I need cutting lengths for tuning antennas?

[mattl3320]

Hi just wondoring if anyone knows the right antenna length for the following bands 30 t0 50 mhz 150 to 170 mhz 450 to 490 mhz 501 to 512mhz 850 to 870mhz ? thank you.

mobile whip antennas is what i am using them for thank you.

 

[davidmc36]

Hi just wondoring if anyone knows the right antenna length for the following bands 30 t0 50 mhz 150 to 170 mhz 450 to 490 mhz 501 to 512mhz 850 to 870mhz ? thank you.

This may help you out:

Antenna Length Calculator KD4SAI

I use that for making ground planes and make it for the middle of the band that I am trying to recieve.

 

[W6KRU]

What kind of antenna element do you need? 1/4 wave? You need to provide more detail on what you are building.

 

[mattl3320]

thanks for the calculator kd4sal it helped out alot mat

 

[WayneH]

Moved to the Antenna forum.

 

[buddrousa]

Before you go cutting on an antenna you might want to check the manufactor's web site. I know this from 2way radio installs that different brands cut different lengths for the same freq. There are more variables than freq and length when tuning an antenna.

 

[N_Jay]

Before you go cutting on an antenna you might want to check the manufactor's web site. I know this from 2way radio installs that different brands cut different lengths for the same freq. There are more variables than freq and length when tuning an antenna.

Ahhhh . . . No.

All 1/4 wave and 1/2 wave antennas of all brands are cut the same.

 

[W6KRU]

Ahhhh . . . No.

All 1/4 wave and 1/2 wave antennas of all brands are cut the same.

I was thinking the same thing and nearly posted but then it occurred to me that I didn't know what kind of antenna the OP was referring to. It might even be a 5/8 wave. Someone unfamiliar with mobile antennas might not realize the difference between the bases on different antenna types.

 

[n5ims]

While I agree in principle with NJay that all are cut the same, you should still check and follow the manufacturer's instructions when trimming your antenna. If not, you may cut your antenna to the correct calculated lenth only to be long or short based on how it is made or what options you have.

Case in point, if your 1/4 wave whip has a spring. If you cut the whip to length, it will be too long by the electrical length of the spring.

 

[N_Jay]

While I agree in principle with NJay that all are cut the same, you should still check and follow the manufacturer's instructions when trimming your antenna. If not, you may cut your antenna to the correct calculated lenth only to be long or short based on how it is made or what options you have.

Case in point, if your 1/4 wave whip has a spring. If you cut the whip to length, it will be too long by the electrical length of the spring.

Oh, come on?????

If you don't know enough to know the length is the total length when working with a simple antenna, then don't cut the whip because you probably can't figure out to keep your fingers out from between the blades.

Just how far do you want to take your argument so you can keep thinking your weer right?:roll:

 

[n5ims]

Sorry if I offended you N Jay, but this was from personal experience. A good friend blew out the finals in his 2 mtr rig by doing just that, forgetting about the spring on his 1/4 wave whip. He cut it for 19" and tightened it down.

Although he knew better, he just didn't think, after all, 19" is the correct length for 2 mtrs, right? After checking everything, we rechecked the length and finally had the "Duh! moment".

 

[N_Jay]

Sorry if I offended you N Jay, but this was from personal experience. A good friend blew out the finals in his 2 mtr rig by doing just that, forgetting about the spring on his 1/4 wave whip. He cut it for 19" and tightened it down.

Although he knew better, he just didn't think, after all, 19" is the correct length for 2 mtrs, right? After checking everything, we rechecked the length and finally had the "Duh! moment".

As Ron White says: . . . .

 

[buddrousa]

So Jay what 2way company do you work for and did you go to electronic school for formal training like I did? The size of the stinger elements also figures into the correct length of a moble antennas MAXRAD for one is not the same lenght as a LARSEN which is not the same as ANTENNEX. Now working in the 2way radio industry on my off days as a firefighter I hae seen the cut charts of all the brands . Just as also stated 5/8 have a coil that also plays a part and just because the spring is 5 inches it might be 6.5 inches by the electronic's that make up the spring thats why you look up the info like stated. Just like making a coil .0100 size wire does not get the same amount of turns as .0250 to make to same coil.

 

[N_Jay]

I'm wrong, your right.

I shouldn't have assumed it was a simple antenna except for the fact he said whip and was happy with the calculator.

As for missing the spring, I still say that is a stretch for using the logic the cutting chart is needed.

Sorry, never worked at a radio shop, but I did stay at a Holiday Inn Express last year.

 

[buddrousa]

No problem it always best to look to the specs that refer to the antenna you are using yes you can get close by doing the standard chart but it still could be off enough to cause a problem. Thats why I own my own Bird 43 meter and use a fluke vom wavetec service monitor and ati sa1300.

 

[mattl3320]

thank you all for your replys but the whip that i was cutting was for my scanners i have several books on it but there all a little confusing as far as what the lenght sould be one would say for 800mhz it sould be 3 inches and another one said 4 inches.

 

[W6KRU]

thank you all for your replys but the whip that i was cutting was for my scanners i have several books on it but there all a little confusing as far as what the lenght sould be one would say for 800mhz it sould be 3 inches and another one said 4 inches.

234/800 = .29 ft x 12 = 3.51 inches

Edit: I assumed you wanted a 1/4 wavelength