Category: Techniques

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.”

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Introduction to Surecom SR-112 Simplex Repeater Controller

The Simplex Repeater Controller Principle

The Surecom SR-112 Simplex Repeater Controller is a device that allows you to setup a “field” or “emergency” simplex repeater. In other words it is -and as we call it locally- a Parrot. It records and replays what it hears from the radio it is connected to.

So what the user has to do, is define the simplex repeater frequency, set it on the radio and connect the radio to a Simplex Repeater Controller by a purpose made/bought cable. The device will start repeating what the user will speak on the radio.

simplex_repeater_controller small

It is a dead simple, easy and economical way to set up a repeater and cover dead ground, but it does have its shortcoming. While simple technically, it is a bit complicated operationally. It requires all involved parties to expect a repetition of what they are hearing.

Let’s assume that a Simplex repeater is placed on the top of a ridge to cover its two sides. The caller will input the message on the repeater and another user on the other side will hear the repetition. but what if there is a third user on this side of the ridge, within range of the caller? It will hear the message twice! And if not advised Not to, he will probably try to respond on the call, disturbing the repetition….

Continue reading “Introduction to Surecom SR-112 Simplex Repeater Controller”

Χρησιμοποιώντας δυο Aσύρματους σαν Repeater

Η ιδέα δεν είναι καινούργια, και μπορεί να το κάνει ο καθένας διασυνδέοντας δύο ασυρμάτους μεταξύ τους ώστε να λειτουργούν σαν Repeater (Επαναλήπτης) για να καλύψει σημεία που δεν έχουν επαφή μεταξύ τους.

Η σύνδεση γίνεται με καλώδιο μεταξύ της εξόδου του μεγαφώνου του πρώτου ασύρματου  (που ακούει), και του δεύτερου που αναμεταδίδει στην υποδοχή του μικροφώνου του.

Στο YouTube υπάρχουν δύο σχετικά βίντεο αλλά κάτι δεν πάει καλά με την συνδεσμολογία τους.

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Setting up 2 Radios as a Repeater

There is a good chance that you have already watched at least one of the following Youtube  videos.

Both show how to make a repeater by linking two radios (usually Baofengs). But I am having my reservations about the wiring they use.

This one has it DEFINETELY wrong.Set up a Baofeng UV-5R Repeater System

Similarly,  Miklor’s site shows the same method in detail.

The reason is explained in the second video, but still I cannot get what he is doing with the wiring.

HAM repeater (field expedient) using UV-5R Radios

So let’s take it from the start.
Below is the Kenwood type interface, applicable to most Chinese radios our there (Baofeng and Wouxons for sure).

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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”

Notable Notes 1: A Typical Short Wave Radio Setup

CommsPreper is always of good source of descriptive videos on Field/Survival Communications and this one is no exception.

In a short time he demonstrates the parts and the setup of a field radio station.

Briefly described, he uses a HF radio connected to a laptop running RMS Express, a (digital) text messaging app. Usually there should be a modem like device between the too, called TNC, that transforms the digital PC signal to Analog and vice versa.

Continue reading “Notable Notes 1: A Typical Short Wave Radio Setup”