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I am researching a low-power-on-one-band symptom on my High Band QDX, Succinctly, the power out was measured into a dummy load via a WM-2 and the rig was powered with a 5AH SLA bucked down to 12.0 VDC. Results below:

??? 20m ~6.0W 0.70A
??? 17m? 5.0W 0.66A
??? 15m ~6.0W 0.74A
??? 12m ~4.3W 0.66A
??? 10m? 2.0W 0.59A

I then did an RF filter sweep of the rig using PuTTY and got the images attached below. Here are my questions:

(1) I checked and compressed and loosened the turns on L4 and L10 to little or no effect on the sweep of 11m or 10m.

(2) To me, 20m looks like crap yet the rig puts out a healthy >5W on that band.

(3) The rest of them looks sort of OK.

(4) The 11M/10M looks great and clearly (to me) does not look like the LPF is causing the low power condition.?? ?

(5) Sorry for the ignorant question, but what do the filter sweeps show to all the trained eyes out there?

I have consulted the LY2H and EX0AA comments on the one-band-low-power matter and am still sorting through the group's anecdotal comments and other resources. Like LY2H, who could live with 3 watts on 10 meters, I could as well -- just not the one watt that my rig outputs on a 10m antenna. Also, I mainly want to get "some steerage" on how to utilize the tools and techniques to solve the problem.

Thanks in advance,??
--
William, k6whp
--------------------
"Cheer up, things could get worse. So I cheered up and things got worse."

Hi,
yesterday I ordered a keyer kit from HamGadgets. They actually had
reasonable shipping, $17 compared to $30 to send only the chips.
Everything seems to be included in the kit and it should take very
litle time to assemble it.

Ron VE8RT

On Sat, 02 Mar 2024 07:51:57 -0800
"EA4HZK" <ea4hzk@...> wrote:

Attiny85 chip very affordable anywhere and you can get the software from github.


--
__________________________
.----------------. .----------------. .----------------. .----------------. .----------------. .----------------.
| .--------------. || .--------------. || .--------------. || .--------------. || .--------------. || .--------------. |
| | _________ | || | __ | || | _ _ | || | ____ ____ | || | ________ | || | ___ ____ | |
| | |_ ___ | | || | / \ | || | | | | | | || | |_ || _| | || | | __ _| | || | |_ ||_ _| | |
| | | |_ \_| | || | / /\ \ | || | | |__| |_ | || | | |__| | | || | |_/ / / | || | | |_/ / | |
| | | _| _ | || | / ____ \ | || | |____ _| | || | | __ | | || | .'.' _ | || | | __'. | |
| | _| |___/ | | || | _/ / \ \_ | || | _| |_ | || | _| | | |_ | || | _/ /__/ | | || | _| | \ \_ | |
| | |_________| | || ||____| |____|| || | |_____| | || | |____||____| | || | |________| | || | |____||____| | |
| | | || | | || | | || | | || | | || | | |
| '--------------' || '--------------' || '--------------' || '--------------' || '--------------' || '--------------' |
'----------------' '----------------' '----------------' '----------------' '----------------' '----------------' .----------------. .----------------. .----------------. .----------------. .----------------. .----------------. | .--------------. || .--------------. || .--------------. || .--------------. || .--------------. || .--------------. | | | _________ | || | __ | || | _ _ | || | ____ ____ | || | ________ | || | ___ ____ | | | | |_ ___ | | || | / \ | || | | | | | | || | |_ || _| | || | | __ _| | || | |_ ||_ _| | | | | | |_ \_| | || | / /\ \ | || | | |__| |_ | || | | |__| | | || | |_/ / / | || | | |_/ / | | | | | _| _ | || | / ____ \ | || | |____ _| | || | | __ | | || | .'.' _ | || | | __'. | | | | _| |___/ | | || | _/ / \ \_ | || | _| |_ | || | _| | | |_ | || | _/ /__/ | | || | _| | \ \_ | | | | |_________| | || ||____| |____|| || | |_____| | || | |____||____| | || | |________| | || | |____||____| | | | | | || | | || | | || | | || | | || | | | | '--------------' || '--------------' || '--------------' || '--------------' || '--------------' || '--------------' | '----------------' '----------------' '----------------' '----------------' '----------------' '----------------'

.----------------. .----------------. .----------------. .----------------. .----------------. .----------------.
| .--------------. || .--------------. || .--------------. || .--------------. || .--------------. || .--------------. |
| | _________ | || | __ | || | _ _ | || | ____ ____ | || | ________ | || | ___ ____ | |
| | |_ ___ | | || | / \ | || | | | | | | || | |_ || _| | || | | __ _| | || | |_ ||_ _| | |
| | | |_ \_| | || | / /\ \ | || | | |__| |_ | || | | |__| | | || | |_/ / / | || | | |_/ / | |
| | | _| _ | || | / ____ \ | || | |____ _| | || | | __ | | || | .'.' _ | || | | __'. | |
| | _| |___/ | | || | _/ / \ \_ | || | _| |_ | || | _| | | |_ | || | _/ /__/ | | || | _| | \ \_ | |
| | |_________| | || ||____| |____|| || | |_____| | || | |____||____| | || | |________| | || | |____||____| | |
| | | || | | || | | || | | || | | || | | |
| '--------------' || '--------------' || '--------------' || '--------------' || '--------------' || '--------------' |
'----------------' '----------------' '----------------' '----------------' '----------------' '----------------'

