RF explorer 6G combo  ghost signal 4.8-5.1 ghz - Page 1
Forum section: electronics / rf-microwave

author: gifsim
author_rank: Newbie
timestamp: February 08, 2020, 08:07:26 am
content: Hello to allI purchased 2 RFE 6g combo with firmware 1.29I noticed that in the 4.8-5.1 ghz band there is a ghost signaleven without connected antennasI also tried in different places thinking about interferenceI also tried all the possible settings (dsp etc.etc)but the ghost signal is always presentthere is an old topic from 3 years agoa forum user says it's a calibration / firmware problemwhich will be fixed with future updatesbut after 3 years the problem is still presentCan users who have RFE verify if they have the ghost signal in 4.8-5.1 ghz?does anyone have more info about it?I am attaching photos to better understandthank you allSimone

author: grizewald
author_rank: Frequent Contributor
timestamp: February 10, 2020, 05:39:20 pm
content: I'll check mine later on when I am at home, but I don't remember seeing anything like this.Are these genuine units?

author: gifsim
author_rank: Newbie
timestamp: February 11, 2020, 08:01:16 am
content: hi grizewaldyes ..... I think I have a genuine unitI attach some photos (I deliberately deleted the serial numb)i opened a tichet of assistance to rf explorerthis is the answer ...." Dear gifsim,Hi Gifsim,Thanks for contacting us.We confirmed your unit is ok. As you correctly report, the RF Explorer does not have a constant noise floor, same as all spectrum analyzers, due to sensitivity differences in the RF circuits. This sensitivity is limited by components used and cannot be improved at this price range.A future firmware version will enable a normalization floor to display the noise flat, but internally will still be there limiting the lowestYour RF Explorer Team,-------------------------Best Regards,Julián CalderónRF Explorer Team "it would seem that all rf explorer 6G have this "problem"perhaps in the various production lots the ghost signal is moved to another band / frequency ....I'm curious to see if yours displays the ghost signalwith a wide span it scans the entire band from 4.85ghz to 6.1 ghz(without connected antennas)what model of rf explorer do you have?thank youSimone

author: grizewald
author_rank: Frequent Contributor
timestamp: February 11, 2020, 08:53:43 am
content: My unit is a 6G combo, just like yours. Although I didn't remember seeing this issue before, maybe I never had it set to the same range as you have in your pictures.I can confirm that my unit displays the same non-linearity if I scan the same band.It's not really a problem for me as when I'm doing testing on antennas in the 5GHz band, the first thing I'll be doing as part of the testing is to normalise the the setup, making the non-linearity disappear.

author: gifsim
author_rank: Newbie
timestamp: February 11, 2020, 04:00:47 pm
content: hihow do you normalize the setup?it does not seem that rf explorer has released a firmware to do the normalizationdo you have the rf explorer signal generator for antenna testing?which directional coupler do you use for testing?

author: grizewald
author_rank: Frequent Contributor
timestamp: February 11, 2020, 04:30:55 pm
content: When you do antenna testing with the RF Explorer Spectrum Analyser, you also need the RF Explorer Signal Generator to create the full SNA configuration. Part of the process involves normalising the test setup. There's a great article describing exactly how this is done on the RF Explorer web site:http://j3.rf-explorer.com/43-rfe/how-to/139-sna-how-to-measuring-reflection-return-lossObviously you need the Windows application and a computer to do this. You can't run the generator and analyser in SNA mode without it. You also need some high quality SMA patch cables and a directional coupler with better than 20dB directivity at the frequency you're interested in (preferably better than 30dB). It's a shame the application only runs on Windows as I'm a Linux user, but I keep a Windows virtual machine for just the RF Explorer application. I make the patch cables myself from some military grade RG405 semi-rigid coax and solder connection SMA connectors. Or, you can buy patch cables ready made from Mini-circuits - just take a deep breath before you look at the price.I have a small collection of mostly Narda branded directional couplers which I've bought on eBay over the years to cover the bands that I'm interested in.The other thing you'll need is a high quality 50 Ohm terminator. It pays not to be cheap when buying a terminator as I've put my various terminators on my NanoVNA and the really cheap ones are just about useless for anything above 300MHz. The Rohde & Schwarz terminators I have are good to 12GHz and have an excellent return loss over the entire range.

author: grizewald
author_rank: Frequent Contributor
timestamp: February 11, 2020, 04:37:11 pm
content: I'd also suggest that you get some good quality male to female SMA adapters and put them on the SMA connectors on your analysers. It's much easier to replace the adapter when it wears out rather than having to replace the ones on the device itself.I also noticed that your analysers are just sitting there with open inputs. To protect them against overload from nearby signals from cell phones, etc. I'd suggest that you always keep a 50 Ohm terminator attached to each input when the devices are not connected to something. The inputs are very sensitive and even without an antenna connected, there's a risk from both static electricity and nearby transmitters unless you keep them protected with a terminator.As you can see in the picture I posted, I have both inputs protected with adapters and terminators as I suggest above.

author: gifsim
author_rank: Newbie
timestamp: February 13, 2020, 11:00:52 am
content: hi grizevaldyes you are right i must learn to mount the terminations on rf exp.otherwise I risk cooking itrf cable i am thinking of using rg402what do you think of the narda 3093 and 3094 directional couplers?https://nardamiteq.com/docs/097-COUPLERS.PDFI realize that if I want to get good measures I have to invest some moneythank youSimone

author: grizewald
author_rank: Frequent Contributor
timestamp: February 17, 2020, 06:29:45 am
content: Both RG402 and RG405 are good for the entire frequency range. The semi-flexible cables are great for this as they stay where you put them and have reasonable minimum bend figures.Those couplers quote very good directivity although they are type N connectors, which will mean N to SMA adapters to go to and from the RF Explorer kit. A necessary evil if everything else is type N, but adapters tend to add their own uncertainties to the measurements.I test the directivity of my couplers with the RF Explorer and signal generator so that I know how well the particular coupler performs. One of the best that I have for the 2.4GHz band is a Narda 4013C-10 2GHz - 4GHz. If you wanted to buy one brand new, list price at DigiKey is nearly $600! I think I paid $25 for mine.This is how the directivity plot looks for mine: