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] 2 Next   Go Down
  Print  
Author Topic: Elmer Advice on Which To Choose  (Read 4143 times)
K4NMO
Member

Posts: 17




Ignore
« on: March 24, 2013, 01:36:32 PM »

I am a new HR HAM and I'm trying to choose my 80 - 10 m antenna.

My receiver is a Kenwood TS-590s and an Icom IC-7000 for HF.  I have a Diamond X50 for VHF/UHF.

I have narrowed down my choices to:

~ OCF/Windom (DX160)
~ Alpha Delta Parallel Dipole (DX-CC)
~ G5RU or possibly a G5RU-Lite

The antenna will be likely be connected on by a pole on a chimney mount with the wires going out my small back yard.  The distance from the dipole to my 2nd floor radio shack is only about 25 feet.

73s,
Chuck Watson
K4NMO
Logged
K5RT
Member

Posts: 144




Ignore
« Reply #1 on: March 24, 2013, 02:13:43 PM »

Congratulations and welcome to the hobby Chuck. You've got two fine transceivers in your station.

Which antenna of the three really depends on how much space you have to work with and how your house is situated on your lot and where the chimney is on the house. All three will provide similar performance assuming the height above ground is the same.

One bit of advice, whenever possible, use a resonant antenna. Use a tuner only when you need to get the SWR below 2:1. A resonant antenna fed with good quality 50 ohm feed line will nearly always be the best performer.

You could make your own set of dipoles easily. You can cut dipoles for 10, 20 and 40 meters connect them to a common feed point. Use a tuner to get the 40 meter dipole to match on 15 meters and you're good to go. With this approach, you only need 66 feet of space for the 40 meter dipole, the 20 and 10 meter dipoles are shorter. You'll save money with this approach as opposed to buying a commercially made wire antenna.

One suggestion you might look into is a multi band vertical mounted on either the chimney, or on 15 or so feet of mast with a pair of radials for each band of interest.

Good luck with your installation. There's lots of good advice on the Internet

Vy 73
Paul.
Logged
N4JTE
Member

Posts: 1155




Ignore
« Reply #2 on: March 24, 2013, 03:41:11 PM »

Congrats; but before you buy anything, please read an article I wrote awhile back. http://www.eham.net/articles/29061
It will save you a lot of time and money.
Regards,
Bob
Logged
N4CR
Member

Posts: 1666




Ignore
« Reply #3 on: March 24, 2013, 04:15:35 PM »

If you MUST spend some money, the DX-CC is the best of that bunch. But you could build 2 or 3 of them for the money they sell for.

There is no magic in a manufactured antenna. You can build anything they can build given time. If your time is worth more than the antenna, buy it.
Logged

73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
K7KBN
Member

Posts: 2802




Ignore
« Reply #4 on: March 24, 2013, 06:18:05 PM »

Experiment with different configurations and different antennas.  Keep a record of what works and what doesn't.  An antenna that works just fine for you might not be so hot for me in my location.

Also - I've never heard of a G5RU.  And I wouldn't have a G5RV.

Have fun and learn...
Logged

73
Pat K7KBN
CWO4 USNR Ret.
AC2EU
Member

Posts: 396


WWW

Ignore
« Reply #5 on: March 24, 2013, 09:16:47 PM »


Also - I've never heard of a G5RU.  And I wouldn't have a G5RV.

Have fun and learn...

Yup. Some kind of resonant antenna(s), but avoid the G5RV.
There is no such thing as an "all band antenna" there are always performance issues.
The closest thing to it may be the fan dipole but that isn't all bands...
Building antennas is half the fun. Enjoy!
Logged

AF5CC
Member

Posts: 863




Ignore
« Reply #6 on: March 24, 2013, 09:34:02 PM »


Also - I've never heard of a G5RU.  And I wouldn't have a G5RV.

Have fun and learn...

Yup. Some kind of resonant antenna(s), but avoid the G5RV.

My only HF antenna right now is a homebrew "more or less a G5RV."  I use 300 ohm Radio Shack Twin Lead instead of the 450ohm stuff and it is a little shorter run that what a true G5RV requires. I have earned 8 band DXCC and WAC using it and 100 watts.  It obviously works.  Cost me $50 or so to build, including the coax.

If you read the aforementioned article "Where do I go from here" you will see that a G5RV is really nothing more than the center fed doublet that the author recommends.  On some bands the G5RV will function pretty much like the extended double zepp.

One problem with a resonant antenna is that it can be limited to one band.  That is fine if you only want to get on 1 band.  However, having more bands to choose from is certainly nice and practical.

John AF5CC
Logged
W5DXP
Member

Posts: 3582


WWW

Ignore
« Reply #7 on: March 25, 2013, 05:59:51 AM »

The distance from the dipole to my 2nd floor radio shack is only about 25 feet.

