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Hi All
Results of L1, 2, 3 uH measured values fitted with QRP Labs supplied toriods and 1 turn removed from L1, 2 & 3
?
In situ (still fitted to board)...........
?
L1 = 0.856 (15t)
L2 = 1.028 (16t)
L3 = 0.915 (15t)
?
On Bench...........
?
L1 = 0.868 (15t)
L2 = 1.076 (16t)
L3 = 0.904 (15t)
I have tried Micrometals toriods with very similar results, but the Q factor on the Micrometals is about 30 as against 60 with the QRP Labs ones (but I don't think this makes much difference?).
Note that the inductance will change dependent on tightness of windings - closer tightness = more inductance by a few %. It is also difficult to get the actual calculated values as you are limited to whole turns.Having said all that the output does not change significantly.
The LCR meter I used was a DE-5000 which has a 0 to 20uH range and Kelvin clips with claimed 2.5% accuracy. If you order one from Japan you will probably get stung for VAT, etc.
Bottom Line................
As fitted but with 0.4mm wire...........
?
L1 = 0.80 (14t)
L2 = 0.89 (15t)
L3 = 0.78 (14t)
On 20M and in round numbers ¨C turns as manual = 1 watt output, with 1 turn removed off L1, 2 & 3 = 2 watts and after removing 2 turns off L1, 2 & 3 = 2.8 watts all at 12V input to QCX board.
I am not able to make any output checks except output watts.
I hope this helps those building the 20M version.
73
Mike
G0CVZ
?
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Mike;
I wired my 20m QCX, #748, with all wire turns, exactly per the manual and at 12volts, it shows 2.5w to a dummy load.? 73, de Karl, KO8S
On Tuesday, November 28, 2017 12:32 PM, "mike@..." <mike@...> wrote:
Hi All
Results of L1, 2, 3 uH measured values fitted with QRP Labs supplied toriods and 1 turn removed from L1, 2 & 3
?
In situ (still fitted to board)...........
?
L1 = 0.856 (15t)
L2 = 1.028 (16t)
L3 = 0.915 (15t)
?
On Bench...........
?
L1 = 0.868 (15t)
L2 = 1.076 (16t)
L3 = 0.904 (15t)
I have tried Micrometals toriods with very similar results, but the Q factor on the Micrometals is about 30 as against 60 with the QRP Labs ones (but I don't think this makes much difference?).
Note that the inductance will change dependent on tightness of windings - closer tightness = more inductance by a few %. It is also difficult to get the actual calculated values as you are limited to whole turns.Having said all that the output does not change significantly.
The LCR meter I used was a DE-5000 which has a 0 to 20uH range and Kelvin clips with claimed 2.5% accuracy. If you order one from Japan you will probably get stung for VAT, etc.
Bottom Line................
As fitted but with 0.4mm wire...........
?
L1 = 0.80 (14t)
L2 = 0.89 (15t)
L3 = 0.78 (14t)
On 20M and in round numbers ¨C turns as manual = 1 watt output, with 1 turn removed off L1, 2 & 3 = 2 watts and after removing 2 turns off L1, 2 & 3 = 2.8 watts all at 12V input to QCX board.
I am not able to make any output checks except output watts.
I hope this helps those building the 20M version.
73
Mike
G0CVZ
?
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HI Gents,
Would any of you be able to test these again with the LCD removed / relocated away from the LPF?
73, Nick VK4PLN
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You can test it yourself. ?Just power it up, set the frequency you want and then with it still powered, remove the LCD temporarily. ?Check your power - Hans said and I checked that the QCX will operate with the LCD removed, you just won't be able to see what it's set for is all.
Jim - W0EB
------ Original Message ------
Sent: 11/28/2017 5:23:44 PM
Subject: Re: [QRPLabs] Power output on 20 meters.
HI Gents,
Would any of you be able to test these again with the LCD removed / relocated away from the LPF?
73, Nick VK4PLN
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Thanks Jim, I will do this too once mine is built, I am just trying to see/ gather more info if this is actually a problem/ solution to the lower output on 20M....
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Hi All,
I would like to share my experiment.
After a several month i have fixed output power for my QCX 20M? (my kit No.#487)
and now i can getting with full power 5 Watts @12Vdc
before I solve my QCX 20M. I can get output only 1.5 ~ 2w maximum
First i observe LPF circuit C25 and C26 (390pf) getting very hot during transmission.
