Don't worry be happy.? The QMX is working fine.? The errors are quite low and there is absolutely nothing to worry about.? SWR readings can vary due to small errors in the SWR bridge circuitry, dummy load being not exactly 50 ohms at all measured frequencies, especially the high end, and differences in accuracy between different SWR bridges.??
-Steve K1RF
------ Original Message ------
Date 7/15/2024 6:56:58 AM
Subject Re: [QRPLabs] QMX 80-20M - High SWR on Dummy Load? #qmx #swr-sweep
Thank you Steve for your response. I was finally able to get the SWR on the QMX to show between 1.05 and 1.18. I rewound the T507 as outlined here
I do have a couple of follow up questions though:
1.) SWR on 80M (according to the QMX) is still 1.18. That's the worst band. Is that considered acceptable? These were all tested on a dummy load.
2.) My external SWR meter is still showing differently. On the 20M band, the QMX shows 1.05, but my external meter shows 2.1. How do we determine which is the "real" reading?
Thank you for your help so far.
|
Fw: [QRPLabs] For Sale, QMX, QCX+ & QDX
Sorry, the QCX+ is for 80m
?
73
?
Ian G4GIR
?
toggle quoted message
Show quoted text
----- Original Message -----
Sent: 15/07/2024 13:36:14
Subject: [QRPLabs] For Sale, QMX, QCX+ & QDX
Hi
?
I have various QRP Labs units for sale.
?
All Rigs built by me and include Enclosures.
?
P&P your choice at your cost.
?
QMX 80 - 20m 2 units available ?70.00 each
QMX 20 - 10m ?70
QDX 80 - 20 ?50
QCX Mini 60m plus TCXO ?50-00
QCX+ plus TCXO AGC Board (commercial unit) 15 Way D Connector Fitted to allow remote connection to ISP, Cat Control and GPS.? ?45.00
?
Please contact me direct QRZ details are?OK
?
72/3 Ian G4GIR
|
For Sale, QMX, QCX+ & QDX
Hi
?
I have various QRP Labs units for sale.
?
All Rigs built by me and include Enclosures.
?
P&P your choice at your cost.
?
QMX 80 - 20m 2 units available ?70.00 each
QMX 20 - 10m ?70
QDX 80 - 20 ?50
QCX Mini 60m plus TCXO ?50-00
QCX+ plus TCXO AGC Board (commercial unit) 15 Way D Connector Fitted to allow remote connection to ISP, Cat Control and GPS.? ?45.00
?
Please contact me direct QRZ details are?OK
?
72/3 Ian G4GIR
|
Re: QMX Rev 1 works great but RIT tune rate doesn't, Hardware?
Thanks Ronan really appreciate that and agree. I was just going through the Ops manual and the rate change was there. I guess it was not implemented.
Again, appreciate the info.
Please take care,
Tim
|
Re: QMX+ Build Report and Low Power Question on 40m and 30m
On Mon, Jul 15, 2024 at 05:23 AM, M0WAS wrote:
The burning off of the enamel was the bit of the build which I was always least happy with
Get yourself one of these Knipex 15 11 120 strippers, happiness awaits. Does anyone else remember Stripex/Strip-X? It was a foul-smalling brownish concoction of phenol etc. which was used to chemically strip enamel. Dip it in, wait a second and wipe off the enamel cleanly. I am sure they pulled from the shelves for a reason but it worked great. 73, Don N2VGU
|
Re: QMX rev4 60m-15m build TX problem
#qmx
On Mon, Jul 15, 2024 at 10:04 AM, toru wrote:
the BS170 gets extremely hot when I do so. At 8V, the current is 1.3A on both 15m and 17m
Hi とる, for both 17 m and 15 m LPF2 is in use. It looks like something is wrong there. A high current means a low load impedance towards the BS170. Looking at your sweep results I guess you was using a dummy load, right? Afaik for results from LPF scan and SWR scan a bit of rf is enough. This means not all the TX problems are affecting these sweeps significantly. (In such cases sometimes the results are not perfect but also not bad.) So far your sweeps are looking good. (Only the SWR is a bit high for lower frequencies. This could be a result from the real winding of T507. But your T507 should be good enough.)
