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It would be helpful if Hans would weigh in on this topic...
Ben
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Hi All
Results on 20M using 9.2 RF test feature......
Output from L1 with 50 ohm load on output = 2.2 watts approx
Input to L3 with 50 ohm load on output = 5.2 watts approx
Input voltage on load prior to protection diode = 12.13 volts
The caps are the correct values, so I am going to change the toroids one by one.
73
Mike
G0CVZ
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Hi Mike
The 9.2 RF Power meter is not bad, but not fantastically accurate. But it is important to realise, this measurement is an RF detector, it will only display a correct power reading for a sinewave into a 50-ohm load. The waveform at L3 is very much NOT a sinewave. The 5.2W measurement is meaningless...
73 Hans G0UPL
On Thu, Nov 2, 2017 at 2:23 PM, <mike@...> wrote: Hi All
Results on 20M using 9.2 RF test feature......
Output from L1 with 50 ohm load on output = 2.2 watts approx
Input to L3 with 50 ohm load on output = 5.2 watts approx
Input voltage on load prior to protection diode = 12.13 volts
The caps are the correct values, so I am going to change the toroids one by one.
73
Mike
G0CVZ
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Ben, Joel, all
If the power output is less than expected, and if other test equipment is not available, then I suggest removing a turn or two from each of the toroids, similar to what Karsten DL3HRT and others have done.?
I think that in the event of the Low Pass Filter having attenuation which reduces the anticipated output, this power has to go *somewhere*... where it is going, is heat. So this is why when you have unwanted attenuation in the Low Pass Filter, people observe heating in the capacitors. 3dB of attenuation at 5W would mean 2.5W lost in the filter, as heat. No wonder, it gets hot... If a capacitor value is too low then this can also alter the shape of the response and cause attenuation at the transmit frequency. Again if you do not have test equipment and you want to be perfectionist, I would suggest just removal of a turn or two or few.?
If at any specific supply voltage, one person gets 3.5W, one person gets 4W and another gets 3W, then I think that this is nothing to worry about. In any case many people do not have accurate means of power measurement. If you get 1W when some others get 3, 4 etc., then this is probably an issue (as long as you are confident of your measurement). When measuring power always be aware of the limitations of the instrument! You must use a 50-ohm dummy load because many power meters will not read accurately if you are transmitting into an antenna - any SWR will just alter the measurement. Also do not trust power measurement readings before the Low Pass Filter, the waveform is not a sinewave and many power meters will therefore not read that accurately either.?
73 Hans G0UPL
On Thu, Nov 2, 2017 at 4:52 AM, Joel Caulkins <caulktel@...> wrote: I agree Ben, Hans opinion would be good. It would be helpful if Hans would weigh in on this topic...
Ben
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Hi Hans
Thanks for the reply and I did take note of your comments in the manual about accuracy.
The problem is that there appears to be a problem on the 20M version and we need some guidance about what do. My simple logic says 5.2 is bigger that 2.2 so there is loss in the LPF. The output should probably be 3.5 watts or so on 20, so if the caps are OK then the problem must be the toroids as the caps and number of windings are "correct"
I have removed L1,2 & 3 but I do not have the means to measure the inductance.
Please help
73
Mike
G0CVZ
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On Thu, Nov 2, 2017 at 04:49 am, Hans Summers wrote:
If the power output is less than expected, and if other test equipment is not available, then I suggest removing a turn or two from each of the toroids,
I agree with Hans. I think the LPF values are derived from the W3NQN designs for standard value components, and are also reproduced by the GQRP CLub literature. I found that the design was just a tad too harsh, and these values would often represent a 1.5db in band loss. (I think G4APB found the same). For the 30m and up designs, I personally knocked >1< turn off each of the 3 coils and that was perfect. (I don't have enough experience yet with the lower band LPF's to offer any experience). Two turns is probably too much, and the harmonic attenuation tends to suffer in my opinion. Users of U2/U3's might like do the same thing whilst we're on the subject. Perhaps one technique to this might be to scrap a bit of the enamel off with a scalpel / sharpie knife on two adjacent turns and place a blob of solder across them to to short them out. The mod can easily be reversed if there are any issues. 73 de Andy
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HI Andy
Good points made.
