Reflect??? anyone care to explain?

[Gummybear]

I am not even sure I spelled it right. but who can explain reflect? I have a certain someone who says low SWR is good but low reflect is where it is at.

In my understanding of SWR, is that your swr was a reading of how well you antenna was tuned or "matched" to your system.

which directly relates to how efficient your antenna is.

But according to someone I speak too, after you rough tune your ant swr with a antenna analyzer then you should tune it with a bird for reflex.


Who can straighten me out and explain reflect to me?

[jessejamesdallas]

If you can get it tuned to 1.0 - 1.1 SWR with 46 to 52 ohm, and X=0 on a Antenna Analyzer...You won't need to do anything else...Reflect will be fine.

[Gummybear]

I dont actually have a antenna analyzer... but was looking for a explanation of reflect...

[Hazelnut 7201]

Reflection is when your transmitted signal reflects off of near by objects (usually metal) and is being received by your antenna.

This may be a dumb example, but the next time you wash your truck. Stand next to the closed truck door and spray the nozzle straight at the door.
You will get wet, right. That is reflect.

SWR is the ratio of the transmitted signal and the reflected signal.

If after tuning your antenna and your SWR's are higher than you would like, the most likely culprit is reflection. Try moving the antenna away from metal objects.
Now, remember that reflection can not only come from reflecting off of the cab, but it can also be reflecting inside a bad coax or connecter.

[Gummybear]

Thanks hazel for the simple explanation, much appreciated.

['Doc]

SWR, Standing Wave Ratio, is a measurement to tell you how well your antenna is 'matched' to the feed line and radio. It does that by measuring the amount of forward voltage or current, and the amount of voltage or current reflected back from the antenna. If there is a very good (perfect) impedance match then the SWR is 1:1, or one to one (there is no '0' on that scale). That 1:1 match is almost never achieved, just too many variables in manufacturing, installation, etc.
The exact same thing can be found by using a forward and reverse reading watt meter. In that case, you have to do the 'ratio' thingy, the meter doesn't do it for you. Very basically, any power reflected back from the antenna is not good. Until it gets fairly high, it isn't necessarily bad, just not as good as it could be. That "Reflect" is just a shortened way of saying 'reflected power'.
One fallacy is that SWR tells you anything about the efficiency of an antenna, it doesn't. It can only tell you how close the impedance of the antenna matches the impedance of the rest of the antenna system, and depending on where that measurement is taken, it doesn't really tell you much about that. If you really want to know how well the antenna matches the feed line, take that reading at the input to the antenna, not on the other end of that feed line where you usually are. That SWR meter can only tell you how what is immediately on the front and back of it match, that's it. You can make assumptions from an SWR reading, but you know what they say about assuming stuff.
- 'Doc

[Hazelnut 7201]

Take a look at this animated SWR calculator link from BesserNet. It was once passed on to me and I found it to be helpfull.

[Please login or register to view this link]

[the_junkie]

If you can get it tuned to 1.0 - 1.1 SWR with 46 to 52 ohm, and X=0 on a Antenna Analyzer...You won't need to do anything else...Reflect will be fine.

If you want to be close enough...

otherwise...get a 1/4w or 1w bird slug and tune until the needle doesn't move...

i still had fine tuning to get rid of my reflect completely after getting 49ohms x=0 1.0swr

reflect is the watts coming back into your system through your coax. You can have a low swr but a lot of reflect because of pushing out lots of power...I fine tuned with reflect and i have no reflect with 600 bird watts coming out...

[Gummybear]

Oh you didn't know? you better call somebody!!!!!


I would like to thank everyone for all the great contributions that where posted.

[Red Warrior]

Antenna resonance is the frequency (in MHz) where the antenna is in a state of electrical balance, which is determined by the length of the antenna. If there is a mismatch between the radio, coax or antenna, part (or all) of the transmitters power is reflected back down the coax. The amount of the power reflected back depends how bad the mismatch is. Some power meters can measure power using a directional coupler allowing both forward and reverse power measurement. Forward power is that moving toward the antenna and reverse power is that being reflected by the antenna back towards the transmitter. The combination of the forward wave traveling down the coax (towards the antenna or opposite during receive) and the reflecting wave is called a standing wave. The ratio of the two waves is known as the Standing Wave Ratio (SWR). Generally you want a low SWR, preferably less than 2:1. In some mobile installation it is not possible to get the ratio lower than this without using a special matching device because the impedance of most mobile antennas are lower than 50 ohms.

At resonance, the input impedance of a decent-quality, correctly-mounted, antenna will be about 25 ohms. By definition, the resonance point is where the reactive component equals zero (X=Ø). Since the impedance of our coax is 50 ohms, the resulting SWR would be 2:1. However, if you adjust the antenna to a frequency higher or lower than the true resonant point, the SWR will decrease, perhaps to 1.5:1. For this reason, you should use an antenna analyzer with a reactance readout, when adjusting the antenna.

You should look for the lowest reactance, not the lowest SWR when adjusting any matching device. Once the matching device is properly adjusted, the minimum SWR point on your transceiver (or external SWR meter) will be very close to the actual resonance point of the antenna.

The antenna is performing at its best when it is resonant, not when SWR is lowest.

[Gummybear]

red warrior, comes in off the bench with 2 seconds left in the game...He gets the ball! drives down court and jumps clean over everyone to provide a dominating one handed slam dunk of a answer!!!


Eat your heart out Micheal Jordan!

[cerberus]

I counted 42 black dots

[Gummybear]

thats funny...

[Double D]

Antenna resonance is the frequency (in MHz) where the antenna is in a state of electrical balance, which is determined by the length of the antenna. If there is a mismatch between the radio, coax or antenna, part (or all) of the transmitters power is reflected back down the coax. The amount of the power reflected back depends how bad the mismatch is. Some power meters can measure power using a directional coupler allowing both forward and reverse power measurement. Forward power is that moving toward the antenna and reverse power is that being reflected by the antenna back towards the transmitter. The combination of the forward wave traveling down the coax (towards the antenna or opposite during receive) and the reflecting wave is called a standing wave. The ratio of the two waves is known as the Standing Wave Ratio (SWR). Generally you want a low SWR, preferably less than 2:1. In some mobile installation it is not possible to get the ratio lower than this without using a special matching device because the impedance of most mobile antennas are lower than 50 ohms.

At resonance, the input impedance of a decent-quality, correctly-mounted, antenna will be about 25 ohms. By definition, the resonance point is where the reactive component equals zero (X=Ø). Since the impedance of our coax is 50 ohms, the resulting SWR would be 2:1. However, if you adjust the antenna to a frequency higher or lower than the true resonant point, the SWR will decrease, perhaps to 1.5:1. For this reason, you should use an antenna analyzer with a reactance readout, when adjusting the antenna.

You should look for the lowest reactance, not the lowest SWR when adjusting any matching device. Once the matching device is properly adjusted, the minimum SWR point on your transceiver (or external SWR meter) will be very close to the actual resonance point of the antenna.

The antenna is performing at its best when it is resonant, not when SWR is lowest.

Agreed...

[SlingShot]

WAy oVer My hEaD.