Nico, manual tuners normally have a "tune" position, which engages some sort of SWR bridge. When the SWR bridge in engaged, the rig sees a maximum SWR that does not exceed? between 2:1 and 3:1 (depending on the SWR bridge employed),? irrespective of the fact that the actual SWR seen by the tuner is 2:1 or 100:1. The low SWR (2:1 to 3:1) you see in the tune position while tuning will NOT kill your QMX finals, even at full power.
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You just key down your QMX with the tuner in the "tune" position, e.g. by using the "TUNE SWR" function in your QMX or by using a key, and turn the knobs to reduce SWR to a minimum (in most manual tuners this is achieved when a high-brightness? LED gets zero current through it).
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I have used exclusively homebrew Z-matches with my QMX and QMX+. I start by turning the knobs until the background noise is maximum (no key down), then I engage the tune position in the tuner and I simply key down at full power for a few seconds at a time, adjusting the knobs to get the LED brightness off. Then I get back to the "tx" position and start operating.
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Tuning can take up to half a minute or more with a new antenna, and sometimes I cannot get the LED off completely (meaning that the SWR is between 1:1 and 2:1 normally), but I have never blown a single QMX final.
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My2Cents
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72/73 de Enzo M0KTZ
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I am getting myself a manual tuner soon. I was watching some videos on YouTube because I had no idea how to use them. I saw people just holding PTT even with 3+ swr. How would I do it? Just quickly press my key and keep changing the settings on tuner?
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I agree with Chuck here: the more you use the rig on the air, the easier the whole zero-beating process will be for you. It's an instructive game.
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Alas, you don't need to literally "zero"-beat on a station outside of a packed contest, as nobody will beat you up if you are 50 or 100 or even 150 Hz off their TX QRG. That's why any CW rig has that nifty 'RIT' function, in the end.
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YMMV here, but running an audio spectrum analyzer on a mobile phone that costs 1k$, just to zero-beat a CW station on a ham rig that costs 100$, well, that looks like an extreme overkill to me.
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Hams have communicated successfully on CW for a century, well before cell phones were invented. What do we do if our phones gets out of battery? We stop playing radio??
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Ham radio is fascinating to me because it removes complications, rather than keeping adding them...
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My2Cents
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72/73 de Enzo M0KTZ
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I have been using Spectroid on my Android phone.? It works pretty well.
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An "Auto Tune" option would be nice in the QMX but in the whole scheme of new function priorities, it would be down farther on the list.
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Brien - KE7WB
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You might consider using an audio spectrum analyzer app on your iPhone. ?I sometimes use a free app called Sonic Tools SVM to listen to my RX audio and then tune my receiver to whatever tone I desire. ?I use this method when using a receiver that has a very wide filter. ?This particular app displays the audio spectrum but it also provides a digital display of the peak (maximum amplitude) frequency being received.
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Don
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Linear voltage regulator for QMX+
The manual and this group agree, that the QMX+ does like to see 12 V or less to have a long and prosperous live. Available here is 13.8V - as well in my shack, from battery or in the car. The small PA and a tuner which I plan to use in combination with the QMX do use 13.8V so keeping the main supply does make sense for me. Furthermore, I'd like to have an option to regulate the output power, which can be achieved by regulating the input power. Using an readily available switching power supply would have been an option, but that might induce unwanted noise, so I opted for a quiet linear voltage regulator. I couldn't find a ready-to use device, but I still had some time until the QMX arrives, so I build one. The circuit is straight-forward and the scrap-box did contain a nice housing and cooler that could be cut to size, so I got to work.
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Components:?
* MIC29512WT Linear Voltage Regulator from Microchip Technology
* Vishay 534-10K Potentiometer, with a nice? turning knob
* 2x 220?F 35V Elco
* 7.5 kΩ Resistor to VOut
* 75 kΩ Resistor to ground
* 0,28" Mini Digital-Voltmeter 3,5-30 V
* Switch
* 2 Lamp Terminals as strain relief
* 3x2 + 1x3 JST Connector
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The schematic is drawn in the datasheet of the power regulator. Using the two resistors, I get the desired regulation range of 6.5 V to 13 V. Between 11 V and 12 V there is about 3/4 of a turn, so the voltage can be regulated quite precise. I did connect the switch to the enable pin of the voltage regulator, so that input voltage is shown when power is supplied to the device - I plan to use that to control the system voltage. Output power is supplied as soon as the device is switched on. The LEDs, especially the green one are a bit bright for my taste, instead of fiddling with that tiny circuit, I opted to use a double layer of tinting film, which is intended for car windows. That film also covers the small imperfections of the hand-filed slots.