On 20M with turns on L1, 2 & 3 as manual using original toroids; and using test feature 9.2 the output was 2.2 watts, with 1 turn off each it was 2.8 watts.
Suggestion ~ when removing solder and to clear holes use Chem-WIK size .050 ~ its a de-soldering wick with resin impregnated in it
73
Mike
G0CVZ
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That meter is also full spectrum, so measuring all frequencies not just 20M.?
Dr.?William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ PJ2/K9HZ ? Owner - Operator Big Signal Ranch ¨C K9ZC Staunton, Illinois ? Owner ¨C Operator Villa Grand Piton - J68HZ Soufriere, St. Lucia W.I. Rent it:
email:??bill@... ?
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On Nov 2, 2017, at 6:31 AM, Hans Summers < hans.summers@...> wrote: Hi Mike
The 9.2 RF Power meter is not bad, but not fantastically accurate. But it is important to realise, this measurement is an RF detector, it will only display a correct power reading for a sinewave into a 50-ohm load. The waveform at L3 is very much NOT a sinewave. The 5.2W measurement is meaningless...
73 Hans G0UPL
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On Thu, Nov 2, 2017 at 06:38 am, <mike@...> wrote:
output was 2.2 watts, with 1 turn off each it was 2.8 watts
Sound about right for an average of 1.3db, plus minus individual measurement error / construction technique on the coils. ( close wound or spaced). Just think, a 3.5w rig might really be? a 5w one for the sake of one less? turn on a coil ;-) I found this out with the designs a little while ago. I was building my own amp, before Hans had one available, but I decided to use his plug in LPF's in my design. But I got less power output that I had anticipated, so I measured them with a VNA and discovered nearly 1.5db loss. After experimenting, it was just a case of removing a turn on each coil. 73 de Andy
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Hi Andy,
I've got resevations about the suggestion in your last
paragraph.? Whilst it would certainly reduce the overal number of
turns in the winding it creates a single shorted turn in the
inductor? which might introduce other problems.? Better to
actually remove turns I feel.
73 Dave G3WUN
On 02/11/2017 12:40, Andy G0FTD via
Groups.Io wrote:
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Show quoted text
On Thu, Nov 2, 2017
at 04:49 am, Hans Summers wrote:
If the power output is less than expected, and if
other test equipment is not available, then I suggest removing a
turn or two from each of the toroids,
I agree with Hans.
I think the LPF values are derived from the W3NQN designs for
standard value components, and are also reproduced by the GQRP
CLub literature.
I found that the design was just a tad too harsh, and these values
would often represent a 1.5db in band loss. (I think G4APB found
the same).
For the 30m and up designs, I personally knocked >1< turn
off each of the 3 coils and that was perfect.
(I don't have enough experience yet with the lower band LPF's to
offer any experience).
Two turns is probably too much, and the harmonic attenuation tends
to suffer in my opinion.
Users of U2/U3's might like do the same thing whilst we're on the
subject.
Perhaps one technique to this might be to scrap a bit of the
enamel off with a scalpel / sharpie knife on two adjacent
turns and place a blob of solder across them to to short them out.
The mod can easily be reversed if there are any issues.
73 de Andy
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On Thu, Nov 2, 2017 at 07:51 am, David wrote:
Whilst it would certainly reduce the overal number of turns in the winding it creates a single shorted turn in the inductor? which might introduce other problems
Different kind of shorted turn. The type of shorted turn to avoid on a toroid is where a closed loop is formed, such as when having a bolt through the middle of the toroid to fix it to a chassis, and then a bracket maybe at the top, which is also going to chassis and forms a a simple loop. That would be like having an extremely low impedance secondary winding being formed, which in a high current situation might well cause some pyrotechnics to form. Well that's my understanding anyway ;-) 73 de Andy
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Update: I have done the LPF mod consisting of removing a turn from each of the LPF toroids, and I added the 10K resistor from the drain of Q5 to +12V. I'm a little hesitant to remove anymore for fear I will go the opposite direction.? I now have a little over 2 watts output at 13.8 volts, up from 1.6 watts. So I guess I'm just going to accept this, as I didn't really gain that much more power after the mods. It works perfect in every other way.
Joel
N6ALT
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If you can measure the inductance on each toroid individually, as in my case I had to remove 1 turn from 1, 2 from another and 3 from another, among L1-L3 if I remember correctly. Otherwise if you still wanted to try to peak more, it may be best to do one of them at a time and one turn at a time if you did not do that already.
