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[Articles Home]  [Add Article]  

HF Antenna Installation Hints

from Don, W8AD on October 22, 2011
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"Editor's Note: Due to the popularity of some of eHam's older articles, many of which you may not have read, the eHam.net team has decided to rerun some of the best articles that we have received since eHam's inception. These articles will be reprinted to add to the quality of eHam's content and in a show of appreciation to the authors of these articles." This article was originally published on: 11/12/2006





This article is for those who are new (and not so new) to HF and need good HF wire antenna installation information, for best performance and lowest SWR across the HF bands.

Problem Solvers for Wire Antenna Installations

Of the many questions we get concerning HF wire dipoles and slopers, many deal with the same common issues of antenna installations and performance problems. Indeed, many of the problems turn out not to be problems at all when we are provided with additional information about the situation, SWR "runs" across each band and the installation "site" itself. Additional information from the customer provides useful clues in helping to solve the problems.

The questions we get seem to follow a fairly consistent pattern from those new (and not so new) to HF. Proper installation and operation of VHF/UHF antennas can beVERY different from proper HF antenna installation and that's where the "rub" can come in for those new to HF.

Due to the wavelengths of the VHF/UHF bands, coupling to surrounding objects is usually minimized by placing these antennas only a few feet or so from things in theclose-in environment (roof tops, attics, gutters, other antenna, etc.). Now, here's where things greatly change when installing HF wire antennas.

The wavelengths of the HF bands are MUCH longer than those of the VHF/UHF bands, and coupling (and therefore antenna de-tuning) to surrounding objects can and does occur when HF antennas are placed close to surrounding objects that would not have affected VHF/UHF antennas. As an example, consider a 40 meter dipole (about 66 ft. Long) installed close to aluminum gutters (40-80 ft. long) along the side of your house and you'll see what we mean. Or consider this same dipole placed close to a roof top and within a few feet of attic wiring and HVAC ducting which can be "part" of the wavelength on HF. Installation SITE factors, therefore, are where most of the problems seem to lie with HF antennas, compared to VHF/UHF antennas, unless proper installation guidelines are followed.

Using fundamental antenna theory, and installation experience we have gained over many, many years of dealing with HF antennas may provide the answers you are seeking. No engineering formulas and complex theory here, just practical information gained from customers themselves, in addition to our own test results and operator knowledge as hams.

You're looking for the "how, why and what to do"! Some of the following points will be very basic for some of you, but in talking to many hams of all levels of experience, we hope you will find these points and suggestions useful and time saving.

A. Slopers (quarter wave) have a unique set of installation requirements compared to the typical half wave dipole. Basically, they require operation on a support/tower (35 feet or higher) with an HF size beam on top to act as a "capacity hat", sort of like an upside down vertical where the beam elements are like the radials of a ground mounted vertical. Also, there needs to be a good ground return path down the tower, and the sloper needs to be "in the clear".

Metal guy wires that are not "broken-up" with insulators, and other wire antennas on or near the tower can cause serious problems (SWR and tuning). SWRs are most likely going to be a problem if these precautions are not considered. Sometimes, an external wide range tuner can help. It has been written that it's a lucky thing for a sloper to work correctly at all, since the support tower, guy wires and other attached antennas are a part of the sloper circuit. And, that can be true. However, with proper installation, a quarter wave sloper can be a very effective low band 160/80 meter DX antenna for those with limited space and lower height capabilities. We have many reports of multiple DXCC awards on these bands with quarter wave slopers.

B. Dipoles are a relatively simple design and usually easy to install and tune with good SWR, but they too require some thought for proper operation. Dipoles operating on 20 through 10 meters should be at 30 feet, or more, in the air. Dipoles operating on 160/80/40 meters should be at least 40 feet in the air for good SWR and at least average performance. Of course, there are exceptions to these numbers based on the customer "site". Higher heights on the low bands significantly improve performance. We have many customer reports of good operation at lower heights, but that depends on how high the "site" is electrically above ground at what's under the antenna. We can't predict that. Even at decent heights, both slopers and dipoles need to be in a clear "site", electrically uncluttered. See " Location" below.

C. Site Location. These antennas need to be as far as possible from any surrounding metal objects. Our tests, and those of customers, show that any antenna wire should be at least 15-20 feet from gutters and metal house siding or fascia. Metal guy wires should be "broken-up" with insulators at non-resonant lengths. Odd as it may seem, attics have a certain capacity characteristic (attic wiring and HVAC ducting) and antenna wires should be no closer than 10-15 feet from any roof top, even if it's a nonconductive roof material. Antenna wires should be at least 20 feet from other similar frequency HF antennas, even verticals.

Power lines must be avoided at all costs, and any antenna that may fall as a result of a storm or support failure must be positioned to NEVER fall across a power line. To reduce power line noise pick up, the antenna must be as far as possible from a line run. 30 feet, or more, is preferable.

