Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: best 2m/440 antenna  (Read 2185 times)
KF6ASC
Member

Posts: 23




Ignore
« on: May 25, 2004, 07:44:02 PM »


What is the best performing 2m/440m antenna? I prefer a shorter antenna if possible.

thanks
David

Logged
KD5JFT
Member

Posts: 82




Ignore
« Reply #1 on: May 25, 2004, 08:31:10 PM »

Do you need vertical (fm) or horizontal (ssb)?  How much power will you be using?  Are you looking for homebrew or manufactured?  What size limitations are you looking at?  Mobile or base?  Let me know and I will have some suggestions for you.  Sorry I couldn't be more helpful just yet.  I have used several different antennas and can give you an idea on how they compare to each other.  

KD5JFT
Logged
KF6ASC
Member

Posts: 23




Ignore
« Reply #2 on: May 25, 2004, 09:35:50 PM »

hi,

Sorry I should've been more detailed. I'm looking for a base manufactured antenna. It will be hooked up to a dual-band mobile, so I'm looking at 35W 440 and 50W 2m. I don't really have any size restrictions but I would like it as short as possible and still get excellent results.

thanks
David
Logged
WB2WIK
Member

Posts: 20542




Ignore
« Reply #3 on: May 26, 2004, 12:55:53 PM »

The Diamond Antennas model X500HNA is recognized as probably the "most bang for the buck" 2m/70cm dual-band omnidirectional vertical antenna on the market currently.  Reasonably priced, not heavy, excellent performer.

However, it is fairly "tall" (about 17 feet from base to tip) -- which is only normal, considering it's a gain antenna system.

There's no such thing as a "short" gain antenna!  The gain is achieved by stacking vertical radiators one above another, and adding phase shift networks between them so they all work in phase to create as much gain (and thus performance) as possible.  The shorter the antenna, the less gain it has.

The X500HNA has quite a bit of gain, thus its height.  But again, a very popular base station VHF/UHF FM antenna simply because it works so well and is easy to assemble and install, as well as being reasonably priced.  High quality, excellent workmanship and materials.  Moderate wind survival (it's rated 90mph --many "commercial" antennas are rated much higher than this, but they're also heavier and cost more).

WB2WIK/6

Logged
K7IHC
Member

Posts: 269




Ignore
« Reply #4 on: May 27, 2004, 03:48:01 AM »

The Diamond X-50 dual-band base antenna is a fairly short *gain type* antenna.  At about 5 1/2 ft tall, it performs quite well for it's size.  Specs list the gain as 4.5/7.2 dB for 2m/70cm.  I used one for some time, with good results.  I would recommend the N-connector version, as the N is a superior RF connector than the UHF type.
My X50NA is now a backup antenna, as I replaced it with an X6000A tri (2m/70cm/23cm) band antenna.
Logged
AE6OX
Member

Posts: 15




Ignore
« Reply #5 on: May 27, 2004, 11:00:12 AM »

It sounds like you're looking to operate FM through repeaters.  You might look at the Arrow Antennas dual band j-pole. www.arrowantennas.com (see the reviews on eham).  They are very well constructed and only about 5 feet long.  Won't give you quite as much gain as some of the longer commercial vertical antennas but are fine for local FM.  
Logged
KB3KYO
Member

Posts: 74




Ignore
« Reply #6 on: May 27, 2004, 10:01:21 PM »

but I'm wondering how much more performance I'd get by upgrading to a good long antenna, like the Comet GP9.

Any idea (I know this is relative) how much gain, if any, a homemade copper J pole provides?  Just like to compare it to the commercial antennas.
Logged
WB2WIK
Member

Posts: 20542




Ignore
« Reply #7 on: May 28, 2004, 11:41:49 AM »

If you can get the GP-9 up high enough above ground to really work properly, it will greatly outperform a j-pole on 2m or 70cm, or both.

A j-pole is a zero-gain antenna.  It's an end-fed 1/2-wave, with a 1/4-wave matching stub, and works *exactly* the same as a vertical center-fed dipole, which would be shorter and lighter.  The reason the j-pole exists is because it's difficult to feed a 1/2-wave center-fed dipole, since the coax comes from the middle of the antenna and should not run down vertically in parallel with the lower half of the antenna; so a j-pole rearranges a 1/2-wave dipole to create a feedpoint near the bottom, rather than the center, making the coax routing much easier.   But it's still a 1/2-wave dipole, no matter how you slice it, and it cannot possibly have any gain at all.

The GP-9, on the other hand, is a multi-section colinear array with multiple radiating elements and phasing networks (internally) that make an antenna equivalent to three 1/2-wave vertical dipoles in phase; as such, it has substantial gain over a dipole, or over a j-pole.  But of course the tradeoff is that it's *much* taller!

The GP-9 achieves its gain by compressing radiation down very close to the horizon.  As such, if you install it too low to the ground, it may not work very well, as it will be blocked by surrounding objects.  If you can install the GP-9 such that its *base* (feedpoint) is above, and completely clear of, all local obstructions including houses, roofs, utility lines and trees, you will be amazed at how well it works.  Not at all unusual for a GP-9 to bring in signals "full quieting" that really can't even be heard on a j-pole in an equivalent installation.

WB2WIK/6
Logged
KE4DRN
Member

Posts: 3714




Ignore
« Reply #8 on: May 28, 2004, 11:34:09 PM »

Hi David,

Just like to add to the good info you already received,

Cushcraft has the ar270 dual band antenna and it is less then 4 feet tall !

http://www.cushcraft.com/amateur/details.asp?catid=160

73 james
Logged
N3ZKP
Member

Posts: 2008




Ignore
« Reply #9 on: May 29, 2004, 10:49:10 AM »

Steve:

<< If you can install the GP-9 such that its *base* (feedpoint) is above, and completely clear of, all local obstructions including houses, roofs, utility lines and trees, >>

Suggested height? Mine is installed on top of a two-story building on a 10-foot mast. The base is therefore 10 feet abouv the steel roof. I generally have no problem hitting the machines in Hagerstown (60 miles from Baltimore with a big ridge in between) and most of the machines in northern Virginia and southern Pennsylvania, all with about 50w.

Lon
Logged
WB2WIK
Member

Posts: 20542




Ignore
« Reply #10 on: June 01, 2004, 11:55:10 AM »

Hi Lon,

There is no reasonable suggested height, because each installation is different.

For such an antenna, I always recommend: Get it *above* everything in the neighborhood, and that's about as high as you need to go.  If you live in a desert with no trees, no utility poles, no overhead wiring and all single-story homes less than twelve feet high, a good height may be twenty feet, as you'll be above everything.

But if you live where there are 2-story (or taller) houses and buildings, trees, overhead utilities and so forth, you'd want to be above those things: In this case, maybe fifty feet will be required to do about the same job as an antenna twenty feet high in the previous example.

Anyone having a crank-up tower with a VHF or UHF antenna on it, and experimenting with height vs. performance, figures this out in a couple of days...

WB2WIK/6
Logged
N3ZKP
Member

Posts: 2008




Ignore
« Reply #11 on: June 01, 2004, 07:51:59 PM »

Thanks,

I am two blocks from the Inner Harbor so EVERYTHING three blocks North (all of downtown Baltimore) of me is taller!

The installation seems to work well enough for my needs, so I guess that's all the really matters. Smiley

Lon


Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!