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.”

HAMsmithing July 2017

This is a DIY USB charging cable for my Kenwood TH-F6A/F7E handheld radio.

web-IGP3869It is the same concept like the Baofeng USB to 10V charging cables that are found on eBay and amazon. But the virtue of the Kenwood HT is that it accepts a wide array of operating and charging voltage. Plugged to a 12V source it both charges and operates.

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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”

Do NOT miss out on Bret’s SurvivalComms Youtube Channel

By a strike of luck the SurvivalComms name is used by me for this blog, and by another guy (Bret) for his YouTube channel.

It also happens that we both are focused on practical HAM radio matters for Survival and Prepping.

Bret is not only knowledgeable but also good at breaking down matters and applications  into simple, layman’s terms. Among these are his DIY simple antennas.

So DO subscribe to his channel.

Radio Communications Musings no1.

What is Communications?

The word has obviously has to do with “Community” in the sense of Sharing. Sharing of information that is. But what kind of information?

To put it straightforward, it is about information that will allow proper decision making on all levels of involved parties, and for the task at hand.

Imagine you are in a rescue team searching for an injured hiker. What kind of information would you beam back to base once you find him?The victim status is an obvious one. Time of arrival is another, needed resources and assistance on route is another, etc.

But does the base needs to know that you have arrived at a tight spot and you will have to rig a way to pass the stretcher along a crevice? So in the process you need to judge what to pass on and what to leave out. Cos too much of data may needlessly  burden and clog the command center, delaying decisions.

Continue reading “Radio Communications Musings no1.”

Charging your Kenwood or Yaesu radio with USB power

If you are an owner of Kenwwod or Yaesu handheld radio, or anyone that accepts a charging input of 12V, then you might try this:

web-igp3669-small

The item regarding, is a USB to 10V adapter made for the Baofeng cradle charger. Its power plug is a 5.5×2.1 one. Then one can add an adapter cable for the plug his radio uses (the Kenwood one is 3.5×1.35mm). And have a way to charge from any USB port.

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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”