Antenna Length

Thread Starter

biferi

Joined Apr 14, 2017
390
I live in the USA so if I want to know how long a Wire will be in Feet to pick up a Frequency I do this.

Half Wave is
468 Over FREQ. in MHz.

Quarter Wave is
234 Over FREQ. in MHz.

Full Wave is
984 Over FREQ. in MHz.

Do I have all of these Right?
 

Papabravo

Joined Feb 24, 2006
21,158
For receiving, you tend not to worry too much about the actual length. It is for transmission that the length becomes important. Make the antenna to match your local geography and enjoy the listening.
 

SamR

Joined Mar 19, 2019
5,031
For receiving, the longer the better! I have seen 65' mentioned as a minimum but no idea why. And... The antenna does not have to be straight. Folding an antenna is acceptable as long as it isn't less than 2-3' apart parallel. Insulators at the ends or to support a bend are an absolute necessity.
 

Ya’akov

Joined Jan 27, 2019
9,069
Resonant antennas are much better for receiving than random longwires. A correct impedance match is just as important to good reception as it is to efficient transmission.

An antenna tuner can help, but there is a limit to what it can compensate for. It's easy to empirically test if a receiver needs a matched antenna by comparing the noise floor at t given frequency with a resonant and non-resonant antenna attached.

The major difference between a mismatch with a transmitter and one with a receiver is that the former will get hot and possibly release the magic smoke with a mismatch while the latter will just be varying degrees of deaf both because the signal of interest will be weak and whatever the antenna's actual working frequency is will be pushing energy into the receiver and desensing it.
 

Papabravo

Joined Feb 24, 2006
21,158
For receiving, you tend not to worry too much about the actual length. It is for transmission that the length becomes important. Make the antenna to match your local geography and enjoy the listening.
You don't want your neighbor Karen, screaming at you that your antenna is harming the Azaleas.
 

SamR

Joined Mar 19, 2019
5,031
Yup, I did not go into impedance matching baluns or ununs or antenna tuning... There are many variables factored into properly performing antennas. Oh, and green jacketed wire helps to hide it from the Karens of the world. And then there is another whole realm of "invisible" hidden antenna designs.
 
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