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Power output on 20 meters.

 

Hi all,

I just finished and aligned # 628. It's working great, however the power output seems a bit low. I'm getting 1.6 watts at 13.8 V and 1.4 watts at 12.8 V. Does this sound about right? What are others getting out of their QCX's. I realize the power output generally goes down as the frequency goes up. 1.5 watts is plenty for WSPR and CW contacts. Just curious.

Joel
N6ALT

James Anderson
 

Hi Joel. 

40m QCX kit. 12volt supply from a battery to keep the noise down. Achieving just over 3 watts. Far to much power for wspr HiHi. 

But it's nice to have if you really do need it. 

That's into a dummy load though. Real world, probably considerably less..! 

Kind regards. James 2E0MUA. 

On 25 Oct 2017, at 16:24, Joel Caulkins <caulktel@...> wrote:

Hi all,

I just finished and aligned # 628. It's working great, however the power output seems a bit low. I'm getting 1.6 watts at 13.8 V and 1.4 watts at 12.8 V. Does this sound about right? What are others getting out of their QCX's. I realize the power output generally goes down as the frequency goes up. 1.5 watts is plenty for WSPR and CW contacts. Just curious.

Joel
N6ALT

Carlos Gorjao
 

.... mine on 20 m is giving me on a 50 Ohm load the same as you .... but only after to take out 2 turns on the LPF and add two trimmers in paralell with the inner LPF´s capacitors C26 and C25 as they after measuring capacitance were not right !!
I did already some nice CW QSO´s, like to USA and Hungary ... from my QTH ( Portugal)

73 de Carlos
CT7AFN

Sem vírus. www.avast.com

On Wed, Oct 25, 2017 at 4:42 PM, James Anderson <james21170@...> wrote:
Hi Joel. 

40m QCX kit. 12volt supply from a battery to keep the noise down. Achieving just over 3 watts. Far to much power for wspr HiHi. 

But it's nice to have if you really do need it. 

That's into a dummy load though. Real world, probably considerably less..! 

Kind regards. James 2E0MUA. 

On 25 Oct 2017, at 16:24, Joel Caulkins <caulktel@...> wrote:

Hi all,

I just finished and aligned # 628. It's working great, however the power output seems a bit low. I'm getting 1.6 watts at 13.8 V and 1.4 watts at 12.8 V. Does this sound about right? What are others getting out of their QCX's. I realize the power output generally goes down as the frequency goes up. 1.5 watts is plenty for WSPR and CW contacts. Just curious.

Joel
N6ALT


 

Thanks Carlos and Choke, I guess this might be normal for 20 meters. I can’t fix it if it isn’t broke. I’d like to know if anybody is getting more than 1.6 watts on 20 meters.

Joel 
N6ALT

On Oct 25, 2017, at 9:17 AM, Carlos Gorjao <gorjowski@...> wrote:

.... mine on 20 m is giving me on a 50 Ohm load the same as you .... but only after to take out 2 turns on the LPF and add two trimmers in paralell with the inner LPF´s capacitors C26 and C25 as they after measuring capacitance were not right !!
I did already some nice CW QSO´s, like to USA and Hungary ... from my QTH ( Portugal)

73 de Carlos
CT7AFN

Sem vírus. www.avast.com

On Wed, Oct 25, 2017 at 4:42 PM, James Anderson <james21170@...> wrote:
Hi Joel. 

40m QCX kit. 12volt supply from a battery to keep the noise down. Achieving just over 3 watts. Far to much power for wspr HiHi. 

But it's nice to have if you really do need it. 

That's into a dummy load though. Real world, probably considerably less..! 

Kind regards. James 2E0MUA. 

On 25 Oct 2017, at 16:24, Joel Caulkins <caulktel@...> wrote:

Hi all,

I just finished and aligned # 628. It's working great, however the power output seems a bit low. I'm getting 1.6 watts at 13.8 V and 1.4 watts at 12.8 V. Does this sound about right? What are others getting out of their QCX's. I realize the power output generally goes down as the frequency goes up. 1.5 watts is plenty for WSPR and CW contacts. Just curious.

Joel
N6ALT


Glenn S
 

Hi Joel,

I am getting 4 watts out at 13.8V on 20 metres as measured on a Bird wattmeter. 


Cheers,
Glenn VK3YY.

