Hi Barb
> The easiest mod is to remove 2xBS170 and run on one BS170. > QCX will be in QRPp range now with this mod.
No... all you do then is fry the BS170. The point of multiple BS170's is less about reducing the effective switch "on" resistance due to paralleling multiple devices. It's more to do with the fact that the power dissipation rating of one device is inadequate. Paralleling multiple devices shares the power dissipation. If you use only ONE BS170 in a QCX then the power output will reduce slightly (due to the higher "ON" resistance of only one) but all the power dissipation will end up in that one transistor, and it will suffer untold pain and suffering.?
73 Hans G0UPL
On Tue, Feb 27, 2024 at 2:19?PM < wb2cba@...> wrote: The easiest mod is to remove 2xBS170 and run on one BS170. QCX will be in QRPp range now with this mod.
--
?
73, Barb
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On 27/02/2024 11:19, wb2cba@... wrote: The easiest mod is to remove 2xBS170 and run on one BS170. QCX will be in QRPp range now with this mod. Barb, I wonder. I seem to remember that essentially the paralleled devices share the load. That has been mentioned with the U3S. Would just one be overloaded? In any case if the power was reduced to 1/3 it still would not be QRPp depending on the definition of QRPp:-) 73 Alan G4ZFQ
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The easiest mod is to remove 2xBS170 and run on one BS170. QCX will be in QRPp range now with this mod. -- ?
73, Barb
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Re: QMX Display Brightness
Question for Hans, are there any plans to be able to control the LCD display brightness in software?? Superficially it seems easy to drive the LCD_LED line with a PWM output which can be adjusted in software to set the brightness.? The existing Backlight ON/OFF setup could be changed to set a number 0-99 maybe.
Or is there a killer? The timer or PWM registers already in use?
I didn't have any plans for such a thing... the LCD_LED line is not connected to a Timer PWM output. Which makes it harder (not impossible); PWM'ing 10mA of LED would also inflict a heavy noise penalty which is why it would be really hard to do cleanly, unless it was reconnected to a Timer pin so could be done by the microcontroller in hardware (timer peripheral) not in software.?
I'll keep it in mind for future, it isn't trivial though.?
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Re: QMX Display Brightness
Question for Hans, are there any plans to be able to control the LCD display brightness in software?? Superficially it seems easy to drive the LCD_LED line with a PWM output which can be adjusted in software to set the brightness.? The existing Backlight ON/OFF setup could be changed to set a number 0-99 maybe.
Or is there a killer? The timer or PWM registers already in use?
Chris, G5CTH
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I have the same problem with a V2 QMX that affects both left and right encoders.? When turning the left encoder the volume level sometimes jumps many steps.? With the right encoder I have the issue described above.
????? Don KC6D
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With respect this sort of thing is good for black box users.
But my feeling is that generating "vast" amounts of power then wasting
it in an attenuator is not really true QRP.
I think reducing power output on all QRP Labs TXs can be achieved by
reducing PA voltage.
I guess there will be a limit, even with 0 volts on the PA something
will get through.
It also has the potential to be wildly misleading. 10dB may be one thing but if you go much beyond that, you will *think* you are really transmitting a certain amount of power, being your produced power minus the wired in attenuation. But in reality your antenna, grounding, shack, etc just isn't an ideal perfect situation and RF radiates from somewhere else other than only going through that big attenuator you put in.?
Like the occasional miraculous report of QSOs on a dummy load. Reality: your power supply cables and everything?else right down to every piece of wet spaghetti you happen to own, radiates *something*.?
Not producing "vast" amounts of power in the first place not only doesn't waste power in attenuators but also ensures more accurate conclusions!?
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On 26/02/2024 22:52, Chris m0pzc wrote: Links to SotaBeams switched attenuator (switched in by relay on transmit/switched out when not transmitting, on receive) Chris, With respect this sort of thing is good for black box users. But my feeling is that generating "vast" amounts of power then wasting it in an attenuator is not really true QRP. I think reducing power output on all QRP Labs TXs can be achieved by reducing PA voltage. I guess there will be a limit, even with 0 volts on the PA something will get through. 73 Alan G4ZFQ
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Hi,
can confirm this problem. My right encoder goes forward and backwards when turned slowly.?
The leftone is working precisely.?
Vy 73, Peter DL4PJ
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Links to SotaBeams switched attenuator (switched in by relay on transmit/switched out when not transmitting, on receive)
?
The schematic should? be straight forward to homebrew ugly/Manhattan style, with individual choice of attenuation level(s), and? powered by a battery.
In fact this is just what I plan to build very soon for QRPp WSPR but should be fine for CW
73
Chris
m0pzc
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Re: #qmx #firmware 1_00_017 AGC, S-meter, LPF sweep
#qmx
#firmware
QMX observations FW 1_00_017
QMX covers the 80m-20m band, but I don't use the 80m band, so I chose it for the 40m-15m band.
?
1.Setting japanese limits to ENABLED.