- So please inspect the region of LPF2 carefully.
- The frequency response of your LPF2 seems to be fine. But we don't know the input impedance. So check especially C516 and the region of C516. Has C516 the right value? Is there a bypass with a low resistance, maybe inside C516? These failures would affect the input impedance a lot but not so much the frequency response.
- If you don't find a problem check the LPF PIN diode switching in RX mode.
73, Ludwig
|
Re: QMX Low Band - TX problem
I remember seeing something in the Operation manual about adjusting the CAT poll time for WSJT-X.
On page 60 of the latest manual version ....
Change the Poll Interval to 10 seconds, the default will be rather chatty with QMX which? probably is not a problem, but anyway I feel more comfortable with the less frequent polling. QMX has no capability to alter its operating frequency for example by itself, it can only do? so at the command of WSJT-X over CAT; therefore the polling is actually redundant? anyway.
I had to do that when testing with Fldigi, which I like to use for the ARRL frequency measuring tests. But of course, no transmitting going on there.?
If that doesn't do it, I'm out of ideas other than to check the CAT logging to see if the digi-ware is actually sending the TX start-stop-start pulse or the stop command before the time interval is up.?
Greg
On Mon, Jul 15, 2024 at 12:53 AM, Rob VK5ZIK <rob.at.theshed@...> wrote: Nothing has been changed at all..!!
I have just updated to the latest Firmware - with no change.
But plugging the KX3 in - there is no "pulse" at the start of transmissions.
Rob
VK5ZIK
|
Thank you Steve for your response. I was finally able to get the SWR on the QMX to show between 1.05 and 1.18. I rewound the T507 as outlined here
I do have a couple of follow up questions though:
1.) SWR on 80M (according to the QMX) is still 1.18. That's the worst band. Is that considered acceptable? These were all tested on a dummy load.
2.) My external SWR meter is still showing differently. On the 20M band, the QMX shows 1.05, but my external meter shows 2.1. How do we determine which is the "real" reading?
Thank you for your help so far.
|
Yes Allison, I do agree at 10W theu are fine, and can handle a poor mismatch. The death of these unit is being over driven, the amp has high overall gain as it is part of another project the SSB transceiver, which may never see the light of day, hugely complicated project.
I have seen other designs running these transistors up to 80W class C, they do get killed off with a mismatch.
I rather like this kit and used it in other projects.
KR
Andrew G8UUG
|
Re: QMX+ Build Report and Low Power Question on 40m and 30m
Okay, resoldered the 6m toroids, got them nice and toasty, the solder flowed nicely. I'm now getting 2.6W output which is broadly in line with everything else. Must have been a bad joint before but they looked okay. 30m and 40m still a concern. I checked the number of toroid turns and they're exactly as the manual says, I shall give the toroids another resolder. They look okay too, but obviously that doesn't necessarily mean anything.
The burning off of the enamel was the bit of the build which I was always least happy with, very little positive feedback that it's been done correctly. I checked continuity after every toroid but who knows.
Anyway, finally got it hooked up to an antenna and got the following results:
CW CQ on RBN
FT8 CQ and QSO on PSKReporter
And little does he know it, but PD5DLB was my first FT8 contact on my QMX+, I was received at +5, and I gave him a +3 report, 500km away.
Interestingly when keying down on CW on 20m I get 2.7W, but when transmitting on FT8 the meter showed 3.2W.
Still working on my CW copy speed so a CW QSO will have to wait a few more weeks/months(/ever?) till I've built up enough confidence.
Both the maps above look quite normal to me, I will have a bit more time towards the end of the week to do a proper test and compare with my QCX+, and QDX (pre-assembled). I also have a Z-Match ATU in transit so I can shift from my attic 20m dipole to my attic G5RV-JR (jury is out on how well that is going to work...) to hopefully get on some different bands (although 40m not looking so promising at the moment).
|
QMX rev4 60m-15m build TX problem
#qmx
Hello everyone.
