Looking for a small high gain antenna at 100MHz

i need a high gain antenna at 100 MHz, a yagi antenna would be around 1.5m long and i need something smaller, any suggestions?
thank you...

You can use loop antennas. For design specifications, you can see some commercial loop antennas designed at 13.56MHz.

That is what everyone wants ....... high gain and small size.

How much gain is high gain?

(Note that gain and size are directly related.)

as hinted at by others hi gain = large size at 100MHz a 10 element yagi is going to produce ~ 12dBi gain and be around 2.5m long.
A 3 ele yagi on a 1 m boom will provide ~ 6dBi gain
If you want at least 6dB gain you aint gonna get a smaller antenna for 100MHz

Dave

An antenna option, smaller than Yagi, is Collinear Antenna. Depending by the number of vertical elements the gain is 3dBd up to 9dBd. It has also the advantage that is omni-directional.
http://www.rfiantennas.com/usDataShe...arAntennas.pdf

a gain of 9 dbi would be fine...is there an antenna smaller than 2m yagi that would provide that at 100MHz?

you're just swapping horizontal length for vertical height that datasheet shows the 5dBi gain colinear at 232 inches long (high) in some cases vertical height may be more easily accomodated that horizontal length :)

farishamam ..... you really have no choice the lower the freq the larger the antenna and adding hi gain into the equation = BIG antennas, "ye canne break the laws of physics, captain" ;)

thats why I love working with the microwave bands ... huge gain and physically small antennas

Dave
VK2TDN

---------- Post added at 23:34 ---------- Previous post was at 23:30 ----------

in a word NO, see my previous post. Even a colinear is gonna be very big to get 9dBi of gain prob in excess of 350 inches
if a 5dBi one is 232 inches long

Dave

OK 9 dBi, what are the pattern shape guidelines? Is the co-linear "omni" an acceptable pattern.

A yagi has two dimensions (and thickness as well). You say you want a smaller antenna. Smaller than what? What are your minimum dimensions?

If you have to trade-off dimensions and performance what can you give up?

Where is the antenna going to be used? What are the other constraints?

Lay out all your requirements else the folks here may get tired of playing twenty questions.

I anticipate that it will not be practical to get the gain you want in a sufficiently small package. That is usually how antenna design goes, it is not unique to this thread. Think seriously about what compromises you can accommodate.

You might also do a preliminary yagi design to see if it works for you.