FB. I get enough e-mail already. Hope your questions were answered. 73, Ron AC7AC
-----Original Message----- From: Elecraft [mailto:[email protected]] On Behalf Of Barry N1EU Sent: Thursday, November 3, 2016 2:35 PM To: Ron D'Eau Claire Cc: elecraft Subject: Re: [Elecraft] KX3 tuner loss? It ends up that John KN5L gave a thorough treatment to the topic in this thread (might need to be a member of the KX3 Yahoo Group to read): https://groups.yahoo.com/neo/groups/KX3/conversations/topics/5869 73, Barry N1EU On Thu, Nov 3, 2016 at 4:08 PM, Ron D'Eau Claire <[email protected]> wrote: > You ask a commonly asked question. And, as usual, no responses so far. > > I can't give you an estimate either because first, the losses are > highly dependent upon the impedance transformation. You'd need to > characterize that doublet and feed line (the length of the feed line > is important) to see what impedance it presents to the ATU. > > Then you need to measure the ohmic losses in the ATU inductors, wiring > and connectors. Dielectric losses may occur but with modern gear they > are very tiny at HF. > > Finally you calculate the currents flowing in the ATU at each > impedance transformation required to achieve a match to your feed line > so you can calculate the losses based on the resistance of the wires, > inductors, and connectors. > > Personally, I accept the idea that an L-network (which all the > Elecraft ATUs > use) is highly efficient and leave it at that. > > If I were really inclined to actually measure the loss, I'd first > measure the RF power output into a stable 50 ohm load without the ATU > in the circuit. Measure with an external wattmeter at the load as well > as the KX3 output power indicated. > > Then I'd breadboard another L-network with a variable cap and variable > inductor, connect it to the 50 ohm load and to the KX3 output, > transmit and adjust the external L-net (not the KX3 ATU) for a 1:1 > match. In that way you have created a known dummy load that presents > the same complex impedance to the KX3 as your antenna system. > > Now you can transmit at the same power at the KX3 as before and see > what the power is at the 50 ohm load. Actually, you will be seeing > what the power is after passing through both matching networks. > > My guess is that you'd find the total loss so low you won't be able to > read the difference on the two power meters. > > A more direct approach would be to isolate the ATU in a very well > insulated enclosure, transmit, and measure the temperature rise until it stabilizes. > You can then calculate how much energy is being dissipated by the ATU > and becoming heat. That requires the ATU be carefully isolated from > the rest of the KX3 and be in a very well insulated enclosure to avoid > loss of heat to the environment, something not practical to do with a > KX3. It is, however, a valid way to determine losses in external > devices like an RF transformer (e.g. "balun"). > > I suspect this explains why few (if any) Hams bother to make the > measurements. > > 73, Ron AC7AC > > > > > > -----Original Message----- > From: Elecraft [mailto:[email protected]] On Behalf Of > Barry N1EU > Sent: Thursday, November 3, 2016 7:20 AM > To: elecraft; [email protected] > Subject: [Elecraft] KX3 tuner loss? > > I'd appreciate knowledgeable estimates of the loss in dB through the > KX3 ATU when working into a 44ft (NorCal) doublet fed with twinlead, > with or without a BL2 balun inline, on 20/17/15M. > > Thanks & 73, > Barry N1EU > ______________________________________________________________ > 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]