Your configuration is somewhat like mine. The ZS6BKW antenna is a G5RV-type antenna that, unlike a G5RV, doesn't need a tuner on 40m, 20m, 17m, and 12m. It is a ~92 foot dipole fed with ~38 feet of ladder-line. Since you (and I) don't need any coax, there are no coax losses. Just feed the ladder-line directly through a 1:1 current balun (choke) as I do. Since 40m and 17m are my favorite bands, I am very happy with the ZS6BKW design. However, when coax is not involved, i.e. no coax losses, the ZS6BKW works well on 80m and 10m with a tuner as I have discovered. So the only problem bands for the ZS6BKW are 30m and 15m where the impedance is very high and some tuners may not be able to achieve a match.

That said, let me say something about the myth that a coax-fed resonant antenna is a lot better than a parallel-feedline non-resonant antenna. A 92 foot dipole is clearly non-resonant on 40m with a feedpoint impedance of around 320+j760 ohms. The transmission line calculator at:

http://www.vk1od.net/calc/tl/tllc.php

says there will be 0.073 dB loss in 40 feet of ladder-line with that non-resonant feedpoint impedance on 40m. If we fed a 50 ohm resonant dipole with 40 feet of RG-8x coax on 40m, the coax loss would be 0.312 dB, about four times more loss in the coax than in the ladder-line. In addition, a 90 foot dipole has about 0.4 dB of gain over a 66 foot resonant dipole on 40m.

If a non-resonant antenna fed with low-loss parallel feedline is conjugately matched, it quite often equals or beats a coax-fed resonant antenna. The purpose of an  antenna tuner is to provide a near-conjugate match at the antenna feedpoint which ensures that maximum available power is delivered to the radiating antenna element(s). Here's an article on the subject.

www.w5dxp.com/OWT1.htm
Logged

73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
AC2EU
Member

Posts: 396


WWW

Ignore
« Reply #8 on: March 25, 2013, 07:02:08 AM »

Quote
If you read the aforementioned article "Where do I go from here" you will see that a G5RV is really nothing more than the center fed doublet that the author recommends.  On some bands the G5RV will function pretty much like the extended double zepp.

One problem with a resonant antenna is that it can be limited to one band.  That is fine if you only want to get on 1 band.  However, having more bands to choose from is certainly nice and practical.

John AF5CC

John,
My favorite article on the G5RV is here:
http://www.karinya.net/g3txq/g5rv/
I have tested some G5RV installations with my antenna analyzer. Most behave worse than described in the article.
As you say, it does work, but how well?
A bicycle may work for transportation, but a car is better.

Resonance is a real benefit for both tx and rx, not an inconvenience.
My first antenna was a 40M dipole. If you are going to have one band 40M is a pretty good choice. It always seems to be active.
The fan antenna is a "collection" of resonant antennas which OK if you can only make one run and live in an area where ice and snow won't collect on it.

If you were close by I would invite you experience the difference that resonance makes. For instance, any antenna will work on receive, but when I click to the correct one for the band, the signal strength jumps dramatically.
Logged

WX2S
Member

Posts: 731




Ignore
« Reply #9 on: March 25, 2013, 09:33:41 AM »

I researched chimney mounts fairly extensively several months ago. The word is, "don't." They'll tear up your chimney if used for anything heavier than a TV antenna.

Many years ago, I nailed a steel bracket to the roof ridge to support one end of a 40m dipole. The bracket was like an upside-down Y made of galvanized steel; forget where I got it but it might have been from a chimney mount bracket like this: http://www.amazon.com/Channel-Master-Y-Type-Antenna-Chimney/dp/B00AO79PC8/ref=pd_sim_sbs_e_5

I also tarred the nails to keep it from leaking. Worked great as long as I had the dipole up.  (Might suggest lag bolts instead of nails, though.)

Definitely try to attach it to the roof rafters if you go this route.

73, -WX2S
« Last Edit: March 25, 2013, 09:45:50 AM by WX2S » Logged

73, - Steve WX2S.
I subscribe to the DX Code of Conduct. http://dx-code.org/
KK4APV
Member

Posts: 22


WWW

Ignore
« Reply #10 on: March 25, 2013, 01:34:48 PM »

I researched chimney mounts fairly extensively several months ago. The word is, "don't." They'll tear up your chimney if used for anything heavier than a TV antenna.


I've got a chimney mount for my vertical antenna (Comet 250B), and I'm an architectural historian, so I know a little about this topic.  Smiley

Before The Great War, mortar often had very little cement in it. Pre-1900, most mortars were lime-based mortars (no cement at all).  Add to that the problems of coal-fired heating systems (which are very corrosive to mortar) and you've got a chimney that can hardly support itself, much less the strain of an antenna mount and/or guy wires.

