Ham-Radio operator blog and resources from Firenze Italy, edited by IW5EDI Simone
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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 38×25mm 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.
Technorati Tags: antenna, ham-radio, amateur radio, HF antenna
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
An easy-to-build general purpose receive only small wire loop antenna
As much as I like my coax loops, I am also quite satisfied with small loops made with wire or tubing. They have the same or better performance as the coax loops, but might require that you invest in a balun to help maintain directivity and avoid common-mode noise ingress from the feedline. If you need to null local noise yet still be able to listen to most skywave signals, these loops really perform.
The antennas described below bridge the gap between operating as a constant-current small loop (0.10 wavelength or less circumference), and intermediate-sized loop a bit larger than 0.17 wavelengths long in circumference.
If you are interested in building loops made entirely from coax cable you may want to check out my earlier project pages on that subject. It has many operational notes and other items of interest that pertain to small plain wire loops as well as to coax types.
The voltage balun was essential to help me fight common-mode noise and maintain directivity. If you don’t use a balun and have good results, you may not have much noise to deal with in the first place, or the skewed directional pattern has a null that works for you - even if it isn’t textbook. See my balun notes below.
I initially chose 14 feet since my noise problem extends up into the 40 meter band; I didn’t want the antenna to be longer than 1/10th wavelength because you start to lose your nulls with larger wavelengths of wire. I just did a quick calculation: (1005 / 7.150 * 0.10)
Note that I have since opted to use 28 feet overall, because I wanted better sensitivity on 160 and 80 meters, and now at 40 meters the 28 feet of wire still gives me a slight null - adequate enough for me to null my local noise on 40. Unfortunately I don’t have the room for a full-sized loop, so I had to wind it with two turns. See the EZNEC® antenna modeling plots below.
Here are some quick construction tips to get you up and running quickly. I’m still studying the antenna and will improve the page as time goes on.
This document was originally posted by K4WW on rttyinfo.net but this domain has expired since some months at time writing. I’ve archived a copy that I believe could be usefull for beginners.
This is not intended to be an “etched in stone” indication of how to operate a RTTY contest, so please don’t take it that way! Whatever works the best for you, is what you should do, as long as it allows your participation to be fun! These hints were obtained from RTTY contesters, world wide, and only reflect how they try to make their operation more efficient! The more efficient “we” make our contest exchanges, the more efficient we make it for all involved! Band conditions certainly play an important part in the exchanged data, so establishing a “different” buffer could make your exchange more efficient in “not so good” band conditions!
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A Simple Telegraph Key
by Arthur R. Nilson, McGraw-Hill, New York, 1942
A professional looking radio key can be made by the beginner or experimenter at a cost of a few cents for parts. This key is very satisfactory in every respect, as will be seen from Fig. 15. It is made of a short piece of 1-inch-square brass rod and a few other parts easily procurable. Its construction is clearly shown in the mechanical drawings, Fig. 16. As exact dimensions are shown in the drawings, no difficulty should be experienced in making this key.
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During last years, waiting to obtain my licence I’ve spent a lot of my “radio-times” listening to broadcast stations and also trying to intercept unknown and strange signals. Monitoring “extra” bands for unknown signals, still give me that taste of misterious that fascinated me so much in past years.
Although in italy the “utility station listening” was not so popular, I’ve been in touch with some friends that were interested in this kind of excercise, expecially, aeronautical and marine listenings.
I do remember that one of the hardest information to obtain were frequency lists of course, and during the early 90’s, some photocopied tables with undeciphrable words and numbers were circulating among shortwave listeners.
Starting in the mid 90’s and the diffusion of the internet those informations become easier to find and more readable.
Today many sources are availbale for scanner enthusiasts, and frequencies are at public domain.
Here you can find some usefull resources.
I’ve also fond copied of articles originally hosted ad the WUN club, went QRT during this year, that are a bit old but still very interesting.
Many more info from old WUN club site, could be retrieved at the wayback machine
Technorati Tags: hamradio, scanning, radio scanning, maritime, shortwave, amateur radio, vhf, ham radio
HamGrids will allow you to perform calculations with the popular Maidenhead Grid Square system. This grid system is used worldwide by amateur radio operators for many aspects of ham radio. Currently in version 0.5 Beta, with HamGrids, you can Convert Latitude and Longitude into a Grid Square, Convert a Grid Square into Latitude and Longitude, calculate the distance between two Grid Squares, and calculatea beam heading between grid squares.
Require Windows 95/98/2000 or Windows NT 4.0 or higher, Visual Basic 5.0 Runtime DLL
Download HamGrid