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Hi VK5EEE
Are your L1, 2, 3 & 4 now as the table (assuming 20M) i.e. L1 & 3 = 0.77uH, L2 = 0.9uH? L4 = 0.4uH
What is your power O/P and transmit current?
73
Mike
G0CVZ
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Hi? Joel,
Your are same with my result.? I have took out 1 turn form L1, L2 and L3. and my output power increase to ~2W? @13.8v I plan to experiment with replace MPS751 to Q6 this weekend and see how it change.
73 de E29AHU Choke
On Wed, Nov 8, 2017 at 5:00 AM, Joel Caulkins <caulktel@...> wrote: Update: I have done the LPF mod consisting of removing a turn from each of the LPF toroids, and I added the 10K resistor from the drain of Q5 to +12V. I'm a little hesitant to remove anymore for fear I will go the opposite direction.? I now have a little over 2 watts output at 13.8 volts, up from 1.6 watts. So I guess I'm just going to accept this, as I didn't really gain that much more power after the mods. It works perfect in every other way.
Joel
N6ALT
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As built, my 20m QCX put out just over 1 Watt, increasing to 1.6 Watts after a few seconds of key-down.? This is with +13.6 VDC from my Astron power supply.? After reading this thread, I replaced the two caps in the LPF with 390 pF, 500 V, 5 % mica caps, and removed a single turn from L2 and L3.? Output power increased to a solid 2.5 Watts regardless of key-down time.? That's plenty of power to make contacts with, but it's still considerably lower than the 4 Watts that other builders are getting.? I can live with it, but I feel like there's more to be had and something still isn't quite right.? Thoughts??
73/72,
Dean K5DH
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Hi Dean,
Did you try squeezing / spreading turns on the LPF toroids to optimise the transmit power ?? I gained a watt or so doing that.
Cheers, Glenn VK3YY.
On 10 November 2017 at 14:02, K5DH <k5dh@...> wrote: As built, my 20m QCX put out just over 1 Watt, increasing to 1.6 Watts after a few seconds of key-down.? This is with +13.6 VDC from my Astron power supply.? After reading this thread, I replaced the two caps in the LPF with 390 pF, 500 V, 5 % mica caps, and removed a single turn from L2 and L3.? Output power increased to a solid 2.5 Watts regardless of key-down time.? That's plenty of power to make contacts with, but it's still considerably lower than the 4 Watts that other builders are getting.? I can live with it, but I feel like there's more to be had and something still isn't quite right.? Thoughts??
73/72,
Dean K5DH
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I used the mod by DJ2QV.
He wrote :? Now the Output power was still low and current too high. Further Investigation indicated that
the Class E amplifier is somehow loaded by the path to the RX/TX Switch via capacitor C33.
My Feeling was that at 14 MHz the value of 1nF is a Little too high. Probably too much RF is
coupled to the drain of Q5 and causes some nasty effects here. So I changed C33 to 150 pF
and immediately the current dropped to about 0.6 A and I had much more power.
Optimization of the bandpassfilter inductors and the L4 choke resulted in 30-32 V p-p at 50
Ohm, so about 2.2 to 2.5 Watt. That was also measured with the internal power meter (really
nice function!).
My QCX has 5 Watt output now.
Good luck
73 John PD7MAA
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As built, my 20m QCX put out just over 1 Watt, increasing to 1.6 Watts after a few seconds of key-down.? This is with +13.6 VDC from my Astron power supply.? After reading this thread, I replaced the two caps in the LPF with 390 pF, 500 V, 5 % mica caps, Dean, It was speculated in that thread that because the inductors were too high in value the mismatch caused the capacitors to heat up causing power to rise. The capacitors are high quality and should not be faulty. and removed a single turn from L2 and L3 Output power increased to a solid 2.5 Watts regardless of key-down time. That's plenty of power to make contacts with, but it's still considerably lower than the 4 Watts that other builders are getting. Not L1 also? Maybe more than one turn needs to be removed from each, I think others have found it necessary to remove two turns. 73 Alan G4ZFQ
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Joel Caulkins/N6ALT
J68HZ
Glenn S
John PD7MAA