Here you can find articles I’ve cached, that are no more available in the net or are very rare to be found. Where possible credit will be given to authors.
This week I’ve started investigating on Inverted L antennas for low bands (160 to 40). Expecially for restricted space scenarios, like mine. I found some interesting articles on the net, and a couple of PDF that I’ve embedded in an article dedicated to Inverted L Antenna for Low Bands
Chooe your antenna
DL9KCE released a new version of his ICNIRPcalc software that allows you to calculate safety distances for many know amateur radio antennas with respect to ICNIRP limits.
Calculations are done by considering many depending factors, like your Antenna characteristics, Band, Gain, Power Output, Coax Line, additional attenuation and many more.
By variating any of these values a different Safety Distance is calculated.
You can choose by many popular antennas, and I found even my GAP Titan DX antenna… but if you cant find it, you can always create your own antenna, from the File Menu you can choose “Construct your own antenna” and you will be able to put your custom values.
The software is free to use, and is based on a german version, that is much older but suited for German antenna safety regulation, that looks like to be very strict.
I’ve enjoyed playing with varing Output Power, coax cable and band and noticing the changes in EIRP or Ant. Input power… very interesting.
You can directly downoload the software from here or by visiting the IARU Page where the software is hosted under the EMC section.
The ICNIRPcalc is a MS windows application of aprox 900Kb, I’ve tested under Windows XP (running on a virtual machine under my MacOS) and is Multilingual too, having an English German and French translated interface.
Choose your feed line
This antenna requires the use of Tuned Open wire feed line , ladder line , window line , etc.
NOT Coax cable !
It is suggested a 450 – 600 ohm line.
This antenna also requires the use of a matching network “Transmatch” at the transmitter end of the feed line.
WH2T used a 75 meter band Double Extended Zepp Antenna with very good success. He affirmed to have worked all 50 states and several countries with 100 Watts using theantenna on the 75 meter band.
Band Coverage
With a good antenna tuner the antenna will work 6 thru 160 meters, but this antenna will only tune the 160 meter band if the open wire feed line is the proper length.
More info on Double Zepp Antennas
Double Zepp Antenna
The Zepp, short for Zeppelin is any resonant antenna end-fed by ladder line.
A Double Zepp is a center-fed 1/2 wavelength antenna.
The double extended Zepp is a dipole type Antenna consisting of two collinear 0.64 wave length elements fed in phase.
This double extended version provides 3 db gain over a dipole on the band it is designed for and each side or leg is about 5/8 wavelength long.
When measuring the wire it is very important to get each of the two sides as close to the same length as possible.
The formula to determine the length of each side is
599/Freq in Mhz = .64 wavelength.
So to design an antenna for 3.85 Mhz take 599 divided by 3.85 = 155.585 Feet per side or 155′ 7″ each side.
Double Extended Zepp Antenna Horizontal Directivity Pattern
This 75 Meter antenna would be about 311′ 2″ overall length.
With this antenna the feed line should be routed away from the antenna at a right angle for as great a distance as possible. This will prevent current imbalance in the feed line caused by RF pickup from the antenna. A right-angle departure of 1/4 wavelength or greater is suggested.
To avoid problems matching any center fed antenna with high impedance open wire lines, keep the feedline around these lengths.
[The WORST POSSIBLE line lengths are shown in brackets]
160 meter antenna 35-60, 170-195 or 210-235 feet
[Avoid 130, 260 ft]
80 meter antenna 34-40, 90-102 or 160-172 feet
[Avoid 66, 135, 190 ft]
40 meter antenna 42-52, 73-83, 112-123 or 145-155 feet
[Avoid 32, 64, 96, 128 ft]
Some slight trimming or adding of feedline may be necessary to accommodate the higher frequency bands.
Copyright to W2HT
This article was originally available at bloomington.in.us/~wh2t/zepp.html
Novice 4 band vertical antenna
Putting your first ham radio station together can be an expensive proposition. One way to cut costs is to keep the antenna simple. Here’s how WB1FSB shaved the price and provided four band operation.
This old QST article illustrate how Marian Anderson WB1FSB setup a four band 80 40 15 and 10 meter band, ground-mounted vertical antenna.
After having read the ARRL antenna book he decided to setup the antenna in the back-yard where restricted space let him desist from setting up dipoles or other type of wire antennas.
Moreover he decided to use the metal fence that delimit the back-yard as an extended ground system.
Total height of antenna, made by telescoping aluminium tubing was 7.62 meters (25 foot).
read the full PDF File, it can be downloaded here
This is a project of an easy to build dual band (UHF and VHF) j-pole antenna done with a common TV twin lead and some coax cable.
Original PDF document can be downloaded here
As published in antennex Dec. 2001
The 40 Meters band stealth vertical antenna by K7ZB
“You’re 30dB over 9 here…” So goes the consistently fine signal reports received from around the USA and beyond – on 40 meters at the peak of Sun Spot Cycle 23. The most common antenna used in ham radio mounted over poor desert soil conductivity still performs beautifully!
