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[Diogo Nunes Pereira]

Hi.

Trying to figure out why some kind of ghost carries show up in my RF Explorer scans. Transmitters are Shure ULXD packs, but same happens with analog transmitters.

Attaching 4 pics (single carriers, both an none)

Thank you all in advance.

Cheers,

Diogo

[Scott Helmke]

Mine does that same thing.

[Scott Holtzman]

Mine does that same thing.

Mixing from the IF oscillator in the RF explorer???

[Don Boomer]

Which model RF Explorer are you using ... a silver one?  Which firmware rev?

[Diogo Nunes Pereira]

Which model RF Explorer are you using ... a silver one?  Which firmware rev?

Hi Don,

it's a WSUB1G unit (silver) running firmware version 1.28.

It's a 3G combo unit, today I'll try and see if the WSUB3G module does the same thing.

[Diogo Nunes Pereira]

Mixing from the IF oscillator in the RF explorer???

It's something that only shows in the RFE.

I'm running a continuos scan in a spare ULXD receiver in WWB, and nothing like that shows up.

Also, I've tryed to minimize it using a 6dB attenuator, fed by a splitter output. But the same effect also shows up with an antenna plugged directly into the unit.

[Scott Holtzman]

It's something that only shows in the RFE.

I'm running a continuos scan in a spare ULXD receiver in WWB, and nothing like that shows up.

Also, I've tryed to minimize it using a 6dB attenuator, fed by a splitter output. But the same effect also shows up with an antenna plugged directly into the unit.

Sorry for the short post, that's exactly what I mean.  The mix or heterodyne product is mixing inside the spectrum analyzer.  Putting a preselector on the front end could help since one of the carriers is probably out of the are of interest.  Front ends on these type of devices are almost non-existent.

[Diogo Nunes Pereira]

Sorry for the short post, that's exactly what I mean.  The mix or heterodyne product is mixing inside the spectrum analyzer.  Putting a preselector on the front end could help since one of the carriers is probably out of the are of interest.  Front ends on these type of devices are almost non-existent.

Thanks Scott. I've came to understand the images are alias of the original signal.

According to RF Explorer team in Google Groups support forum:

"These spike signals at 1.8MHz are called Image Frequency, and are visible only for strong signals with about 30dB attenuation for the images in the WSUB1G left-side connector.
However, you have a 3G Combo model and, as such, can use the WSUB3G right-side SMA connector including an advanced DSP mode to remove the spikes automatically for you. We suggest you use the right-side not the left-side connector in your 3G Combo."

https://groups.google.com/forum/#!topic/rf-explorer/3VSAWWy32MA

I've checked my WSUB3G module and images frequencies don't show up.

Best,

d

[Scott Helmke]

Mine is also a silver (direct from China) model, firmware 3.11.  I imagine if you buy the QC'd version from RF Venue you don't get this little bonus feature. 

[Rui Lisboa]

Thanks Scott. I've came to understand the images are alias of the original signal.
I've checked my WSUB3G module and images frequencies don't show up.

Best,

d

Hi Diogo,

I've had the same issue and the good people at RF Explorer Support stated that this was indeed an imaging issue.
The RF Venue's Explorer Pro (rebranded 3G combo with upconverter and a BNC connector) solves it with software filtering and it's definitely a required step up without emptying pockets.
Even the Signal Hound SA44B which is a more expensive unit exhibits a similar but equally annoying imaging issue although at 21.4Mhz since the IF is at 10.7Mhz.
I guess that things don't get much better than the 3G combo until the investment reaches TTI territory.
Diogo thanks for sharing this as it will prevent others to be baffled when they realize it. When I first stumbled into this I thought I had somehow toasted my SA´s input.
Rui

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