Re: 50W Amp Curious Questions - Why does 40 meter AMP put out so much more gain?
#50w
#output
Hi Greg,
AFAIK, IRF510 was designed to be a power switching device. Many years ago, some kind soul found that it can also be used as a low cost HF power amp, with more than decent results. But, as there's no free lunch in this universe, so is the case with IRF510 - due to it's internal capacities, it works best in the low bands and kinda so-so under 20m.
Incidentally, my first amp that didn't oscillate and actually worked was a IRF510 design for 80 and 40 meter, published by a DL ham. It was 25 years ago, I think I still have it somewhere under the bed :-)?
Using some sort of resistive attenuator is probably a good idea, if you can't power the QMX from something lower than 12V. While tinkering with atten. and bias, it would be nice to have a scope to make sure that you actually output a sine.
Regards,
YO3GFH
op. Adrian
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Re: QMX - Any progress on key clicks please?
I tried factory reset and f/w017 reload with no change in clicks ?- ?still there. Power cycle or no, any and all changes in settings and it's still the same.?
?
If I turn the volume down to zero or just above, I get no clicks and as I turn up the volume, the clicks just get louder and louder.?
?
*** I think the following is why there is such disparity between different observers: ?If the Side Tone is set To Relative instead of Absolute, then the clicks are much, much less and only become objectionable when the volume is turned up to distorting levels.***
?
I believe it has to do with the tx>rx change over. However, that doesn't quite explain why it is so much worse with Absolute rather than Relative ST volume.
I believe the f/w needs to do what was done in h/w on the QCX. Of course, I am no programmer and I haven't a clue HOW that can be done, but I'm pretty sure it CAN be done. After all, it's been done on many other SDR radios
-- 73, Dan? NM3A There are moments when everything turns out right .... Don't let them alarm you; they pass.?
-Jules Renard
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Re: 50W Amp Curious Questions - Why does 40 meter AMP put out so much more gain?
#50w
#output
It¡¯s possible the 40M amp is oscillating. Also possible that the input Pi attenuaor has an issue.?
I have 2 of those 40M amps and one gets 25W with 4 W in at 13V
2nd gets 50W with 4W in at 22V
Larry KB3CUF?
On Thu, Mar 14, 2024 at 7:13?AM Greg McCain via <gamccain50= [email protected]> wrote: Yes.
K2 - 50W Amp - QrpGuys SWR/Power meter.
Greg On Thu, Mar 14, 2024 at 12:29 AM, Larry Acklin Hi- is this into a watt/swr meter then dummy load?? Antenna connections with SWR issues can fool inexpensive watt meters.?
Larry KB3CUF? On Wed, Mar 13, 2024 at 11:23?PM Greg McCain via <gamccain50= [email protected]> wrote: Hi gang,? Not complaining ...? ?Just curious.
I had recently built 3 of the 50W amps ( 15M, 20M and 40M). Want to use them for a little extra punch (say 10 to no more than 20 watts out) for field semi-portable 'digi' work (FT8, J8Call, WSPR) . . .? well, just because.??I built all three as '12 volt' versions.?
?I set the drive bias exactly as described in the instructions. The builds went well and the amps appear to output as described in the manual(s)./graphs.
I was just wondering why the 40 meter version is 'hotter' than say the 20 meter version which is hotter than the 15 meter version.
I found that I can get 10 Watts OUT with the following Watts IN from my K2.
15M - approx 4.5 Watts IN
20M - approx 2 Watts IN
40M -? LOTS of WATTS OUT (Too Many) with Just 1 Watt in !!
** For the 40M, I found if I backed down the bias, I could get 10 Watts out by setting the K2 for between 0.1 and 0.2 Watts out. Yep 'tenths' of a Watt.?
Is my stumbling on the bias backdown a potential problem point?
Or, perhaps I should make up some PI attenuator circuits to add to the Transmit circuit chains in the AMPs where needed to tone down the 3.6 - 3.9 Watts that my new QMX is producing??