On 26 October 2017 at 03:33, Joel Caulkins <caulktel@...> wrote:
Thanks Carlos and Choke, I guess this might be normal for 20 meters. I can’t fix it if it isn’t broke. I’d like to know if anybody is getting more than 1.6 watts on 20 meters.

Joel 
N6ALT

On Oct 25, 2017, at 9:17 AM, Carlos Gorjao <gorjowski@...> wrote:

.... mine on 20 m is giving me on a 50 Ohm load the same as you .... but only after to take out 2 turns on the LPF and add two trimmers in paralell with the inner LPF´s capacitors C26 and C25 as they after measuring capacitance were not right !!
I did already some nice CW QSO´s, like to USA and Hungary ... from my QTH ( Portugal)

73 de Carlos
CT7AFN

Sem vírus. www.avast.com

On Wed, Oct 25, 2017 at 4:42 PM, James Anderson <james21170@...> wrote:
Hi Joel. 

40m QCX kit. 12volt supply from a battery to keep the noise down. Achieving just over 3 watts. Far to much power for wspr HiHi. 

But it's nice to have if you really do need it. 

That's into a dummy load though. Real world, probably considerably less..! 

Kind regards. James 2E0MUA. 

On 25 Oct 2017, at 16:24, Joel Caulkins <caulktel@...> wrote:

Hi all,

I just finished and aligned # 628. It's working great, however the power output seems a bit low. I'm getting 1.6 watts at 13.8 V and 1.4 watts at 12.8 V. Does this sound about right? What are others getting out of their QCX's. I realize the power output generally goes down as the frequency goes up. 1.5 watts is plenty for WSPR and CW contacts. Just curious.

Joel
N6ALT



 

Thanks Glenn,

Looks like you found the problem, now to find some suitable caps.

Joel 
N6ALT

On Oct 25, 2017, at 3:24 PM, Glenn S <glenn.vk3yy@...> wrote:

Hi Joel,

I am getting 4 watts out at 13.8V on 20 metres as measured on a Bird wattmeter. 


Cheers,
Glenn VK3YY.

On 26 October 2017 at 03:33, Joel Caulkins <caulktel@...> wrote:
Thanks Carlos and Choke, I guess this might be normal for 20 meters. I can’t fix it if it isn’t broke. I’d like to know if anybody is getting more than 1.6 watts on 20 meters.

Joel 
N6ALT

On Oct 25, 2017, at 9:17 AM, Carlos Gorjao <gorjowski@...> wrote:

.... mine on 20 m is giving me on a 50 Ohm load the same as you .... but only after to take out 2 turns on the LPF and add two trimmers in paralell with the inner LPF´s capacitors C26 and C25 as they after measuring capacitance were not right !!
I did already some nice CW QSO´s, like to USA and Hungary ... from my QTH ( Portugal)

73 de Carlos
CT7AFN

Sem vírus. www.avast.com

On Wed, Oct 25, 2017 at 4:42 PM, James Anderson <james21170@...> wrote:
Hi Joel. 

40m QCX kit. 12volt supply from a battery to keep the noise down. Achieving just over 3 watts. Far to much power for wspr HiHi. 

But it's nice to have if you really do need it. 

That's into a dummy load though. Real world, probably considerably less..! 

Kind regards. James 2E0MUA. 

On 25 Oct 2017, at 16:24, Joel Caulkins <caulktel@...> wrote:

Hi all,

I just finished and aligned # 628. It's working great, however the power output seems a bit low. I'm getting 1.6 watts at 13.8 V and 1.4 watts at 12.8 V. Does this sound about right? What are others getting out of their QCX's. I realize the power output generally goes down as the frequency goes up. 1.5 watts is plenty for WSPR and CW contacts. Just curious.

Joel
N6ALT



Leland L. Bahr
 

Glenn,

You said you replaced the two 390pf caps in the pi net.  I take it you used the same value of 390pf caps in the replacements.  Is that correct?  If that is the case I am going to try a couple 390pf Silver Mica caps as I have some of these. I've seen the multilayer small caps used many times in 1 watt rigs, but they make me nervous,  especially if they are not COG types. (Especially if they are of the 50 volt variety rather then 100 volt caps.)  Then too I wonder about SWR.  I realize we don't want any here but it happens especially when using a tuner to tune out reactance.  I know a 300 volt silver mica may be overkill, but I am thinking they would be trouble free for a very long time. Certainly not marginal!  I checked and they will clear the display if deployed.

