> Your tuner/transmitter/amplifier will not know you're using 75 ohm
> feedline IF you tune the output FOR 75 ohms impedance.
> As for the antenna ... if you adjust the feedpoint match ... you can
> MAKE it a 75 ohm antenna and feed it directly with the hardline.
> Why are WE, the hams, so hung-up on making everything 50 ohms impedance?
> Those 50:75 ohm transformers are generally a waste of time.
> If you think this isn't a possibility, make a 75 ohm dummy load and tune
> into it. You'll need a 75 ohm SWR meter [does bird make a 75 ohm
> wattmeter?] and you will find you CAN tune your amp/rig/tuner for a 75
> ohm load.
> Just my 2 kopeks.
> Don
> N8DE
.........
First of all, Bird does not make a 75 ohm wattmeter as standard
equipment. They used to custom build one for you, but expect to pay
about 3 times what a normal Bird will cost.
Don't know if they still do.
Although Don has a valid point that most tuners will adjust for 70
ohms, amplifiers and transceivers will not, unless you want to modify
the finals.
Blame WWII for the hang-up on 50 ohms, although a 1.5:1 mismatch is
hardly worth working on. But I seem to get the impression that Don is
generally referring to that old wives tale that adjusting the length
of the coax will change the SWR. It will not, and never will. Sure,
you might get a lower reading in the shack, and that will make your
amp/transceiver a little more happy, but the SWR on the line will not
change.
And any way you tune it, a 75 ohm load is still a 75 ohm load with a
amp/tranceiver hoping to see 50 ohms. Some loss but not excessive.
73
Ed
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|