Yaesu’s Quadra VL-1000 Will do 70MHz

So I had noticed a while back, when developing my Icom (CI-V or band Data) to Yaesu BCD Band Data Converter that occasionally I could get 70MHz to show up as the band.


I always had it in mind to investigate this further.  Today I set about finding the BCD which selected 4m (70MHz) and found it with all BCD lines high (Band A=1, Band B=1, Band C=1, Band D=1, ) great!  On page 5 of the manual it shows the pin-outs, on BAND-DATA 1 or BAND-DATA 2 connect pins 4, 5, 6 & 7 together and then to 12v via a 1k resistor to get 70MHz. I noticed the amp would only allow LOW which I presume is to stop the PA’s overdriving into a non-optimized filter.  The fact that LOW is only fixed when on the 70MHz band lends me to believe the designers know this and allow it. Now to the interesting part.

With 25w in I get about 240w output, rather useful as the UK limit is 160w. Id was about 25amps though which at 33v is about 825w and means it’s about 30% efficient but none the less the amp does it.


However with 65w in I was getting a peak of 500w. 35% efficient.


I’ve not run this long term so it’s all at your own risk! I did run it for about 10 minutes to keep the dummy load cool, but for UK legal this should be a good option to get you to 160w with about 20w drive.

Update 2/1/12: G6UW ran their Quadra for 2.5 hours in the first 4m RSGB UKAC contest of the year without issue. On air their signal was clean and caused us no issue, they were an S9+50 signal with us being less than 10km away.


  1. Ari

    I was plaing with the band data and also notice this option with 70 Mhz
    I did look at the drawing and there is filter in the Amplifier for 70 Mhz
    but have a look at the VDD, when you switch to 70 Mhz it drop to around 35 from 50Volts,that is why you get half the power and amplifier do not get warm 🙂

  2. John


    thank you for this very interesting finding. I wonder which output filter the QUADRA is using for 70MHz (the 50MHz one ?). If “YES” can this filter be optimzed for 70MHz (I think – like you mentioned- that this is the main reason for only 35% efficency)

    In DL 70Mhz is not allowed (I hope YET)..I have built a transceiver for “beeing prpared” an listen in 4m openings….I also have prpared the elemnts to add to my 3ele SteppIR for building a 5 ele 70MHz yagi out of it.

    73 de John, DL5RDI


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