Thanks in advance,?
Greg? KI4NVX
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Re: 50W Amp Curious Questions - Why does 40 meter AMP put out so much more gain?
#50w
#output
When you see an amplifier provide loads of gain in a particular band or frequency it is usually because there is a circuit self resonance, so losses are minimal, or there is some negative feedback that due to phase shifts is becoming less so. ?It is not much fun when the amplifier gain and phase shifts flip into the positive region and oscillation begins.
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On Mar 14, 2024, at 07:13, Greg McCain via groups.io <gamccain50@...> wrote:
?Yes.
K2 - 50W Amp - QrpGuys SWR/Power meter.
Greg On Thu, Mar 14, 2024 at 12:29 AM, Larry Acklin <acklin@...> wrote: Hi- is this into a watt/swr meter then dummy load?? Antenna connections with SWR issues can fool inexpensive watt meters.?
Larry KB3CUF? On Wed, Mar 13, 2024 at 11:23?PM Greg McCain via <gamccain50= [email protected]> wrote: Hi gang,? Not complaining ...? ?Just curious.
I had recently built 3 of the 50W amps ( 15M, 20M and 40M). Want to use them for a little extra punch (say 10 to no more than 20 watts out) for field semi-portable 'digi' work (FT8, J8Call, WSPR) . . .? well, just because.??I built all three as '12 volt' versions.?
?I set the drive bias exactly as described in the instructions. The builds went well and the amps appear to output as described in the manual(s)./graphs.
I was just wondering why the 40 meter version is 'hotter' than say the 20 meter version which is hotter than the 15 meter version.
I found that I can get 10 Watts OUT with the following Watts IN from my K2.
15M - approx 4.5 Watts IN
20M - approx 2 Watts IN
40M -? LOTS of WATTS OUT (Too Many) with Just 1 Watt in !!
** For the 40M, I found if I backed down the bias, I could get 10 Watts out by setting the K2 for between 0.1 and 0.2 Watts out. Yep 'tenths' of a Watt.?
Is my stumbling on the bias backdown a potential problem point?
Or, perhaps I should make up some PI attenuator circuits to add to the Transmit circuit chains in the AMPs where needed to tone down the 3.6 - 3.9 Watts that my new QMX is producing??
Thanks in advance,?
Greg? KI4NVX
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Re: For Sale: Two Assembled QDX Rigs - Hi/Lo bands
Items sold - thanks for any inquiries.
--
Jim / K7TXA
Eagle, ID
SKCC 10447T
BUG 301
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I believe that the EXT jack is for tuning control/triggering by (if I recall correctly) Icom transceivers. I think it is a 3.5mm TRS jack.
The USB port on front is used (on my unit) to charge the batteries.
73, Don N2VGU
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Re: 50W Amp Curious Questions - Why does 40 meter AMP put out so much more gain?
#50w
#output
Yes.
K2 - 50W Amp - QrpGuys SWR/Power meter.
On Thu, Mar 14, 2024 at 12:29 AM, Larry Acklin <acklin@...> wrote: Hi- is this into a watt/swr meter then dummy load?? Antenna connections with SWR issues can fool inexpensive watt meters.?
Larry KB3CUF? On Wed, Mar 13, 2024 at 11:23?PM Greg McCain via <gamccain50= [email protected]> wrote: Hi gang,? Not complaining ...? ?Just curious.
I had recently built 3 of the 50W amps ( 15M, 20M and 40M). Want to use them for a little extra punch (say 10 to no more than 20 watts out) for field semi-portable 'digi' work (FT8, J8Call, WSPR) . . .? well, just because.??I built all three as '12 volt' versions.?
?I set the drive bias exactly as described in the instructions. The builds went well and the amps appear to output as described in the manual(s)./graphs.
I was just wondering why the 40 meter version is 'hotter' than say the 20 meter version which is hotter than the 15 meter version.
