antenna differences

Status
Not open for further replies.

elrod

Member
Premium Subscriber
Joined
Jan 10, 2009
Messages
134
Location
R'ville,IL.
Can some please tell me what is the difference in anntenna types such as discone,ground plane,log periodic,yagi,beam,etc.
Thanks
Chuck
 

kc2rgw

Member
Premium Subscriber
Joined
Dec 22, 2008
Messages
287
Can some please tell me what is the difference in anntenna types such as discone,ground plane,log periodic,yagi,beam,etc.
Thanks
Chuck
Generally speaking....

discone - multiband omni-directional vertical antenna, 1/4 wave elements most of the time per band useful for broad band reception and can generally transmit on the bands it is designed for too.

ground plane - generally refers to a 1/4 or 5/8 wave vertical antenna used for a single band frequency range simple antenna, from no to very little gain vs a plain 1/4 w vertical.

yagi is a type of beam antenna, it is directional, sometimes in the extreme and has 'gain' in a particular direction. The design depends on how focused or narrow the beam width is and the narrower, the higher 'gain' it has in that direction.
 

iMONITOR

Member
Premium Subscriber
Joined
Sep 20, 2006
Messages
7,050
Location
MACOMB, MI.
A log periodic antenna is a multi element wide-band design, with moderate gain. Some roof-top TV antennas are log periodics.

Here is an example from DPD Productions:
 
Last edited:

kb2vxa

Completely Banned for the Greater Good
Banned
Joined
Mar 22, 2005
Messages
6,126
Location
Point Pleasant Beach, N.J.
Eh, you forgot to mention a ground plane antenna is an end fed vertical radiating element working against ground counterpoise. Large ground planes such as AM broadcast towers work against the ground itself while smaller elevated ground planes must have the ground raised up to the radiator. That's the function of the horizontal radial elements, an artificial ground.

By way of comparison the not mentioned thus far half wave center fed dipole is a complete antenna not requiring ground, it is its own counterpoise. On the other hand with a ground plane the ground counterpoise is the other half of the antenna making it complete. Imagine that broadcast tower with an equally tall phantom tower directly under it below ground and you have the dipole equivalent, the Earth being the opposite pole. Consider a magnet has two poles, so does an antenna.

Now don't confuse yourself here, all antennas including the discone and Yagi beam all work on the dipole (two pole) principle one way or another although it may not be apparent from their physical appearance.
 

elrod

Member
Premium Subscriber
Joined
Jan 10, 2009
Messages
134
Location
R'ville,IL.
Eh, you forgot to mention a ground plane antenna is an end fed vertical radiating element working against ground counterpoise. Large ground planes such as AM broadcast towers work against the ground itself while smaller elevated ground planes must have the ground raised up to the radiator. That's the function of the horizontal radial elements, an artificial ground.

By way of comparison the not mentioned thus far half wave center fed dipole is a complete antenna not requiring ground, it is its own counterpoise. On the other hand with a ground plane the ground counterpoise is the other half of the antenna making it complete. Imagine that broadcast tower with an equally tall phantom tower directly under it below ground and you have the dipole equivalent, the Earth being the opposite pole. Consider a magnet has two poles, so does an antenna.

Now don't confuse yourself here, all antennas including the discone and Yagi beam all work on the dipole (two pole) principle one way or another although it may not be apparent from their physical appearance.
Wow!! Thats a whole lot of info to handle-way above my head. I want to put up an antenna in my attic or maybe on my roof. I have 4 scanners that I want to connect. I have 1 used for vhf high and 3 used mostly for 800 mghz. Ihave read the forums and everyone has a differt opinion. I really have no idea.
Any sugestions will be appreciated.
Thanks
Chuck
 

DPD1

Member
Joined
Jul 24, 2005
Messages
1,991
Wow!! Thats a whole lot of info to handle-way above my head. I want to put up an antenna in my attic or maybe on my roof. I have 4 scanners that I want to connect. I have 1 used for vhf high and 3 used mostly for 800 mghz. Ihave read the forums and everyone has a differt opinion. I really have no idea.
Any sugestions will be appreciated.
Thanks
Chuck
Since you've already separated bands between radios, you're a perfect candidate for having each radio dedicated to a band, with band specific antennas. One for VHF, some for 800 and so on. Which ones you get depends on a lot of stuff. If you get everything OK already, then you don't need much. If you struggle to hear stuff over in the next county or something, then get something directional. If you struggle to hear something in all directions, then go with omni high gain. The thing to remember is that gain comes from stacking elements... Either horizontally (directional), or vertically (omni). Either way, the bigger the antenna, the better... In correlation to the wavelength of course. But comparing this ground plane to that one, or this discone to that one, is not going to be a huge difference.
 

elrod

Member
Premium Subscriber
Joined
Jan 10, 2009
Messages
134
Location
R'ville,IL.
Hi

I recommended DPD productions antenna, I have both the scanner LP antenna and the omni X and they are great antenna.

