7 May 2018

Powering a ham radio transmitter

by

Last week I announced the crowdfunding campaign to help run a ham radio station at OSCAL. Thanks to all those people who already donated or expressed interest in volunteering.

Modern electronics are very compact and most of what I need to run the station can be transported in my hand luggage. The two big challenges are power supplies and antenna masts. In this blog post there are more details about the former.

Here is a picture of all the equipment I hope to use:

The laptop is able to detect incoming signals using the RTL-SDR dongle and up-converter. After finding a signal, we can then put the frequency into the radio transmitter (in the middle of the table), switch the antenna from the SDR to the radio and talk to the other station.

The RTL-SDR and up-converter run on USB power and a phone charger. The transmitter, however, needs about 22A at 12V DC. This typically means getting a large linear power supply or a large battery.

In the photo, I've got a Varta LA60 AGM battery, here is a close up:

There are many ways to connect to a large battery. For example, it is possible to use terminals like these with holes in them for the 8 awg wire or to crimp ring terminals onto a wire and screw the ring onto any regular battery terminal. The type of terminal with these extra holes in it is typically sold for car audio purposes. In the photo, the wire is 10 awg superflex. There is a blade fuse along the wire and the other end has a PowerPole 45 plug. You can easily make cables like this yourself with a PowerPole crimping tool, everything can be purchased online from sites like eBay.

The wire from the battery goes into a fused power distributor with six PowerPole outlets for connecting the transmitter and other small devices, for example, the lamp in the ATU or charging the handheld:

The AGM battery in the photo weighs about 18kg and is unlikely to be accepted in my luggage, hence the crowdfunding campaign to help buy one for the local community. For many of the young people and students in the Balkans, the price of one of the larger AGM batteries is equivalent to about one month of their income so nobody there is going to buy one on their own. Please consider making a small donation if you would like to help as it won't be possible to run demonstrations like this without power.

tags: promote