# Antenna For Frequency Sweep 10Mhz to 100Mhz

#### Tigera

Joined Apr 20, 2016
11
Hello,
I need to transmit 10 Mhz to 100 Mhz Frequency Sweep equal in all directions so the antenna gain is about 0 db, but the thing is really matter is the antenna size.
for 10 Mhz---- λ=30 M ---- (λ/4) = 7.5 M
for 100 Mhz---- λ=3 M ----- (λ/4)= 75 cm

Because the frequency varies from 10 Mhz to 100 Mhz , the antenna lenght varies from 7.5 m to 75 cm.

What kind of Antenna Should I USE???

#### SLK001

Joined Nov 29, 2011
1,549
I need to transmit 10 Mhz to 100 Mhz Frequency Sweep equal in all directions so the antenna gain is about 0 db...
Ain't gonna happen.

#### bertus

Joined Apr 5, 2008
22,307
Hello,

Why would you like to sweep 10 - 100 Mhz using a transmitter?

A wide band transmitter antenna can not be made.
A vertical antenna must have odd quarters on the lenght.
An 7.5 Meter antenna will work on 1/4 λ,3/4λ,5/4λ,7/4λ and 9/4λ or 10,30,50,70 and 90 Mhz.
On the even quarters the SWR will be the worst, so at 2/4λ,4/4λ,6/4λ,8/4λ and 10/4λ or 20,40,60,80 and 100 Mhz.
You can not sweep the whole range from 10 to 100 Mhz with only one antenna.

Bertus

#### Tigera

Joined Apr 20, 2016
11
Thanks Guys.

#### atferrari

Joined Jan 6, 2004
4,800
No idea about the power output at final stage but you would be crossing several different bands for very dissimilar services. No matter where in the world you will do, the situation is similar. Have you the respective authorizations to do it?

Omnidirectional you say, good to affect as much people as you can, methinks.

#### bertus

Joined Apr 5, 2008
22,307

#### DickCappels

Joined Aug 21, 2008
10,247
Nobody said it was going to be small

Using any of these antennas over a decade range will require connection for the sensitivity variation off if any kind of calibration is needed.

#### DickCappels

Joined Aug 21, 2008
10,247
If you don't mind tuning as the frequency changes, this can be a good solution.

#### bertus

Joined Apr 5, 2008
22,307
Hello,

Again, Why do you want to transmit from 10 to 100 Mhz sweeping?
There are many shortwave radio stations and amateur radio bands in that range.

Bertus

#### Tigera

Joined Apr 20, 2016
11
Hello,

Again, Why do you want to transmit from 10 to 100 Mhz sweeping?
There are many shortwave radio stations and amateur radio bands in that range.

Bertus
It's for a molecular frequency resonance system,and continuously make different objects and material to resonance just for exp experimental use.(Like breaking glass by resonance frequency).Actually The Frequency range may be more than 10 Mhz to 100 Mhz.

Is there any voltage/frequency controlled Antenna Tuner (Like VCO's,AGC(automatic gain control),......) ??

So The Tuner automatically tuning as frequency changes.

#### bertus

Joined Apr 5, 2008
22,307

#### Tigera

Joined Apr 20, 2016
11
Hello,

In NMR (nuclear magnetic resonance) you are not using an antenna.
You are using a resonant coil around the sample.
You are also using one frequency for exiting the nucleus of interest.
The frequency of the nucleus depends on the strength of the magnetic field.

Have a look here for a frequency table for NMR:
http://web.mit.edu/speclab/www/Facility/nmrfreq.html

And here how NMR works:
http://www.cis.rit.edu/htbooks/nmr/inside.htm

Bertus
I Know nothing about NMR and Physics , but one of my friend asked me to design a system to radiate a frequency sweep. He explained about it but I don't get it and aslo I'm not sure even it is about NMR ...

It's not important, the only issue is the radiating the frequency sweep.

the frequency sweep circuit is simple but the main problem is the antenna!!

#### bertus

Joined Apr 5, 2008
22,307
Hello,

What you are trying to do is like pseudo science.

You will not get materials into resonance without a strong magnetic field.

Bertus

#### Wendy

Joined Mar 24, 2008
23,483
Not to mention having several government services hunting you down. Military and civilian authorities look very poorly on jamming, which is what you are proposing. The only way to not get into trouble, regardless of your country of origin, is a RF shielded room (AKA Faraday cage).