Receive antennas Vs. Transmit antennas

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Hello I wanted to know is there much of a difference between receive antennas and transmit antennas. Like Laird and Radioshack antennas is there a difference. Sorry if this is the wrong fourm or not. I was not sure what fourm to put it in. If someone could explain to me the difference because I am not sure if there is a difference or not.

Thank you
 

signal500

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Receive antennas vs Transmit antennas

Hello I wanted to know is there much of a difference between receive antennas and transmit antennas. Like Laird and Radioshack antennas is there a difference. Sorry if this is the wrong fourm or not. I was not sure what fourm to put it in. If someone could explain to me the difference because I am not sure if there is a difference or not.

Thank you
Antennas come in all shapes and sizes, depending on the frequency the antenna is trying to receive. The idea behind an antenna in a radio transmitter is to launch the radio waves into space. In a receiver, the idea is to pick up as much of the transmitter's power as possible and supply it to the tuner. The size of an optimum radio antenna is related to the frequency of the signal that the antenna is trying to transmit or receive.

So, you have to look at what frequencies you are trying to receive and find an antenna that closely matches the frequencies you want to receive. Laird makes professional commercial antennas and they work very well. RadioShack also has good antennas, but you need to look at what you would like to receive. If you just need a all band scanner antenna, then both companies sell them. If your looking to purchase an antenna for a specific band, then Laird would be the brand to use.

I hope that was the answer you were looking for.
 

R8000

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Transmit antennas are built to handle RF transmit power. Coils, caps and other components often found in antennas bases are built to withstand XX amount of transmit power. Durability is also a factor. If transmit is a concern, then there is a good chance the antenna will be built for commercial service durability.
 

SpectreOZ

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Antennas designed specifically for transmitting need to resonate on the intended frequency of use, being out of tune effects both transmit & receive to varying degrees.

Antennas intended primarily as receiving antennas are optimised to cover as much RF spectrum as possible but may exhibit some transmission friendly characteristics (ie. disk cone) however resonance whilst important isn't as critical in an RX only antenna a good example of which is the random longwire antenna.

In comparison a readily available VHF/UHF amateur radio HT antenna will exhibit better performance receiving signals in those bands compared to say the originally supplied broadband scanner antenna but still less than a tuned resonant antenna (either commercial or DIY), an example of which is my home brew Airband 5/8 wave flower pot antenna which receives awesome on the Airband it was designed for but also works well from the FM broadcast band up to the VHF hi band (performance degrades thereon after).
 

PACNWDude

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Like previous posters have said, the antenna needs to be built and tuned for the specifics of receiving only or transmit only or both. And then be able to handle the power output of your transmitter.

The antenna is the most important part of your system. Many people spend a lot of money on the radio and then use the cheapest antenna they can find. You will do better to buy the best antenna you can afford.

A good all around Transmit and Receive antenna I have used is the Diamond Discone. Discone antennas are good if you are transmitting and receiving over a wide bandwidth of frequencies. The cheaper Radio Shack ones will work, but tend to corrode apart after a few years depending on where they are used.

During hurricane's Katrina, Rita and Wilma I used many Larson ground plane antennas to good effect also.

The Shakespeare, Icom and Harris military antennas work well too.
 
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In addition, as an example 800/900 have a 45mhz offset between TX and RX, so if you get an antenna that is tuned for TX (higher on the freq. band) its performance RXing MAY not be so good, and vice versa. Some antennas, do cover the entire ie 800 band some don't. Something else to look into, 800/900 is 45mhz offset, and UHF is 5mhz offset, VHF is not generally defined. Just have to take all factors into consideration.
 

n5ims

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Folks, an antenna is an antenna is an antenna. There's no such thing as a transmit antenna vs. a receive antenna, a digital antenna vs. an analog antenna, a TV antenna vs. a scanner antenna (although the specific design of an antenna may make it more optimized for one function over another, the antenna itself doesn't care).

The important part of an antenna is the frequency range (or frequency ranges for multi-band antennas) it's optimized to work on. The design is also of some importance (some have more gain, others less; some are directional, others not; some are designed for 50 ohm feedline, others 75 ohm, even others 300 ohm; etc.). For receive, most of these are not all that important, but for transmit they are. A transmitter may burn out if things don't match while a receiver will just pick up better or worse as the match goes from perfect to not so much.

One thing to remember, an antenna that covers a very wide frequency range will give up signal strength to do so. An antenna that has high gain will have a narrow frequency range (those designed for multiple bands may have several narrow frequency ranges).

Why would a receive antenna not work for transmitting you ask? Simple, the manufacturer may have used components that have a very low power rating that is fine when you receive (think microvolts and microamps here) but will burn out from the transmitter's power (think volts and amps here).

Why wouldn't a TV antenna be great for a scanner you ask? Simple, TV transmissions use horizontally polarized antenna while 2 way radios use vertically polarized ones. Flip the antenna around to have the correct polarization and it should be fine.

Why wouldn't an "analog" antenna work on a "digital" system you ask? Simply, it will work just fine, but "analog" is old technology and "digital" is new so folks can charge much more for a "digital" antenna than they can for an "analog" one. It's probably the same antenna in the same box so you're paying extra for that bright yellow sticker that says "Digital" or "HDTV".

"But they said this antenna would work on all bands." Yes, but "work" doesn't say "work well". The engineer designed it to "work" on 140 - 150 MHz and 430 - 450 MHz. He also said it will handle up to 100 watts of transmitter power on those ranges. They made a million of them, packaged them up and shipped them out with the words "Dual Band Antenna for 140-150 MHz, 430-450 MHz, 100W. Will also cover 30-70, 100-140, 150-170, 450-500, 700/800/900 MHz bands for scanner use. It slices! It dices! It makes great pancakes with no mess! ...". You get the idea, it was designed and tested for one thing but to sell them they have to say it will do everything anybody could possibly want. It will work well where it was designed to and "work" (but not very well) on everything else.
 
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