Do I need to install RF terminator at the end of RF attenuator? Let's say that max power output for RM port is 50W and I'm using 100W 50dB attenuator. What if I was using 50W 40dB attenuator? Is there a possibility that without proper RF load some power may reflect from the end of attenuator?
Electronic – RF load (terminator) at the end of RF attenuator
attenuatorimpedance-matchingloadRF
Related Solutions
You need power resistors (e.g. from Ohmite). Simple, not that expensive (~$5 US).
I wouldn't mess around with the regulator.
EDIT: As @Alan Christopher Thomas pointed out, this will get hot. For extended use (more than a few seconds) consider an additional heat sink.
A Smith Chart is not so much an attenuator design aid
as a means of evaluating and adjusting a design.
So - see attenuator articles below and then Smith chart articles.
Carbon resistors may be carbon film or carbon composition?
Carbon film are not suitable for UHF work as they are formed by cutting a spiral track in a carbon film cylinder, so have very substantial inductance.
Carbon composition have a solid carbon body and may be suitable for UHF work depending on other factors.
UHF Attenuators:
Attenuator design tutorial - looks good.
Interest - Commercial products
What is a Smith Chart?
Wikipedia gives a better than average concise summary:
From here
- The Smith chart, invented by Phillip H. Smith (1905–1987),1[2] is a graphical aid or nomogram designed for electrical and electronics engineers specializing in radio frequency (RF) engineering to assist in solving problems with transmission lines and matching circuits.[3] Use of the Smith chart utility has grown steadily over the years and it is still widely used today, not only as a problem solving aid, but as a graphical demonstrator of how many RF parameters behave at one or more frequencies, an alternative to using tabular information. The Smith chart can be used to represent many parameters including impedances, admittances, reflection coefficients, scattering parameters, noise figure circles, constant gain contours and regions for unconditional stability, including mechanical vibrations analysis.[4][5] The Smith chart is most frequently used at or within the unity radius region. However, the remainder is still mathematically relevant, being used, for example, in oscillator design and stability analysis.[6]
Somewhat gentle introduction - 27 page powerpoint intro - still gets deep quite quickly BUT a Smith Chart can be very very useful with almost no maths or numerics involved.
Superb Smith Chart resource - essentially an index of indexes - breaks subject up into sections and provides many references for each.
Another good list of references
Smith Chart tutorial from Maxim - reasonable "dense" but looks understandable.
You'll understand this once you've read it :-)
Related Topic
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- Electronic – Circuit for turn on a led when load connected
- Electronic – RF 50 ohm dumthe load PCB design
- Electronic – 50 ohm Dumthe Load With 50dB Attenuator
- Electronic – Understanding L-Pad attenuator
Best Answer
If your attenuator is beefy enough, you should be fine without a terminator. If a signal does bounce off and come back, it will be attenuated by 2x the value of the attenuator since it passes through the attenuator twice. Say, if you have a 50 dB attenuator, a signal that passes through the attenuator and reflects back should be attenuated by 100 dB. So some will reflect, it's just a question of whether it is small enough to cause a problem or not. 100 dB return loss is pretty darn good even for a terminator. The return loss of a loose connector is probably worse than that.