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The soldering work is really not the nicest in the world, but there's no shorts and the connections are good, so it does the job. The MIC29512WT is rated 5A, which should be plenty for the QMX+. It needs 0.7 V dropout, and has a max input of 16 V which does allow a near-empty car battery as well as an overpowered car alternator. One drawback might be, that this device may consume a few watts, in particular on lower output voltages. That's what the cooler is for and I'm not planing for a absolute minimal setup, so I can absolutely live with that.
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Yours, Joe, DJ0CHE
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Is it possible that you are over thinking things a bit? You should be able to get close enough by tuning for maximum signal loudness, with a 700 Hz'ish sounding tone. If the other guy keeps drifting up, or down, after you stop sending, that might mean you are guessing wrongly... I doubt anyone you work on CW will think less of you if you are off frequency a smidge. -Chuck Harris, WA3UQV On Thu, 20 Feb 2025 14:26:50 -0800 "Pierre Robillard VE3HQZ via groups.io" <probillard@...> wrote: To be clear the reason I'm thinking of getting "The Magic Eye" is
that it eliminates zero beating via the sound of the tones. I have
been playing a sound file of 700 Hz from my iPhone and adjusting the
frequency until they zero beat. Depending on band conditions,
adjusting the volume and probably my hearing ability to get an exact
zero beat on an incoming CW signal is not always easy.
Pierre
VE3HQZ
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Re: Anyone Recognise this GPS Antenna?
Jupiter GPS receivers are popular still for GPS locked oscillators as they have a 10kHz output
They normally sell quickly on eBay if you don't intend to use it yourself for this.
Andy
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Show quoted text
On 20/02/2025 21:56, Dave VE3GSO via groups.io wrote: Recently I was given an unused GPS antenna and a Rockwell Jupiter GPS receiver.? He thought they were purchased from QRP-Labs, but wasn't sure. Given the age of the Jupiter GPS receiver, the doccumentation I found is dated 1998, I'm not sure if this is possible.? I'll attach a photo of both.
I'm wondering if anyone recognizes the antenna. It is a shallow black plastic dome with a threaded mounting shaft on the underneath and a fair length of coax terminated in an SMA.? Is it passive or active? Any idea where I might find the specifications?
Dave
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Re: Antenna Tuners for QMX and QMX+?
On Thu, Feb 20, 2025 at 01:09 PM, Richard Dyer wrote:
however the QMX+ still goes into protection
Any of the switched-element tuners will generate very high VSWRs as they search for a tuning solution; a manual tuner much less so.?
The worst is toggling the high/low Z switch, it presents an open circuit to the radio as it switches over; the only VSWR limitation is due to the losses in the tuner.
The VSWR probably trips more readily on the higher bands because the return loss bridge has poorer directivity there, showing a higher than actual VSWR, or maybe the tuner doesn't present as good a match.
73, Don N2VGU
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On Thu, Feb 20, 2025 at 11:59 AM, Stan Dye wrote:
This makes the wire lay flatter against the outside of the toroid - but I think it is mostly cosmetic and doesn't likely change anything operationally.
I let it bulge a little, it allows some slack if you need to spread turns.
73, Don N2VGU
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Re: Testing for a dead QMX board
On Thu, Feb 20, 2025 at 10:07 AM, Nathan W wrote:
I don't have enough hands to hold the prescribed jewelers loupe whilst operating a soldering iron and scalpel.?
A headworn magnifier may be what you need.? besides freeing up a hand, it provides binocular vision. ?
I prefer these to the kind which pivot on the headband, they block both air and light.
73, Don N2VGU
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Re: Anyone Recognise this GPS Antenna?
Given the SMA connector I'd say it is simply an antenna, so passive.
A receiver from 1998 is unlikely to be considered a good one given what is available nowadays. It will be slow and GPS only so not GNSS capable. Others may be able to correct me on this.
--
Compton
VK2HRX
Sydney, Australia
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To be clear the reason I'm thinking of getting "The Magic Eye" is that it eliminates zero beating via the sound of the tones. I have been playing a sound file of 700 Hz from my iPhone and adjusting the frequency until they zero beat. Depending on band conditions, adjusting the volume and probably my hearing ability to get an exact zero beat on an incoming CW signal is not always easy.