Lee, w0vt

Alchemy in Action


I am getting 4 watts out at 13.8V on 20 metres as measured on a Bird wattmeter.

https://vk3yy.wordpress.com/2017/09/30/qcx-qrp-portable-transceiver-build/

Cheers,
Glenn VK3YY.

Glenn S
 

Hi Lee,

Yes, I used the same values of cap in the LPF as original.  I had an ATC ceramic designers kit on hand (200V), so just used those caps for replacements.  I may have taken a turn off one of the toroids, as well will have a look tonight.

Cheers,
Glenn VK3YY.

On 26 October 2017 at 10:33, Leland L. Bahr <l@...> wrote:
Glenn,

You said you replaced the two 390pf caps in the pi net.  I take it you used the same value of 390pf caps in the replacements.  Is that correct?  If that is the case I am going to try a couple 390pf Silver Mica caps as I have some of these. I've seen the multilayer small caps used many times in 1 watt rigs, but they make me nervous,  especially if they are not COG types. (Especially if they are of the 50 volt variety rather then 100 volt caps.)  Then too I wonder about SWR.  I realize we don't want any here but it happens especially when using a tuner to tune out reactance.  I know a 300 volt silver mica may be overkill, but I am thinking they would be trouble free for a very long time. Certainly not marginal!  I checked and they will clear the display if deployed.

Lee, w0vt

Alchemy in Action



I am getting 4 watts out at 13.8V on 20 metres as measured on a Bird wattmeter.

https://vk3yy.wordpress.com/2017/09/30/qcx-qrp-portable-transceiver-build/

Cheers,
Glenn VK3YY.







Leland L. Bahr
 

Glenn, Sure would like to know if you removed a turn or two. Thanks for the cap confirmation.

Lee, w0vt

On 10/25/2017 8:45 PM, Glenn S wrote:
Hi Lee,

Yes, I used the same values of cap in the LPF as original. I had an ATC ceramic designers kit on hand (200V), so just used those caps for replacements.  I may have taken a turn off one of the toroids, as well will have a look tonight.

Cheers,
Glenn VK3YY.

Glenn S
 

Hi Lee,
I took a turn off both L2 and L3, so L3 is 15T and L2 is 16T now.  It didn't make a big difference, but I noticed that with the original turns, the windings had to be spread right out on L2 and L3.  
Cheers,
Glenn VK3YY.

Leland L. Bahr
 

Thanks, Glenn.

Lee, w0vt


On 10/26/2017 4:05 AM, Glenn S wrote:
Hi Lee,
I took a turn off both L2 and L3, so L3 is 15T and L2 is 16T now.  It didn't make a big difference, but I noticed that with the original turns, the windings had to be spread right out on L2 and L3.  
Cheers,
Glenn VK3YY.


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DL3HRT- Karsten
 

Hi all,

I did some optimization on the low pass filter. Finally I had to remove 1 turn from L2 and 1 turn from L3. Power output is as expected now.

I recorded some thermal images with my Seek Reveal Pro. The QCX was running in WSPR-beacon mode with almost continuous transmission. The BS170 heated up to almost 100°C. I think that is safe without heatsink.


 

Hi DL3HRT, your name would be good. So why take 1 turn from L1 and L2 but not L3, L3 is part of the LPF also, just curious. I would think that if L2 is high in inductance and attenuating the output that L3 would be the same. I have the same low output on my 20 meter QCX, (1.6 watts), so I would like a more definitive solution to figure out exactly what to do as I don’t want to hack my board up experimenting with different things. Thanks for your help.

Joel 
N6ALT

On Nov 1, 2017, at 2:37 AM, DL3HRT <dl3hrt@...> wrote:

Hi all,

I did some optimization on the low pass filter. Finally I had to remove 1 turn from L2 and 1 turn from L3. Power output is as expected now.

I recorded some thermal images with my Seek Reveal Pro. The QCX was running in WSPR-beacon mode with almost continuous transmission. The BS170 heated up to almost 100°C. I think that is safe without heatsink.
<DL3HRT _ BS170 heating.PNG>

<DL3HRT _ 20m_QCX _ output power.png>

Ben Bangerter, K0IKR
 

On my just-completed unit, with a 12 V supply (11.6 V on the collector of Q6) I am seeing 1.2 W output (22 V p-p into 50Ω) on key down, rising to 1.6 W after ~ 10 sec (25 V p-p).  I removed C29, the dc blocking cap at the input to the filter and fed my signal generator (AD9850-based homebrew) into the filter at that point and measured the output into a 50Ω load at the input to my TEK 2247A scope.  I saw a loss of 2.32 dB at 14.000 MHz, 2.49 dB at 14.100, and 2.56 dB T 14.200.  This seems excessive.  1.5 W is only a half S unit below the expected 3 W, but with a report of RST 319 it could be important!  Guess I need to work on the lpf a bit.

