[TowerTalk] Fwd: Stacking question - another reality data point

[jimlux]

On 8/11/16 10:28 AM, Richard (Rick) Karlquist wrote:
>
>
> On 8/11/2016 8:48 AM, Hans Hammarquist via TowerTalk wrote:
>>
>>  I have had an idea for some time: When you feed all these stacked
>> antennas in phase you will have optimum radiation to the horizon (or
>> just above). My idea is to add switchable delay lines to the higher
>> located antennas. (You could rather easily replace the damping
>> networks in an attenuator with some coax do make this.) Thereby you
>> will be able to get optimum angle for "higher up" propagation. You
>> should select the steps to be small enough not to get "gaps".
>>
>> Any taker? (K1TTT?)
>>
>> Hans - N2JFS
>>
>
> I tried modeling stacks with phase shifts of both polarities
> and was never able to come up with a configuration that seemed
> like it would be useful.  It is one of those "squeezing on a
> balloon" problems.
>
> Although you describe this as "your idea" it is inconceivable
> that it wasn't around decades ago.  If it made sense, someone
> would be doing it.  As you say "beam tilt" for UHF TV antennas
> is something else again and not analogous to HF radio.
>

phasing a vertical stack has been done for HF for a number of decades. 
Systems like the "woodpecker" are an example.

Radio France International has some huge steerable arrays, as well.

I'm not aware of any hams doing it, other than a BIP/BOP scheme which 
flips the phase.

I think that for most "real time adjustment" scenarios, a 
BIP/BOP/TOP/BOTTOM of sorts is probably as good as anything else.  That 
lets you move the nulls in the pattern around in elevation, so you can 
place the null on a strong interfering signal(s), to dig out the faint one.


Using switched transmission lines (coax) as delay lines is the classic 
"true time delay" scheme for a wideband phased array.