on temperature.
The datasheet punts, and says 1 volt max at 5ma, should be good down to 100mv or so with the currents involved in an RF probe at 10megaohms:
    http://www.nteinc.com/specs/original/1N34A.pdf
    https://electronics.stackexchange.com/questions/223813/the-classic-1n34a-ge-diode-has-a-vf-of-1v-how-could-a-diode-with-such-a-high

N5ESE tries to explain the probe, but only goes so far.
That RF probe design assumes a voltmeter with an input resistance of 10megaohms,
some DVM's will have an input resistance that is considerably less.
So don't count on that probe reading RMS voltages accurately until somehow calibrated.
As the RF voltages approach the forward voltage drop across the diode it will become less and less accurate,
though can still be surprisingly useful (perhaps with a calibration chart) down to a few tens of millivolts if you have the right diode.
Also, N5ESE fails to mention that the capacitance between the probes into the DVM is an integral part of the design,
that capacitance along with his 4.7megaohm resistor forms a low pass filter so that the meter sees DC instead of rectified RF.


We should have a spare Bat54s plus cap and resistor into an analog Nano pin, 
so we can all have a common way of measuring RF voltages when debugging.
With different diodes and different voltmeters, we will all get different results and cannot usefully compare our measurements.

Jerry, KE7ER



On Sun, Feb 11, 2018 at 01:14 pm, M Garza wrote:
Since you do not have a watt meter, and you have a multimeter, you could build a rf probe.  You can see the rf voltage and calculate the wattage.
Here is a link to one you can build.  It is very easy:
 


Arv Evans
 

FYI

It is possible to forward bias the detector diode to get much higher sensitivity.

https://goo.gl/mgZuYA


Of course this does require DC power to the RF detector probe, or a small battery.

Arv K7HKL
_._

On Sun, Feb 11, 2018 at 8:30 PM, Jack Purdum via Groups.Io <jjpurdum@...> wrote:
taydaelectronics.com has the 1N34a for $.24. Combine with some other stuff you need/want to cut down on shipping costs.

Jack, W8TEE



From: Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io>
To: BITX20@groups.io
Sent: Sunday, February 11, 2018 5:08 PM
Subject: Re: [BITX20] Bitx40 - receiver works great, but do not transmit #bitx40help

Good advice, build a diode RF probe.
A germanium diode such as the 1n34a or 1n60 works well, but they are expensive now and hard to get.
A schottky diode (such as the Bat54s used on the Bitx40 diode mixers) works reasonably well.
A standard silicon diode such as a 1n4148 might be good enough for measuring fairly high RF power nodes 
such as at the antenna port of a working transmitter, but definitely will not see the expected RF voltage at the base of Q13.
The issue here is the forward voltage drop for small currents, perhaps 0.3v for the Schottky and 0.6v for the 1n4148.

The germanium diodes will be less than the Schottky but dependent on temperature.
The datasheet punts, and says 1 volt max at 5ma, should be good down to 100mv or so with the currents involved in an RF probe at 10megaohms:
    http://www.nteinc.com/specs/original/1N34A.pdf
    https://electronics.stackexchange.com/questions/223813/the-classic-1n34a-ge-diode-has-a-vf-of-1v-how-could-a-diode-with-such-a-high

N5ESE tries to explain the probe, but only goes so far.
That RF probe design assumes a voltmeter with an input resistance of 10megaohms,
some DVM's will have an input resistance that is considerably less.
So don't count on that probe reading RMS voltages accurately until somehow calibrated.
As the RF voltages approach the forward voltage drop across the diode it will become less and less accurate,
though can still be surprisingly useful (perhaps with a calibration chart) down to a few tens of millivolts if you have the right diode.
Also, N5ESE fails to mention that the capacitance between the probes into the DVM is an integral part of the design,
that capacitance along with his 4.7megaohm resistor forms a low pass filter so that the meter sees DC instead of rectified RF.


We should have a spare Bat54s plus cap and resistor into an analog Nano pin, 
so we can all have a common way of measuring RF voltages when debugging.
With different diodes and different voltmeters, we will all get different results and cannot usefully compare our measurements.

Jerry, KE7ER



On Sun, Feb 11, 2018 at 01:14 pm, M Garza wrote:
Since you do not have a watt meter, and you have a multimeter, you could build a rf probe.  You can see the rf voltage and calculate the wattage.
Here is a link to one you can build.  It is very easy: