Date   

Re: How to Reduce CS-series Power?

Adam Rong
 

John,

It is not a good idea to reduce power by reducing IRF510's bias because it will make it work in poor situation.

How much power can you get so far? If you can get 5 watt or more, adding a power amplifier of 10 watt seems not very justified. If you really need higher power, you can consider raising the power supply voltage a little bit to somewhere at 14 volt.

Thanks,
Adam

在 2017年8月1日,上午12:30,landrjoh@... [CHINA_QRP] <CHINA_QRP@...> 写道:

 

Does anyone know if there's a safe way to REDUCE the transmit power of a CS-series transceiver using the existing circuitry?  Would simply reducing the IRF510's bias current do the trick or would that harm the IRF510?


I ask because I'm interested in exploring the use of an external 10W RF amplifier for 20M.  It has a limit on the input power it can accept.


Thanks,


John

AA7US


How to Reduce CS-series Power?

AA7US
 

Does anyone know if there's a safe way to REDUCE the transmit power of a CS-series transceiver using the existing circuitry?  Would simply reducing the IRF510's bias current do the trick or would that harm the IRF510?


I ask because I'm interested in exploring the use of an external 10W RF amplifier for 20M.  It has a limit on the input power it can accept.


Thanks,


John

AA7US


Re: Sandwich VFO Noise

AA7US
 

Thank you for the suggestions gents.

I removed the coax shield ground connections at the Sandwich VFO and left them at the main PCB so only one end of the coax is grounded.  Unfortunately there was no change in the noise.

I also tested it both with and without an additional insulated ground wire running between the Sandwich VFO and main PCB (like the manual calls for).  This didn't make any difference either.

I believe I've narrowed down the noise source to the tuning encoder.  But I'm also beginning to think maybe this noise was always been present... even before I moved with the capacitors and added the coax jumpers.  I suspect I've become overly fixated on it and it's really not significant.

73,

John
AA7US

---In CHINA_QRP@..., <larry.lovell@...> wrote :

Ground just one side of the coax.  You have probably created what is called a ground loop.


Re: Sandwich VFO Noise

n7rgw
 

Ground just one side of the coax.  You have probably created what is called a ground loop.


On Thursday, July 27, 2017 8:52 PM, "zack hackiz hackizzz@... [CHINA_QRP]" wrote:


 
Try grounding just one side of the coax.


On Thursday, July 27, 2017 9:31 PM, "landrjoh@... [CHINA_QRP]" wrote:


 
I recently completed building a CS-40.  Everything works great.

The Sandwich VFO was connected to the main PCB via two bare 0.1uF (104) capacitors and a separate insulated ground wire just as shown in the Sandwich VFO and CS-series assembly manuals.

I couldn't leave well enough alone and have already started making some modifications.  A modification I made today was to relocate the two 0.1uF capacitors down to the main PCB and from there running a couple of RG-174 coaxes back up to the Sandwich VFO.  The shields on the coax have been soldered to grounds on both the main PCB and the Sandwich VFO.  Assuming those shields provide adequate ground paths, I removed the separate insulated ground wire previously run between the main PCB and Sandwich VFO.

With this mod in place I'm now hearing a brief noise each time I change the frequency when rotating the tuning knob.  I don't THINK this noise was there before, or if it was, it wasn't as noticeable.  The best way I can describe this noise is it sounds "digital" which leads me to think it must be coming from the Sandwich VFO.  It's not so bad I can't live with it, especially since I don't hear it except when changing frequencies.

By chance does anyone have a suggestion on how I might eliminate or suppress this noise?

73,

John
AA7US





Re: Sandwich VFO Noise

zack hackiz
 

Try grounding just one side of the coax.


On Thursday, July 27, 2017 9:31 PM, "landrjoh@... [CHINA_QRP]" wrote:


 
I recently completed building a CS-40.  Everything works great.

The Sandwich VFO was connected to the main PCB via two bare 0.1uF (104) capacitors and a separate insulated ground wire just as shown in the Sandwich VFO and CS-series assembly manuals.

I couldn't leave well enough alone and have already started making some modifications.  A modification I made today was to relocate the two 0.1uF capacitors down to the main PCB and from there running a couple of RG-174 coaxes back up to the Sandwich VFO.  The shields on the coax have been soldered to grounds on both the main PCB and the Sandwich VFO.  Assuming those shields provide adequate ground paths, I removed the separate insulated ground wire previously run between the main PCB and Sandwich VFO.

With this mod in place I'm now hearing a brief noise each time I change the frequency when rotating the tuning knob.  I don't THINK this noise was there before, or if it was, it wasn't as noticeable.  The best way I can describe this noise is it sounds "digital" which leads me to think it must be coming from the Sandwich VFO.  It's not so bad I can't live with it, especially since I don't hear it except when changing frequencies.

By chance does anyone have a suggestion on how I might eliminate or suppress this noise?

73,

John
AA7US



Sandwich VFO Noise

AA7US
 

I recently completed building a CS-40.  Everything works great.

The Sandwich VFO was connected to the main PCB via two bare 0.1uF (104) capacitors and a separate insulated ground wire just as shown in the Sandwich VFO and CS-series assembly manuals.


I couldn't leave well enough alone and have already started making some modifications.  A modification I made today was to relocate the two 0.1uF capacitors down to the main PCB and from there running a couple of RG-174 coaxes back up to the Sandwich VFO.  The shields on the coax have been soldered to grounds on both the main PCB and the Sandwich VFO.  Assuming those shields provide adequate ground paths, I removed the separate insulated ground wire previously run between the main PCB and Sandwich VFO.

With this mod in place I'm now hearing a brief noise each time I change the frequency when rotating the tuning knob.  I don't THINK this noise was there before, or if it was, it wasn't as noticeable.  The best way I can describe this noise is it sounds "digital" which leads me to think it must be coming from the Sandwich VFO.  It's not so bad I can't live with it, especially since I don't hear it except when changing frequencies.

By chance does anyone have a suggestion on how I might eliminate or suppress this noise?

73,

John
AA7US


Re: Yet another BITX on Choc Perf Board

AA7US
 

Beautiful work Adam!

John
AA7US


Yet another BITX on Choc Perf Board

Adam Rong
 

Gang,

A photo is more than thousands of words.

Thanks,
Adam


Re: Bias current problems

AA7US
 


That's exactly how I plan to wire up a power switch for mine.

73,

John
AA7US 

---In CHINA_QRP@..., <johncronhelm@...> wrote :

I could perhaps could cut the axial lead after the large diode connected to the power supply and connect a power lead to both cut ends to check bias current. When I am finished with the tests I can make it into a switch to turn the radio on and off.


Re: Bias current problems

JOHN CRONHELM
 

Thanks,At last I have got it now.   I have no fused power cable from my gel cell. I could perhaps could cut the axial lead after the large diode connected to the power supply and connect a power lead to both cut ends to check bias current. When I am finished with the tests I can make it into a switch to turn the radio on and off.
What do you think?
73 de John vo1jcc.


On Jul 22, 2017, at 9:54 PM, Robert Hudson vk2aor@... [CHINA_QRP] <CHINA_QRP@...> wrote:

 

Hi John


I used a power cable plugged into my fused supply and removed the fuse and using crocodile clips on my AVO 7 multimeter  so it is in series with my power supply, the red lead goes to the plus supply and the black lead goes to the radio.  The negative has no connection.   Hope that helps.

Bob Hudson








Re: Bias current problems

Robert Hudson
 

Hi All thanks for your comments and help .   To John AA7US a very concise description.  Thank you John


Bob Hudson








Re: Bias current problems

Robert Hudson
 

Hi John

I used a power cable plugged into my fused supply and removed the fuse and using crocodile clips on my AVO 7 multimeter  so it is in series with my power supply, the red lead goes to the plus supply and the black lead goes to the radio.  The negative has no connection.   Hope that helps.

Bob Hudson








Re: Bias current problems

Adam Rong
 

The gate bias for IRF510 60-mA is a good point to work in class AB to balance amplification linearity and power consumption. From my observation, if it is too small, the RF output will be a bit negatively affected. In your senario, if you increase from 50-mA to 60-mA, probably you can get a bit more output but don't set it any bigger.

于 2017-7-23 8:04, landrjoh@... [CHINA_QRP] 写道:

 

Question for Adam:


How does the IRF510's gate bias current affect transmit power?

Thank you,

John
AA7US


Re: Bias current problems

AA7US
 

Question for Adam:

How does the IRF510's gate bias current affect transmit power?

Thank you,

John
AA7US


Re: Bias current problems

AA7US
 

That's a good point to remember about the CS series transceivers having higher RX current due to the operation of the sandwich VFO.

Keep in mind the sandwich VFO assembly instructions mention you can disable (destroy) the status LED on the Arduio Pro Mini's circuit board to save 1.5mA of current consumption.  I opted not to do this because I was too worried I'd inadvertently harm the circuit board.

73,

John
AA7US

---In CHINA_QRP@..., <rongxh@...> wrote :

The RX mode current is increased from around 40-mA to around 70-mA for CS series because the added Sandwich digital VFO will consume more.

