[CQ-Contest] Stacking on separate towers, take off angles?

Thu Mar 14 08:49:35 EDT 2013

I think that someone did some work maybe 10 years ago on the theory (and 
practice) of feeding two antennas on different towers.  IIRC, the 
process mainly involved experimenting with different phasing for 
different directions, using one of those phasing boxes designed for 
phasing two verticals to produce a wide variety of patterns.

Jukka's solution sounds like it worked out very well for him, but I 
think that he was pretty lucky.  More years ago than I'll admit to, I 
had a college astronomy course where I had to manually calculate the 
broadside pattern of a 22 MHz interferometer that used two dissimilar 
yagis pointed perpendicular to a 1500-foot baseline.  Much trig later, I 
had a pattern of many very narrow beams with deep nulls in between.  My 
point is that in terms of the phase of signals being emitted from two 
antennas on 20 meters, 65 feet is pretty near a full wavelength, and 
depending on the angle of that baseline to the desired direction, the 
signals will arrive at the target with very different phases, some 
reinforcing and some cancelling.

A final comment - in Europe I can see front-to-back and front to side 
being of major importance - I'm not sure that's quite so important in 
VE9.  I'd much rather have the broader vertical pattern and pattern 
options that a conventional stack affords, but you gotta run what you 
have.   And Mike, you might want to check the archives of the Towertalk 
reflector, an excellent source for smart practical antenna advice.

73, Pete N4ZR
Check out the Reverse Beacon Network at
http://reversebeacon.net,
blog at reversebeacon.blogspot.com.
For spots, please go to your favorite
ARC V6 or VE7CC DX cluster node.

On 3/14/2013 3:37 AM, Jukka Klemola wrote:
> Hi Mike,
> No problem.
>
> Just connect them and if they work as separate antennas, they pretty
> often work stacked, too.
>
> I have two towers, separation about 65ft.
> They are broadside to North America. Looking from here, the exact
> direction is east coast, to be precise.
>
> But, to be precise is not often needed.
>
> On 40, the antennas work OK together, but I see no benefit as the
> other is a FS stack and other is to me a pretty low (75ft or so) LL 2
> element.
>
> On 20 they work Great together. Some measurement results show real
> gain to whole U.S. despite West Coast (looking from here is on the
> _Right_) about 25-30 degrees off. The 3+3 = 6 yagis work OK to the
> West Coast as well,
> I just rotate the towers there, a little to the right.
>
> To Japan the towers are in-line; about two waves separation.
> I have not been measuring that so accurately but from what I have
> experimented I can say the QRM level is reduced, so the yagis - when
> connected together and beaming to JA short path function better than
> the front stack alone.
>
> Antennas being to other directions that are more odd . .
> Just experiment with the relays.
> The receiving conditions change from QSO to QSO.
> Be prepared to experience that it is almost only about QRM management.
>
> The antennas you are building will do Great.
>
>
> The flaw I did with my system, was I had the stacks connected together
> all the time in the beginning. I built a power divider so I can feed
> the two tower together or just one of them. It gave extra capability
> to the station.
>
>
> Have Fun experimenting.
> It is wonderful to learn there are people building stations that will
> push through even in a little worse conditions.
>
> About my system, you can see some pictures on
> www.oh4a.fi
> www.qsl.net/oh4a (this has not been updated for a long time)
>
>
> 73,
> Jukka OH6LI
>
>
>
> 2013/3/14 Mike <ve9aa at nbnet.nb.ca>:
>> Hello from  New Brunswick, Canada de VE9AA, Mike
>>
>>
>>
>> If anyone runs ‘stacked’ antennas on separate towers, I’d like to hear what
>> has been your experience  .
>>
>>
>>
>> I have 2 (self-supporting) tower bases, aprox 65-70’ apart. (never measured
>> it—I put them in mni yrs ago)
>>
>>
>>
>> They run on a line about N-S (EU is NE from here and USA is SW); same as
>> from W1.
>>
>>
>>
>> The North tower will have a CC A3S at the ~74’ level and the South tower
>> will have another A3S
>>
>> @ aprox the ~42’ level.  I can tweak those heights a little bit if need be.
>> I’ll have other antennas in the vicinity.
>>
>>
>>
>> I have good ideas about “stacking” them either with a Array Solutions WX0B
>> Stackmatch II I already own, or something else I conjure up
>>
>> here allowing me U/L/BIP…even flip one 180º out of phase for BOP, I think
>> coax phasing lines for a tribander might be a mess when attempting BOP, so I
>> may do a relay at one yagis feedpoint  if I go that route…. BUT...that’s not
>> the problem. (or the question)
>>
>>
>>
>> My idea is to usually spray in 2 directions at a time when contesting,
>> however certain contests require I beam only in 1 direction.
>>
>> WAG ( I beam Germany) .ARRL SS, 95% of the time, I beam SW or WSW….you get
>> the idea.\
>>
>>
>>
>> I am relatively certain I can make a good guess of what the pattern will be
>> like when I beam due east or due west with both antennas.
>>
>> (again, towers are N-S from one another)
>>
>>
>>
>> The issue is when I put both antennas on EU or USA (NE or SW).  I am
>> envisioning the elevation pattern will be messed up (as in out of phase and
>> thus HIGH,…..good for E-skip or noon hour prop on 20m…. or else
>> unpredictable(?) as the wavefronts are both arriving at different times to
>> each antenna, thus they’ll be out of phase once you get anywhere away from
>> straight East or West (guessing a little here).
>>
>>
>>
>> Is there anything that can be done to counteract that, or even guess as to
>> what it may be, or is it a total cr at pshoot?
>>
>>
>>
>> I’ve searched and searched and searched on the web and on contesting.com and
>> found mere snippets here and there where someone mentioned stacking antennas
>> on separate towers, but never if it was better when BOTH antenna were aimed
>> the same way. (I guess most times in a contest it’s nice to cover 2
>> directions) I just see where there is a need for general DXing for P5RS7,
>> BS7H, KP1 or VU7 when you need to eek out every 10th of a dB or like I
>> mentioned before, in contests where I am lucky enough to be in the far North
>> East to just leavem’ parked NE or SW where I don’t know what I’ll be faced
>> with.
>>
>>
>>
>> If anyone runs ‘stacked’ antennas on separate towers, I’d like to hear what
>> has been your experience  - J
>>
>>
>>
>> Comments? (even anecdotal is fine…I am not a scientist or engineer, just a
>> technologist)
>>
>>
>>
>> 73, TNX !
>>
>> Dit dit, Mike VE9AA
>>
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