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Newly QDX - First Checks - Question about Power Out
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Good Afternoon Folks
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Just put my new LB QDX? on the air after finishing up assembly and 1st bench checkouts late yesterday.
This morning I ran some benchtop frequency checks with my Leo Bodnar dual output GPS Disciplined Clock and tweaked the tcxo to +5 to get 0.5Hz low at 7020000 and 0.8Hz low at 14020000.
WSJT-X and FLDigi agree within a few 100ths of a Hz.?
Those figures have stayed nice and stable over several hours now (note: top cover off)
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I also bumped up the 40 and 20 meters audio gains to 75 to get a nice solid signal into WSJT-X and FLDigi. (30 +/- a bit depending on the band)
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I'm seeing and decoding a bunch of FT8 from the US and Western Europe and ran a couple of XMT runs on WSPR with my power output attenuated down to 2W/33dBm.
Lots of WSPR spots of me seen in the US, a few in Europe and from the terrific listeners in Australia and the coast of northwest Africa.
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Pretty happy with the QD, I must say. Simple and easy to assemble. Should pair nicely when going mobile with my Levnovo 12.4 in, IDEAPAD Duet 5i running Windows 11.?
I built it for 9V and am running fine off an INIU 25000maH Power Bank with a "no name, tweak the voltage and assemble the housing yourself" PD power trigger that I found on Amazon.
It was a 5-pack and cost about $15.?
They come defaulted to 12V with a micro SMD, 120K ohm resistor installed above a couple of much larger pre-solder-blobbed pads.
Changing voltages is a relatively simple matter of removing the one super tiny resistor and installing a larger sized SMD resistor on the pre-blobbed pads for the V out you want.?
The package came with about 10 extra resistors for each of 9, 12, and 15 Volts out. No Connect gives 5V and shorting the pads gives 20V (5v, 15V and 20V not tested). ??
I have been running one of those at 12V ( they come defaulted to 12V) on my QMX HB for hours and hours without any issues over the past couple of weeks.
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I did replace the DC power-in jack with a front panel mounted 5.5mm x 2.5mm locking barrel jack and am using the mating locking ring plug that came with the 4 pack (another Amazon find).?
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Liked the PD triggers and locking DC barrel connectors so much I bought extras in case they disappeared.??
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So ONTO the Question . . .?
I'm getting the following power out readings checked on two different meters that reasonably agree when connected to my Elecraft dummy load.
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AND my question is . .
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. . . Is the 6+ Watts Out indicative of a potential problem?
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BAND? ? ? ? ?POWER OUT
20? ? ? ? ? ? ? ?5.2
30? ? ? ? ? ? ? ?6.5
40? ? ? ? ? ? ? ?5.7
60? ? ? ? ? ? ? ?6.8
80? ? ? ? ? ? ? ?6.9
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Thanks for all the great kits, great support, great tips and guidance and general good cheer? . . . .
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GREG? KI4NVX
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So if I understand correctly, you built it for 9V, but you are running it at (PD) 12V, and as a result you are getting 5-7W out instead of the normal 3.5-5W out.?
Assuming the above is correct, and if I understand correctly what Hans wrote regarding operation voltage in the assembly guide, this means you are operating the PA transistors in dangerous territory, and they will be more likely to fail, especially if you get in a poor SWR situation.? If that is worth it to you to get the extra 1-2dB of power out, then keep doing it.? At some point you will likely have to replace your finals (they are very inexpensive, and not too painful to replace).?? If you would rather avoid that, then set your PD for 9V and be safe.
Stan KC7XE |
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Thanks for the reply Stan.
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Nope? 9V build, 9V supply. Vin reading 9.01V. VCC is 3.28 volts and Vdd is dead on 5.0 volts at the test points on the PCB.? All diag tests look good, though a few of the bands could have better BPF results. WSPR transmission ran at a 20% duty cycle on 20 meters for a couple of hours without any undue heating noted. Lots of spots.? Great receive on the bands I've checked today via an adjustable, vertical, ground mount antenna including 80, 40 and 20. I also checked 60 and 30 by weak, lay by coupling of signals from my Leo Bodnar GPS disciplined clock. Signals look much like my QMX HB and my two QMX+'s on WSJT-X FT8 and Frequency measurement modes and FLDigi in Frequency Measurement Mode.? One thing I failed to mention earlier is that I did wind all transformer and filter toroids with with smaller 28 gauge wire.? Tomorrow I'm going to measure power out with a DMM using both the test point on my Elecraft dummy load and with a QRPKits Accuprobe to see how those compare to my QRP Guys SWR/Power meter and my Elecraft W1. The numbers I posted were those from the QRP Guys meter. SWR into the dummy loads and antenna settings measure from 1:1 to 1:1.2).? Unfortunately, I couldn't bring my O-scope with me to my winter QTH in Florida. But, as noted, lots of WSPR spots. Tomorrow I'll attempt a few FT8 contacts too.? Interesting condition .... GREG. KI4NVX?
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Thx Stan.
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I won't really be using 60 or 30 at all and likely just 80 for receiving during FMT runs. 40 and 20 are in the 5 watt ballpark.? And you are right about changing out BS170's. Not an awful chore. ? Did that once already on my QMX HB. Complete operator error - probing with a thermocouple one afternoon; pretty well toasted one or more BS 's along with the nearby support IC with one simple slip.? GREG KI4NVX?
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FWIW, my QRPGuys power meter seems to be....a bit optimistic when compared with O-scope measurements. Now I know you said you tried this on 2 diifferent meters, so maybe it IS real. Curious what results you get with a different meter yet.
The trends look right to me for a QDX MB... IIRC 40m and 20m make less power on mine than 30m or 60m.?
Whether this is a problem.....I think you're getting close/on the edge.... not sure. But if it IS real, interesting that the transformer wire may be helping. This is the WTST winding?
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How are your RF sweeps?
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-Nate
N8BTR |
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Thanks for the follow-up Nate.
I believe I agree with you about the QRPGuys meter - especially on 30M AND 60m.
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I reran TX tests today with my Elecraft DL1 dummy load and measured via DMM using:
-- a QRPKits Accuprobe? at the center pin input on the Elecraft Dummy load
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AND . .
-- the test point on the Elecraft DL1 with regular DMM leads?
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Both agree nicely within a few, small percents.
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Here's an updated list of what I think the Power Out is:
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80? ? ? ? ? 5.2
60? ? ? ? ? 6.0
40? ? ? ? ? 5.1
30? ? ? ? ? 5.6
20? ? ? ? ? 4.5
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When I get back north in the spring, I'll fire up the O-scope and see exactly what's what.?
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And yes, used the WTST winding for 9V using 28 gauge wire.? (And all the other toroid winds)
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RF sweeps are OK especially for 40 and 20 where the radio will be used the most.
The other bands have the center frequency at varying levels down from the peak.
I might try adjusting sections of L12 but decided to just play the darn thing and see if its really needed :)
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GREG KI4NVX
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On Sun, Nov 17, 2024 at 10:44 AM, Greg McCain wrote:
Greg, this looks now just like a decently strong LB QDX, I don't think there's anything to worry about, especially if you don't plan to use 60m.?
Enjoy!
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-Nate
N8BTR
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Roger Wilco!! :)?
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GREG KI4NVX?
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