OK, Here Is something I have been curious about when I see benches full of meters,testers, etc and only one coax connection to a radio.
How does having multiple coax jumpers affect the antenna SWR? Say you have a radio, amp, power meter, switch between antenna and dummy load, freq injector for alignments, etc.. that 's a lot of 1-3 foot jumpers.
Does coax length really affect things for a base rig?
Ok, I got slammed last time so I'll rephrase it so the RF Kops don't crash this thread again...
A lot of bench equipment may not be all connected...it may just sit there only to be pulled down and used...some devices pull power from the plug all the time for the heating and calibration; temperature and themal as well as instant start with little wait time for stability reasons - it can be a considerable drain of a budget, or a generator - depending on whom is, and where this is - all taking place.
But, if you pay closer attention to those "Benches" (Ahemn@Martin) they have a jumper to a box that is a switcher - it connects one device and branches off to others.
At least they should...
Some of those switchers have branches that go to a Tee fitting that is set up to "sample" the RF going thru it, terminated to going into a Dummy load or an antenna. That let's you see the signal thru whatever means they want to process and view it.
Yes, Coax is a connection from one to another - but with each connection - comes the price of insertion loss - it can get quite considerable as you expand the number of connections - not necessarily just the length of them. Part of the insertion loss is an impedance transformation too - so each connection generates a reflection due to itself.
Now back to why I said what I said earlier -
Don't take the stuff you see in their "pictures" or vids of their bench equipment as faithfully installed properly and for granted. Because unless they really need to show you something - I'd like to think common sense lines of thought as; they don't want to damage their finer pieces of equipment - they'd rather keep it offline and unused and protected from potential damages from the equipment that they are investigating. Thinking - well you certainly don't want any high power RF signal entering into equipment that is only set up for low level signal sniffing...that would be suicide...So while the edits and cutaways and fades and blurs are for the reason to them to shift focus on one piece of equipment to another and back to the task at hand of the radio under examination...that is their means of showing off their works.
Now this is not meant to slam all - just YOU NEED TO BE AWARE OF DECEPTION. (After all you did ask the question and you raised up some very valuable lessons to be learned here...) Any good tech, knowledgeable in their field, would be more than happy to talk about the device used for testing - they just can't do it for the vid, post, blog or streaming - is for the subject the audience wants to see - so unless it is about the scopes ability to use X, Y and Luminance to show you fancy ray tracing - it's usually about a device the scope is being used to show the issue of...
So, while I tell you of the PREVIOUS Post - you should consider the premise of that post. For in many cases the equipment that they have may not be "certified" or even new, or working - they need to prove that to you - not just to those that need to see proof - they need to show the viewer what it does and why it is even used for the shoot.
Because in some ways, it's a ego stroking for their benefit to show others that they have equipment on hand. But what they may not tell you is, if they even know what purpose it is for, let alone how to use it.