Mrscanner2008
Thanks for the help guys. I will try to decide on what to use hopefully soon.
Chuck
 

radiopro52

Member
Joined
Dec 27, 2007
Messages
203
Location
North Alabama
Thanks for the help guys. I will try to decide on what to use hopefully soon.
Chuck
As Dave (DPD1) already mentioned, if you have multiple scanners to receive different bands, connecting one antenna to each scanner that is designed to receive that band will give you the best performance. But if you don't have the room or the funds available for that, the DPD LP antenna would be a good choice, although I'd recommend a rotor if you don't have one currently.
 

kb2vxa

Completely Banned for the Greater Good
Banned
Joined
Mar 22, 2005
Messages
6,126
Location
Point Pleasant Beach, N.J.
"Wow!! Thats a whole lot of info to handle-way above my head."
It clarified a point someone made regarding your question, trouble is you asked the wrong question. You finally got around to it in response to my post only it was not in the form of a question. Oh well, at least we're on the right track now.

"Ihave read the forums and everyone has a differt opinion."
That's all you'll get unless you narrow it down considerably and then there's a good possibility all you'll get are more opinions. Such is the nature of a forum.

"I really have no idea."
That's always the way it is at first but sooner or later discussion sorts it all out, again such is the nature of a forum. You have to bat it around for a while and sort through what's left and draw your own conclusions. In other words answers often lead to more questions and such is the nature of discussion.

"I will try to decide on what to use hopefully soon."
See? You're making progress already. As for the soon part that's another thing open to debate, quite often it goes on page after page and just when you think it has run its course someone will dig it out of the archives and worry the bone some more.

Oh and good luck, whatever you put up there at least it will be an antenna. (;->)
 

Kennrth

Member
Premium Subscriber
Joined
Jul 24, 2006
Messages
143
Location
Bay Shore Long Island NY
Hi Chuck
If your looking to broadcast (transmit) all these antennas have different attributes as many have already mentioned. If you are looking to receive only there is no need for any of these fancy tennas.
If it is for a scanner all you need is a cheap discone as high as you get get it. Above 50mhz everything is line of site with the exception of periods of atmospheric transconductance. And then you may find after all that you will need to use rf attenuation. Most scanners are under $500 bucks and have limited ability for crossband rejection. Strong signals will swamp your receiver. The receivers in scanners are extremely sensitive and are designed to work with low gain antennas like the one that comes with the radio or mobile mounted tennas. If your looking to receive long distance signals you need to be in an area where signals coming into your radio are low. So you should be in a rural area to consider a high gain antenna on a scanner type radio. Reception is a whole different set of issues than transmission.
The higher you put the antenna the further away you should be able to hear above 50 mhz. The longer the bnc cable the more loss in the line. But that usually is the best mix for a scanner. A lower antenna and lower loss in the receiving bnc will surely swamp your radio with nearby strong signals.
If your on a second story or higher a small antenna is sufficient.
Tenna polarity is of little issue on a receiving antenna. Most signals arrive via mutipath distribution.
A 1S unit is = 6db change. A differnence in antenna receiving polarity results in only 3 db change 1/2 an S unit. Also half the signals reaching your receivers antenna cross polarized by the time it reaches it. Polarity makes little difference on receiving end.
Keep in mind tenna makers are no longer aloud to publish gain specs in ARRL publications because Hams have tested them and found they are all full of crap. An antenna has no amplification capability any how. Gain refers to signal level difference over at isotropic source. These are issues concerning mostly emmisions not reception.
There are very sophisticated techniques to increase reception signals and lower noise which require phasing dipoles and niose blanking dipole and rf mixer. Pretty much useless for most of us.
and your talking about receiving one a specific frequency using these techniques.

