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
|
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
|
Re: QMX Digital Modes Bug
So, is this "resolved" or ??
TIA for an answer.
es vy 73 de "baab" w9ya
|
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
|
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
|
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
|
I am a nubie to the group so be easy.
where do i find instructions for the above unit?
dave k7da
|
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
|
Re: QDX SWR protection circuit?
#qdx
I once set up a BIOS EPROM to flash SOS on the carry light.? Well actually any message in Morse.
Chris, G5CTH
|
Re: #qmx #firmware 1_00_017 AGC, S-meter, LPF sweep
#qmx
#firmware
Hans, I know upgrade is easy, I've done that before ;) Believe it or not, my (yes, MY) problem is, that PC I use on daily basis is unable to write USB drives. Can read but cannot write. Unbelievable? :)? So firmware update means I gotta go grab some other PC. And that's the reason I'd prefer to know in advance.
No worries, just do your job and if I'm one version behind, that's no big deal.
|
Re: QMX if Vaudeville Still Existed
It was a standard routine done back in the Vaudeville days performed by many acts. The 3 Stooges and Abbott and Costello both have famously recorded versions. A true classic!
|
No... don't worry, it will all come good in a few days!
On Mon, Feb 26, 2024 at 8:00?PM Loky < mrloky@...> wrote: Should I be worried if order 82084 shipped but 81846 is still just showing as "Complete"? I just want to make sure that mine hasn't slipped through the cracks or something, since I never got any confirmation or shipping email.
Thanks!
|
Should I be worried if order 82084 shipped but 81846 is still just showing as "Complete"? I just want to make sure that mine hasn't slipped through the cracks or something, since I never got any confirmation or shipping email.
Thanks!
|
Re: QMX FW 17 and side tone clicks
I'm not clear on what Simon is saying.? In my case, I have the clicks all the time, but they are much worse if there are are other signals in the receive passband.
73,
Randy, KS4L
|
QMX v3 rev017 Digital Modes Receive Gain Low
When using Win 10 and 11 I see? receive gain is easily adjustable, usually 50db range with my FT991A? utilized
on Digital modes?
However with QMX and W10 &W11 computers on WSJT-x best I get is 30db and? about 35 db on JTDX max.
Question Is there an adjustment I missed in the manual or in Putty?
|
Re: QMX if Vaudeville Still Existed
Thanks for posting this!? It's been AGES since I've seen it.? Is 'Niagara Falls' strictly a Three Stooges skit or have other comics done it, too?
|
Hyelec PS-28A 0-15 VDC, 0-2ADC power supply plus a simple crowbar circuit for protecting all of my QRP rigs
Added to the output of the Hyelec PS-28A is a 12 VDC, 3ADC, 50w zener, the NTE 5254AK, mounted on a 3 inch x 5 inch extruded aluminum heatsink.
Well, so far, so good. I shouldn't be breaking any more of my favorite rigs PLUS, the crowbar helps to keep the shack warm!
72,
Bill, N4QA/4 in Oak Island ( OKI ), North Carolina, USA
|
Re: QDX version 1 voltage regulator mod?
On 26/02/2024 14:08, Stephen Farthing G0XAR JO92ON97 wrote: I’m starting to learn Micropython and thought this might be a suitable starter project. Steve, Oh, OK then my thought of a U3S defeats your purpose:-) Best of luck! 73 Alan
|
Re: QMX HIGH BAND NO RF OUT AFTER ANOTHER 10 hour WSPR TRANSMISSION
OK so you have a different problem then I do.
My QMX just stops transmiting WSPR after 10 hours or so even though the display still shows the transmission when the time comes.
I have noticed this all along (with other firmware revisions).
If I turn the QMX off and on it will work fine again most likely for 10 hours in the WSPR mode.
Michael N2ZDB
|
Re: QDX version 1 voltage regulator mod?
Alan,?
WSPR Transmit only.? My idea is to get the QDX to transmit WSPR on a frequency and at a time determined by a microcontroller rather than a computer. This would allow the automation of a multi band beacon without tying up a computer.?
My “rough” design is to use a rasberry pi Pico with an I2C real time clock. The software would have a hard coded WSPR string (as shown by Andy Talbot and others) ?and a Kenwood TS480 CAT protocol emulator. The Pico would send a message to the QDX using the CAT protocol at a time, duration and ?frequency defined in the code which will use the RTC for timing purposes.?
What I don’t know is if the Pico can use its USB interface for serial port communications with the QDX A raspberry pi Zero might be a better option.
Using a microcontroller would offer the possibility of switching an appropriate aerial matching circuit as well.?
I’m starting to learn Micropython and thought this might be a suitable starter project.?
Er, that’s it,?
Steve?
|
Gwen Patton
Burt Wizeman
Randy
Bill, N4QA/QRP