.----------------. .----------------. .----------------. .----------------. .----------------. .----------------.
| .--------------. || .--------------. || .--------------. || .--------------. || .--------------. || .--------------. |
| | _________ | || | __ | || | _ _ | || | ____ ____ | || | ________ | || | ___ ____ | |
| | |_ ___ | | || | / \ | || | | | | | | || | |_ || _| | || | | __ _| | || | |_ ||_ _| | |
| | | |_ \_| | || | / /\ \ | || | | |__| |_ | || | | |__| | | || | |_/ / / | || | | |_/ / | |
| | | _| _ | || | / ____ \ | || | |____ _| | || | | __ | | || | .'.' _ | || | | __'. | |
| | _| |___/ | | || | _/ / \ \_ | || | _| |_ | || | _| | | |_ | || | _/ /__/ | | || | _| | \ \_ | |
| | |_________| | || ||____| |____|| || | |_____| | || | |____||____| | || | |________| | || | |____||____| | |
| | | || | | || | | || | | || | | || | | |
| '--------------' || '--------------' || '--------------' || '--------------' || '--------------' || '--------------' |
'----------------' '----------------' '----------------' '----------------' '----------------' '----------------'

.----------------. .----------------. .----------------. .----------------. .----------------. .----------------.
| .--------------. || .--------------. || .--------------. || .--------------. || .--------------. || .--------------. |
| | _________ | || | __ | || | _ _ | || | ____ ____ | || | ________ | || | ___ ____ | |
| | |_ ___ | | || | / \ | || | | | | | | || | |_ || _| | || | | __ _| | || | |_ ||_ _| | |
| | | |_ \_| | || | / /\ \ | || | | |__| |_ | || | | |__| | | || | |_/ / / | || | | |_/ / | |
| | | _| _ | || | / ____ \ | || | |____ _| | || | | __ | | || | .'.' _ | || | | __'. | |
| | _| |___/ | | || | _/ / \ \_ | || | _| |_ | || | _| | | |_ | || | _/ /__/ | | || | _| | \ \_ | |
| | |_________| | || ||____| |____|| || | |_____| | || | |____||____| | || | |________| | || | |____||____| | |
| | | || | | || | | || | | || | | || | | |
| '--------------' || '--------------' || '--------------' || '--------------' || '--------------' || '--------------' |
'----------------' '----------------' '----------------' '----------------' '----------------' '----------------'

.----------------. .----------------. .----------------. .----------------. .----------------. .----------------.
| .--------------. || .--------------. || .--------------. || .--------------. || .--------------. || .--------------. |
| | _________ | || | __ | || | _ _ | || | ____ ____ | || | ________ | || | ___ ____ | |
| | |_ ___ | | || | / \ | || | | | | | | || | |_ || _| | || | | __ _| | || | |_ ||_ _| | |
| | | |_ \_| | || | / /\ \ | || | | |__| |_ | || | | |__| | | || | |_/ / / | || | | |_/ / | |
| | | _| _ | || | / ____ \ | || | |____ _| | || | | __ | | || | .'.' _ | || | | __'. | |
| | _| |___/ | | || | _/ / \ \_ | || | _| |_ | || | _| | | |_ | || | _/ /__/ | | || | _| | \ \_ | |
| | |_________| | || ||____| |____|| || | |_____| | || | |____||____| | || | |________| | || | |____||____| | |
| | | || | | || | | || | | || | | || | | |
| '--------------' || '--------------' || '--------------' || '--------------' || '--------------' || '--------------' |
'----------------' '----------------' '----------------' '----------------' '----------------' '----------------'

___ ___ __ _ _ ____ _ __
| __>| . | /. | | | ||_ /| / /
| _> | |/_ .|| | / / | \
|___>|_|_| |_| |_|_|/___||_\_\
___ ___ __ _ _ ____ _ __
| __>| . | /. | | | ||_ /| / /
| _> | |/_ .|| | / / | \
|___>|_|_| |_| |_|_|/___||_\_\


___ ___ __ _ _ ____ _ __
| __>| . | /. | | | ||_ /| / /
| _> | |/_ .|| | / / | \
|___>|_|_| |_| |_|_|/___||_\_\


___ ___ __ _ _ ____ _ __
| __>| . | /. | | | ||_ /| / /
| _> | |/_ .|| | / / | \
|___>|_|_| |_| |_|_|/___||_\_\


___ ___ __ _ _ ____ _ __
| __>| . | /. | | | ||_ /| / /
| _> | |/_ .|| | / / | \
|___>|_|_| |_| |_|_|/___||_\_\

73's !

