Help me identify this dongle?

[pbarton]

Bought a scope recently and this device was in the lid.
Can you identify what it is, preferably with a manufacturers name/model number?
I suspect that its missing a probe (with a TNC connector) of some description.
The only marking is 'SMA 13'

[pbarton]

Initially thought it may be a 'standard probe compensation network'.
However, a 'standard probe compensation network' is designed to give the probe a flat response across a wide range of frequencies.
This device contains a tuned circuit, which is unlikely to give a flat response.
Looks quite old, could date back to 1960's or 1970's?

[pbarton]

Connected it between an oscillator and a scope.
It appears to be a low pass device. No attenuation at frequencies below 1MHz.
3dB point around 3MHz.
So, maybe it is a ‘probe compensation network’?

[magic]

I think you would have more luck moving this thread to the RF subforum.
There should be a button for that at the bottom of this page.

[StillTrying]

It looks like a TNC connector version of these.  https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=8613

[pbarton]

As THORlabs are selling low pass filters, as a front end input for a scope, then I have to assume that there is indeed a market for a low pass probe.
I don’t think that I have ever encountered one before.
Probes with BNC connectors are the norm nowadays, although I have some old Tektronix P6006 probes using the PL-259 connector.
I don’t think that I have ever encountered a probe using a TNC connector before. Has anybody out there seen a probe using a TNC connector?

[szoftveres]

Reminds me of the dongles that allowed cable viewers to watch HBO on analog TV sets in the '90s.
HBO came through the cable network along with all other channels, but it came modulated with a 2-3MHz signal, so that it was unwatchable for the general public.
HBO subscribers got a small dongle that they had to install in series of the antenna cable, that filtered out this particular signal. It was a very simple filter circuit, so it was often replicated by "pirate" HBO watchers.
Couldn't find a picture of a legit one, but here's how the pirate versions looked like::
https://translate.google.com/translate?sl=hu&tl=en&u=http%3A%2F%2Fwww.szetszedtem.hu%2F193hbo%2Fdekoderek.htm