Category: Antennas

A Practical Interpretation of Antenna Gain, donuts included.

Antenna gain is not an easy notion for a new radio operator to pick up. Some even go as far as supposing that the antenna gain shows the increase in radio power.

But is not that the actual energy radiated is increased by the better antenna, this is not allowed by the law of the conservation of energy. It is because the radiated energy is handled, shaped-formed and directed better towards you.

A look at wikipedia tells us: ” In electromagnetics, an antenna’s power gain or simply gain is a key performance number which combines the antenna’s directivity and electrical efficiency. In a transmitting antenna, the gain describes how well the antenna converts input power into radio waves headed in a specified direction. In a receiving antenna, the gain describes how well the antenna converts radio waves arriving from a specified direction into electrical power.”

Now this explanation is correct but let’s make it simpler.

Continue reading “A Practical Interpretation of Antenna Gain, donuts included.”

Μια ματιά στις Απώλειες των Ομοαξονικών Καλωδίων των Κεραιών μας

Ο παρακάτω πίνακας συντάχθηκε κατά την προετοιμασία της παρουσίασης για το επόμενο Σεμινάριο Ραδιοεπικοινωνιών.

Δεν είναι λίγες οι φορές που ένας νέος ραδιοερασιτέχνης ή χειριστής επιλέγει ένα κοινό ομοαξονικών καλώδιο μεταφοράς για την κεραία του, το RG-58. Αυτό βρίσκεται εύκολα, είναι σχετικά οικονομικό, εύχρηστο αλλά παρουσιάζει μεγάλες απώλειες ισχύος, ειδικά στις μεγάλες συχνότητες.

cable-losses

Continue reading “Μια ματιά στις Απώλειες των Ομοαξονικών Καλωδίων των Κεραιών μας”

More Easy Antennas for the VHF/UHF

For the purposes of the next Radio Communications Seminar I constructed 2 antennas.

The first one is a ground plane field antenna using a folding handheld radio antenna.

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An SMA to chassis mount adapter is used and the radials are just solid core wire twisted through the adapter mount holes. The good thing about this method is that the antenna requires no tuning as the vertical element is already pretuned.

Continue reading “More Easy Antennas for the VHF/UHF”

One more DIY Groundplane Field Antenna version

Bret at the SurvivalComms Youtube channel (it is not me, just a name coincidence I did not expect) has built his own version of the Jungle Antenna (Link 1, Link 2)

He uses a ring made from ABS rods to “hang” and position the ground wires, and the handheld’s radio own antenna. From the looks of it performance can further be increased with a telescopic antenna like the Diamond RH-770.

He also has a build of a discone antenna with the same method.

DIY folding VHF / UHF Discone Antenna

Check him out!

 

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Easy DIY VHF Antennas with the BNC Male to Banana Jack Connector

In this short piece I will exploring the uses of the BNC Male to Banana Jack Connector in VHF antenna building.

It is a very controversial item cos it allows easy connection of the antenna elements, has a build-in coax connector, is stout enough for field work, and has also 2 mounting holes to pass your wire or paracord through. Practically you can build anything with it as long as you can cut and strip some wire.

Unfortunately I am too  occupied with lesser stuff to make and tune the actual antennas, so please make do with their simulations and a few comments.

The Vertical Dipole

Dipole

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Prototype Build: Backpackable Foldable Yagi antenna

This is only the proof-of-concept prototype.

I have been cooking a design for a backpackable 4-element Yagi antenna for some time now.

The basic idea is to make a telescopic boom out of two PVC pipes and have removable elements that store inside it.

It took me some time to figure the method of attaching the aluminum welding rod elements (used Kosh electrical connectors) and how to integrate the feed point inside the boom. This will be the next build step.web-0593-640

Feedpoint detail

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Basic Antennas for VHF-UHF Field Communications part 1

You have your first radio for some time now, you want to increase its performance in the field and also make a better radio kit for it. If you haven’t heard or read yet, the three most important words in radio communications are: Antenna, Antenna, Antenna

(which are followed by the next three: Location, Location, Location)

So, let’s see what your starter antenna options are . And that means simple, economic, easy to deploy -or even make- radio antennas for the VHF and UHF bands.

 

The Groundplane

It is the antenna that uses an artificial “ground” to work. In a base antenna the “ground” is the 3 or 4 radials that extend from its base. In a mobile (car) antenna the “ground” is defined by the car’s metallic body.

So a way for a ready-made option is to take a mobile antenna (that is already pre-tuned) and create its ground yourself.

One option is to get a magnetic base antenna and nail a metal sheet on top of a pole. This can be a lid of a paint can, a cookie baking tray etc etc. Then you stick the magnetic mount antenna on top.

Continue reading “Basic Antennas for VHF-UHF Field Communications part 1”

A look at some Older Articles of ours

The SurvivalComs blog sprouted from our other blog, the GreekPreparedness Blog.

In there one can also find articles on survival communications.

Yu can have a look at them by following the relevant links.

 

A Spare-Emergency Cell Phone Kit

 

Battery Banks for Handheld Radios

DIY Handheld Radio External Battery Pack

My HT Radio Powerbank, Generation 2

Continue reading “A look at some Older Articles of ours”