My house is a 1962 brick ranch with an unusually wide chimney (three flues: fireplace/furnace and water-heater flue) poking through the hipped roof. It's strong and sturdy and I have no compunction about putting an antenna mount on it.

In short, if a house was built before 1920, I'd be very hesitant to install any type of chimney mount. Post-1960, I wouldn't be too worried. In-between those years, I'd carefully examine the brick and mortar.


Rose
Logged
W5DXP
Member

Posts: 3582


WWW

Ignore
« Reply #11 on: March 25, 2013, 02:01:02 PM »

Resonance is a real benefit for both tx and rx, not an inconvenience.

System resonance is a real benefit, but resonance in the antenna alone doesn't much matter. What some people don't realize is that system resonance is achieved anytime the impedance at the tuner input is 50 ohms if the power delivered to the tuner falls off on either side of that resonant frequency, according to the IEEE definition of resonance.

Tuned feeders are used to resonant an antenna system as are antenna tuners.

Let's take an example of a ZS6BKW antenna on 40m. My 92 foot non-resonant dipole fed with 38 feet of ladder-line shows an impedance 88 ohms resistive looking into the ladder-line at 7.21 MHz. That's system resonance according to the IEEE definition.
« Last Edit: March 25, 2013, 02:03:37 PM by W5DXP » Logged

73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
AC2EU
Member

Posts: 396


WWW

Ignore
« Reply #12 on: March 25, 2013, 03:18:49 PM »

Resonance is a real benefit for both tx and rx, not an inconvenience.

System resonance is a real benefit, but resonance in the antenna alone doesn't much matter. What some people don't realize is that system resonance is achieved anytime the impedance at the tuner input is 50 ohms if the power delivered to the tuner falls off on either side of that resonant frequency, according to the IEEE definition of resonance.

Tuned feeders are used to resonant an antenna system as are antenna tuners.

Let's take an example of a ZS6BKW antenna on 40m. My 92 foot non-resonant dipole fed with 38 feet of ladder-line shows an impedance 88 ohms resistive looking into the ladder-line at 7.21 MHz. That's system resonance according to the IEEE definition.

System resonance is one thing, antenna resonance is another. It's best to have both.
How does the 88 ohms stack up with a 50 ohm TX? maximum transfer occurs when  Rs = RL.

Your myth-buster article is a special case.
Real antennas are rarely 50 ohms, so there is an impedance translation that occurs through the coax related to:
1) mismatch at antenna
2) frequency
3) VF
4) cable length.
That -500 X may be translated to to something else on the shack end depending on the factors listed above.

Also, I could put an LC circuit on the antenna side that has a characteristic impedance of 50 ohms at resonance. That doesn't make it a good antenna!
Logged

N4CR
Member

Posts: 1666




Ignore
« Reply #13 on: March 25, 2013, 04:57:56 PM »

System resonance is one thing, antenna resonance is another. It's best to have both.

It's best to deliver all of the power you can to the antenna and radiate it. Antenna resonance does not one single thing to accomplish that.
Logged

73 de N4CR, Phil

We are Coulomb of Borg. Resistance is futile. Voltage, on the other hand, has potential.
K0ZN
Member

Posts: 1547




Ignore
« Reply #14 on: March 25, 2013, 05:35:39 PM »

Respectfully, antennas and feedlines do not lend themselves to guessing and assumptions and opinions; commercial or homebrew. To have an antenna system work well, one really needs a basic understanding of what is an acceptable practice and what isn't. Basic antenna theory is not complex, but it is also often not intuitive, which is
why a good book, like the ARRL Antenna Book helps so much.

Seriously and respectfully: Amateur Radio is a technical hobby. There is no way around it, so, BY FAR, the best possible thing you can do at this point is to pick up some correct/factual knowledge about antennas, transmission lines and tuners BEFORE you buy something. Pick up a copy of the ARRL Antenna Book and put in a couple of hours of study time on the basics. The knowledge you gain will save you a ton of frustration and give you a much better signal and you will enjoy the hobby much more.
You will also quickly see that building wire antennas is extremely easy (and profitable if you sell them !!). There is a lot of satisfaction in working people on an antenna
that you built yourself.

You can pick up an older copy of the ARRL Antenna Book on Ebay quite cheap and the info in it is still totally valid and accurate.

The old saying that: "What you get out of something is equal to the effort you put into it." is very, very true for a technical hobby like Amateur Radio.

Put in a little time studying the Antenna Book before you blow some money on a "commercial" wire antenna; the reward(s) for your effort will be paid back many times over.

73,  K0ZN
Logged
Pages: [1] 2 Next   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!