13 votes

Do these look like amateur radio antennas?

It looks like a fibre or telephone cable strung between buildings. It sets a good precedent for setting up your antenna though - if you can get access to the other rooftop at night, and a catapault or ...
tomnexus's user avatar
  • 11.2k
11 votes
Accepted

Conductive boom vs non conductive boom: what's the difference on a Yagi?

So, by design, the elements of any Yagi have a zero current going through the center point. That's pretty obvious be symmetry: assuming you excite the "left and right" halves of the driving dipole ...
Marcus Müller's user avatar
8 votes
Accepted

Can I use two yagi aerials back-to-back for a bi-directional system?

Two Yagi antennas on the same antenna port could work for this application. Join the feed lines from the two antennas with a power divider for proper impedance matching. Make sure that they are ...
Kevin Reid AG6YO's user avatar
  • 24.5k
6 votes

Steel Directors with Copper DE

It's probably OK to use a different metal for the directors than the driven element, as long as you don't have dissimilar metals touching that would create a galvanic corrosion problem. But steel is ...
rclocher3's user avatar
  • 9,222
6 votes

Yagi vs Parabolic Dish for 2.4GHz Campus Wifi from 1,800ft away?

Depends on the particular Yagi or dish. Look for a published gain. Beware of low-quality manufacturers that publish erroneous data. Higher gain will correlate with higher probability of working. Point-...
Phil Frost - W8II's user avatar
6 votes
Accepted

Yagi vs Parabolic Dish for 2.4GHz Campus Wifi from 1,800ft away?

You can make a first order approximation by using typical WiFi ranges in combination with two free space path loss calculations. 802.11b/g has a typical indoor range of 150 feet. By calculating the ...
Glenn W9IQ's user avatar
  • 18.6k
6 votes

Can half of a directional antenna (Yagi-Uda, HB9CV) be replaced by a ground plane?

Yes, this is a time-honored practice, particularly at the longer wavelengths where horizontal antennas need to be mounted quite high to provide low-angle radiation for DX work. Callum, M0MCX, presents ...
Brian K1LI's user avatar
  • 7,848
6 votes

How do 'plumber's delight' type Yagi antennas have a bandwidth?

The elements of a Yagi are dipoles. If you look at a dipole at any instant, the voltage at one tip will be some value, and the voltage at the other tip has the same magnitude, but opposite polarity. ...
Phil Frost - W8II's user avatar
6 votes

I'm looking for an effective beam antenna for both 20 meters and 10 meters

From some research, beam antennas only seem to come as monoband antennas. Not true — actually 20/15/10m tri-band beams are very popular. Multi-band yagis come in two basic flavors. Trapped. Works on ...
hobbs - KC2G's user avatar
  • 12.4k
6 votes
Accepted

Which way is a yagi polarized?

For a Yagi antenna the electrical polarisation matches the mechanical orientation of the elements. So to receive your vertically polarised signals the elements of your antenna will need to be vertical ...
Graham G8URP's user avatar
5 votes

Receive directionality of a sub-optimal Yagi

A few things to start off with: You don't care about efficiency, unless the antenna efficiency is truly abysmal, or your receiver is of very poor quality. Efficiency on the receive side is a measure ...
Hamsterdave's user avatar
  • 1,844
5 votes

Intermittent High SWR

The MA5B is rated for 1,200 watts PEP. 200 watts is certainly well below that threshold. Things to check: Arcing, corrosion or moisture inside the match box A loose or corroded connection from the ...
Glenn W9IQ's user avatar
  • 18.6k
5 votes

What happens to a vertical Yagi when you mount it on a vertical metal pole?

You definitely don't want to mount a long metal pole through a Yagi. My rule of thumb is that it at best cuts off the Yagi at that point, perhaps worse. You have three options to avoid this. Mount ...
tomnexus's user avatar
  • 11.2k
5 votes

Yagi Antenna - Elements Length

I suspect your results are an artifact of your optimization methodology. I simulated the design described in the link with NEC2 using the EZNEC front-end. For reference, EZNEC calculates the gain as ...
Brian K1LI's user avatar
  • 7,848
5 votes

Do these look like amateur radio antennas?

