bowtie panel antenna

The reflector does several things. It gives gain to the antenna, it sets the impedance of the antenna, and in a minor sense it prevents the signals off the back from being received very well.

Antenna gain can only be had by modifying the antenna pattern. Just like a light bulb with a reflector. The more gain , the narror the beam. Think of a light bulb , it sends light out in almost all directions. PUt a reflector and it sends the light out in mostly one direction and is much brighter. It also works similar in reverse when receiving light or radio/TV waves.

YOu can try with out a reflector and see if you get the signal you need for the stations.

Or by making the antenna bigger, to intercept more power.

On a sunny day (Thu, 6 Jan 2022 07:47:44 -0800 (PST)) it happened Sid 03 snipped-for-privacy@gmail.com wrote in snipped-for-privacy@googlegroups.com:

Antennas and RF fields are a bit of a mystical thing for the not initiated. I have a big nice bowtie (was once for TV) and got no usable signal at all in this location for DVB-T.

Using a cheap Chinese DVB-T2 reeiver from ebay. So now the magic Took a piece of 75 Ohm coax made the magic move and removed something like 12 cm from the shield, then moved it around along the wall INSIDE and hit a point where reception was error free, bended it a bit and taped it to the wall with double sided tape.

is probably the iron of the bridge, And no, the transmitter is miles away. The magical hotspot is well guarded as you can see,

Bigger antennas only work better because they modify the pattern.

Big does not get you anyting unless the antenna is designed to use the larger size.

<snip>

Notwithstanding big business' belief in too-big-too-fail, bigger isn't better for a microwave bowtie antenna etched on FR-4.

In regards to the OP's question, instead of reflector removal, perhaps, if your budget permits, you can put two reflective bowties back-to-back?

Danke,

If a dipole gathers a milliwatt, another dipole some modest distance away will gather another milliwatt. Seems to me that the powers can be added without altering the far-field patterns.

UHF bowties are easily made; its harder to make the mounts. Suggest two bowties, one on each side, with two feedlines or a two-signal combiner.

Your action reminds me of Mr Bean's TV aerial:

Arie

That is true about gain if the spacing and impedance matching are correct, but the pattern still changes. If the dipoles are too close or too far apart the phasing is not correct and the signals cancel. Instead of gain, the pattern breaks up and you may get no signal at all or a very small signal. They still modify the pattern in some way.

If and only if the spacing is correct two dipoles will double the signal, not counting on a small loss of interconnecting cables . To double that you need 4 dipoles for 8, to double that you need 16 dipoles all phased correctly. With each set of dipoles the beam will narrow so you have to aim the antenna closer to the station.

I see a lot of articles where combiners are mentioned, but I find it hard to find good information on the subject. From what I have read if the two antennas are not combined correctly the signal received from one antenna is simply radiated out by the 2nd antenna. Some splitters are advertised as combiners and other websites caution against using splitters/combiners are combiners. Can I get some clarification on the subject ? maybe some links to info on the subject, where to buy one, how to build one ? Thanks

Some power is _always_ radiated out by the antenna. In fact, even with a single antenna, at least 50% of the power which reaches the antenna from the transmitter, is re-radiated by the antenna. If the antenna system is mismatched to the feedline and load, even more of the power will reflect from the mismatch point and re-radiated.

What's important, in the case of a "stacked" antenna pair, is that the signals from the two antennas reach the combining point in the proper phase. This helps minimize the mismatch and thus the amount of "lost" power.

The worst case is if the two signals reach the combiner 180 degrees out of phase, and cancel at the combining point. You'll get no power into your TV or tuner, and everything will be re-radiated (or lost as heat into the cables' resistance).

an excellent archive of PDFs of the late, lamented Audio Magazine. I subscribed to this quite steadily from my college years in the

1970s until they folded/merged (into High Fidelity Magainze, I think).

What I found, looking back, is a very nice five-part series of articles on FM antennas, feedlines, preamplifiers, and distribution systems, by M.J. Salvati, in the January - April issues in 1978 and the January issue in 1979.

This was followed up by the article I had remembered reading when it first appeared - "Kill FM interference with two antennas", by Richard Modafferi, in the January 1980 issue.

Although the specific equipment models described in these six articles are surely all obsolete by now, the information and knowledge is not - I gave them a quick skim and they're a great read.

I think signals from multiple dipoles can be combined without altering the far-field pattern. I can think of several ways to do that.

Then you have exceeded the laws of antennas.

Care to tell a way to do that in any prctical antenna ?

snipped-for-privacy@highlandsniptechnology.com wrote: ===================================

** Both remarks are ambiguous as written.

The first can be reworded as " for a given ( VHF / UHF ) antenna, increased forward gain = more directivity".

The second can be restated as : " an antenna array has more forward gain than a single unit "

Simples.

...... Phil

It's widely done in radar systems. It's called spoiling the beam. This is typically done to the transmit beam, so multiple overlapping receive beams can be used per TX pulse.

All it takes is some random detuning of the drive phases at the various elements.

Joe Gwinn

The antenna uses around 1000 to 2000 dipoles. The beam width is about 1 or 2 degrees. The antennas are phased electrically so you sweep that small segment over a larger area. It replaces the mechanical need to rotate the whole antenna.

So with the beam width being so small instead of 180 degrees of a dipole you have modified the pattern of a single dipole.

John Larkin wrote: ===============

** Yep - one type is called a "collinear " antenna.

The one caveat is the "pattern" is only being considered in the horizontal plane. Standard practice for any broadcast antenna set up.

..... Phil

The collinear modifies the horizontal patern by taking some signal from the vertical. Think of a baloon. You press it from the top and bottom and the horizontal gets larger. If the antenna is high enough stations close in will often loose most of the signal as the pattern shoots over the top of lower stations. Been there and done that .

Pattern still modified for gain.

Laws of antennas? Or folklore?

One obvious way: run a feeder from N antennas to a central point. There, run each signal into a receiver. Combine the receiver outputs. The RF phase information is lost.

There's probably a passive way to combine an array of dipoles but keep the same far-field pattern.