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Author Topic: Yaesu 817 vs 857 / 5W vs 100W  (Read 971 times)

RadioRay

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Re: Yaesu 817 vs 857 / 5W vs 100W
« Reply #15 on: March 31, 2018, 05:28:03 PM »
The two major products of the transmitted signal are :

1. Signal
2. Heat


Tuner, coax and connector losses are really very stated, in almost all cases.  Something to consider; if the losses were significant, then the lost energy from the transmitted signal would be converted into HEAT in the tuner/matching components - which is rarely the case.  Most 'losses' would require lab equipment to detect.  As an example, RG-58A at the HIGHEST HF frequency (30 MHz) has a loss of only 2.5dB per 100 foot.  At hald that frequency (20 meter band) it's roughly half that, use a long piece like 50 feet and it's half again.

so ay 100 feet, it's less that half an S unit on the received signal meter at 30 MHz, fhalve that to 1.25 at 14 MHz and it's 1/8 S-unit and halve that again with a  LONG 50 foot run = 1/16th S-unit.  Outside of a closed loop test, in a labaratory, it's not even measurable in any practical manner. The same lessons goes for your ATU (antenna coupler) if it's eating part of the 100 Watt signel, it's going to heat at a rate consistent with that absorbed Wattage.  In short: if it's not warm to the touch at 100 Watts, it's not wasting significant energy.


However, the dipole and the EFHW are very efficient antennas.  Note that I saide the EFHW, because that's a half wavelength ( or multiple of half wavelength) at the operating frequency.  Other single wire antennas are not nearly as efficient, but to provide a reasonable match over harmonically unrelated frequencies, usually by using autotransformers.  They work, but likely you might find wasted energy there - I am not personally certain. Gil's EFHW, from his Florida apartment and at while out camping, kept us in touch during our daily scheduled contacts at QRP levels in Morse code for two years, at well over 680 miles distance.


In short - wire is your friend and dipoles / EFHWs are superb and quite up/down.



Keep us posted on your portable operations, please. 


de RadioRay ..._  ._
"When we cannot do the good we would, we must be ready to do the good we can."  ~ Matthew Henry

ve3ips

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Re: Yaesu 817 vs 857 / 5W vs 100W
« Reply #16 on: Today at 05:41:30 PM »
The FT-891 is a great alternative as you can just leave it at 5 w and if you need more just dial it in. You dont need 100w or the 25A draw when you can make contacts at 20watts with a good antenna like a linked dipole

gil

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Re: Yaesu 817 vs 857 / 5W vs 100W
« Reply #17 on: Today at 05:51:55 PM »
The FT-891 is a great alternative as you can just leave it at 5 w and if you need more just dial it in. You dont need 100w or the 25A draw when you can make contacts at 20watts with a good antenna like a linked dipole
Certainly... But the 891 burns 5A at 5W output. My MTR burns 0.7A at the same power output... Not to mention the 35mA on receive...
Gil

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