Thanks,
Adam


Re: Bias current problems

Brian Schmitt
 

Bob,

If I remeber correctly from my build of knq7a, the counterclockwise  amperage is approx 480mA (540mA - 60mA). The pot gets turned clockwise to increase the bias approx  60mA up to 540mA. 

I do remeber having to re read that part of the manual a few times.

Brian



On Sat, Jul 22, 2017 at 3:56 AM, vk2aor@... [CHINA_QRP]
wrote:
 

Hi

Working on 40m Txcr with Ver 2.2 board.

A little confused about the Bias Current setting.    The procedure says with the bias setting pot turned fully anti-clockwise start turning it clockwise slowly until the current increases 60mA to about 0.54A (that is 540mA).

This seems like a high current.   I have worked on another Tx where the idle current was 60mA only.

 

What current should be drawn with the pot in the anti-clock position?   Is my understanding out  or is it a typing error?


I managed to destroy the final FET and have replaced it, also removed the bias pot to check it, appears ok .

I have made up a test mic plug with a switch as PTT and have a 2 tone board for checking peak envelope power.    The Rx draws 44mA and when the the switch (PTT) is operated the current goes to 1200mA and am unable to adjust it with the bias pot.


 The board was built by a friend and trying to help him out.     

The  Low Pass Filter coils have the correct number of turns (15) but seem loosely wound,  check the circuits with an ohm meter and all appear ok.  Check the toroid transformers and the same applies loose windings but correct turns and continuity with an ohmmeter.   The receiver seems to be working fine.   Just Stuck on the bias current.   Any help would be appreciated.


Bob VK2AOR


Re: Bias current problems

n7rgw
 

Don't forget to make sure the Final FET is insulated from the case.


On Saturday, July 22, 2017 4:56 AM, "vk2aor@... [CHINA_QRP]" wrote:


 
Hi
Working on 40m Txcr with Ver 2.2 board.
A little confused about the Bias Current setting.    The procedure says with the bias setting pot turned fully anti-clockwise start turning it clockwise slowly until the current increases 60mA to about 0.54A (that is 540mA).
This seems like a high current.   I have worked on another Tx where the idle current was 60mA only.
 
What current should be drawn with the pot in the anti-clock position?   Is my understanding out  or is it a typing error?

I managed to destroy the final FET and have replaced it, also removed the bias pot to check it, appears ok .
I have made up a test mic plug with a switch as PTT and have a 2 tone board for checking peak envelope power.    The Rx draws 44mA and when the the switch (PTT) is operated the current goes to 1200mA and am unable to adjust it with the bias pot.

 The board was built by a friend and trying to help him out.     
The  Low Pass Filter coils have the correct number of turns (15) but seem loosely wound,  check the circuits with an ohm meter and all appear ok.  Check the toroid transformers and the same applies loose windings but correct turns and continuity with an ohmmeter.   The receiver seems to be working fine.   Just Stuck on the bias current.   Any help would be appreciated.

Bob VK2AOR



Re: Bias current problems

JOHN CRONHELM
 

Thanks John,
Your explanation is excellent and very clear.  Will help me a lot when I get to that point.
Regards,
John  Vo1jcc

On Jul 22, 2017 1:15 PM, "landrjoh@... [CHINA_QRP]" <CHINA_QRP@...> wrote:
 

Hey gang,


I just finished assembling a CS-40 yesterday and went through the TX alignment.  After reading about all the destroyed IRF510's, I was a bit nervous when setting the bias current.

Here's how it's done:

1. Connect ammeter in the transceiver's power supply lead.  Keep in mind that the current can approach 1.5 amps during the entire alignment process (including TX power peaking), so pick an appropriate range on your ammeter.

2. Make double (triple) sure the SET BIAS trimmer (pot) on the main PCB is fully counter clockwise.

3. IF you've already fiddled with the TX IFT coils, I'd suggest returning them to their factory setting by screwing them back fully clockwise, gently.

4. Apply power to the transceiver.  Take note of the idle receive current draw.  My CS-40 shows about 0.07 amps at 12.7v input power.

5. Key up the transceiver via the PTT switch but DO NOT TALK into the mic.  Write down the current shown on the ammeter for reference.  My CS-40 showed 0.54 amps.

6. With the PTT switch still pressed, turn the SET BIAS trimmer clockwise VERY VERY VERY slowly while carefully watching the ammeter for an increase in current.

7. Somewhere beyond the middle travel of the SET BIAS trimmer's rotation the power supply current will begin to increase.  Occasionally pause between SLOWLY turning the SET BIAS trimmer to let the supply current stabilize.

8. Once the supply current has increased (and stabilized) to approx. 60mA (0.06 amps) beyond the current you started with, STOP.  In the case of my CS-40, I stopped at 0.59 amps total.  That works out as 0.54 amps beginning + 0.05 amps increase of bias current.

