Topband: Apparent Multiple Resonances on a single antenna

[i4jmy at iol.it]

Beeing Bills’ antenna shortened, resonances will not appear on odd harmonics, neither on even ones. With linear elements (not shortened) resonances actually occur also on even harmonics. There, anyway, impedance is high and there’s no match with 50 Ohms. 
A full size dipole/vertical will show resonances at fundamental and its multiples, more or less showing the same impedance it has on its fundamental, on the odd harmonics. 
A loaded dipole/vertical won’t instead follow this rule because the loading reactive device (inductor or capacitor) and its proportional placement along the antenna element will make it behaving differently depending on frequency, and there won’t be resonances on exact harmonics, odds and even. 
This well known property of what happens when placing a lumped constant device along a linear element makes for example living together without interactions a 40 meter shortend antenna and a 15 meter one. 

73,
Mauri I4JMY



> 
> If your antenna is properly fed with a good balun,
> you'd get resonances on odd harmonics with SWR
> generally increasing with frequency due to
> increasing radiation resistance. This implies that
> both radials and balun are functional over entire
> frequency range, which most likely doesn't hold.
> 
> Without a balun, or with a bad one, you'd also
> get resonances from the entire system = coax + balun + antenna.
> Such resonances are unpredictable.
> 
> 
> 73,
> 
> Sinisa  YT1NT, VA3TTN