Original article by K7ZB
Results
The simple 15′ vertical antenna shown mounted on the railing of our second floor deck has produced almost 200 countries worked around the world… VQ9′s in Chagos and 3B8′s on Mauritius in the Indian Ocean, TX0DX on Chesterfield Reef, VK0MM on Macquarie Island in the Antarctic region, BQ9P on Pratas Island off Taiwan, ZM7ZB on Chatham Island in the South Pacific along with FO0AAA on Clipperton, 9M0OO on Spratly Island in the South China Sea, JT1CO in Mongolia and on and on. What I hear, I can usually work with this little wonder and the small size and profile make it feasible for use in deed restricted neighborhoods.
A radio amateur friend and antenna designer came up with a simple design for a 10 meter vertical, which another friend and I modified to make work for the 14, 18, 21, 24 and 28 MHz ham bands. Its performance surpised us, and I’ll share it with you, in case you too are looking for a simple, inexpensive DX antenna that really performs well.
Main Antenna Concept
The basic concept is to put up a piece of aluminum tubing with a telescopic section held by a small hose clamp to adjust the height. By attaching the center conductor of a coax feedline to the tubing, and the shield of the coax to a couple of radials from the base of the tubing you can load the vertical across quite a broad range of frequencies.
Of course, with a vertical element of approximately 15′ this is a non-resonant antenna for the 10, 12, 15, 17 and 20 meter bands. I chose this length on purpose to allow the system to be tuned to resonance with an antenna runer.
Tuning
Since the SWR in an antenna system of this type will be relatively high, an antenna tuner unit will definitely be required. You may need an external ATU if the one in your transceiver can’t handle the impedance mismatches involved. Here at K7ZB, I drive my TS570 (which has a built-in ATU) thru the amplifier, which then drives a high power ATU to the antenna. I put the SWR/Power meter between the amplifier and ATU to ensure a good match for the amp, and in cases where I run barefoot without the amp, I can still use the ATU to assist the transceiver’s ATU in ensuring a good match.
In this way, everything is matched for maximum power output: from the transceiver to the amp, and amp to the antenna. And, even though the SWR’s are high at the feedline and the antenna, it doesn’t matter because the system is matched with the ATU.
Need a general purpose antenna on “6 – the magic band” ?
The J-Pole is an easy-to-build and inexpensive device that provides an omni-directional vertically polarised antenna without the need for a ground plane. In technical terms, it is an end fed vertical 1/2 wave which is fed via a 1/4 wave matching stub.
If you need more info or dimensions for other frequencies, check out the web on J-Pole antennas.
This construction will take your 1-2 hours and it will cost you about $25.
cost breakdown below is for the material actually used, longer tubing lengths may be required that inflate the apparent cost.
Materials :
1 x 6.1 metre length 19mmx1.5mm round aluminium tubing ($12.75)
1 x 1000mm length 16mmx1.2mm round aluminium tubing ($1.50)
1 x 200mm length 38x25mm rectangular aluminium tube (x 1.0mm wall) ($1.80)
4 x 12-23mm stainless steel worm-style hose clamps ($1.50 each)
2 x 16mm (tubing size) plastic chair tips ($0.70 each)
16 x aluminium pop rivets
50 ohm coax cable, eg RG58A/U, minimum length 3-4 metres
200mm x 32mm white outdoor conduit
Nylon cable ties etc…
I’m looking to setup a hidden / indoor antenna, and i’ve found a couple of interesting articles on hidden / stealth antennas
This small antenna can allow hams which lack space to install an antenna for 40 meters. This project has been originally produced by F6CYV. I’m going to test this antenna in the coming weeks. I will try to setup this inside my balcony.
According to his experience, using it form inside the apartament, european singals are all very readable, he has worked over 150 countries.
The antenna is made of 2mm wire.
The 2 coils are constituted by 18 turns of 2 mm wire, distance of tunrs is also 2 mm.
The diametre of the coils is of 7,8 centimeters.
The Feed of the dipole is done with a 75 ohms tv coaxial cable.
A 1/1 balun would be recommand for a correct feed of the coaxial cable to the dipole.
It is not necessary to use a coupler, it is enough to set the length of both extremities of
the dipole in order to have at 7.050 mhz a low SWR, and especially to pay attention what the lenght of the 2 sides of the dipole to be identical.
[tags]antenna,ham-radio,amateur radio,HF antenna[/tags]
G5RV verses Superloop 80
Many operators with small lots, a G5RV is what can fit for the 80 and 40 meter bands. The G5RV is 102 feet long and has a 34 foot
section of twinlead followed by coax into the shack, possibly with some sort of RF choke on the coax. The ends are typically supported by ropes up in
the trees. An 80 meter dipole would be about 134 feet long.
A tiny lot is limited in antenna potential and zoning laws prevent real towers.
RadioWorks “Superloop III” designed by Jim, W4FTU, and refined over the years, is a good alternative