I found that I can get 10 Watts OUT with the following Watts IN from my K2.
15M - approx 4.5 Watts IN
20M - approx 2 Watts IN
40M -? LOTS of WATTS OUT (Too Many) with Just 1 Watt in !!
** For the 40M, I found if I backed down the bias, I could get 10 Watts out by setting the K2 for between 0.1 and 0.2 Watts out. Yep 'tenths' of a Watt.?
Is my stumbling on the bias backdown a potential problem point?
Or, perhaps I should make up some PI attenuator circuits to add to the Transmit circuit chains in the AMPs where needed to tone down the 3.6 - 3.9 Watts that my new QMX is producing??
Thanks in advance,?
Greg? KI4NVX
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Re: QDX - stops on 10m after a few seconds
Good morning :)
Thanks a lot for your time and hints!!
Yesterday afternoon/evening I did some more tests.
(dummyload instead antenna; battery driven equipment; psu driven equipment; other computer)
For me it looks like the problem is kernel and/or chipset related - because using a Raspberry running jtdx on 10m works without any problems.
I'll do some more tests with other systems.
Cheers,
Torsten
PS:
Current system (information generated by inxi):
System:
Host: lab Kernel: 6.1.0-18-amd64 arch: x86_64 bits: 64 Desktop: LXDE
v: 0.10.1 Distro: Debian GNU/Linux 12 (bookworm)
Machine:
Type: Desktop Mobo: AZW model: MINI S v: 10 serial: <superuser required>
UEFI: American Megatrends LLC. v: ADLNV104 date: 02/06/2023
CPU:
Info: quad core Intel N95 [MCP] speed (MHz): avg: 800 min/max: 800/3400
Graphics:
Device-1: Intel Alder Lake-N [UHD Graphics] driver: i915 v: kernel
Display: x11 server: X.Org v: 1.21.1.7 driver: X: loaded: modesetting
unloaded: fbdev,vesa dri: swrast gpu: i915 resolution: 1440x900~50Hz
API: OpenGL v: 4.5 Mesa 22.3.6 renderer: llvmpipe (LLVM 15.0.6 256 bits)
Network:
Device-1: Realtek RTL8111/8168/8411 PCI Express Gigabit Ethernet
driver: r8169
Device-2: Intel Wireless 7265 driver: iwlwifi
Device-3: Intel Bluetooth wireless interface type: USB driver: btusb
Drives:
Local Storage: total: 238.47 GiB used: 61.66 GiB (25.9%)
Info:
Processes: 185 Uptime: 1d 8m Memory: 7.54 GiB used: 943.6 MiB (12.2%)
Shell: Bash inxi: 3.3.26
Am 13.03.2024 um 20:01 schrieb AB9LM:
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Show quoted text
I had the same issue for a while. I tried snap-on ferrites on everything, but that didn't help in my case. I finally made a proper choke with 14 turns of coax on a ft-220-43 -- Nipped it in the bud for good.
James - AB9LM
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Re: QMX - Any progress on key clicks please?
On Thu, Mar 14, 2024 at 05:03 AM, Charles Johnson wrote:
so you're loading down the audio output amplifiers significantly more when you plug into a line-level input.
It's the other way round, Charles. A lower impedance load will place a higher burden on the output amp.
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Re: QMX - Any progress on key clicks please?
Greetings all,
I do not have a QMX, but upon reading that the problem went away when the audio output was connected to a line-level input AND that it seems to be volume-related, the sound engineer in me saw a couple of flags. First, ear buds are usually in the 32-ohm and less range while headphones, while varying wildly, can range up to 150-ohms (maybe higher). For reference, my Sony MDR-7506s are spec'ed at 63-ohms. That said, a line-level input is usually going to have a load of at least 1.5k-ohms, so you're loading down the audio output amplifiers significantly more when you plug into a line-level input. Second, since people are reporting that it gets worse as the volume is increased, perhaps what's happening is simply the audio output amplifiers are clipping and/or there is clipping (either analog or digital) elsewhere.
