antenna length

[thomasbillman1]

i am scanning the federal government frequencies 163.00 to 174.00 what is the length of my antenna should be at? I have it fully extended at 20 ft.

 

[mmckenna]

i am scanning the federal government frequencies 163.00 to 174.00 what is the length of my antenna should be at? I have it fully extended at 20 ft.

Huh? 20 feet or 20 inches? Are you talking about a telescopic whip antenna, or something else?

If it is a telescopic whip antenna, you should experiment to see what works best for you, your radio and your exact situation.

If you are trying to make it 1/4 wavelength so it's resonate, you'd want it around 16 to 17 inches.

 

[thomasbillman1]

20 ft, I have a tram outdoor antenna attached to a home patrol 2 radio

 

[prcguy]

Is it a Tram CB antenna?

20 ft, I have a tram outdoor antenna attached to a home patrol 2 radio

 

[Mikejo]

If your antenna is a telescoping one, you can use this
frequency formula:

468\frequency in MHz x12 to convert to inches

example: for 168.5 (halfway between 163 and 174 MHz)

468\168.5 = 2.777448071216617
Times 12 = 33.32937685459941 inches for a half wave antenna.

Divide 33.32937685459941 by 2 to get a 1/4 wave antenna length.

33.32937685459941 \ 2 = 16.6646884272997 inches.

round it up , it would be 16 and 11/16 inches.

hope this helps!

 

[Mikejo]

Also I forgot to mention, if you have your antenna up at 20 feet outside this is a very good thing.

One of the first rules of antennas is: “height is might”

73

 

[jwt873]

Would help to know exactly what antenna you're using. Not sure what you mean by 'fully extended at 20 feet". Tram makes quite a few antennas.. What's the model number?

 

[IC-R20]

Sounds like he's talking about the antenna elevation with that 20ft stuff.

 

[dlwtrunked]

If your antenna is a telescoping one, you can use this
frequency formula:
468\frequency in MHz x12 to convert to inches
example: for 168.5 (halfway between 163 and 174 MHz)
468\168.5 = 2.777448071216617
Times 12 = 33.32937685459941 inches for a half wave antenna.
Divide 33.32937685459941 by 2 to get a 1/4 wave antenna length.
33.32937685459941 \ 2 = 16.6646884272997 inches.
round it up , it would be 16 and 11/16 inches.
hope this helps!

Minor note that the Federal band starts at 162.0000 not 163.0000 MHz. the 162-163 does include other Federal operations besides just NOAA weather radio. That makes mid-band 168.0 MHz rather than 168.5 MHz.

 

[Mikejo]

No problem, just went off of We the OP referenced at the beginning of the thread. It’s receive only, so 16 or 17 inches should be fine.

 

[dlwtrunked]

No problem, just went off of We the OP referenced at the beginning of the thread. It’s receive only, so 16 or 17 inches should be fine.

Understood--the correction was really for anyone reading the thread who might walk away with a wrong thought.

 

[thomasbillman1]

Also I forgot to mention, if you have your antenna up at 20 feet outside this is a very good thing.

One of the first rules of antennas is: “height is might”

73

it 50 ft off the ground n extended about 20 ft in the air also using lmr 240 coax

 

[prcguy]

I'll ask again, what brand and model antenna do you have? Saying its 20ft long and 50ft in the air is about as meaningful as saying its aluminum when someone asks what kind of antenna you have. Without specific info about your antenna, nobody can help you.

it 50 ft off the ground n extended about 20 ft in the air also using lmr 240 coax

 

[StoliRaz]

i am scanning the federal government frequencies 163.00 to 174.00 what is the length of my antenna should be at? I have it fully extended at 20 ft.

I just pictured someone with a 20 foot antenna on top of a portable when I read this and had a chuckle..look out for power lines 😅