Wild Idea or genius solution?

Status
Not open for further replies.

RFI-EMI-GUY

Member
Joined
Dec 22, 2013
Messages
6,859
Lets say I have a base loaded NMO antenna on my vehicle field tuned to 43 MHz. Could I without further cutting, tune this antenna to 52 MHz by simply sliding a ferrite sleeve over a portion of the top of the rod and securing it? Practical considerations?
 

prcguy

Member
Joined
Jun 30, 2006
Messages
15,230
Location
So Cal - Richardson, TX - Tewksbury, MA
No.

You could slide brass or aluminum inside the loading coil and it will raise the frequency slightly but probably not enough to reach 52MHz. You might be able to steal a small loading coil from another antenna, the type with set screws on both sides then cut your whip down for 52MHz but cut near the middle, then make the loading coil into a trap for 52MHz then install the remaining whip on top of the trap and tune that for 43MHz. You would then have a dual band 43/52MHz antenna.

Lets say I have a base loaded NMO antenna on my vehicle field tuned to 43 MHz. Could I without further cutting, tune this antenna to 52 MHz by simply sliding a ferrite sleeve over a portion of the top of the rod and securing it? Practical considerations?
 

RFI-EMI-GUY

Member
Joined
Dec 22, 2013
Messages
6,859
No.

You could slide brass or aluminum inside the loading coil and it will raise the frequency slightly but probably not enough to reach 52MHz. You might be able to steal a small loading coil from another antenna, the type with set screws on both sides then cut your whip down for 52MHz but cut near the middle, then make the loading coil into a trap for 52MHz then install the remaining whip on top of the trap and tune that for 43MHz. You would then have a dual band 43/52MHz antenna.
That is an interesting idea. Mine was to use the ferrite sleeve to choke the remainder of the antenna whip when I wished to use it temporarily at 52 MHz, not dual band.
 

prcguy

Member
Joined
Jun 30, 2006
Messages
15,230
Location
So Cal - Richardson, TX - Tewksbury, MA
Ferrite over just a whip can do various things but I don't think it will do what you want. I believe it will change the tuning some and absorb RF but I don't think it will electrically end a whip at a new point where you placed the ferrite and raise its resonant frequency. You need a parallel resonant circuit or trap for that. If you put ferrite over a loading coil it will increase inductance and lower the resonant frequency. You want to go higher in frequency so ferrite is not the right stuff for that either.

That is an interesting idea. Mine was to use the ferrite sleeve to choke the remainder of the antenna whip when I wished to use it temporarily at 52 MHz, not dual band.
 
Status
Not open for further replies.
Top