We Wind and Test a LOT of Cores
The cores we use in our products aren’t just chosen because they look nice or feel good in some way – and we admit those are good qualities but they’re optional. We actually wind a few, test them, put them in a prototype product and evaluate.
One of the surprises in our journey of discovery has been that Jaycar cores really do hold up well against brand name FairRite cores and in fact offer some marginal improvement. This was completely the opposite of our expectation and shows the value of actually testing and documenting results.
Build Your Own Transformer
At left is the completed core that has good efficiency in the low ninety percent range as revealed by a VNA using the resistor termination method.
It is built on a Jaycar LO1238 core 35mm in diameter, similar to the popular FT140-43.
We have used this with 100W SSB for long overs, many times, and with minimal core heating.
Build Your Own 1:1 Current Balun
In just an hour or less you can build a really quite effective 1:1 Guanella current balun with low insertion loss and good SWR. It is cheap to make and readily reproducible.
This was designed by Owen Duffy – from his blog – https://owenduffy.net/blog/?p=7404
Saying anything is ‘fool proof’ is fool hardy, but this one comes very close. Just hot melt the cores together then wrap the RG316 through them and terminate.
I like to use radials with my EFHW and reduce common mode current on the coax using a current balun. This is the “standard” balun I use to compare others against.
In the full article there are NanoVNA scan results.
This was built using a pair of Jaycar LO1260 ferrite sleeves and 3.5 turns of RG316 cable.There are alternate sleeves available for those without access to Jaycar.