I'm having a problem with the QMX rev4 12V build and can't solve it. I'd appreciate some advice.
I can't transmit on 15m and 17m, and the BS170 gets extremely hot when I do so. At 8V, the current is 1.3A on both 15m and 17m, and about 0.7A on a normal 20m. The SWR value in the Diagostics menu changes randomly from 1.3 to infinity. There doesn't seem to be a problem with the SWR sweep and LPF sweep.
I searched the Groups topics and the wiki, but I couldn't find any articles that could solve the problem.
I'd be grateful if someone could give me some advice. Thank you.
--
JI3VOV_toru
|
Quite a few questionably soldered joints on the pics so reviewing and if necessary using rework flux to re solder anything without the correct solder joint profile is a good place to start.
Not sure you can directly measure power at the BS170s on the internal meter. It’s measuring voltage and so should be across 50 ohms. What dummy load are you using ? Is the radio software set for the band it’s built for ?
Start with power supplies. Identify the 12 and 5V and 3V (5351) power rails and measure/trace them to their major components.
|
Re: QMX Rev 1 works great but RIT tune rate doesn't, Hardware?
Hi Tim.
It sounds like your radio is working normally.
I'm not sure that you can alter the RIT tuning rate. Once you double-tap the "RIT" button, just rotate the "TUNE" encoder to set your RIT offset then single-tap the "RIT" button again to go back to VFO.
To cancel RIT, go back into RIT adjustment mode, if you're not already in it, and single-press the right hand "VFO A/B" button.
Cheers,
Ronan
MM0IVR
|
Re: QMX Low Band - TX problem
This is the setup - very basic.
The attached video shows the fault where the QMX drops out after a short (aprox 4 second) transmission.
In this video the "Pulse" when TX begins was not as obvious.
This morning it was very hard to catch the fault - this afternoon it is 2 out of 3 Transmission cycles.
Now that I am watching for it - it is happening on both the Hi & Low band QMX's. (But no sign of either the dropped Tx or Pulse on the KX3 - with same cables pc etc)
At the moment - it happens more often on the Antenna -but it occasionally happens on the Dummy Load as well.
As mentioned previously - different USB sockets, Cables, RF Cables, Power Cables & Supplies - make no difference.
Chokes etc on the antenna cable also had no effect.
The antenna is resonant - see SWR Meter in video.
Cheers
Rob VK5ZIK
|
It is true, one learns alot by building these. Hopefully Ron will see this. He knows alot about these radios and can be a great help.
--
Wayne S.
KF7RCM
|
Re: Neq QMX+ Loud Tone all bands
#qmx
Hi Tonio, did you solve the problem? today I finished my qmx plus, I have the same problem of the audio tone in reception on almost all bands except, 160-11-12 meters, where receives clean! the other bands I have reception but strongly disturbed by the cursed tone! any advice??
|
Re: QMX Low Band - TX problem
Nothing has been changed at all..!!
I have just updated to the latest Firmware - with no change.
But plugging the KX3 in - there is no "pulse" at the start of transmissions.
Rob
VK5ZIK
|
Re: QMX Low Band - TX problem
Well that surely is odd.? Has anything changed recently like the firmware levels on the QMX 's or the OS's running on your older toughbooks or the versions of WSJT-X or JS8Call?
I haven't looked at the CAT logging function available on the QMX family nor am I familiar with the CAT protocol per se to be able to know what to look for exactly. Though some pattern in the CAT exchanges might be discernable based on the odd TX drop and reappearance behavior.
Hopefully others in the group might be watching this thread and could help out.
On Sun, Jul 14, 2024 at 9:29 PM, Rob VK5ZIK <rob.at.theshed@...> wrote: G'Day Greg
Using the Hardware TX Diagnostic Test - the TX Bargraph is a steady switch on/ switch off (The result is what I expect)
Having gotten totally confused - I have gone through this morning logically retesting everything that I can think of..
