Is it better to use a bulkhead like this to run cable through concrete block or run a tube with heliax?
You didn't say what the intended use was (HF rig, VHF/UHF rig, repeater, ???), but generally speaking, you do NOT want to use any kind of extended-length UHF bulkhead feedthrough like that. The impedance of any "UHF" device is quite a ways off 50 ohms, typically in the 30-40 ohm range depending on dielectric. A 4-inch bulkhead would effectively be a 35 ohm Q-section on 440 - your 50 ohm antenna would become a 25 ohm load (2:1 VSWR) as seen by your radio.
Again, I don't know all of the details of your installation, but my first instinct whenever running cables through a wall is to use a Microflect port...
--- Jeff WN3A
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