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Really Weird Twisted Sister Transformer.? This is the 12-volt version of the Wierd Twisted Sister Transformer for 9 volts.

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This is in the transformer manual introduction:

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73

Evan

AC9TU

What does the acronym 'RWTST' mean, or translate into?? Mr Google has not been helpful.

Hi Yoon,

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I was inspired by your post and tried myself with MFJ1720, the major problem is RFI. Have you seen RFI problem in your handheld setting?

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I can put battery in my pocket to reduce weight/volume and I agree ATU is not needed if you tune the antenna first.

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73,

Wei AG6AQ

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Elapsed time 3 days...

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--

Allison
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Post online only,?
direct email will go to a bit bucket.

It seems any photos attached to a thread are gone after a couple of weeks? So instead of posting my handheld QMX photos here again, I recommend you to visit my QRZ page to see how I'm operating QMX as HT -

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I have integrated it with the battery (3s1p 14500 li-ion cells with BMS), the internal speaker (though not much useful for noisy outdoor), and the plugin single lever cw paddle. For the whip antenna and the reel counterpoise wire combined with the QMX's built-in SWR bridge, I don't need an ATU.

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73,

Yoon KM6KJI

Hans

Could you take a moment to let us know the status.

I'm sure there are lots of eager to get it.

Thanks

Ludwig, thanks again for reply! The ?QMX QMX_plus Startup is good advise.

I will try to measure some of those voltages and the currents as well.

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But still, I do not understand how all this happened.

A full working equipment stops working by just pressing some buttons of the user interface.

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The shutdown process did not show the shutdown message which is usually visible for about one second.

Instead, some message, possibly the shutdown message, flashed on the screen so quickly that I could not read it.

Then everything dark. Forever.

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How could this be caused by some hardware failure??

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73 Matti OH6BEX

On Fri, Feb 21, 2025 at 06:11 PM, Wei AG6AQ wrote:

Somehow, handheld HF is an under-served market segment.

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Try putting a simple 50-150cm whip antenna on an HF TX and then

measure the performance / narrow bandwidths / low effiency / variable

impedance due to numerous external factors whilst actually operating.

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Interesting and educational , but you'll soon move on ;-)

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[Same practical issues for 27/28Mhz/50Mhz HT's, and why barely

anyone bothers with their EDC operations].

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Just stick to throwing a wire up a tree / convenient sky hook with a

mini rig.

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- Andy -

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So, what I did while using an old crystal controlled transmitter, combined with an SDRplay RSP-1, was to put an RF triggered TR switch between them. That could be done with a transceiver like the QMX too. I used the 4SQRP K8IQY Magic Box for that. The SDRplay receivers are great receivers all by themselves.?

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73, Dan - W2DLC

This might interest some. It could be used with a switch that turns this receiver's RF input off when the transceiver is transmitting. Several companies make these switches.

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Somehow, handheld HF is an under-served market segment. I have seen some very nice modifications in this group and I tried myself but failed, I end up brought a KH1.

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If you have a full-time job and you want to chance SOTA, KH1 is your only choice for now. I buy KH1 not for this performance, but for its quick-deployment. Its 1.3m whip antenna performed very well, especially when you're on the roof of a parking structure.

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But KH1 doesn't support 10/12m(while having an over-kill battery runs for weeks). If Hans can add a small battery, a small ATU to QMX(10-40m)and turn it to vertical, it will generate some momentum. Let's call it QMX# since M stands for multi-mode/band.

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73

Wei AG6AQ

Perfect solution Joe, thanks for sharing. Will keep your idea for when I get my QMX+

Cheers.

Gert

Thank you all, for your valuable replies! I did, indeed, only read the QMX docs - even though it is mentioned on various locations that one design is based on another so now I have to ask myself why I did not use that obvious sources of information...

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On my superhets, I do use that buffer-board on the IF with great success, using the not-so-cheap Airspy-HF, I have great signal quality to work with, be it in GQRX, SDRangel, GnuRadio or even feeding it to flgigi / wsjtx after converting it to audio. Most of the time, working on SSB, I just use the panadapter do have the signals on the band in view - and checking out some new signals while working a pileup...

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I do now have a lot of information to work with - and a lot more manuals to read. I even found the longed-for block diagram. That, besides all the real-life necessities, should keep me busy some weeks.

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If someone has anything to add to: Please feel free, I absolutely appreciate it! I might come up with more questions down the road... and hopefully with a nice solution at a later stage!

Hi,

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It can be done using an electronic T/R switch in parallel to the antenna port and controlled by a PTT signal.

I have used this with several QRP radios feeding a RSP1A SDR.

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73,

Roelof, pa0rdt

The receiver gets RX_IN from Q508 in the upper middle of the final page of the schematics (page 5).

Q508 is where the transmitter is blocked from the receiver, though there will still be

a very strong signal on RX_IN when transmitting.??

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The receiver is on page 4, RX_IN goes into IC408 which steers the signal into the appropriate band pass filter,

IC402 selects the output from the appropriate band pass filter and has the received signal coming out on pin 9.

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So your SDR receiver could grab RX_IN, or it could try grabbing IC408 pin 9 and get it after all the local

AM broadcast band stations and (most of) the other amateur bands have been filtered out.?

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A buffer is a good idea, driving coax to your SDR receiver.

Mostly because you don't want a bare wire picking up other crud from the SMPS's and such.

No buffer would probably work fine, an extra 50 ohm coax load on RX_IN would drop the received signal

for the QMX by maybe 3dB, or half an S unit.

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You might want to use the "RX" signal on page 5 to desense your SDR receiver somehow,

perhaps by clamping the output of your new buffer when "RX" is logic low (0v).

"RX" goes low when transmitting, logic high (3v) when receiving.

Seeing some of the transmitted signal on the SDR could be a good thing,

it will tell you exactly what the receiver is tuned to.

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Your SDR receiver will inevitably see a very strong signal from CLK1 and CLK2 going into IC403

a few KHz away (12 KHz?) from the received signal.? Since they are at the same frequency?

but 90 degrees out of phase, they will be seen as a single signal.

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Using a cheap RTL-SDR type receiver for your panadapter might be sufficient.

If it works well, I'd expect such a solution to be very popular with QMX users.

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Jerry, KE7ER

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On Fri, Feb 21, 2025 at 07:15 AM, <410733@...> wrote:

This tread has hit a nerve.? I plan on doing something like this with my QMX+.? Proposal is to use a hi-z input buffer board at the receive frequency inside the QMX+ and send it to an AirSpy Discovery Plus mounted internally in the QMX+.? I can then use either HDSDR or SDRSharp as a pan adapter *and* a second receiver on my laptop.? This would require two USB cable to the laptop - and I presume the QMX+ and the SDR program can control each other (OmniRig?)? I do this with my TS-590.? If I want to use the QMX+ portable without the pan adapter, I can.? The AirSpy unit is tiny and light and gets power from the USB port.? So it doesn't draw power if it isn't plugged into a USB port.

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Many variations possible here....? SDR dongles, programs, etc.? I like the AirSpy with SDRSharp - the DNR in SDRSharp is the best I've used.

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73 Dave kx3dx

See also this post from a few weeks ago.

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And if you want to do it fully externally,? the QMX does have a PTT signal output that you can use for rx/tx switch.