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Pierre
VE3HQZ
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I was thinking of ordering "The Magic Eye" from Kanga Products....
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Pierre
VE3HQZ
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Anyone Recognise this GPS Antenna?
Recently I was given an unused GPS antenna and a Rockwell Jupiter GPS receiver.? He thought they were purchased from QRP-Labs, but wasn't sure. Given the age of the Jupiter GPS receiver, the doccumentation I found is dated 1998, I'm not sure if this is possible.? I'll attach a photo of both.
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I'm wondering if anyone recognizes the antenna. It is a shallow black plastic dome with a threaded mounting shaft on the underneath and a fair length of coax terminated in an SMA.? Is it passive or active? Any idea where I might find the specifications?
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Dave
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Finished my QCX mini build (20m) about a week ago and was only getting about 1.38 watts out of it so I decided to try Hans's tune up video from 4 years ago.? I took out 2 turns from L3 and then played with the winds on L1 thru L3 and was able to increase the output to 2.05 watts.? While adjusting the turns on L2 I noticed the first/last turn was crossed with the adjacent wind so I desoldered and removed the cross and its turn, then started adjusting winds to see if the power came up.? Well, the power out came up to 2.5 watts, but while I was fidgeting with the turns the power dropped to 0 watts and smoke erupted from ic TI37A2QDM/CBT3253C.? What did I do wrong?? I am not skilled enough to change the 16 pin IC so I'll probably just have to chock it up as a poor decision to play with the winds, although, did having the cross in L2 cause my low power out in the first place?? Any advice would be appreciated.
Rich, ad?sn
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Re: Trying to understand linear PA 10W construction
The following paper published at Designcon East back in 2005 by Steve Weir presents some interesting information on the effects caused by the interaction of multiple decoupling capacitors in power distribution networks.
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Thank you, Jerry,?
It appears that this issue is fixed.? I just made 40 restarts with IC401 replaced and suffered no very loud or very quiet starts.
Thanks to everyone who chimed in on the problem.? Learned to look for the ground connection, and that chip labels have a standard orientation with respect to ground, and that Hans draws the silk labels in standard orientation, except when he doesn't (eg IC407) where he puts an explicit pin 1 marker instead,
And thanks to Mehmet for the excellent photo which does help cement everything.
Now to figure out why the QMX+ thinks my antenna is better than NanoVNA does.
-- 73 -- rec -- ad5dz --
Roger,
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You have it figured out.
On my IC401, there's a shiny flat round dimple over pin 1.
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When holding an SOIC package such as IC401 such that the print is right side up,
pin one should be in the lower left corner.? Counting from pin 1 counter-clockwise
around the chip to go from pin 1 to pin 8.? The schematic has pin 6 grounded, if
you look closely with a bit of magnification (or at least better eyes than mine)
you will see an obvious connection to the ground plane around it.
You can check this connection with an ohmmeter to one of the big round mounting holes,
which are also connected to ground.? Pin 7 has VCC,? there's a labled VCC pin at JP106
near the far end of the front panel that you can check connection to.
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Try looking at the chip under whatever magnification you have with a very strong light.
Slowly turn the chip this way and that, at the proper angle the text on the chip (and the dimple)
should suddenly stand out.? The text is perhaps laser etched, not printed with ink which
could wear off.
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Jerry, KE7Er
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On Wed, Feb 19, 2025 at 03:00 PM, Roger E Critchlow Jr wrote:
Going to need some help here.? I'm replacing the IC401, the CS4334 DAC, because of intermittent bad audio output levels at startup.? But I need confirmation on the proper orientation of the chip.
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Correction:
JP103
1 ? +12V ? ? ? ?7.02
2 ? ADC_3V3 ? ? 1.19
3 ? LIN_REG_EN ?6.49
4 ? VDD ? ? ? ? 3.10
5 ? PWM_3V3 ? ? 0 ?
6 ? GND ? ? ? ? 0
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SVHFS Conference 2025, Call for Papers & Presentations
Here's an update on the SVHFS 2025 Conference;? Deadline for papers has been extended to March 17 Conference & hotel registration is open; details are in the attached file.
Thanks,
Robin Midgett K4IDC
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Brien - KE7WB
Donald S Brant Jr
Compton
Pierre Robillard VE3HQZ
rsmith
Robin Midgett