Ben  -  K0IKR

Karl Schwab
 

Ben; keep us posted on your findings with your 20m build as I have one coming in the mail soon!  Tks, Karl


On Wednesday, November 1, 2017 11:26 AM, "Ben Bangerter, K0IKR via Groups.Io" <bwbangerter@...> wrote:


On my just-completed unit, with a 12 V supply (11.6 V on the collector of Q6) I am seeing 1.2 W output (22 V p-p into 50Ω) on key down, rising to 1.6 W after ~ 10 sec (25 V p-p).  I removed C29, the dc blocking cap at the input to the filter and fed my signal generator (AD9850-based homebrew) into the filter at that point and measured the output into a 50Ω load at the input to my TEK 2247A scope.  I saw a loss of 2.32 dB at 14.000 MHz, 2.49 dB at 14.100, and 2.56 dB T 14.200.  This seems excessive.  1.5 W is only a half S unit below the expected 3 W, but with a report of RST 319 it could be important!  Guess I need to work on the lpf a bit.

Ben  -  K0IKR


DL3HRT- Karsten
 

It was just trial and error. I realized that I had to spread windings over the whole core. So I decided to remove one turn. I did it with L2 and L3 and have good results now. I stopped at this point and did not change anything else.

What I realized in the thermal images is that the 390pF capacitors heat up.

Regards

Karsten

Mike Bowthorpe
 

Hi All

I also have a 20M version. The output is about 1.4W on 11.5V taking 400mA on T/X (all these are approx values). We need to get some more information about what is going on i.e. is it a loss through the LPF? ~ so hopefully on Thursday I will use the RF test feature of 9.2 to measure the RF at the following points...........

1. BS170 outputs at the junction of C29 & C30 
2. Junction of C29/C27 & L3
3. Junction of L3 & L2
4. Junction of L2 & L1

Sounds like a plan? That will give 4 RF levels and hopefully more info on where the problem is? There must be some standard figures about the losses through the LPF?

.............and the the nuclear option..........I did think that one option is to parallel up some more BS170's (they arrived this morning) but I am not sure if that is wise when the issue maybe elsewhere?

73
Mike
G0CVZ
  

Leland L. Bahr
 

I always use silver mica capacitors in a pi network.  They cost more but I have never had a problem when using them.

Lee, w0vt


On 11/1/2017 11:22 AM, DL3HRT- Karsten wrote:
It was just trial and error. I realized that I had to spread windings over the whole core. So I decided to remove one turn. I did it with L2 and L3 and have good results now. I stopped at this point and did not change anything else.

What I realized in the thermal images is that the 390pF capacitors heat up.

Regards

Karsten
_.


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On Nov 1, 2017, at 11:54 AM, mike@... wrote:

Hi All

I also have a 20M version. The output is about 1.4W on 11.5V taking 400mA on T/X (all these are approx values). We need to get some more information about what is going on i.e. is it a loss through the LPF? ~ so hopefully on Thursday I will use the RF test feature of 9.2 to measure the RF at the following points...........

1. BS170 outputs at the junction of C29 & C30 
2. Junction of C29/C27 & L3
3. Junction of L3 & L2
4. Junction of L2 & L1

Sounds like a plan? That will give 4 RF levels and hopefully more info on where the problem is? There must be some standard figures about the losses through the LPF?

.............and the the nuclear option..........I did think that one option is to parallel up some more BS170's (they arrived this morning) but I am not sure if that is wise when the issue maybe elsewhere?

73
Mike
G0CVZ
  

Steve MW0KST
 

If it's any help, with my 30m version I was only getting about 1W out, with the power rising slowly to around 1.2W on a prolonged key down. I replaced the blue inner caps (they measured about 30pF low) and took 2 turns from each of the LPF inductors. The result is a steady 3.5W output with no gradual increase on key down. Taking the 2 turns off improved the output by about 0.5W. Power measurements were with my LP100A Wattmeter.

No other mods done.

Steve MW0KST