I find it to be much better in some circumstances. I find that the noise floor is actually reduced, not brought up by the 2dB that would be expected. This is very similar to when I adjust the RF Gain down to about 3 o'clock. Yet it works much faster because I can simply push the button on and off when I need it. > From: drew...@verizon.net > To: ab...@arrl.net > Date: Wed, 11 Aug 2010 10:16:40 -0400 > CC: Elecraft@mailman.qth.net > Subject: Re: [Elecraft] K3: PRE/ATT Bug or feature? > > You are right about the ATU. It was my mistake comparing the ATU-ON > which had been tuned at other than 50 ohm load compared to the > ATU-OFF. > > As for PRE+ATT, I just measured MDS with the PRE and ATT settings > either both on or both off. Having both PRE and ATT switched on gives > 2 db poorer MDS than having both off. That is unnoticeable of course, > just a point of interest since the specs would seem to indicate it > should be a couple of db better. > > Does anyone use both PRE+ATT ON and find it noticeably better? I can't > hear any difference myself. > > 73, > Drew > AF2Z > > > > On Wed, 11 Aug 2010 06:21:05 -0700 (PDT), AB2TC - Knut wrote: > > > > >Why do you think you gain in MDS (presumably you mean a *lower* MDS) by > >bypassing the ATU? If the ATU is needed for transmit, it will also be > >benficial in receive. I don't have the K3 ATU, but both manual and automatic > >tuners in my antenna system and can certainly certify that when switching in > >the tuner when needed, the receive signal goes up (mismatch loses receive > >signal too). > > > >AB2TC - Knut > > > > > >drewko wrote: > >> > >> Actually, you will probably LOSE a couple of db by switching on both > >> preamp and attenuator compared to having both switched off. (Measure > >> your MDS and compare results if you don't believe...) > >> > >> Regarding weak signals, one factor that is overlooked is the ATU. By > >> switching it to bypass you can gain 5 or 6 db in MDS. Of course, you > >> would want to switch it back on when you transmit. > >> > >> I wonder if the ATU could be programmed to automatically be bypassed > >> on receive? You would perhaps not want the ATU to be switched in and > >> out at break-in speeds, but after a suitable semi-breakin delay. I > >> think that would be a handy option for weak signal work for those of > >> us who must use the ATU. > >> > >> 73, > >> Drew > >> AF2Z > >> > >> > >> <snip > >> > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:Elecraft@mailman.qth.net > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net
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