9. Unkey the PTT switch.

10. Now you can peak the TX band pass filters (IFT coils) for maximum TX power following the instructions in the assembly manual.

My CS-40 wound up with approx. 8 watts of TX out at full modulation with 12.7v input power.

Hope this helps clear things up for someone.

73,

John
AA7US



Re: Bias current problems

Adam Rong
 

Thanks, John.

In TX mode, even there is no voice to drive the RF output, the current consumption is still much bigger than RX mode because of the TX chain bias current and relay coil current consumption. It is the nature of SSB mode that you get RF output only when you speak to microphone. You speak louder, you get higher power before it is saturated.

The RX mode current is increased from around 40-mA to around 70-mA for CS series because the added Sandwich digital VFO will consume more.

Thanks,
Adam

在 2017年7月22日,下午11:45,landrjoh@... [CHINA_QRP] <CHINA_QRP@...> 写道:

Hey gang,


I just finished assembling a CS-40 yesterday and went through the TX alignment.  After reading about all the destroyed IRF510's, I was a bit nervous when setting the bias current.

Here's how it's done:

1. Connect ammeter in the transceiver's power supply lead.  Keep in mind that the current can approach 1.5 amps during the entire alignment process (including TX power peaking), so pick an appropriate range on your ammeter.

2. Make double (triple) sure the SET BIAS trimmer (pot) on the main PCB is fully counter clockwise.

3. IF you've already fiddled with the TX IFT coils, I'd suggest returning them to their factory setting by screwing them back fully clockwise, gently.

4. Apply power to the transceiver.  Take note of the idle receive current draw.  My CS-40 shows about 0.07 amps at 12.7v input power.

5. Key up the transceiver via the PTT switch but DO NOT TALK into the mic.  Write down the current shown on the ammeter for reference.  My CS-40 showed 0.54 amps.

6. With the PTT switch still pressed, turn the SET BIAS trimmer clockwise VERY VERY VERY slowly while carefully watching the ammeter for an increase in current.

7. Somewhere beyond the middle travel of the SET BIAS trimmer's rotation the power supply current will begin to increase.  Occasionally pause between SLOWLY turning the SET BIAS trimmer to let the supply current stabilize.

8. Once the supply current has increased (and stabilized) to approx. 60mA (0.06 amps) beyond the current you started with, STOP.  In the case of my CS-40, I stopped at 0.59 amps total.  That works out as 0.54 amps beginning + 0.05 amps increase of bias current.

9. Unkey the PTT switch.

10. Now you can peak the TX band pass filters (IFT coils) for maximum TX power following the instructions in the assembly manual.

My CS-40 wound up with approx. 8 watts of TX out at full modulation with 12.7v input power.

Hope this helps clear things up for someone.

73,

John
AA7US




Re: Bias current problems

AA7US
 

Hey gang,

I just finished assembling a CS-40 yesterday and went through the TX alignment.  After reading about all the destroyed IRF510's, I was a bit nervous when setting the bias current.

Here's how it's done:

1. Connect ammeter in the transceiver's power supply lead.  Keep in mind that the current can approach 1.5 amps during the entire alignment process (including TX power peaking), so pick an appropriate range on your ammeter.

2. Make double (triple) sure the SET BIAS trimmer (pot) on the main PCB is fully counter clockwise.

3. IF you've already fiddled with the TX IFT coils, I'd suggest returning them to their factory setting by screwing them back fully clockwise, gently.

4. Apply power to the transceiver.  Take note of the idle receive current draw.  My CS-40 shows about 0.07 amps at 12.7v input power.

5. Key up the transceiver via the PTT switch but DO NOT TALK into the mic.  Write down the current shown on the ammeter for reference.  My CS-40 showed 0.54 amps.

6. With the PTT switch still pressed, turn the SET BIAS trimmer clockwise VERY VERY VERY slowly while carefully watching the ammeter for an increase in current.

7. Somewhere beyond the middle travel of the SET BIAS trimmer's rotation the power supply current will begin to increase.  Occasionally pause between SLOWLY turning the SET BIAS trimmer to let the supply current stabilize.

8. Once the supply current has increased (and stabilized) to approx. 60mA (0.06 amps) beyond the current you started with, STOP.  In the case of my CS-40, I stopped at 0.59 amps total.  That works out as 0.54 amps beginning + 0.05 amps increase of bias current.

9. Unkey the PTT switch.

10. Now you can peak the TX band pass filters (IFT coils) for maximum TX power following the instructions in the assembly manual.

My CS-40 wound up with approx. 8 watts of TX out at full modulation with 12.7v input power.

Hope this helps clear things up for someone.

73,

John
AA7US

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