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I have both of the above combinations and they work well with an Agilent MSO-X 3104A. The N2744A is more convenient, but the 1103 allows the P6249 and other active Tek probes (with TekProbe II) to be used with any equipment (e.g., spectrum analyzers, non-Agilent/Tek scopes, etc.).
I like the Tek 1103 too for versatility, but have you swept it up to 2 GHz? I haven't tried it (my fastest TekProbe active probe is probably 1 GHz, and I typically use it with slower differential probes), but I would be worried about skin loss and reflections introduced by the extra two BNC connectors in the signal path. I'd expect the Agilent/Keysight adapter to be better.
You have a good point. I haven't swept it up to 2GHz, and my MSO-X 3104A only goes up to 1GHz.
However, if we assume the probe behaves the same in both scenarios, then we're only talking about the added effects of a BNC jumper from the 1103 to the scope. I don't have a VNA to do a detailed analysis, but I *can* sweep it on a 8595E spectrum analyzer with a tracking generator.
The following is using Pomona 2249-C-24 jumpers, which is a RG58C/U 50R 24" BNC jumper of reasonable quality. Admittedly better ones are available.
The SA has N to BNC adapters on it. The SA display is normalized using one 24" BNC jumper from TG output to SA input.
Below is a sweep where the TG is connected to the probe input on the 1103 through the normalized cable, and the 1103 output is connected with a second 24" jumper to the SA input. So, this sweep represents one run of 24" BNC jumper. It's about -1.3dB at 2GHz, which I would consider tolerable. Using simple extrapolation, at 4GHz it should end up being around -3dB which is also the BW of the P6249.
Because I had it laying around, the second sweep is using a no-name N to SMA jumper, with an SMA to BNC adapter on the 1103 end. Better, but I'm guessing it's probably better coax.
I also checked the N2744A by itself, inserted at the SA input, and it is hardly even noticeable. I didn't bother to attach the sweep here.
An interesting project is a mini TekProbe II power supply, like this one:
https://www.eevblog.com/forum/circuit-studio/example-project-tektronix-tekprobe-adapterbreakoutIt has an absolutely minimal transmission line like the N2744A, but is not tied to a specific scope manufacturer. I didn't get the impression the OP was looking for a sub-project.