Today 27th November 2022 is launch day.

We have been designing and testing for over 12 months now and confidence is high our products meet all our goals.

In mid March 2022 field tests in country Victoria on the John Moyle Memorial Field Day revealed that the QRP and the 100W EFHW antenna solutions had very comparable performance to an OCF at a slightly higher elevation. We used an antenna switch and swapped between antennas over the course of an afternoon. The difference was approx 1/2 an ‘S’ point with the EFHW and the OCF each having a slight advantage depending on where the signal was (we assume). Most of the time we were unable to detect a difference either by ear or on the IC-7300 ‘S’ meter. I also made a 1,400 klm contact in Northern Qld and into Italy and Germany all on 50W SSB.

Since then many QSO’s later by a number of people, not jut myself, mean we are ready to go. Also, a few extra products have been added to the products page.

Our designs feature a hybrid UnUn that is efficient and offers unique benefits.

We started with common internet designs that were surprisingly lossy for a number of reasons. Then after widely reading blogs, experimenting and testing, we came up with designs that we use and consider very good.

Our EFHW has proven itself to me and others to be a capable performer so long as some simple guidelines are followed and its shortcomings understood.

About OZ-Tenna design(s) & EFHWs

  • Ours is are efficient designs,
  • Our design reduces common mode current and coax length issues,
  • The EFHW has setup flexibility. Inverted “L” is best, sloper and Inverted-“V” can be used also,
  • Offer a reduced footprint.

I hated EFHW’s initially because of common mode current and the awful efficiency of common internet designs. They seemed to be based on folk lore and “works great” kind of testing.

I am a QRP operator. I want my watts to be radiated and have some surety that it happens.

So in about August 2021 at the behest of a friend I started testing, building, designing and repeating.

The end result is an antenna system that has proven itself to meet my goals for efficiency and be able to deploy easily with minimal issues.

They are an easy antenna to have trouble with, for a bunch of reasons and no great surprise.

Many internet designs really aren’t all that good. They can have reasonably low efficiency leading to core heating and in extreme situations damage. Some designs compensate by using large cores which is just hiding the problem.

Next, some lengths of coax will behave differently to others. This is because they form part of the antenna system, the shield radiates, and some lengths will cause problems with the transceiver and may not tune as expected.

Lastly, many EFHW users are SOTA or POTA operators and just need to make a few contacts then move on. They quite often use a low sloper installation of the antenna radiator, no radials, feed point close to the ground, they make the contacts and all is good. Quite frankly this is the least efficient antenna system possible I found when in my testing.

Yes and No! We don’t have an antenna range and view WSPR tests as being difficult to extract meaningful data from (read that as a lot of effort and then of dubious results).

For a field test, it really is subjective and every antenna type will have differences that may render comparison invalid. You really need more information about the installations and how the tests were done to get an idea of what is being reported.

So here it is.

The OCF was cut for 80m and hence for 40m and 20m it would have lobes, but it was installed at 12 meters high as an inverted “V” – so the lobes may not have been as sharp as a flat top.

The EFHW was installed with the apex at 9m and then sloping down to about 5m – so not a flat top and actually probably close to a standard (lazy) install I would do.

Clearly the OCF was installed better and should have had a minor advantage.

The antennas were at right angles to each other.

The soil was dry, in a forest, and not overly mineralised or rocky or sandy. It could be termed farmland perhaps.

Yet performance on 40m and 20m was really quite comparable with perhaps 1/2 an ‘S’ point better or worse depending on the signal source (we assume).

Modelling suggest the EFHW as an inverted “L” has NVIS pattern on 40m and mainly vertical pattern on 20m.

We tested for a few hours, made local and international contacts and listened to a lot of contacts OZ wide. A VK6 contact in Esperance 2,700klms was pleasing as was the Charleville Qld 1,400klms contact both on 40m and 50W SSB. The OCF vs the EFHW were hard to differentiate.

On 20m Italy and Germany both gave me S5 for 50W SSB. They were running Yagis and probably a KW or more and coming in at S9+10 or more.

Probably not unless you have a real reason such as ease of deployment, efficiency, and want an antenna that works rather well.

Do you want the truth? If your antenna is 10% or 20% or 30% less efficient than ours and you use SSB, you will probably never hear the difference on air. You’ll probably never see the “S” meter show any or much difference.

One difference is that our hybrid baluns reduce common mode current on the coax. You should not need a 1:1 – also called a line isolator – in the coax if you use one of our hybrid UnUns.

Another difference is that our QRP Square hybrid UnUn is super small yet it handles 20 watts of SSB with ease. It packs down beautifully and if you need a small light weight antenna system it is an ideal choice.

However, and a big difference, if you use digital modes beware! Seriously. The loss is mainly in the transformer and causes heating. If the transformer gets much hotter than 100c it can fail, shatter, and then may cause other damage. OZ-Tenna designs are as efficient as we can make them for this reason.

Remember. The transformer is in a box without air flow. It will heat up a lot faster than it will cool.

Our goal is to publish calculated realistic heating values under various scenarios so you can have some indication of how an antenna will perform.

That is a work in progress.


Yes you do. Sorry but there is no option.

Do not buy our hybrid UnUns and not expect to use radials unless explicitly stated.

Note. The radials are short. They are quick to deploy and really not onerous to use.

Our hybrid UnUns include a 1:1 current balun. This means the coax shield will have far less interaction with the antenna radiator and hence a radial system is required. This will reduce common mode current on the coax, and help improve signal strength (we believe).

Sure. Not a problem. We have no issue with that – however there is one consideration.

The radials will need to be changed to suit.

These should be 1/20th the wavelength of the lowest band. For example, for 80m they should be 4m long.

I did this recently to get onto 80m. Adding 20m of wire for a total of 40m brought the SWR down quite nicely. However until I added 2 off 4m long radials, the antenna was really quite deaf. This is an artifact of having a Hybrid Balun – you must use radials and they really should be 1/20 the wavelength of the lowest frequency in use.

Sure. Not a problem.

Sloper is common for SOTA and POTA if I have read correctly.

I like inverted-“L” because is has given me the best performance.

When I ran as a low to the ground sloper it was approx 3 to 4 “S” points down on the OCF. The sloper was much lower to the ground and I think that was the cause.

You can but performance is rubbish.

We actually did this on our John Moyle Field Day tests. The IC-7300 actually tuned it on 80m (I thought that odd – it is far too short for 80m).

For the 40/20 EFHW it was down about 6 to 7 “S” points compared to the 80m OCF.

A recent test showed that for best performance, really, 40m of wire and 4m long radials do work a whole lot betterer.

The little coil placed where it is lowers the resonant points more on higher bands. The effect of this is make 40m and 20m band resonances fit the bands better.

Without the coil you’ll find that if you get 40m into resonance, on 20m it is a little high.

It all depends which product of ours you use.

The FRC-100W is the best option for a base station. You can run SSB 100W into it and most importantly, the box is reasonably weather sealed. I would suggest adding a little extra weather sealing, and particularly for the coax as well. Wet getting into the coax is no fun at all.