--
Ron VE8RT <ve8rt@...>

Attiny85 chip very affordable anywhere and you can get the software from github.



--
__________________________
73's !

Lo and behold, of course the back cover didn't fit thanks to the diode, I knew that but didn't remember when tacking it on.? So I took that off and put another on closer down at board level.? Since I was in there with the iron hot I reflowed the IC.? Cleaned it up, put it back together, and powered it up.? Sounds coming through again, nice and clean.? Yay, happy night.? Thanks for the advice John!

John, got some ICs in and did the fix tonight.? If you wouldn't mind glancing over this and giving me some experienced feedback before I power it on again it'd be much appreciated.

Masked it off with some duct tape so hot air wouldn't affect much else.? Came off rather clean.? After this photo I added some flux and wicked a bit of the raised solder off.


Verified old to new and started tacking it on.? Looks decent from the top.




Until I get it around to about this angle and I see pin 1 especially is a little blobby but ok, nothing _looks_ touching.


But I go ahead with the diode which turned out good (imo).? But then I get another angle at the 1-8 pins and see it looks much different in that light.? Especially 1, 4, 8, and maybe 2.? Guessing it's worth going back and putting some more flux on and reflow.? Thoughts?


Thanks so much for your advice.

Hans Hi

Using 5 Volts (you can not blow anything :) ) from an USB and no LPFs no BPFs (bypass 7805)

I tested 2200m, 630m, 160m, 80m, 60m, 40m, 30m, 20m, 17m, 15m, 12m, 11m, 10m and 6m on transmit with the same QDX-M

all working (I transmitted less than 5 seconds each)

do not, repeat again do not try this with more than 5 Volts with no LPFs

you will definetely blow your Q6 and/or BS170s and/or IC5

73 DE muhsin TA1MHS

--Ooops, the power meter was between the QMX and the Tuner

Chuck, W5USJ
EM22cv, Rains Co., Texas

Evan,
I had Vcc at 9V this last time. I think the power with WM-2 and dummy load was about 1.2W
Next I switched to antenna with tuner in adjust mode. The bridge is about 1.5:1 SWR.
The failure happened when I switched to operate mode.

--

Chuck, W5USJ
EM22cv, Rains Co., Texas

Thanks, Evan,
I do have two dummy loads, the larger of which can handle up to 150W.? So I'll plan to build either the Salas or Hayward 40dB pickoff and follow it with a step attenuator.

Eric

Further info: The QMX, like the QDX power, will change with the impedance.? I have noted an increase in power ratings for SWRs that, when I put it on a dummy load, are 1.5 watts or more lower.? This could happen while you are adjusting for the LED dip.

73
Evan
AC9TU

Try using 12v rather than 13.6v. ?They are not the same for QMX purposes.

Hi Chuck,

Sorry to read of your problem.??

I believe that the QMX has an SWR function that is at reduced power.? It might be better to use it to adjust the Z-Match.? That would give you an easier-to-read number rather than an LED intensity.

Just a suggestion/
73
Evan
AC9TU

Hi Eric,

For best results, keep the input at the TinySA under -25DBm.? That means for 5 watts, a total of 36-(-25) = 61 DB.? An additional power attenuator of either 20 or 30 DB would be a good addition.? Get one rated for the highest power that you will be measuring.? If you intend to measure 100-watt QRO rigs, use a 40-db attenuator.


A Tap would be a lower-cost choice if you already have a 100-watt dummy load.? Here are directions on how to build one:


I built a slightly different tap from a no longer available webpage.? I have attached the PDF that I got from the site.

73
Evan
AC9TU

Thanks. ? I am getting a QRP Kits 41dB step attenuator, recommended in this forum.? What isn't clear to me, from the tinySA Ultra specifications, is whether its "recommended input power below -25dBm" is before or after the SA's built-in attenuator.? How do you read it?

Eric

I've used variations pretty much the same Z-Match tuner for many years.
Since the first NorCal BLT

Wasn't trying to get more power, just reducing the reflected RF for better SWR.
Supply voltage was 13.6 and band was 20 m.?

I don't recall exactly what happened the first time. But it was when I switched from
Adjust to Operate.? One suggestion was to reduce power and don't hot-switch.
I don't think I hot-switched. Another suggestion was an inductive spike.
Anyway, sent it off, got it fixed, and the same thing happened again. This time
supply voltage at 9, 30m, and I know I didn't hot switch. Also adjusted for noise
peak first.



I've used this tuner with everything from Rock-Mites to a uSDX+ with no problems. uSDX finals are
similar to the QMX, I think.? Used the same setup with the uSDX right after and no problem.?

Clueless in the suburbs of Point and Emory, Rains Co., Texas? EM22cv.


Chuck, W5USJ
EM22cv, Rains Co., Texas