Re: How to count and identify carrier frequencies?
Posted: Wed Mar 15, 2017 2:45 pm
For your use it it is not important to have a precise value of attenuation to the tenth of a dB like it is necessary for measurements, but that the Pi or T Attenuator used, which consists of 3 resistors, matches the impedance of your cable/receiver/antenna.
An ATT overview and explanations can be found here http://www.radio-electronics.com/info/r ... values.php
A DIY design proposal for a multiple stage ATT from QST here https://www.arrl.org/files/file/Technol ... nuator.pdf which should work up to VHF/UHF, since it makes more sense to be able to switch the attenuation on/off than having to unsrew the attenuator.
More guidance and resistor tables for 50 and 75 Ohm here https://translate.google.co.nz/translat ... edit-text=
An ATT calculator to calculate the required resistor values and optimize them to available resistor values and tolerances is here http://chemandy.com/calculators/matchin ... ulator.htm
There are also costly variable Attenuators available which cannot be built by yourself.
However for satellite IF reception purposes cheap variable 0-20 dB are available, which are unlike the high quality ones for labarotory use, not designed to be adjusted to often e.g. https://www.amazon.de/SAT-D%C3%A4mpfung ... B0020JC69C.
An ATT overview and explanations can be found here http://www.radio-electronics.com/info/r ... values.php
A DIY design proposal for a multiple stage ATT from QST here https://www.arrl.org/files/file/Technol ... nuator.pdf which should work up to VHF/UHF, since it makes more sense to be able to switch the attenuation on/off than having to unsrew the attenuator.
More guidance and resistor tables for 50 and 75 Ohm here https://translate.google.co.nz/translat ... edit-text=
An ATT calculator to calculate the required resistor values and optimize them to available resistor values and tolerances is here http://chemandy.com/calculators/matchin ... ulator.htm
There are also costly variable Attenuators available which cannot be built by yourself.
However for satellite IF reception purposes cheap variable 0-20 dB are available, which are unlike the high quality ones for labarotory use, not designed to be adjusted to often e.g. https://www.amazon.de/SAT-D%C3%A4mpfung ... B0020JC69C.