Thursday, June 27, 2019

Ferrite rods for transmitting

We normally associate ferrite rods as receiving antennas in AM radios. However they can be used for transmitting as well. They're not the most efficient antenna but they're still worth playing around with. Especially since amateurs got access to bands below 500 kHz and the rise of efficient digital modes like WSPR. 

Here's some accounts of other peoples experiences with ferrite rod antennas for transmitting: 

* G3XBM's experiments

* US Dept of Interior report on ferrite rods for VLF mine communication antennas Also see this

* Vintage Radio discussion forum thread

* UA6CA & UA6ACA Antentop article

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  1. Peter
    I started playing with a ferrite rod antenna a couple of months before this post. The assembly consisted of 3 ferrite rods from Jaycar with about 12 turns for the tank circuit and 3 turns for the coax feed. I could tune it from about 160M to 40M with either 1 or 2 gangs of the tuning capacitor.
    After several tests using WSPR I was ready to conclude that it worked as an acceptable dummy load when tuned. (on received reports and nothing received) While looking at some of your references I noted that a tapped coil was used i.e. there was conductor extending beyond the tank circuit. I clipped a clip lead (about 60 cm of wire) onto the shell of the tuning capacitor and started to get a report from VK2ALC (admittedly -25db to -30db) on 80M which was where I was sending WSPR test frequency. I only received VK3MI so as one would expect not the most efficient antenna but it did do something.

    If you are interested in playing with such an antenna I hope this feedback helps.

    Philip VK3BAL

    1. Hi Philip , VK3BAL , I am also checking and playing with ferrite emitter antenna in 630m band and WSPR test . Could you give us, some more details or photo link about your improvement comment : “ noted that a tapped coil was used i.e. there was conductor extending beyond the tank circuit.” Thanks 73

  2. Hi. Thank you for these references. I made my own version of a transmit ferrite antenna and I am pleased to say it works well. Just did a 20 meter WSPR test and not only did I get across the country, I gad about half a dozen European stations that heard it. 5W.


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