My $0.02 :-)
Charles Johnson
KF4AYT
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Re: 50W Amp Curious Questions - Why does 40 meter AMP put out so much more gain?
#50w
#output
Hi- is this into a watt/swr meter then dummy load?? Antenna connections with SWR issues can fool inexpensive watt meters.?
Larry KB3CUF?
On Wed, Mar 13, 2024 at 11:23?PM Greg McCain via <gamccain50= [email protected]> wrote: Hi gang,? Not complaining ...? ?Just curious.
I had recently built 3 of the 50W amps ( 15M, 20M and 40M). Want to use them for a little extra punch (say 10 to no more than 20 watts out) for field semi-portable 'digi' work (FT8, J8Call, WSPR) . . .? well, just because.??I built all three as '12 volt' versions.?
?I set the drive bias exactly as described in the instructions. The builds went well and the amps appear to output as described in the manual(s)./graphs.
I was just wondering why the 40 meter version is 'hotter' than say the 20 meter version which is hotter than the 15 meter version.
I found that I can get 10 Watts OUT with the following Watts IN from my K2.
15M - approx 4.5 Watts IN
20M - approx 2 Watts IN
40M -? LOTS of WATTS OUT (Too Many) with Just 1 Watt in !!
** For the 40M, I found if I backed down the bias, I could get 10 Watts out by setting the K2 for between 0.1 and 0.2 Watts out. Yep 'tenths' of a Watt.?
Is my stumbling on the bias backdown a potential problem point?
Or, perhaps I should make up some PI attenuator circuits to add to the Transmit circuit chains in the AMPs where needed to tone down the 3.6 - 3.9 Watts that my new QMX is producing??
Thanks in advance,?
Greg? KI4NVX
|
50W Amp Curious Questions - Why does 40 meter AMP put out so much more gain?
#50w
#output
Hi gang,? Not complaining ...? ?Just curious.
I had recently built 3 of the 50W amps ( 15M, 20M and 40M). Want to use them for a little extra punch (say 10 to no more than 20 watts out) for field semi-portable 'digi' work (FT8, J8Call, WSPR) . . .? well, just because.??I built all three as '12 volt' versions.?
?I set the drive bias exactly as described in the instructions. The builds went well and the amps appear to output as described in the manual(s)./graphs.
I was just wondering why the 40 meter version is 'hotter' than say the 20 meter version which is hotter than the 15 meter version.
I found that I can get 10 Watts OUT with the following Watts IN from my K2.
15M - approx 4.5 Watts IN
20M - approx 2 Watts IN
40M -? LOTS of WATTS OUT (Too Many) with Just 1 Watt in !!
** For the 40M, I found if I backed down the bias, I could get 10 Watts out by setting the K2 for between 0.1 and 0.2 Watts out. Yep 'tenths' of a Watt.?
Is my stumbling on the bias backdown a potential problem point?
Or, perhaps I should make up some PI attenuator circuits to add to the Transmit circuit chains in the AMPs where needed to tone down the 3.6 - 3.9 Watts that my new QMX is producing??
Thanks in advance,?
Greg? KI4NVX
|
Larry,
I did the factory reset and reloaded latest
firmware.? No change.
Re did solder on both torids for 10 and 12
meters, no change.
Next step is try and check the diodes as Evan
suggested.
Thank you? 73
Emory? WM3M
On 3/13/2024 7:26 PM, Larry VE7EA
wrote:
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Emory: before you go to all the hassle of checking the LPF's I
would definitely try a simple factory reset as Evan suggested
above.
Have you tried that?
The reason I ask is that yesterday I experienced very, very low RF
out on 12 and 10m only. My QMX had been working just fine
previously so I was scratching my head.
