| Author |
Message |
    
Dale
Senior Member
Username: Dale
Post Number: 2118
Registered: 12-2002
| | Posted on Sunday, October 05, 2014 - 8:13 am: | 
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something ive never truly understood is some antennas have a great bandwith then others
does having a greater bandwith take away from gain
of the antenna a little.[what ive been told]or
i was told about the dummyload theory and how it covers alot but doesnt transmit very much
dale/a.k.a.hotrod
cef426
cvc#64
454 [dx numbers]
38lsb
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Tech237
Moderator
Username: Tech237
Post Number: 1820
Registered: 4-2004
| | Posted on Sunday, October 05, 2014 - 5:51 pm: |
|
The short simple answer is yes gain and bandwidth do interact, but I'm sure that doesn't really start to answer your questions.
Antennas are not a simple subject because many factors can affect gain, bandwidth, frequency etc.
For example a thin wire dipole cut for 27.360Mhz will have a certain gain (and it may be a negative one) and a bandwidth.
Now cut a dipole from 3/8" tubing to the same dimensions. Guess what?? Bandwidth and more than likely the frequency of resonance have changed.
The best way for you to really answer this question, in your own mind, is to play -either with antenna modeling software and/or real antennas. Also read some books on antennas such as "easy-Up Antennas for radio Listeners" by Edward M Noll, or "Practical Wire Antenna" by John D Heys, just to name two that start out simple.
I'm sure Tech833 will chime in with more information too.
Tech237
N7AUS
God made me an athiest, who are you to question his wisdom?
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Charliebrown
Intermediate Member
Username: Charliebrown
Post Number: 377
Registered: 10-2002
| | Posted on Sunday, October 05, 2014 - 7:43 pm: |
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Dale, I have always been told that a mono band antenna will give you the best gain for the band it is design for and that there is a little sacrifice made on the gain for multi band antenna's. With today's advanced antenna design I would guess that the difference would be very little. |
Dale
Senior Member
Username: Dale
Post Number: 2120
Registered: 12-2002
| | Posted on Monday, October 06, 2014 - 5:58 pm: |
|
thanks tech237. that does help actually.
but im nowhere smaart enough for antanna
modeling.ive tried swapping out antennas
i used base loaded mobile antennas as they
were easier than dipoles to swap out.
sirio z180 vs wilson 1000/5000
both had same coax ,mounted on same vehicle
z180 was by far had more bandwith. HOWEVER on my mfj 259 ohms or R was only 35..hmmmm????
wilson 5k was much more narrow bandwith
and tuned nearly perfect
mobile to base couldnt tell much difference
between the two dven though the wilson seems to
tune much better.the wilson may have been slightly quieter on rx but more testing needed
on that.tech 237 what do u think of my results so far. charliebrown what u said is what i was told years ago any tring to figure out how a antenna that has bandwith like a dummyload [not really] can talk at all
dale/a.k.a.hotrod
cef426
cvc#64
454 [dx numbers]
38lsb
|
Charliebrown
Intermediate Member
Username: Charliebrown
Post Number: 378
Registered: 10-2002
| | Posted on Tuesday, October 07, 2014 - 10:35 pm: |
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Dale, this is just my guess and only a guess but , I would think that the disc caps with the coil design on the antenna is what would give it the bandwidth. Help us out 833. Dale has a very good question and we need to be taught and we want to learn. Set us straight. See ya later HOTROD. |
