| Author |
Message |
    
Dale
Senior Member
Username: Dale
Post Number: 1645
Registered: 12-2002
| | Posted on Friday, November 05, 2010 - 9:56 pm: | 
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ok antennas myth busters heres a good one.
i was listening to a group of local ham opt. on 2meters on my scanner.and this discussion started and i thought the one guy made sense.
he said a narrow banded antenna is better cause
it doesnt have to cover so much bandwith.ok now i know i just opened a can of worms but listened to this for 1hr on the scanner and really got me
wondering if a narrowbanded antenna would have more [punch] than a widebanded antenna of same lenth
dale/a.k.a.hotrod
cef426
cvc#64
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Moonraker
Intermediate Member
Username: Moonraker
Post Number: 261
Registered: 3-2005
| | Posted on Saturday, November 06, 2010 - 12:26 pm: |
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I'm far from an antenna expert but have always been under the impression that a wide banded antenna has less gain than a narrow banded antenna. |
Dale
Senior Member
Username: Dale
Post Number: 1646
Registered: 12-2002
| | Posted on Saturday, November 06, 2010 - 3:57 pm: |
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thank-you. well thats what i heard on my
scanner listing to the local 2 meter group
and it does make sense.hopefully we,ll keep
the posts coming
dale/a.k.a.hotrod
cef426
cvc#64
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Tech237
Moderator
Username: Tech237
Post Number: 1376
Registered: 4-2004
| | Posted on Sunday, November 07, 2010 - 9:49 am: |
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OK, to put the cat amongst the pidgeons WHY would a wideband antenna have less gain than a narrowband one??
I am not saying I agree or disagree, but you made a blanket statement with nothing to support it..
Tech237
N7AUS
God only made some many perfect head, on the rest he put hair.
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Tech237
Moderator
Username: Tech237
Post Number: 1377
Registered: 4-2004
| | Posted on Sunday, November 07, 2010 - 9:58 am: |
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I should have added to my prior post - I can name narrowband antennas that have low gain - like the Hustler 10M mobile antenna bandwidth is around 200Khz, and no gain compared to a dipole, adn Arecebo is a wideband antenna that has heaps of gain across it's whole bandwidth.
Tech237
N7AUS
God only made some many perfect head, on the rest he put hair.
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Dale
Senior Member
Username: Dale
Post Number: 1648
Registered: 12-2002
| | Posted on Sunday, November 07, 2010 - 3:14 pm: |
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no i just stated what i heard listening
to amature radio on my scanner. there [support]
was the antenna was covering so many bands
at one time with a usable swr that it would sacrice performance.bacically a tradeoff.
they worded it better than i did.to my nontechnical opinion this kinda makes sense
and thats were i leave it.for me to honestly believe it id have to actually would have to
try it.now tech 237 do u agree or disagree
dale/a.k.a.hotrod
cef426
cvc#64
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Tech237
Moderator
Username: Tech237
Post Number: 1378
Registered: 4-2004
| | Posted on Monday, November 08, 2010 - 10:47 am: |
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Multi-band and wideband are two different things. Any multiband antenna is not going to be as good as a monoband one because of compromises needed to make it multi-band. One of which is it usually has gaps in it's coverage - there are exceptions to that, but not many.
A wideband antenna is one that covers a range of frequencies without gaps. For example a Discone would be considered a wideband antenna, as is the previously mentioned Arecebo dish, while an Outback would be a multi-band antenna.
Not sure exactly what Arecebo's gain is but I know it a pretty high factor, while the Outback is close enough to 0dbd. I will add that the Discone gains is around that of a dipole, maybe a little less. So there we have two wideband antennas one with almost no gain and one with heaps of gain.
Whereas, in general, the person maybe close to the truth, it is not as cut and dried as he may have made it sound.
Southgate Amateur Radio Club's website shows a gain of 60dBi at 432MHz for Aricebo's 300m dish, and Aricebo's own site lists a gain of 80dBi at 10Ghz.
Tech237
N7AUS
God only made some many perfect head, on the rest he put hair.
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Dale
Senior Member
Username: Dale
Post Number: 1649
Registered: 12-2002
| | Posted on Monday, November 08, 2010 - 7:06 pm: |
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thank-you sir thats whats i was
wanting to know. i didnt have an honest answer
just my opinion.why i asked you. figured you
be the best one 2 ask
dale/a.k.a.hotrod
cef426
cvc#64
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Tech833
Moderator
Username: Tech833
Post Number: 1888
Registered: 8-2002
| | Posted on Tuesday, November 09, 2010 - 11:33 am: |
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I don't know how I missed this one. Tech 237 nailed it, exactly.
I'd like to add- A wideband antenna (not talking multiband here) is not always better than a narrowband one. Wilson likes to use the Q measurements to say that their trucker antennas have more gain than other large coil antennas because their coil has a higher Q (Which means it also has less bandwidth). The recent "Giant Coil Antennas Exposed" article shows that the exact opposite is true.
In our tests, the antennas with the highest Q just happened to have LESS gain on the horizon than the lower Q antennas 90% of the time. So, broad bandwidth does NOT equal lower performance, and we can prove it. Read the article for detailed explanation as to why.
Now, as for multi band antennas vs. mono band antennas, you have to keep in mind that most of the time, the multi band antenna is a compromise. They compromise performance for the multi band capability. There are some exceptions, like the Rhombic or the V-beam. But, most of the time, for the same given number of elements, the elements tuned for a specific frequency will work better than elements with traps or other multi-band techniques. That is just a simple example of efficiency. It's also worth pointing out that a multi band antenna (like a trap vertical) typically has a higher Q than a mono band antenna, yet lower gain. So, that blows the "higher Q = higher gain" argument out of the water.
If you want high gain AND multi band capability, look up the TCI 530 or TCI 540 antennas. But, I warn you, you may have to put lights on them (due to size) depending on your location.
Your radio 'Mythbuster' since 1998
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Dale
Senior Member
Username: Dale
Post Number: 1652
Registered: 12-2002
| | Posted on Friday, November 12, 2010 - 6:07 pm: |
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thanks tech 833. and i did read your review very nice btw. just curious what kinda equiment
do u need to measure [Q]will a mfj 259 work?
also considering doing a quick review of 2
base antennas at copper .maco 5/8 and sirio2016.
i got the 2016 and the maco is setup at a local
operators place. so im not sure if im going to.
but im pretty sure both are 20ft. in lenth and
the maco has 4-9ft radials and the sirio has multi short radials.now the maco is what i consider a narrow band antenna. and the sirio
covers 10-11 meters easily and i think maybe 12
but cant remember for sure.so was wonder if the sirio has some loss due to it being so widebanded
and how would i measure the [Q]
dale/a.k.a.hotrod
cef426
cvc#64
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Tech833
Moderator
Username: Tech833
Post Number: 1891
Registered: 8-2002
| | Posted on Sunday, November 14, 2010 - 6:20 pm: |
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Hi Dale.
If your antenna has a wider bandwidth, it will have a lower Q.
Measuring Q isn't as simple as hooking a meter to it. The Q of a coil is easy enough to measure, even using a simple grid dip meter. However, measuring an antenna's overall Q is a bit more complicated. Several measurements are required, and software is helpful.
Your radio 'Mythbuster' since 1998
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Dale
Senior Member
Username: Dale
Post Number: 1654
Registered: 12-2002
| | Posted on Monday, November 15, 2010 - 8:53 pm: |
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thanks tech 833 what i thought
dale/a.k.a.hotrod
cef426
cvc#64
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