This is my modification.
1. remove 1 turn of L1 and L3 (use only 15 turns) --> power improve abit to ~ 2.5w
2. remove C25 and C26 (390pf) and i replace with 2 series of MLCC capacitor 680pf (because there are in my stock) --> this big improve my power to 5w !!!
I believe?my issue is mismatch at LPF especially?at C25 and C26 (390pf).
thanks group for good knowledge?sharing?and Hans for the grate kits.?
73
Choke E29AHU
during experiment
finally soldering in the right place
output power @12vdc
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Interesting experiment. I had a miserable half a watt out of my 20m unit after completion at 13.8V DC which was a bit disappointing. In fact I was a bit deflated and put it away for the night. The next morning after some coffee, I stuffed the input signal of the filter on the scope and it looked about right for the expected 3.5-4W out so suspected the filter design. I yanked all the parts off and substituted the values in from the GQRP documentation on LPF design here:??... I naively assumed 50 ohms output from the PA which isn't necessarily the case but it worked. Got 4W out at 13.8V DC which is good and no heating problems with the PA throwing out WSPR into a dummy load as a test case.
I have since converted it to 30m which is a little quieter and easier to navigate as it is contest free. Unfortunately I appear to have knackered something during conversion as the audio gives out on the receiver and haven't had the time to fix it yet. Oops. Moral of the story: band conversion is risky; just buy another QCX :)
Chris
M0XTE
On Mon, 6 Aug 2018, at 15:51, chokelive E29AHU wrote:
Hi All,
I would like to share my experiment.
After a several month i have fixed output power for my QCX 20M? (my kit No.#487)
and now i can getting with full power 5 Watts @12Vdc
before I solve my QCX 20M. I can get output only 1.5 ~ 2w maximum
First i observe LPF circuit C25 and C26 (390pf) getting very hot during transmission.
This is my modification.
1. remove 1 turn of L1 and L3 (use only 15 turns) --> power improve abit to ~ 2.5w
2. remove C25 and C26 (390pf) and i replace with 2 series of MLCC capacitor 680pf (because there are in my stock) --> this big improve my power to 5w !!!
I believe?my issue is mismatch at LPF especially?at C25 and C26 (390pf).
thanks group for good knowledge?sharing?and Hans for the grate kits.?
73
Choke E29AHU
during experiment
finally soldering in the right place
output power @12vdc
|
Interesting what you did Choke to achieve more power from your QCX 20 xcvr.? I just measured mine yesterday, #748, that I built I built to the exact specifications in the manual.? My power output into a dummy load is:? 2.5 watts at 13.8volts and 3 watts at 15.0 volts.? There has been much discussion to power output levels with the QCX on 20m.? Yesterday, I upgraded the chip to version 1.00e, and did a modification to the QCX case to allow me to use the on board CW key.? 73, Karl, KO8S ?
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I had 1.86W at 12.0 volts. Removed 1 turn each from coils L1, L2, L3. Increase output to 2.12 W, not a great change.?Measured loss prior to change was -2.29 dB through the filter at 14.020 MHz.
May replace capacitors next. Don't really mind 2 W since its QRP and 5 is too much, but can't let well enough alone.
Fred
WD9HNU
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My experience with a 30m QCX? was exactly the same as Steve MW0KST. My unit as built had 2.5dB loss in the LPF and also too low a cutoff frequency when measured on a spectrum analyser, meaning that the filter roll-off was already a significant factor at 10.1-10.15MHz.
I replaced the two "blue blob" ceramic capacitors in the inner part of the PF and also took 1 turn off each of the three toroid coils in the LPF. Power output increased from less than 1W to around 2.5W with a 12V DC supply, which I'm happy with. Measuring the modified LPF on the spectrum analyser (and doing some modelling using RFSim99) convinced me that taking more than 1 turn off the coils would not give any further beneficial effect in my case.
These turquoise-blue blob capacitors do seem to be entirely unsuitable for use in the LPF as they appear to be low-Q/lossy - if you have these in the kit, my advice would be DO NOT use them - or if they've already been fitted, immediately replace them with higher-quality types (ceramics, polystyrene, SM or whatever - I used 160V polystyrene as that's what I had available).