When transmitting at 17m and 15m BAND in CW mode, an abnormally large amount of current flows and the BS170 will be damage.
It works normally in Digi mode.?
I think this also happens with QMX Hi-Band Version.
Setting japanese limits to DISABLED makes it works normally.
?
2.In the case of CW mode in system config LSB, the RX frequency and TX frequency differ by 1.40KHz.
The RX frequency is 1.40KHz higher than the displayed frequency.
Normal when using USB in CW mode.
In digi mode, both LSB/USB are normal.
This is the case when CW-R is OFF.
?
When CW-R is ON and USB in CW mode, the RX frequency and TX frequency differ by 1.40KHz.
The RX frequency is 1.40KHz lower than the displayed frequency.?
The CW-R function remains OFF.
When CW-R is ON and LSB in CW mode, RX frequency = TX frequency.?
normal. The CW-R function is turned on.
?
In other words, if you want to? CW-R OFF in CW mode, use USB + CW-R OFF.
When turning CW-R ON in CW mode, it is necessary to use LSB + CW-R ON.
Do not use USB + CW-R ON and LSB + CW-R OFF in CW mode.
?
I would like LSB/USB switching to be enabled only in digi mode, and only CW-R ON/OFF in CW mode.
?
?
syuji ota? ?JH3AQQ
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Re: #qmx filter testing and adjustment
#qmx
I touched up the solder joints on all the LPF capacitors and toroids, and also adjusted the turns spacings on L401 to match more closely the photo in the assembly manual.? Reconnected the radio to the QRP Labs dummy load.? After this, the RF sweeps and LPF sweeps looked very good, in terms of BPF peak frequencies and LPF cutoff frequencies and stopband levels.? There were, however, no improvements to the output powers, which ranged from 1.3W (15m) to 3W (17m) before and after these tweaks.
Next I removed the ShortStopper from the power cable, since I am past testing for power-ground shorts.? I ran the power tests again, and saw improvement across the board, from 1.7W (15m) to 4.3W (17m).? "PA voltage" was in the 7.5V range on all bands. The radio draws 120mA on receive and 900mA in transmit, according to the meter on my power supply.
After this, I followed Hans' tip in the "52 tips" video and squeezed the turns together on the antenna-side toroids for LPFs 1 and 2, which cover 17-10m.? There was no improvement in output power; in fact, 15m went down.? I observed that this change to the toroid made the LPF narrower, putting the test frequency out of the passband into the transition band, hence decreasing the output power.
I am happy enough with 17m and 20m, but would sure like to get more than 1.7W out on 15m.? Any suggestions?
Thanks very much,
Eric
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Re: QDX SWR protection circuit?
#qdx
On Sun, Feb 25, 2024 at 01:19 AM, Howard wrote:
Apologies if this has been discussed. I searched and did not find anything relevant.
Are there are any plans to implement the SWR protection circuit from the QMX in the QDX? The QDX is perfect for certain applications due to the absence of controls.
I agree that it is unlikely that Hans will want to find time for incorporate a reflectometer into the QDX with associated extra software in the controller.? Part of the problem is that, unlike the QMX, there is no easy way of reducing the supply to the final amplifier in the QDX. This would mean that the only way for a reflectometer to operate would be to completely shutdown the transmitter by removing the RF drive. By itself, this may protect the final amplifier, but would give little help to resolve the poor SWR situation.? A better way would be switching to reduced power operation, which might allow matching adjustments to be made before going back to full power.
?
It could be possible to make an outboard unit to implement such protection. Transmitter output would pass through a tandem bridge reflectometer (as at the output of the QMX).? Rather than using a processor to monitor the forward and reverse waves, I think an op-amp based circuit might be better because it would operate far faster than any processor based system.? Speed of operation is essential to give maximum protection to the output BS170 transistors (although it still may not be fast enough for high voltages across the transistors). The reflectometer circuit would be arranged to trip at an appropriate SWR (perhaps 2:1) whereupon a MOSFET switch in series with the 12V QRX supply would open to put a string of silicon diodes to reduce the supply to around 8V. This voltage would reduce output to around 1W which would lessen the stress on the output transistors. Once operating at reduced power, antenna matching could be adjusted as required, returning the QDX to full power afterwards by pressing a reset button. Note that this assumes the QDX is built for 12v operation rather than the 9V option.
?
With regard to the op-amp circuit, the simplest arrangement would be to just monitor the reverse wave detector and trip the protection when its absolute voltage exceeds that for a 2:1 SWR.? However, it may actually be better to monitor both forward and reverse wave to that the trip would operate at a defined SWR (i.e. for example 2:1). This would require additional complexity in the op-amp circuitry.
?
The diagram below shows the elements of the outboard protection unit.
? -- Peter Lee G3SPL
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Re: #key #qmx QMX Straight Key Mode incorrect
#key
#qmx
Yes, that one had me questioning my sanity when I first connected the straight key. Ring is tip and tip is ring! J ? 73, -Lloyd ? ?
toggle quoted message
Show quoted text
From: [email protected] [mailto:[email protected]] On Behalf Of Gary W9TD
Sent: Saturday, February 24, 2024 9:13 PM
To: [email protected]
Subject: Re: [QRPLabs] #key #qmx QMX Straight Key Mode incorrect ? It works correctly with a paddle but the ring/tip option for a straight key is wrong.