Only two things had I done in the meantime between working and
non-working and that was:
1) playing around testing key clicks by turning AGC on and off and
2) I mistakenly tried to tune my IC7300 (10W out) nearby my QMX
while the antenna switch was set to the QMX. This would mean some
SWR and RF at the antenna switch itself (not into the QMX
directly). I think that perhaps the RF caused some glitch in my
QMX, but I cannot be certain.
At any rate, a simple factory reset cured my problem. No idea why!
So try this first...
Larry VE7EA
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Emory: before you go to all the hassle of checking the LPF's I would definitely try a simple factory reset as Evan suggested above.
Have you tried that?
The reason I ask is that yesterday I experienced very, very low RF out on 12 and 10m only. My QMX had been working just fine previously so I was scratching my head.
Only two things had I done in the meantime between working and non-working and that was:
1) playing around testing key clicks by turning AGC on and off and
2) I mistakenly tried to tune my IC7300 (10W out) nearby my QMX while the antenna switch was set to the QMX. This would mean some SWR and RF at the antenna switch itself (not into the QMX directly). I think that perhaps the RF caused some glitch in my QMX, but I cannot be certain.
At any rate, a simple factory reset cured my problem. No idea why! So try this first...
Larry VE7EA
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Re: QMX - Any progress on key clicks please?
It's a strange bug(?) for sure.? I repeated my headphone versus pc soundcard input test again this evening and the sidetone audio was perfect using both!?? I definitely had the problem before but will continue to monitor if any changes I make cause it to return.
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Re: QMX - Any progress on key clicks please?
Hans,
I just went back and checked. The clicks were there as far back as 004 (Rev1 PCB). However they didn't become nearly as obvious until ver 012 when the volume control was fixed. But the max gain prior to ver 12 was much lower. So I believe that the clicks have been there all along, but didn't become really bad in ver 12 (or 11, which I didn't test.) That was when you could really crank up the volume.?
--
73, Dan? NM3A
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QDX, 5 Watt Amp, and QCXO Synth Kits For Sale
QDX Lo Band Kit with pre wound and pre tinned toroids for sale. Version 3A. With Enclosure. Shipped Conus $90 PayPal.
Also...these are discontinued at QRP Labs...2 each 5 Watt amp kits and 2 each QCXO Synth SI5351A kits for sale. All 4 Kits sold and shipped for Conus $75 PayPal.
Chuck KE9UW email good in QRZ
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Re: QMX - Any progress on key clicks please?
It goes back at least as far as 10, which was the firmware on my first delivered QMX. It¡¯s noticeable in headphones and amplified external speakers and in RF and practice mode, into a 50ohm load and an antenna.?
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Good morning
is there anyone using an n7dcc atu10 (Chinese copy) that has a jack on the back labeled ext.
is that external power to charge the internal batteries?
if so what type of plug does it use?
thanks dave k7da
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Evan,
Really appreciate your help and info.
Will try again to make sure toroids are good
and check the diode voltages.
One problem I have is identifying? right
solder point on bottom side of board, since it is so crowded.
Will advise with results.
Thank you? 73
Emory? WM3M
On 3/13/2024 1:48 AM, Evan Hand wrote:
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Hello Emory,
12, 11, and 10 meters share the same low pass filter (LPF).? This
would point to a problem there.? The most common is one of the
toroid connections did not burn through the enamel.? This assumes
that the configuration is correct.? I suggest the following:
1 - Update to the latest firmware from the QRP-Labs web page:?
2 - Do a factory reset
If the above does not solve the issue, then:
3 - Verify that the LPF diode selection is working correctly.?
This also verifies that the toroid connections are good, as the
toroids are used to conduct the DC bias.? The LPF diodes are D508
through D513.? D510 and D513 select the 12/11/10 meter LPF.? The
banded end (Cathode) should be close to 0 volts.? The other four
should be close to the supplied voltage to the QMX.? This test is
while receiving, not transmitting.
The next steps would depend on your findings from the above.?
Please post your results, including the version of the firmware.
73
Evan
AC9TU
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Donald S Brant Jr
Chuck ke9uw