73, Kevin ZL3KE
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What I do, if for somehow, my 2~3 watts QRP doesn't make it to a rare DX station, I use it drive my HF Packer V4 (kit built) linear amplifier.? Using this amp, with about 2~3 watts of drive from my QCX 20m, I get about 30 watts to my antenna!? Thus, I don't feel like tearing in my operating QCX to get one more watt or so out of it and possibly destroying the PA transistors!? This above mentioned amp, operates 10 ~ 160m, SSB/CW; power out depends on band and mode.? I use this amp also with my Yaesu FT-817ND radio.? 73, de Karl, KO8S
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I have a QCX20 in the mail and I'm wondering if it might be worth replacing the LPF with one of the 'new' (1999) CWAZ filters presented by Ed W3NQN in QEX, .? Based on the simulations in the article, adding a capacitor in parallel with the middle inductor to create a tuned circuit increases attenuation at the 2nd harmonic and also reduces return loss in the 20m band (Figures 2 and 3.)? Has anybody tried playing with these filter designs before?? Also, which capacitors should I use?? The article recommends the Philips 680 line of ceramic capacitors but I've been having a hard time finding them.? Would any 100V, NP0/C0G ceramic capacitor of reasonable tolerance do?
Cheers,
John VA7JBE
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John? VA7JBE
I might suggest using LTSpice to play with adding parallel caps and with adding series traps.?
This lets you juggle component values to match particular needs, and to see the probable
attenuation these changes might provide.
Arv? K7HKL
_._
On Fri, Aug 17, 2018 at 12:58 PM John VA7JBE via Groups.Io <va7jbe= [email protected]> wrote: I have a QCX20 in the mail and I'm wondering if it might be worth replacing the LPF with one of the 'new' (1999) CWAZ filters presented by Ed W3NQN in QEX, .? Based on the simulations in the article, adding a capacitor in parallel with the middle inductor to create a tuned circuit increases attenuation at the 2nd harmonic and also reduces return loss in the 20m band (Figures 2 and 3.)? Has anybody tried playing with these filter designs before?? Also, which capacitors should I use?? The article recommends the Philips 680 line of ceramic capacitors but I've been having a hard time finding them.? Would any 100V, NP0/C0G ceramic capacitor of reasonable tolerance do?
Cheers,
John VA7JBE
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Philips sold off its capacitor business to Vishay. Vishay also bought
the former Sprague capacitor line. Their capacitors should be a good
substitute.
I expect that capacitors from other quality manufacturers would also
work well. AVX, Kemet, Murata, and TDK are manufacturers that I know
of that make good ceramic capacitors. There are likely others as well.
All of those are available from the usual distributors.
If you want to focus on experimenting with filter design rather than
on capacitor testing, I recommend sticking with first-quality caps
from reputable sources. Leave the cheap caps from unknown sources in
China for less critical circuits, or for when you're in the next phase
of optimizing cost of a design.
toggle quoted message
Show quoted text
On Fri, Aug 17, 2018 at 3:33 PM, Arv Evans <arvid.evans@...> wrote: John VA7JBE
I might suggest using LTSpice to play with adding parallel caps and with
adding series traps.
This lets you juggle component values to match particular needs, and to see
the probable
attenuation these changes might provide.
Arv K7HKL
_._
On Fri, Aug 17, 2018 at 12:58 PM John VA7JBE via Groups.Io
<va7jbe@...> wrote:
I have a QCX20 in the mail and I'm wondering if it might be worth
replacing the LPF with one of the 'new' (1999) CWAZ filters presented by Ed
W3NQN in QEX,
. Based
on the simulations in the article, adding a capacitor in parallel with the
middle inductor to create a tuned circuit increases attenuation at the 2nd
harmonic and also reduces return loss in the 20m band (Figures 2 and 3.)
Has anybody tried playing with these filter designs before? Also, which
capacitors should I use? The article recommends the Philips 680 line of
ceramic capacitors but I've been having a hard time finding them. Would any
100V, NP0/C0G ceramic capacitor of reasonable tolerance do?
Cheers,
John VA7JBE
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Nick VK4PP
Jim Sheldon
Fred Piering WD9HNU
Shirley Dulcey KE1L