Gary
W9TD
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Re: QMX Digital Modes Bug
So, is this "resolved" or ??
TIA for an answer.
es vy 73 de "baab" w9ya
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Kjell,
When I'm in a mood for QRPp, I haul out my Zachtek "Flea" transmitter and the ATS-25 general coverage receiver I use with it. It's only 300mw, on 20, 30, and 40m. It doesn't have to be that particular receiver, I just chose that one because Harry from Zachtek used it for his own Flea and knows it works properly. The Flea handles antenna swapping between the receiver and transmitter, and it has a very imaginative frequency spotting feature that makes it dirt simple to find the transmitter frequency. It's a VERY small transmitter, about the size of an index card. The receiver is actually larger than the transmitter in my case. I power the transmitter using a USB-C Power Delivery battery bank and a 12v trigger cable with the correct DC coaxial barrel plug on it. I have a link dipole for 20/30/40m that's resonant in the CW portion of each band, so I don't even need to tune the antenna, just make sure the correct links are connected.
I used this setup at Field Day a couple of years ago, and was making contacts 800+ miles away from our ham radio club's usual Philadelphia-area camp in a local State Park that has camping. I was being heard quite effectively near the Illinois-Wisconsin border and thereabouts.
For those concerned, the PD setup I use is not plagued with birdies or other noise. I routinely operate out and about using such power supplies. I do have a couple of LiFePO4 12v batteries that I can bring to bear, but they're heavy and bulky, and need special chargers. (Not as heavy as the Sealed Lead-Acid Batteries I was using prior to LiFePO4 availability, but still heavier than a 10-20Ah USB-C PD power bank. I've even operated using the 4,000mAh PD bank I keep in a pouch in my pocket. Works great. I had an article in QRP Quarterly some years ago that showed my first PD trigger board (I found it on Tindie) connecting a compatible PD power bank to one of my original QCX radios. As long as I used the correct size of barrel plug, it always worked like a champ.
But I do seriously recommend the Flea as a very useful QRPp transmitter. It's also relatively inexpensive.?
The software for the Flea was created by Kevin Loughin, KB9RLW. He has a whole series of YouTube videos on the Flea project, from various stages in development. He also operated at Field Day, using a Malahit receiver. Kevin hasn't been doing a lot since he caught Covid and was laid low with Long Covid and is still having difficulty getting back into the swing of things. Here's his video relating his Field Day operations.
Worth a look, even if you never get your own Flea.
73,
Gwen, NG3P
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Re: QDX SWR protection circuit?
#qdx
Rather than try to add SWR protection circuitry, try protecting the BS170's:
I also added the zener across L14 for good measure. My Final blew for no known reason once. I replaced the BS170,s added zeners per Sverre plus the one across L14 and have had no issues since (6 + months and hundreds os QSOs). I did this to both the high and low band QDX radios.
I moved one of the antennas from the switch to the Icom so my Grandson could listen to the QDX transmit, then forgot to move the coax back. I was transmitting into an open switch port at full power ( I always operate the 12v radios at 11 volts) with no ill effects.
YMMV
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On 26/02/2024 18:52, David Alexander wrote: where do i find instructions for the above unit? Dave Lots linked from that page. 73 Alan G4ZFQ
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I am a nubie to the group so be easy.
where do i find instructions for the above unit?
dave k7da
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Re: #qmx wrong inductances for LPF?
#qmx
Ludwig,?
? ? Am I understanding that you were finding T37-17s to measure 25%+ high when you wound them??
And your further work with T37-10s is validating your measurements?
I'm working on a QDX HB, with the T37-17s. I've been trying to measure the toroids by using a series LC circuit with a capacitor, and using the frequency of resonance to find the inductance. With 12 turns on a T37-17, I was somewhere around 0.35uH. Taking it all the way down to 8 turns got me 0.22, and 10 turns on another got me 0.248. (Target is 0.202 and 0.25).??
On one with more windings, I found I needed 20 turns (to get 0.74uH) instead of the 21 listed to get to the 0.722 target.?
I'm questioning my measurements, especially at low turns.....Modeling the QDX 17/15 LPF in Elsie...I find that one is pretty sensitive to getting the inductance values correct.?
If my 8 and 10 turn windings are really closer to the calculated 0.10 and 0.15 that Toroids.info comes to, the input SWR of that LPF gets REALLY bad... But if my measurements are correct, then the filter performance is right where it needs to be.?
I'm considering building a whole LPF on a breadboard and measuring the response to help validate what I've measured (jsut like you did), but just double-checking that you were seeing high AL values with the T37-17s.?
-Nate?
N8BTR
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Barb WB2CBA
Don Karon
Chris m0pzc
Gwen Patton