A low frequency dipole (80/40 meters) can be put up to within 10 feet or so under a higher frequency (20/15/10 meters) beam with little if any problems. In an inverted-V configuration, the end of the wires should be about 8-10 feet, or higher, from the ground. The center feed point of an inverted-V should be offset from a metal support or tower leg by about 18 inches, on a nonconductive arm, to minimize couplingand thus higher minimum SWR. It is also IMPORTANT to note that antenna wires should not touch, or come closer than about 4-6 feet from any tree branch/limb or leaves. This may not be readily known but they can really upset resonant frequency or SWR.

If a dipole is fed with balanced line, the balanced line itself should be at least 6 feet from any metal objects, throughout the length of its run. It should never touch any metal, like window or door frames, as it enters the property. Of course there are exceptions, but this is generally the case. Close coupling of any metal to balanced line can significantly upset the system. Also, balanced line running down along side a metal tower leg or mast can cause serious coupling problems. If the balanced line is feeding a tower mounted dipole, it should come away from the tower at about a 45 degree angle and not near any guy wires or other wire antennas.

D. Attic installations. We have many successful customer reports of attic installations. HOWEVER--and this is a BIGGIE! Attic installations and performances (SWR) are unpredictable due to the fact that HF antennas in attics can be upset by attic wiring and heat/air ducting being nearby. Also, metal gutters and roof/wall material can be a factor. The height above ground (single story, multistory) is also an important consideration as with any "site" conditions.

Depending upon your residence, RFI coupling into stereos, TVs, burglar alarms and even garage door openers can also be a problem, particularly with high power. Due to the coupling effect of attic installations, an external wide range tuner is usually required for proper SWR tuning and operation.

These ideas are passed along to answer some of the questions we get concerning HF wire antenna installations. It is not meant to get into antenna theory and design as there are volumes and volumes of antenna books available from a variety of sources. However, it is interesting to note that in all those volumes, there is very little about antenna installation "site" information. There is information about antenna height Vs angle of radiation and patterns, but that's about it. It's probably because all the theory assumes antennas that are theoretically "in the clear" and in free space (called isotropic). The problem is, that's usually not too practical!

(There is NO commercial content here. These thoughts apply to ANYONE's HF wire antennas (good info for beams too). Pick whichever one is best for you.)

Welcome to HF, and have fun!

Don, W8AD, Alpha Delta Communications, inc.

Member Comments:
This article has expired. No more comments may be added.
 
HF Antenna Installation Hints  
by K9MHZ on October 22, 2011 Mail this to a friend!
Hey Don,

With regard to attic installations, I thought I would be limited to a DX-EE due to the straight run dimension, tip to tip. A friend in our lunch bunch installed a DX-CC in an attic about the same size as mine, drooping the ends down. The thinking is that drooping down and out or even straight down is OK, just don't droop down and inward.

Does this sound right? Hope so, since I may have another band to use if true.

Cheers,
Brad, K9MHZ

 
RE: HF Antenna Installation Hints  
by W8AD on October 22, 2011 Mail this to a friend!
Hi Brad,

Yes, we have many reports of good DX with the wires "drooping down and/or out" but not down and back in toward the main antenna wires. Of course, this depends on what's in the attic (attic wiring, HVAC ducting, nearby outside aluminum gutters, etc.) And, how high the attic is above ground such as a single story house or two story.

If you can use a good wide range tuner and keep the wires 4-5 ft from metal objects, there is a good chance of good performance. Terry, W0FM, tells us he has over 240 countries worked now from his attic installation. We have other reports of various DXCC accomplishments with these attic installations, but the results can be varied and unpredictable.

Don, W8AD
 
RE: HF Antenna Installation Hints  
by K9MHZ on October 22, 2011 Mail this to a friend!
Thanks Don!
 
HF Antenna Installation Hints: outside the USA  
by XE1GXG on October 22, 2011 Mail this to a friend!
Here in México (and I am sure in other parts of the world) most construction is brick-cement. The notion of an attic and wood frame homes are familiar topics to those of us who have lived in USA or Europe, of course. Anyway, I have found that one must keep the twinlead or 450ohm ladder line a few cms away from the walls, that it can and may contact cement walls here and there with some noticeable bad effects, but these are not the end of the world. Here major concerns are 1. getting decent height, 2. avoiding coupling with rebar, 3. being creative with ground systems, 4. living in small, closely spaced lots requires creative interaction with the neighbours (i.e. permission to run the sloper on their roof, a leg of a dipole, etc.). For those with towers and beams, everything else is the same (the capacity hat notion, etc.).

One advantage of living in a five storey condo here is that unlike the USA, there are fewer regulators or regulations, and one can often "take over" the roof, as I have, allowing a full 80m dipole to be up at a low but adequate height for NVIS and then some.