A transmitting antenna requires different designs because of how mother earth behaves on resonance throughout the emission spectrum. Earth is part of the antenna circuit and determines angle of radiation and absorbion characteristics. Its behavior varies tremendously depend what frequency you want to emit. Resonance is not a dire receiving antenna issue.
Some variations in design are focusing techniques such as beams antennas. All this has very little impact on reception antenna design.
There are exceptions here Extremely long wave or Microwave receiving antennas a satelite doppler antennas.
Receiving signals from moving satelites does require special receiving antennas. Receiving energy has no polarization and tend to roll 360 degrees. Signals are more focused and require tracking antenna mounts that have to lock on to the target satelite and move with it. And they use circular polarity antennas (dish antennas parabolic receivers). Any you cannot use a common receiver to track these signals. Special receivers capable of Doppler Shifting as the satalite moves.
Microwaves are highly focused and so are the antennas on the receiving end. Radar antennas fall into this catagory. Essentially requiring bore siting.
Very low frequency reception requires design techniques beyond using metal elements which would have to be miles long. Ferrite Inductive tuning is commonly used similar to an AM radio. Effectively making a tuning element look longer to rf energy than it really is.

Remember you are at he mercy of mother nature. Radio conditions vary everyday. They vary through out the day and tend to change dramatically through the evening and accross the seasons. Solar Flux and geomagnetic activity constantly changes the way signals propagate. Weather both local and distant can render some parts of the spectrum unusable at times. The Earths inner core tends to attenuater lateral low band emissions. Sometimes conductive wave guides form in the earths atmosphere allowing long distant transmission in the high bands which are normally line of site emissions.

The earth itself can be an antenuator or conductor depending on band an conditions your operating at.
VLF very low level signals can travel long distances in certain deep depths of the Ocean.

The are thousands of books on the subject of antenna enissions but not much on receiving antenna technology. There just isn't much too it. Unless your trying to do something very special.


Ken C. N2MAC
 

elrod

Member
Premium Subscriber
Joined
Jan 10, 2009
Messages
134
Location
R'ville,IL.
Well: I think ? I have made up my mind to go with the DPD LP scanner antenna. 200 bills is alot,but it looks well made and the reviews seem good. Now I am loocking over coax and splitters.I've read LMR400 is real good,but pricey. I can probably get by with 50'.Was wondering how bad RG-6 would be since I have apartial rll left from a dish install. A stridesberg splitter is supposed to be tops,but also very pricey. Some posts I have read,guys have used an Electroline splitter and have had good luck.
That's more inline with my budget. Considering the RG-6 and Electroline to save money,but will wait and see what you guys have to say-good,bad,or ok.
Thanks
Chuck
 

elrod

Member
Premium Subscriber
Joined
Jan 10, 2009
Messages
134
Location
R'ville,IL.
Hi Chuck
If your looking to broadcast (transmit) all these antennas have different attributes as many have already mentioned. If you are looking to receive only there is no need for any of these fancy tennas.
If it is for a scanner all you need is a cheap discone as high as you get get it. Above 50mhz everything is line of site with the exception of periods of atmospheric transconductance. And then you may find after all that you will need to use rf attenuation. Most scanners are under $500 bucks and have limited ability for crossband rejection. Strong signals will swamp your receiver. The receivers in scanners are extremely sensitive and are designed to work with low gain antennas like the one that comes with the radio or mobile mounted tennas. If your looking to receive long distance signals you need to be in an area where signals coming into your radio are low. So you should be in a rural area to consider a high gain antenna on a scanner type radio. Reception is a whole different set of issues than transmission.
The higher you put the antenna the further away you should be able to hear above 50 mhz. The longer the bnc cable the more loss in the line. But that usually is the best mix for a scanner. A lower antenna and lower loss in the receiving bnc will surely swamp your radio with nearby strong signals.
If your on a second story or higher a small antenna is sufficient.
Tenna polarity is of little issue on a receiving antenna. Most signals arrive via mutipath distribution.
A 1S unit is = 6db change. A differnence in antenna receiving polarity results in only 3 db change 1/2 an S unit. Also half the signals reaching your receivers antenna cross polarized by the time it reaches it. Polarity makes little difference on receiving end.
Keep in mind tenna makers are no longer aloud to publish gain specs in ARRL publications because Hams have tested them and found they are all full of crap. An antenna has no amplification capability any how. Gain refers to signal level difference over at isotropic source. These are issues concerning mostly emmisions not reception.
There are very sophisticated techniques to increase reception signals and lower noise which require phasing dipoles and niose blanking dipole and rf mixer. Pretty much useless for most of us.
and your talking about receiving one a specific frequency using these techniques.

