If you make your 75 Ohm lines a multiple of one HALF wavelength on 40M,
the load impedance will be presented back at the input end on 10, 15, 20,
& 40M,
with no need for any transformers since impedances repeat themselves
every
half wavelength in a transmission line. This works well up to 225 ft.
For longer
lines, the wide bandwidth on 10M plus the number of half wavelengths in
lines
of 8 wavelengths or more, creates unequal transformations between the
10M CW and SSB bands.
Multiples of a halfwavelength on 80M will transform 10, 12, 15, 17, 20,
40, 80
and are not too far off on 30M. ( I use my 80M dipoles on the WARC bands
with no tuner. SWR on 30M is around 3:1 and under 2:1 on 17 and 12M )
de Tom N4KG
............................
On Sun, 19 Oct 1997 11:26:29 -0400 Brian Petku <bpetku@ix.netcom.com>
writes:
>Hello All,
>
>I am using 3/4" 75 ohm CATV from the house to my towers. On my
>monoband
>antennas I am using a synchronous transformer whch works very well. I
>am
>looking for 75:50 ohm transformers for my multiband antennas.
>
>Any recommendations?
>
>73,
>Brian / W8WD
>
>
>--
>FAQ on WWW: http://www.contesting.com/towertalkfaq.html
>Submissions: towertalk@contesting.com
>Administrative requests: towertalk-REQUEST@contesting.com
>Problems: owner-towertalk@contesting.com
>Search: http://www.contesting.com/km9p/search
>
--
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
Search: http://www.contesting.com/km9p/search
|