How about it? ? It is getting very hard to search and find posts just for the radio I have. ?

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Yeah, a mag loop will do a great job of attenuating not only the spurs or harmonics into oblivion----and almost that destination for your desired signal as well!!? ?I've seen efficiency figures of -10 dB.? ?

?

Hoping that's not true foryou.....

Gordon

Hi Bo

With my experience using mag loops, I would expect that the narrow tuning of the beast might effectively take care of any spurs or harmonics. I have one that tunes 40- 15, and unless the tuning is very close, I can't hear anything on RX.?

Brent

Good job W4OP!

Yes, good data makes all the difference, and I really appreciate all the excellent info presented here. I remember seeing an ad for an antenna which recommended a long feed line to keep the swr down. I fully agree, an LC match at the feed point? is the way to go. FWIW, the best all around simple multi band antenna I've used was a 40 meter doublet fed with parallel line and balanced tuner, followed by end fed with an LC? match. Just my 2 cents

Brent

Indeed I think the threads here have been much more informative than the Facebook group and those magic videos.

Mike

I don't think this is IMD per se. It looks to me like harmonics of the modulating tone. Those harmonics could be present in the tone itself or they could be generated by non-linearities in the audio chain.

For IMD measurements you need two tones with the pair centered in your filter passband and the tones must not be harmonically related. The difference between one of the tones and its adjacent product tone is the figure of merit for IMD. Your span and RBW are ok although if you have a lower RBW, 30 or 10 Hz, you will get better resolution and may see some close in products that are covered up at 100 Hz.

W

Most, if not all, of the design information presented on that FB group is simply wrong. The gimmicky transformer that is advocated works well only with truly resonant half wave wires and only on the bands on which the system is resonant. And even then it is not nearly as good as a simple LC tuner. The reason that group keeps going and propagating their rubbish is they systematically exclude and block anyone who produces actual data that refutes their ridiculous claims. Read the EFHW trail here and you will be much better informed than if you rely on those videos and the group chat.

WA8TOD

I think Arne has a BitX40 and the confusion is that the wire up instructions say to connect the 5-pin connector to the Raduino, but there no longer is a 5 pin header to match. Instead, HFSignals is currently shipping the same physical Raduino package for both the BitX40 and the uBitX, just with different software loaded. So, to answer the question, use the 5 pins closest to the blue pot to connect to.

=Vic=

Warren thanks,

I googled around and discovered I'm not the only one trying to prototype things with tiny chips. So, thanks for pointing the Adafruit one out. I'll order the Adafruit one or see what Digi-Key has.

Tom, wb6b

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Jim

Gordon,

"the uBitx is mounted on a PLASTIC upturned Dollar Tree desk organizer"

Well it looks good, anyway. I'm a fan of dollar tree stuff myself.

I have to take the long path and build a SA first, then I'll try the heavy metal and straps approach on my uBITX. Even if it improves things, it may or may not be enough. Then I'm going to see if the 15V suggestion actually improves the TX chain gain, without making a bunch of mods to improve the gain running at lower voltages, like 12v. And make sure it is a good solution, not one that leads to overdriving things and creating more spurious emissions. (I'll put a 9v regulator on my audio amplifier IC, before I go cranking up the voltage to the whole uBITX).?

I like the added relays approach, it should work. It is one of the simpler and doable solutions offered on these forums.

Tom, wb6b

I don't agree at all with that pragmatic rule. A transmitter has to have a clean output. Your TV may be interfered if it has an external low quality and high gain amplifier which is saturated by out of band signals whatever clean is your TX. On the other hand your TV may not be affected but you may produce QRM everywhere on the HF which,depending on propagation conditions, can be heard thousands miles away.

Hi Terry,

Now that we know about it, I suppose people should do what they can to mitigate it.

But I do wonder if, for us to build own equipment, only those who invest in thousands of dollars of lab equipment will be able to certify their creations and participate in the hobby (other than buying gear from established manufactures). That would be unfortunate.?

It sounds like the UK regulations are much more sensible and realistic.

Maybe the market will respond with low cost test equipment solutions allowing hams to make more of these kind of measurements (less than the cost of an antenna analyzer). That would be good with or without regulations, and advance the state of the art.

Tom, wb6b

Hi Allison,

"However most are run at such low loaded?Q they are not very useful for harmonic control"

Very good, a second and even better reason for not relying an L antenna tuner to help with harmonics.

Tom, wb6b
?

hi

i am rather mystified as to how the American ham test his rig to meet fcc requirements for -43 db

does he have to have a spectrum analyser

in the uk ofcom is rather more pragmatic - if you are not causing interference then your rig is ok.

i test mine by looking at my tv for interference. if my tv is not interfered with then my neighbours are almost certainly not.

73 de terry gm4dso

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No, the uBitx is mounted on a PLASTIC upturned Dollar Tree desk organizer. ? Sorry!