Beehive vs. Tekbox EMC probes and amplifier

[matthuszagh]

I'm looking for an EMC probe set with an accompanying preamp. Both the Beehive (probes: https://beehive-electronics.com/probes.html, amplifier: https://beehive-electronics.com/Amplifiers.html) and Tekbox (https://www.tekbox.com/product/tekbox-tbps01-emc-near-field-probes/) look nice.

From a quick read-through of the datasheets, the specs look pretty similar. But, the total price for all probes + amplifier is much less for the Tekbox than for the Beehive set. The Tekbox set also comes in a wooden box, which is nice.

Any opinions on either of these products, including thoughts on one vs. the other? Or, are there other products that people prefer?

[nctnico]

Why do you need a preamp? I never use a preamp with near field probes together with a spectrum analyser for EMC work.

This cheap amplifier likely performs better compared to the amplifiers you linked to as it is build around one of the lowest noise MMICs out there:
https://www.amazon.com/Jadeshay-Noise-Amplifier-50M-4Ghz-Amateur/dp/B0BTBZXHN4/

Cut a USB cable and solder the power wires to the amplifier and there you have your universal preamp.

[matthuszagh]

I'd like the increased sensitivity without needing to go to smaller resolution bandwidths. The DANL of the 8566 I'm using is probably higher than many modern SAs (though admittedly I haven't looked much at the modern options). Additionally, it doesn't have a built-in preamp and the sweep times for smaller RBWs is pretty slow in comparison to modern SAs that process the IF signal digitally, rather than with analog filters as is done in the 8566.

Thanks for that recommendation. Do you happen to know the IC it uses?

[nctnico]

Some pictures in this post:
https://www.eevblog.com/forum/rf-microwave/diy-emc-test-cage/msg4394122

The amplifier is the SPF5189

[pdenisowski]

Why do you need a preamp? I never use a preamp with near field probes together with a spectrum analyser for EMC work.

As someone else stated, a spec an with poor DANL can benefit from a preamp.  Also, many people use scopes for EMC work and (in my experience) this is a case where a preamp often goes from a "nice to have" to a "must have"

I also address the preamp question in my video on near field probes (beginning at 7:52)

[nctnico]

@pdenisowski: It would be nice if you could also measure the 'Amazon' pre-amplifier to see how it stacks up. 

[matthuszagh]

Several differences between the Beehive and Tekbox preamps: the beehive unit is protected against +/- 10VDC whereas the Tekbox unit does not say anything about this (at least not that I could find). Additionally, the beehive unit extends down to 100 kHz vs. 2 MHz for the Tekbox unit. But, of course, the beehive preamp is almost 600 USD, which is almost double the price of the tekbox probes and amplifier together.

[pdenisowski]

@pdenisowski: It would be nice if you could also measure the 'Amazon' pre-amplifier to see how it stacks up. 

"typical noise figure of 0.6dB, a typical gain of 19dB, and 23dB P1dB" ... all for less than 20 USD  🤔🤔🤔

[nctnico]

@pdenisowski: It would be nice if you could also measure the 'Amazon' pre-amplifier to see how it stacks up. 

"typical noise figure of 0.6dB, a typical gain of 19dB, and 23dB P1dB" ... all for less than 20 USD  🤔🤔🤔

Something has got to give. Looking at the spec of tha MMIC used in the cheap amplifier, I can see the gain drops off to about 10dB at frequencies around 2GHz. Likely the Beehive and Tekbox amplifiers have a flatter frequency response. So the latter are likely more useful as wideband pre-amplifiers. OTOH the cheap Amazon amplifier should add less noise making it more useful for doing EMC pre-compliance testing. From my experience frequencies below 1GHz (and more often below 300MHz) are where the biggest problems are.

[pdenisowski]

Something has got to give. Looking at the spec of tha MMIC used in the cheap amplifier, I can see the gain drops off to about 10dB at frequencies around 2GHz. Likely the Beehive and Tekbox amplifiers have a flatter frequency response. So the latter are likely more useful as wideband pre-amplifiers.

