I got a shipment of cores in today. There were 2 off FT240-43’s and 25 off FT82-43’s. Yes. All are type 43 material from Fair-rite. They were purchased in Aus from a highly reputable supplier so I believe they would be the genuine article. I wouldn’t buy them if I hadn’t already tested with them …
Suppliers Should Know Better I’ve just been looking around the internet recently and I saw some head-scratchingly poor advice and, ah, dodgy tech onfo. Seriously, I expected better from what I thought was a professional supplier of baluns. Here are some claims and my refutations. You Can’t Get Good Efficiency With QRP Designs My tiny …
I saw one of these last week on the internet. It is a beautifully packaged FT82-43 UnUn that has a 2 turn primary and 14 turn secondary, the turns are spread out and has the magical bifilar primary. It was well made and looked pretty good. There is one problem. It is very inefficient. It …
A 100W 49:1 UnUn in the palm of your hand. This looks too small to handle 100W – even to me. It is only 64mm long excluding connectors, and 33mm in diameter. Yet I’ve pushed 100W SSB into this for an hour QSO and without ill effects. The reason is that it is a high …
It’s An Addiction – Product Development The week before last I was triggered by a YouTube video that led to an internet rabbit-hole experience. On YouTube the simple 49:1 UnUn rules supreme and ‘works great’ for everyone with its lovely 1:1 SWR range across a bunch of bands. With that SWR it just must be …
Does EFHW Efficiency Matter? If you go looking at common and popular designs for EFHW UnUns on the internet they mostly follow the same general formula. You put a 2 turn bifilar primary winding onto a toroid and a 14 turn secondary so you get a 49:1 impedance transformation. The turns are spread out and …
EFHW UnUn Testing – The Tales It Tells The saying, “You can’t test quality into a product” was said to me quite a few decades ago now and to this day I still like it. With respect to EFHW UnUns it is actually rather prophetic. I’ve seen EFHW designs and kits that have efficiencies around …
Radials and Hybrid Baluns OZ-Tenna Hybrid UnUns isolate the coax from the UnUn and hence to work properly radials must be used. In the pic above, the 2 radials at the base of the antenna do carry a small amount of current – you have to squint a little – but it is there. Why …
Hybrid UnUn – The OZ-Tenna Advantage What are Hybrid UnUn’s? Marketing hype is something that annoys me at a deep and painful fundamental level. In the past I’ve been the victim of such and it has always left a bad taste in my mouth. The term ‘Hybrid UnUn’ just hints at that, and I have …
Modelling And testing At OZ-Tenna In the last week Amateur Radio activities have had to take a back seat to work and family life, but some maybe interesting things have happened. Common Mode Current Measurement Ages ago I made a clip-on ferrite based sensor, added a diode and some caps and a burden resistor to …