I wanted to repair some of my old receivers in Mhz band because I always eard that the length was very important.
after small researchs in the ternet and the advices of The boss of the antenna in my job, I found that.
The length of the antenna should be apaired with each frequency but for our materials apaired with the frequency band is enough.
The formula is : light speed divided per the frequency.
the speed in m/s and the frequency in Hz.
The result is:
for the 26mhz => 11,53m
for the 27mhz => 11,10m
for the 40mhz => 7,49m
for the 41mhz => 7,31m
for the 72mhz => 4,16m
for the 75mhz => 4,00m
in the reality, these lenghts are too long for our small vehicles. So, scientists found the solution
the use of the harmonics.
with the advices, I used the fourth and the fifth harmonics.
1st=2
2nd=4
3rd=8
4th=16
5th=32
Now, I just need to divide the "normal" length per the harmonic and that give me a more coherent result.
first is with the 4th harmonic and 2nd with the 5th one.
for the 26mhz=>72cm/36cm
for the 27mhz=>69cm/35cm
for the 40mhz=>47cm/23,5cm
for the 41mhz=>46cm/23cm
for the 72mhz=>26cm/13cm
for the 75mhz=>25cm/12,5cm
These results are generic results. They can help us to repair our rx but they aren't perfect. They are some electronic parts in the receiver which amplify the signal but it could be efficient. more to find the rx band of an unknown rx with all the length antenna....
