On 11/6/2016 11:06 AM, Ron D'Eau Claire wrote:
Sri Jim: You must have misunderstood. You defined the rig as the 'load' so I used your definition. Perhaps that's the problem.
I thought that too. Jim was here for dinner last night but I forgot to ask him.
You are right; the antenna is usually up in the air, and some hams climb towers to make the adjustments at the antenna in order to ensure a good impedance match with the transmission line to minimize transmission line losses.
Well, except mine at home. It's an EF 80-10 wire strung along the top of the 6' fence. I can "measure" the SWR anywhere on it I want to since I'm 6'2" tall. :-) While its claim to fame is being HOA-proof, its doing a surprisingly good job on 20 and 15 this AM in SS. Just S&P as fresh meat on Sun AM, but almost no IMI's.
If you're willing to cut a 180 deg length of low-loss transmission line for the band(s) in question, you can measure the characteristics at the elevated antenna.
But most of us with dipoles, etc., make do with an approximate match based on physical measurements. We measure the SWR at the rig to reassure ourselves that the SWR at the antenna is reasonable.
It it's at the minimum at the rig, it's at the minimum at the antenna too, even if the actual value may be different because of transmission line loss.
And, of course, if the rig is not equipped with an ATU, we are concerned that the SWR at the rig is not high enough to be reduce final amplifier efficiency and increase heat dissipation. That was the original concern that started this thread.
Indeed 73, Fred K6DGW - Sparks NV DM09dn - Northern California Contest Club - CU in the Cal QSO Party 7-8 Oct 2017 - www.cqp.org ______________________________________________________________ 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]