A transmitting antenna requires different designs because of how mother earth behaves on resonance throughout the emission spectrum. Earth is part of the antenna circuit and determines angle of radiation and absorbion characteristics. Its behavior varies tremendously depend what frequency you want to emit. Resonance is not a dire receiving antenna issue.
Some variations in design are focusing techniques such as beams antennas. All this has very little impact on reception antenna design.
There are exceptions here Extremely long wave or Microwave receiving antennas a satelite doppler antennas.
Receiving signals from moving satelites does require special receiving antennas. Receiving energy has no polarization and tend to roll 360 degrees. Signals are more focused and require tracking antenna mounts that have to lock on to the target satelite and move with it. And they use circular polarity antennas (dish antennas parabolic receivers). Any you cannot use a common receiver to track these signals. Special receivers capable of Doppler Shifting as the satalite moves.
Microwaves are highly focused and so are the antennas on the receiving end. Radar antennas fall into this catagory. Essentially requiring bore siting.
Very low frequency reception requires design techniques beyond using metal elements which would have to be miles long. Ferrite Inductive tuning is commonly used similar to an AM radio. Effectively making a tuning element look longer to rf energy than it really is.

Remember you are at he mercy of mother nature. Radio conditions vary everyday. They vary through out the day and tend to change dramatically through the evening and accross the seasons. Solar Flux and geomagnetic activity constantly changes the way signals propagate. Weather both local and distant can render some parts of the spectrum unusable at times. The Earths inner core tends to attenuater lateral low band emissions. Sometimes conductive wave guides form in the earths atmosphere allowing long distant transmission in the high bands which are normally line of site emissions.

The earth itself can be an antenuator or conductor depending on band an conditions your operating at.
VLF very low level signals can travel long distances in certain deep depths of the Ocean.

The are thousands of books on the subject of antenna enissions but not much on receiving antenna technology. There just isn't much too it. Unless your trying to do something very special.


Ken C. N2MAC
WOW again.Over my head. I am only going to be recieving. After the last post maybe 200 is to much to spend an an antenna.
Chuck
 

radiopro52

Member
Joined
Dec 27, 2007
Messages
203
Location
North Alabama
Well: I think ? I have made up my mind to go with the DPD LP scanner antenna. 200 bills is alot,but it looks well made and the reviews seem good. Now I am loocking over coax and splitters.I've read LMR400 is real good,but pricey. I can probably get by with 50'.Was wondering how bad RG-6 would be since I have apartial rll left from a dish install. A stridesberg splitter is supposed to be tops,but also very pricey. Some posts I have read,guys have used an Electroline splitter and have had good luck.
That's more inline with my budget. Considering the RG-6 and Electroline to save money,but will wait and see what you guys have to say-good,bad,or ok.
Thanks
Chuck
I use 50 feet of LMR-400 and it's a very excellent coax. RG6 is usually used for TV but it will work fine. It will have more signal loss than the LMR-400 though, but LMR-400 is also thicker and less flexible.

As for antennas, if you're receiving signals coming mainly from one direction, then the LP would work great for you. If you're receiving signals from all kinds of directions though, maybe you should choose the OmniX as it receives equally in all directions.
 

kb2vxa

Completely Banned for the Greater Good
Banned
Joined
Mar 22, 2005
Messages
6,126
Location
Point Pleasant Beach, N.J.
"Now ya did it! He's probably going to sell the scanner and go fishing!"
Not yet but he will.
As for the soon part that's another thing open to debate, quite often it goes on page after page and just when you think it has run its course someone will dig it out of the archives and worry the bone some more.

Lookie here Chuck, rather than get all tangled up in blue why not KISS? Keep it simple stupid, a good all round antenna to start off with is a discone. Never mind all the discussion, just take my word for it. For outdoors I recommend the Diamond D-130J due to its rugged construction but if it's going in an attic the less expensive Rat Shack will do.
Diamond® Antenna ~ D130J Super Discone Antenna
Diamond D-130J Discone Antenna

As for coax you can do it on the cheap, RG6 quad shield used for cable TV is an excellent choice, just make sure it's RG6 and not the inferior but similar looking RG59. Being new to the game I suggest you trot on down to Wally Mart or Home Despot and pick up a pre-assembled length according to your needs rather than buying tools and trying to make one up yourself. You'll need F connector adapters but you'll find them on line, I only know of one store that stocks them and it's a long way to New Jersey.

When it comes to complicating matters your best bet is waiting until spring thaw, by then this thread should have run its course. Putting up one antenna in the dead of winter is bad enough and you might get frozen to the mast as it is. What will the neighbors say? Oh well, you can hide among the Christmas decorations and wait until spring. (;->)
 
Status
Not open for further replies.
Top