It'd be nice to have some tips for those of us living in these sorts of cement and brick type of constructions.

73
Rob
 
RE: HF Antenna Installation Hints: outside the USA  
by K0IZ on October 23, 2011 Mail this to a friend!
I would add a few additional comments re window line:

1. Don't roll up excess into a coil.
2. Don't bundle with other wires, against tower leg, etc. Keep at least 6" away from everything.
3. Don't bury. Don't put inside conduit.
 
HF Antenna Installation Hints  
by AB6ND on October 23, 2011 Mail this to a friend!
Thanks Don for some good common sense.

Regarding item D - Attic Antennas and performance not being predictable, I wish this could be ponted out to new comers regarding any antenna errected in domestic locations.

Best wishes.
Roy
 
RE: HF Antenna Installation Hints: outside the USA  
by W4VR on October 23, 2011 Mail this to a friend!
Good summary, Don, for newcomers and experienced hams alike. I see a lot of questions being asked repeatedly in various forums concerning proximity of antennas to each other and proper routing of open wire feeders. Hopefully these same individuals will read your excellent article.
 
HF Antenna Installation Hints  
by N7RCS on October 23, 2011 Mail this to a friend!
I'd like to add a contrarian opinion, though the information shared here in the article and comments is great. Often times QTH's are extremely limiting when it comes to antennas and feedlines. In those situations I believe the best advice may be to simply ignore theory and press on! Just last evening I worked the T32C DXpedition on Christmas Island atoll using a 60 foot dipole that's physically touching my home (in fact, it's wrapped around it at about 20 feet high). The feedline (homebrew twin lead) is also touching the house. On top of that, I'm running QRP (about 1-2 watts output). So, despite the fact that I probably broke every rule of theory, I still managed to launch a signal into the ionosphere that somehow traveled nearly 4,000 miles.

Sure, this kind of set up is not ideal, but it goes to show that it can be done.

Jim
N7RCS
 
RE: HF Antenna Installation Hints  
by W3DL on October 29, 2011 Mail this to a friend!
Nice article. I have been through a lot of antennas in 40 some years as a ham operator, and I can't believe it took me so long to discover and appreciate the Off Center Fed Dipole. I never paid any attention to its design principle of a feedpoint placement that would offer impedance values close to the same on several bands. Pure genius. I have been using an OCF Dipole from Buckmaster for a while now and get all the band coverage I need with 1 antenna and coax feed. 7 bands from 80 to 6 meters, no tuner. Height 35' or so in the center, a 45' leg and a 90' leg. All those years I spent with multiple antennas and tuners, and this works as well! Performance is great! Look into an OCF Dipole for simple, effective access to HF radio.
 
RE: HF Antenna Installation Hints  
by KC9TND on November 4, 2011 Mail this to a friend!
I agree this is an excellent article, but I also agree with N7RCS that we often get a bit wrapped around the axle chasing perfect antenna theory in our installations. Few of us live in an environment allowing the ideal antenna. That ought not discourage either a new or experienced ham. Part of the ham "job description" is experimentation. An antenna can be suboptimal yet pretty darn effective. Sometimes you just have to get on the air and make adjustments as you go.
 
RE: HF Antenna Installation Hints  
by K6IHC on November 5, 2011 Mail this to a friend!
I also agree that most residential HF antenna installations are "substandard", compared to the "proper" way to install one. Still, most of us continue to make DX contacts on HF with our less-than-ideal antenna setups. Mine is a homebrew G5RV Jr antenna with the 51 ft dipole section, fed with 17 ft of 450 ohm window line and 35 ft of RG8X co-ax. The antenna runs along the ridgeline of a comp shingled wood frame roof, at about 20+ ft AGL. It is run through a simple MFJ travel tuner and fed with less than 100 watts. I have made some decent solid contacts on 20 and 10m, with a few on 40m, too.

You gotta do what you gotta do and just get on the air...
 
HF Antenna Installation Hints  
by N9AMI on November 7, 2011 Mail this to a friend!
Thanks Don nice article. I had one of your antennas years ago.. Had a fun time with it.. I lit it on fire with the use a good sized HF amplifier. Wife came in hey your antenna is on fire. Total meltdown of a couple of the loading coils.. Very fun..
 
RE: HF Antenna Installation Hints  
by N6XJP on November 10, 2011 Mail this to a friend!
Brilliant. But don't get hung up on details. The antenna doesn't read forum articles...

Hang it. If it works, work it. If it doesn't hang it differently. Your are less likely to get interference with 1 watt than 100 watts. Right?


Theory is theory. QRP is Magic.

Cheers

Dave , N6XJP
 
RE: HF Antenna Installation Hints  
by W9DL on November 24, 2011 Mail this to a friend!
DL
I have more fun with wire antenns. In the summer time my back yard looks like a spider web
W9DL
Conrad
 
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