We are developing a dual band QRO version for the 40 and 80 meter band. The first experiments are done with three and four toroids together good for 600Watt PEP and 800 Watt PEP.
It is until now not possible to combine other bands into the design. Due the bigger cores there is a little window to play with the primairy winding.
On 80 meter a antenna tuner will be necessary for covering the whole band. On 40 meter there is no tuner necessary.
A tuner is a bit of disadvantage because there will be standing waves on the coax which coases interference in the shack.
So we are making up our mind if we will accept this or focus on a QRO dual band for 40 and 20 without the use of a tuner.
update: april 7, 2012
We decided not to continue with the dual band for 40 and 80. We focused on 40 meter QRO monoband only.
The result is a HyEndFed Monoband with a very flat SWR respons for the whole 40 meter band and High efficiency . Power will be 600 to 800 Watt PEP.
We tested in a long SSB qso with 1500 watt. No single problem..
Ron, pa3rk working on the QRO HyEndFed Monoband for 40 meter
The 40 meter Monoband QRO version under test. The the design with a optimized transformer the bandwidh is much
more than 200 KHz. Also there is no static charge buildup because the antenne wire is grounded for DC.
Checking the SWR of the QRO 40 meter monoband HyEndFed.
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