The annoying thing about the Tekbox was that the USB power input is right next to the SMA RF out connector, making it impossible to connect it directly into a spec an (see attached photo).  Power connector should have been on the side of the unit.

From my experience frequencies below 1GHz (and more often below 300MHz) are where the biggest problems are.

That's been my experience as well.

[pdenisowski]

Here are the gain and noise figure of the Tekbox preamp (TBWA2 - 20 dB version, measured with a R&S FSW spectrum analyzer and the FS-SNS (smart noise source)

[matthuszagh]

Well it sounds like their "specifications" are more like typical performance and that typical performance really isn't so typical, considering this is a good deal worse than the spec sheet. Good to know...

[_Wim_]

@pdenisowski: It would be nice if you could also measure the 'Amazon' pre-amplifier to see how it stacks up. 

Hi, a while ago I measured another Chinese preamp (see pictures attached) with an HP8970A & 346B noise source, and it did meet it spec quite reasonable.


Spec according to Ali-Express:

Gain: typical value 31dB-0.5G input output impedance: 50Ω
Maximum output power: P1db 11dBm-0.5G
Input signal: <0dBm (>0dBm input signal has been distortion)
Bandwidth: 50K-2GHZ (different gain in different frequency)
Noise coefficient: 2dB-0.5G

As I did not want to bother writing an application for the HP 8970A, I just used in XY plotting outputs. My picoscope does not have a blanking option, so the retrace is also visible.

Plot is from 0 to 1.6GHz (so 160MHz per division)

Bottom trace is the noise figure (1dB per division): noise figure stays below 2dB up to 1GHz, and never goes above 3dB.
Top trace is the gain (4dB per division): gain up to 800Mhz is fairly flat and around 32dB and drops to 25dB at 1600MHz.

For only 14€ including shipping, this is quite a useful amplifier.

I also have one based on a SPF5189 that looks like the one in the attached picture, when I have some time in the lab I will try to measure this one also.

[_Wim_]

I also have one based on a SPF5189 that looks like the one in the attached picture, when I have some time in the lab I will try to measure this one also.

Also this amplifier seems to reasonable meet is specs (and the specs of the SPF5189). I am picking up some noise in the lab, the spikes on the noise factor come and go. For about 4€ including shipping a very useable device also.

[pdenisowski]

I am picking up some noise in the lab, the spikes on the noise factor come and go.

Not much you can do about direct pickup, but noise figure is one of the few measurements where I use a proper torque wrench to tighten connectors    

It's very easy to get screwy NF results from environmental noise, especially if your lab is anything like my lab.

[_Wim_]

but noise figure is one of the few measurements where I use a proper torque wrench to tighten connectors    

Yes, I do to. I did try if some pick-up was via the power supply lead by adding a  few ferrites, but that did not help.

Anyway, the result remains useful typically, even with the noise pick-up

[coppercone2]

I say beehive they put a switch on the amplifier and it has better connectors

you will never get the tekbox powered up, it looks like it has that esoteric usb connector on it

[pdenisowski]

you will never get the tekbox powered up, it looks like it has that esoteric usb connector on it

It's a standard USB Mini-B connector (not sure if that counts as "esoteric" these days )   It did come with a cable too.

The probes and preamp also all came in a very nice, high-quality wooden box:  I was kind of surprised by that.

[_Wim_]

Also this amplifier seems to reasonable meet is specs (and the specs of the SPF5189). I am picking up some noise in the lab, the spikes on the noise factor come and go. For about 4€ including shipping a very useable device also.

It does seem to be a hit an miss with these boards. A friend of mine bought 2 board from this seller (https://www.aliexpress.com/store/2961268?spm=a2g0o.detail.100005.2.623e2421xlV5yH) and the response looks completely different. NF >3db but gain is a little flatter. Visually his 2 devices look identical to mine.

[nctnico]

Are these using the same amplifier? If the gain is flatter then I doubt it. Or there is something wrong with the boards.

[_Wim_]

Are these using the same amplifier? If the gain is flatter then I doubt it. Or there is something wrong with the boards.

I did not desolder the shield, but I expect the amplifier will be labeled as an SPF5189 (for whatever that means of course)...