Using WSJT-X & JS8Call on both my laptop (Panasonic CF-31) & Tablet (Panasonic FZ-G1) produces the "pulse" at the start of the transmissions.. this is occurring on BOTH the Hi & Low Band QMX's
It is there regardless of which USB socket or cable I use. Sometimes the very 1st transmission is a clean switch on. (No pulse)
Occasionally - rarely, & not at repeatable in
tervals the LOW Band QMX does not complete a full TX cycle on the on 20M Band (Dummy Load or antenna makes no difference).
This morning I watched every Transmission (I think) for a full hour & it didn't drop out once - Frustration..!!
It has probably always done it & I haven't noticed. When it does drop out, it transmits normally for around 3 to 4 seconds then the bargraph drops to zero & no power output. The switch to Rx & next cycle are fine.
QRZ tells me I have worked 210 QSO's through 42 Countries since May - so the QMX's are working - It is just a minor glitch that I am trying to get my head around...!!
Though the occasional Tx failure after 3 - 4 seconds is obviously not right.
I have attached a short 5 sec video showing the "Pulse" at the start of the transmit sequence.
Rob
VK5ZIK
|
Hello, I recently assembled a 20m QCX+ kit (including TCXO and AGC add-ons) and am having some strange problems with it. Many measurements are abnormal and fall far outside what I'd consider normal variations.
1. I have no RF output power, as measured by the rig's internal tool. I have continuity across L1-L3, and the RF power measurement at the BS170 drain is 5.2 watts. Strangely, there is a huge power drop across the series capacitor C29 in the LPF: the power measured at the bottom pin (when the board is oriented so that "QRP Labs" is right-way up) is 5.2 watts, but on the top pin it is only about 0.15 watts. I replaced C29 with a different 104 capacitor but saw the same behavior.
2. There is no volume on receive. Even on a strong signal, such as the 20m FT8 frequency 14.074, there is nothing audible. Touching a lead to the Clk0 pin of the Si3531 makes some scratchy noise audible. This is one of the strangest issues - when the kit was first assembled, signals actually were audible (though still unusually quiet) and now the problem has gotten worse. I suspect there was some issue with the initial build that was exacerbated when I soldered on the jumpers for the breakout board.
3. Voltage measurements in many points in the circuit are wrong. Using the internal DVM, I measured all the points listed in section 6.4 of the assembly manual. The following measurements are abnormal (all others are within seemingly normal variations):
- IC5: pin 3 is 1.5v, pin 5 is 1.5v
- IC6: pin 3 is 2.77v
- IC8: pin 3 is 0.28v, pin 5 is 0.39v
- IC9: pin 3 is 0.04v, pin 5 is 0.35v
- IC10: pin 6 is 1.06v
- LCD: pin 3 is 0.91v, pin 4 is 0.04v, pin 6 is 0v, pin 7 is 1.3v, pins 8-11 are all 1.4v, pin 15 is 5.39v
- T1: pins 5-8 are all 1.7v
- C43: top pin (closest to IC4) is 1.5v
- C44: top pin (closest to IC4) is 1.95v
- C46: top pin (closest to IC4) is 1.42v
I have had a lot of fun with the kit, but I'm a bit disappointed it's not working better. (I am a new kit builder, so it's quite likely I just made some newbie mistakes.) Any ideas on what to test or look at next are very much appreciated. I'm also including pictures of the top and bottom of the main board, in case it helps.
|
Re: 2024 Flight of the Bumblebees
One year Dave Yarnes, W7AQK was taking me back to Phoenix to catch a plane home after Ft. Tuthill hamfest. We stopped and operated Bumblebee #72 from Bumblebee, AZ. Fond memories. Doug, KI6DS
|
Donald S Brant Jr
Andrew Lenton
Bruce Akhurst
Rob VK5ZIK
