Hmm,ill have to do a qso and ask the other party to record so i can hear it.
Hi Takeo,
I don’t own a (Tr)uSDX, but based on similarities of hardware with uSDX, I hope that my result would help, related to the Third Order of Intermodulation measured on homebrew uSDX and modified uSDX with Two Tone Test.
KX3 result from ARRL for comparison = -30dBc
Homebrew gate modulated uSDX = -10dBc
Homebrew drain modulated uSDX = -20dBc
PE1NNZ claimed QCX-SSB (pre-uSDX from Hans QCX modification) = -33dBc
All details of my test:
73 from Pascal
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A lot of interting info! Thank you!
73, Takeo
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My pre-built shouldn’t have passed QC. The internal mic doesn’t work. Going to try to self-repair since it would cost about as much as a new one to return. I have good continuity with no shorts from Pin 1 to ground and Pin 2 to Pin 16 on the Mega. Appears to be a bad mic or it got too hot during the soldering process.
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The truSDX uses a rather clever modulation scheme that is claimed to mitigate class E non linearity. However, if you listen to one locally it sounds really dreadful. On the truSDX reflector they gloss over this by saying that it sounds fine at a distance. Just one of several comments that should be sounding alarm bells…
Hence my interest in seeing a two tone test on a spec-an.
If anyone local has a spec-an, I can lend you the radio and a two tone generator. SK10.
Hi Pascal
Your measurements don’t surprise me. Poor to very poor sounds about right.
I recently bought one of the TrUsdx models from one of the approved suppliers.
I have yet to test it. One radio of unknown type I heard on the air was awful (on ssb) but I was hoping that was not representative of these radios.
I remember an article in, I think, Ham Radio magazine in the 70s, about tripling ssb from 144 to 432 using a remodulation scheme, the voice waveform was first converted to an digital signal, then divided by 3, then fm modulated on a 144 mhz carrier, amplified at 144, then tripled, then remodulated by the original waveform. All about generating power at 432, with a view (I think) to using the technique to produce power on a higher band once the idea was proven. I think it’s true to say it did not take off, mainly because generating ssb on higher frequencies became much easier as new solid state linear amplifiers became feasible. I don’t know whether the scheme used in the Usdx series is at all similar but if the on air signal is not suitable for a crowded band it should probably not be used. And certainly not amplified.
I don’t have access to a Spec An but I do have a useful display on the Icom 7610 home station. When a signal looks wide on that, it is wide. With suitable attenuation it should be feasible to examine the ssb signal and assess it.
If nothing else it will become a backup lightweight CW rig, if it works ok in that mode.
Andrew VK1DA/VK2DA
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Audio sample. Internal microphone. 20m. Recorded locally. truSDX on dummy load.
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Richard’s @G3CWI audio sample sounds not too bad. One has to bear in mind that Manuel DL2MAN constructed the radio primarily as an emergency radio. It was not the intention to compete with a commercial radio.
I like the tr(u)SDX because
- it is so small that it fits in a pocket,
- it operates on five bands (!),
- it includes power and SWR measurement
- it is able to both CW and SSB operation.
I agree that the audio/sound can be awful. However, I was able to make SSB and CW contacts. It is is hardcore though to make contacts with 3W in SSB. I primarily use it as CW trx. The AGC is slow, as mentioned above and it sometimes hurts the first fraction of a second if a loud signal comes in.
Compared to other rigs such as mountain topper or KX-1, the tr(u)SDX can not be beaten in terms of size, weight and functionality.
The main reason I bought the kit was because I could assemble the radio myself. I have learned a lot and it is just great to walk onto a summit and use a home-made radio.
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I have to agree with DL1GKC. While the (tr)usdx may be an attempt to put 10 gallons in a 5 gallon bucket , try to match it’s capabilities with any other radio it’s size and/or cost. CW/SSB in the palm of your hand, CAT control, I can use it with N1MM or my logging program, a speaker, albeit not a very good one, but if I forgot my earbuds, the radio is still useful.
We have gotten spoiled with inexpensive CW only radios, with no speakers, no CAT control, limited filtering, etc, that this rig includes. It’s a step change in capability and size. Accept it for what it is, and in truth, what it was advertised to be.
Given all it’s faults, I enjoy the radio.
Mike AD5A
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For 150 usd sounds alright to me.
Karlo
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I’ve now had an opportunity to listen to the transmitted ssb of a trUSDX and look at the spectrum on a RS918 radio that was lent to me for evaluation. As expected there is similar distortion to that in Richard’s recording on the resolved ssb and also a wide spread of distortion products across about 20khz centred on the nominal sideband. This was done using a dummy load on the trUSDX and a signal level of s9 on the RS918.
Listening on the opposite sideband and same carrier freq there were unresolvable distorted signals in time with the modulating voice but the signal was not understandable.
Yes, a remarkably capable and cheap emergency radio with nice receiver and keyer features esp on cw. Mine operates on 80-60-40-30-20m.
I have not looked at whether the amplifier bias adjustments change or improve the distortion on ssb.
73 Andrew VK1DA/VK2DA
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What sort of emergency situation do you envisage where this might be the best radio solution?
Three summit contacts achieved on 2m FM, and no further chasers heard.
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Great reply! I was expecting the Zombie Apocalypse.
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Not qualifying a summit is far worse than encountering a few marauding zombies.
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My use case is to keep it in my pack, with a 40m dipole and tiny key, in order to use if an activation is difficult to qualify.
I have a usb-c pd cable with powerpole connectors on the other end so I can power at 12v from a powerbank.
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1.When my primary radio fails
2. When my primary radio requires earbuds and I don’t have them
3. I can run this radio on 5V when my primary radio can’t
4. I have a CW only radio and need to make an SSB call
These come to mind off the top of my head, I’m sure there are more scenarios.
Mike AD5A
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The amateur radio definition of an “emergency” is fascinating.
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Hi Richard…
While in the context of this reflector, i.e. SOTA, my comments might appear to be only SOTA points related. The same points could apply in a hurricane, blizzard, tornado, lost, etc… Not just in the context of getting SOTA points, although that too can be an emergency of sorts:-)
One other point, the rig is also an SWR meter…
Mike AD5A
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