Cheap vs. Expensive Near Field Probes (and realtime spectrum analyzers) - Page 1
Forum section: electronics / testgear

author: BA_ED
author_rank: Newbie
timestamp: August 03, 2021, 03:00:26 pm
content: I'd like to start debugging some EMC issues on a product my small company produces. We have interference between a device performing video encoding and a GPS unit, both fairly close to each other. GPS runs approx 1600 MHz 50 MHz BW so we would need a test setup that can measure up to 2GHz if not better.I'm looking to identify sources of interference so that I can combat them with shielding / RF absorption, wire twisting etc.I'm putting together a purchase list but we have a small budget at the moment. I think we just need to buy a live spectrum analyser (no SA function on my current scope) and a near field probe set.For the spectrum analyser, I was considering using a HackRF One or going upmarket to a SSA3021X or RSA306B (why does the HackRF One have a higher freq range up to 6GHz vs the 10x more expensive options? What's the downside?)I've found a few options for probe sets:Aliexpress special:https://www.aliexpress.com/item/32948421683.html- £25Beehive 101A:https://uk.farnell.com/beehive-electronics/101a/emc-probe-set-probe-amplifier/dp/2786222- £250Tektronix EMI-NF-PROBE:https://uk.farnell.com/tektronix/emi-nf-probe/near-field-probe-33db-6-ghz/dp/2853483- £800Given the simple construction of near field probes, what gives? Is there some magic pixie dust in the Tek probes or is it just the certificate / calibration which is adding all that cost?

author: 2N3055
author_rank: Super Contributor
timestamp: August 03, 2021, 04:26:34 pm
content: No magic dust. Just branding.There is also this:https://www.tekbox.com/product/tekbox-tbps01-emc-near-field-probes/I have TekBox TBPS01-TBWA2/20dB. It works very well, and amp helps sometimes.As for SA, SAs are proper instruments. HackRF can be used in a pinch, you can even use a cheap SDR USB stick to find something.Proper SA will have many tools that will help you.There is a lot of money between Siglent SA-s and Tek RSA306B. Also one is standalone instrument, other is PC connected. Also make sure to take into account what software you will get for free and what you need to pay additionally.Also Tex RSA306B is realtime instruments, and Siglent also have those. And Rigol and SignalHound (another PC based instrument)...You really need to fix the budget first.

author: BA_ED
author_rank: Newbie
timestamp: August 03, 2021, 05:15:05 pm
content: Thanks - so the £25 generic Aliexpress probes will perform similarly to the £200 / 250 / 800 probes?!On the topic of real time SAs, it looks like the cheapest option for 2GHz is Rigol RSA3030E @ £2700, with the Siglent SSA3032X-R being the next big jump up with a similar freq range but 25MHz realtime BW (compared to 10MHz on the Rigol) - though Rigol and Siglent both offer a range of instruments in this price bracket and upwards.Budget is undefined currently. Realtime spectrum analyzers seem to be really helpful in identifying sporadic signals, and I'm certain the extra cost is due to much more demanding RF design.

author: 2N3055
author_rank: Super Contributor
timestamp: August 03, 2021, 05:50:51 pm
content: Ali exprees probes might or might not.. But Beehive and Tekbox will do same job as expensive ones.Realtime SA will have very high POI (probability of intercept) and will detect fast bursts scaning SA wont.Difference is actually in digital part.Put together few potential candidates, compare datasheets and user manuals, and ask for clsrificationsThere arev few members that have equipment mentioned so they might help.

author: tautech
author_rank: Super Contributor
timestamp: August 03, 2021, 11:09:36 pm
content: Quote from: BA_ED on August 03, 2021, 03:00:26 pmYes proper characterization.I was getting some reasonable EMI probes in a nice little set from Aliexpress that came with a generic characterization for each probe however when Siglent offered their EMI promotion with a better EMI probe set and licensing thrown in for a quite reasonable cost for both I've stocked up on them.EMI probe set with license bundle:https://int.siglent.com/info/detail-40.htmlhttps://siglentna.com/wp-content/uploads/dlm_uploads/2017/12/SRF5030T_Users_Manual_122017.pdf

author: bdunham7
author_rank: Super Contributor
timestamp: August 03, 2021, 11:35:54 pm
content: Unfortunately that promotion just expired!I've been eyeing these EMC probe sets for a while, for diagnostics not pre-compliance, but I just haven't pulled the trigger. It looks like the TekBox, BK Precision, Siglent and maybe the Tektronix are all the same OEM? They sure look similar.

author: tautech
author_rank: Super Contributor
timestamp: August 03, 2021, 11:42:57 pm
content: Quote from: bdunham7 on August 03, 2021, 11:35:54 pmSeems so.However if the OP shops around he may find a dealer still holding promotional stock.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 04, 2021, 03:12:20 am
content: Maybe of interest:https://www.eevblog.com/forum/rf-microwave/ferrite-bead-pcb-track-current-probe/msg1724408/#msg1724408