Wednesday, April 3, 2019

Whatever happened to the crossed field antenna?

About 20 or 30 years go there was a lot of excitement about the crossed field antenna. They promised a solution to a problem many amateurs face - how can one efficiently transmit HF from a tiny space such as an apartment balcony or small courtyard. A CFA could be tiny - as small as 1% of a wavelength in size. 

Conventional wisdom was that such micro antennas were lossy compared to the usual regular full-sized dipole or ground plane. So, yes, you could transmit on one, but most people would struggle to hear you, at least on voice modes. 

Amateurs were both curious and wary when news of the cross field antenna came out. Suspicions were that the antenna got most of its claimed performance by causing the feedline to radiate. Concerns were not quelled by secrecy on the part of the developers and promoters of these antennas.
For example reviewers were not given design information or allowed to look inside review units. This did not go down well - 'open science' and 'build it yourself' being two of amateur radio's tenets. 

It's been many years since I last saw an article on this type of antenna in a magazine or on a recent website. And other types of ultra-compact antennas (such as the EH) have come and (I think) mostly gone.

Anyway, if you're curious about the crossed field antenna story, here's some articles worth reading. 

* Kabbary Antenna Technology Co (from one of the inventors) 

* What's wrong with the cross field antenna by AA6PZ

* G0KYA's account of cross field loop antennas (also see blog post & RadCom review)

* VK2EDB crossed field antenna for 14 MHz

* VK5BR crossed field loop antenna for 3.5 MHz (pdf)

* Academic article from Kirk T McDonald on crossed field and EH antennas

* Is this AM antenna for real? by WC Alexander

PS: Want more practical antenna ideas? Consider this selection of antenna books. They are affiliate links meaning that I receive a small commission (at no extra cost to you) if you decide to purchase.


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