I have a plain K3 that I bypass the built-in tuner on 80 all the time. On 20 and 40 it is in-line all the time. de Frank KG9H
> On Jul 5, 2019, at 4:42 PM, Jack Brindle via Elecraft > <[email protected]> wrote: > > Good observation, George. The KAT3A indeed does have a bypass relay, while > the KAT3 (in the original K3) does not. As I recall, the KAT3 switches the > inductors and capacitors out in bypass mode, but does not necessarily provide > the best 50 match. This is due to variances in the components and placement > from unit to unit. Tuning into a good 50 ohm dummy load can provide a better > 50 ohm match, but it has the slight down side of adding a slight amount of > loss to the path. In the end they do pretty much the same thing, but if > someone wanted to be a real perfectionist (and I’ll admit to that with many > things), then tuning into a dummy load will provide an oh-so slightly better > match. > > The important point here is that it really needs to tune into a known-good 50 > ohm resistive load to get what you want. Tuning into the BPF might get you > there depending on the output of the BPF. > > As I stated earlier, I set my K3s to bypass mode for driving either my BPFs > or my KPA500s. > > 73! > Jack, W6FB > >> On Jul 5, 2019, at 12:56 PM, Gmail - George <[email protected]> wrote: >> >> >> >> -----Original Message----- >> From: Jack Brindle via Elecraft >> >> ... >> >> Now having said this, the ATU can also be bypassed in the K3, and that >> circuit may provide a proper 50 ohm source/load for the BPF. I would >> probably take this approach myself (and in fact do so in my station). The >> reason I take this approach is to avoid the small loss that the internal ATU >> presents. In contesting, every db matters. >> >> Note that we are talking nits at this point. Unless the ATU was tuned for a >> load quite a bit off 50 ohms resistive, (quite possible), then retuning >> won’t make much difference. Perhaps the op had this situation, and thought >> it better to return the ATU than to bypass it, or he didn’t even think to >> bypass it. The point is, both methods will work, and I doubt he did anything >> wrong it performing the tune. >> >> >> Jack, >> If I'm not mistaken - the KAT3 is not able to be physically bypassed in a >> K3 - don't know in a K3S; but I thought the KAT3A did a physical bypass. >> My understanding is that when you bypass the ATU (KAT3), it is merely being >> set to a value that cancels the internal L & C of the board. >> I would think a tune would not actually actually change much of anything; >> but leave it to someone to actually test the true output impedance in both. >> >> 73 >> George AI4VZ >> >> --- >> This email has been checked for viruses by Avast antivirus software. >> https://www.avast.com/antivirus >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[email protected] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> Message delivered to [email protected] > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