The cable strung between the two buildings has two parts, a strong wire probably made of stainless steel or similar, then you can see some form of cable, as Tommexus said it's probably fibre or ...
Andrew's user avatar
  • 3,685
4 votes

Can I use two yagi aerials back-to-back for a bi-directional system?

Merely trim the reflector element of one yagi to the length of the first director and it will become bi-directional enough to get the job done without the expense of another yagi and harness. Some ...
Jim Navotney's user avatar
4 votes
Accepted

What happens to a vertical Yagi when you mount it on a vertical metal pole?

Mounting a vertically-polarized Yagi on a vertical conductive mast usually screws up the pattern. You either have to use a non-conductive mast, or offset them from it with a horizontal boom. 40 years ...
Mike Waters's user avatar
  • 7,978
4 votes

3D Printed yagi antenna

Some general hints from my experience: Use wires not printed metal. You could stop the print for a while to drop in the wires, then finish it, or push them in later. For sanity's sake, design your ...
tomnexus's user avatar
  • 11.2k
4 votes

I'm looking for an effective beam antenna for both 20 meters and 10 meters

Engineer999. The driven element of a yagi antenna is normally a half wave dipole, and it's true that a dipole antenna is resonant on multiple harmonically related frequencies. An ideal 10 m long ...
Andrew's user avatar
  • 3,685
4 votes

Is a boom important to a Yagi?

The boom on a yagi is critical. As you've discovered, without it, it falls apart. :-P Seriously, though, the real function of the boom is to hold the mechanical positions of the elements. It does ...
user10489's user avatar
  • 6,255
4 votes
Accepted

Is a boom important to a Yagi?

A couple of quick pointers for RFID and antennas in general. First, read the free book "Antennas in Practice" by Clark and Fourie has some excellent background on antennas, yagis, helixes, ...
tomnexus's user avatar
  • 11.2k
4 votes

Can I use different materials when building an antenna?

Yes any metal tubing will work for a yagi. If you join tubes make sure there is a good electrical connection, and one that will withstand some rain and movement without coming loose or rusting. ...
tomnexus's user avatar
  • 11.2k
4 votes

Can I use different materials when building an antenna?

Different metals have different conductivity, so changing the metal can affect antenna performance. The higher resistance of non-copper will decrease the efficiency of the antenna. (Although ...
user10489's user avatar
  • 6,255
3 votes

Which antenna would you use?

What you need is a link budget. A higher gain antenna (such as a Yagi) adds gain to your budget and makes the link more likely to work, or allows for less transmit power. I'm not sure what you mean ...
Phil Frost - W8II's user avatar
3 votes
Accepted

Which antenna would you use?

A complete analysis of this situation first must consider the propagation path performance, and then the types(s) of antennas to use w.r.t. the losses on that path. This short propagation path has ...
Richard Fry's user avatar
  • 2,922
3 votes

What is the easiest way to eliminate a beam antenna's backward radiation (rear lobe)?

No real world antenna exhibits "zero" power in any particular direction. Careful design can minimize the power in the unwanted direction but not eliminate it. In a yagi antenna, the front to back ...
Glenn W9IQ's user avatar
  • 18.6k
3 votes

Receive directionality of a sub-optimal Yagi

If a full-sized VHF antenna is too big, then look at how people do direction finding on HF. A longer wavelengh means bigger antennas, so HF direction finders have been dealing with the "too big" ...
Phil Frost - W8II's user avatar
3 votes

Conductive boom vs non conductive boom: what's the difference on a Yagi?

Without all the technical banter take a look at G0KSC site on Yagi design. Justin explains it quite well... The bottom line is when using a non conductive boom or simply isolating the element's from a ...
brian's user avatar
  • 31
3 votes

Can 2 uhf beam yagi antennas be used on a transmitter to get a diversity effect?

In your post the thing that leaps out is about using a horizontally polarized Yagi to contact a repeater which is commonly a vertical antenna. The signal loss in this situation is large. Try your ...
Dick Reid's user avatar
  • 173
3 votes

Can 2 uhf beam yagi antennas be used on a transmitter to get a diversity effect?

For diversity gain, you'd need to have two receivers (or you just switch to the currently "better" antenna; that's called selection combining in MIMO technology and kind of is the worst possible ...
Marcus Müller's user avatar

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