Sure; a dipole antenna has a figure-eight reception pattern, you'd be aiming a lobe at each of the sources.
Usually, a reflector removes one lobe, replacing it with a stronger 'other' lobe (but this is all frequency-dependent, the reflector spacing can be important). That'd be 3 dB gain. There's usually a broad range of acceptable sensitivity for an antenna, the 'extra gain'' isn't crucial.
If the antenna is somethat higher or lower than another antenna even the horizontal pattern will seem to change as one antenna over shoots the other.
Ralph Mowery wrote: ==================
** Did you read my caveat comment at all ?** But not relevant to the original question re BROADCAST reception.
Context, context, context, context !!!!!!.
...... Phil
I think he's talking about a wollenweber array of dipoles, with preamplification then phase-shifting and combination afterward. That worked with lots of operators trying combinations, for directing fighter craft against bombers, around (for instance) Berlin, 1943. The linkage used by wool thread spinners to gather their product is a 'wool-weaver' which is what the dipole array must have suggested.
Alert operators can do the tuning dynamically (those fighter craft MOVED).
John Larkin wrote: ===============
** Smartarse.** Loud ring goes off !! That idea is *outside* the parameters of the question re:
" signals from multiple dipoles can be combined "
** But JL has no idea nor cares a hoot what it is..... Phil
On a sunny day (Thu, 06 Jan 2022 15:32:16 -0800) it happened John Larkin <jlarkin@highland_atwork_technology.com> wrote in snipped-for-privacy@4ax.com:
One important thing to take into account is all the cable losses. The reason mine works so well is
1) length cable only 2 meters 2) antenna is about 1/4 wavelength 3) no connector losses 4) indoors fields and phases combine and all sort of wave patterns exist, use a local one that is strong. 5) no pre-amps no power needed.
Passive combining of multiple antennas will always change the directional response in some way. Combining the outputs of multiple receivers to improve performance without modifying the directional response is standard practice and was first done about 100 years ago.
John
Given a defense-sized budget, one could digitize each antenna signal and combine them digitally. Add phase shifts as needed. That's a project but it's not totally crazy, with modern multichannel ADCs and an FPGA.
At one frequency, move the dipoles around to tweak the pattern.
Or switch in some delays with relays or something. That could be cool. Try every combination for max signal strength.
You only win SNR like the square root when you combine the demodulated outputs, whereas you win linearly with coherent combining.
Cheers
Phil Hobbs
On Friday, 7 January 2022 at 08:06:10 UTC-8, snipped-for-privacy@highlandsniptechnology.com wrote: ...
...
That's how most automotive (and many military) radars work. You can do four receivers for $25 and cascade up to four of the devices together to give 16 receivers (and 12 transmitters)
Yes, but the reason for combining receiver outputs is often to overcome fading rather than just to improve snr. In that case, the final output will usually be the "best" of the multiple receiver outputs or a weighted combination rather than just a linear sum.
John
You're mistaken. if you build a phased-array antenna you get increased directionality (so a tighter far field pattern) and a stronger signal.
Gain and directionality are inextricably linked for passive antannnae.
If you have some way to connect multiple antennae without creating a phased array I'd like to hear about it.
====================
** ROTFL - insects have "antennae" !!!Worse than that idiocy, is that everyone but me has arrogantly ignored the OP's context. Colossal pedant Ralph Mowery kicked it off and all the sheep here followed.
For fixed location antennas, only the *horizontal * pattern ever matters and is the only one speced. So "directionality" = horizontal pattern.
FFS when are you going to learn that queries posted here are NOT f****ng exam questions.
( except when some wanker sneakily posts one they need to answer)
..... Phil
Almost every antenna data sheet I have looked at gives horizontal and vertical radiation patterns. For TV antennas - which are relevant to the OP's question - both are needed because the manufacturer will not know whether the transmissions to be received are horizontally or vertically polarised and therefore will not know which orientation of the antenna is horizontal when installed. Around here, for example, there are two TV transmitters within range and one is horizontally polarised while the other is vertically polarised. Mobile phone base station antennas definitely have vertical as well as horizontal radiation patterns specified. Both are important.
John
If some idea violates a basic conservation principle, it can be instantly rejected... but actually shouldn't be too soon.
Most people are hostile to new ideas. They live at the bottom of the pay scale.
One widely used application where one does care about it a lot is for mobile phone base stations.
John
Once you have a lot of antennas and a lot of DSP, most any antenna pattern is possible.
If one digitizes the signals from an array of dipoles, it should be possible to synthesize any pattern.
And for HF DX, you care a lot about low-angle radiation because that's what bounces off the ionosphere most readily.
Cheers
Phil Hobbs
On Saturday, 8 January 2022 at 09:24:38 UTC-8, snipped-for-privacy@highlandsniptechnology.com wrote: ...
...
And that is what is commonly done in cellular base stations, radar and astronomy.
There are still limits set by the various propagation rules regarding beam width and gain - there is no free lunch.
The system I an involved with currently has 192 virtual antenna elements and requires about 4 million FFT's a second for the processing, all with a power budget of a few Watts. The one I worked many years ago took about 100W to do about 150 FFTs/sec.
kw
Another parameter which nobody has mentioned so far is bandwidth. Trying to get an array of radiators to form a desired beam shape at one frequency involves some unavoidable trade-offs, but doing so over a wide bandwidth gets even harder.
John
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