Mick,
Alan Chester (G3CCB)(SK) proposed a solution for the high end impedance of a
1/2 wave antenna. Mr. Chester rationalized that there might be some
impedance-friendly length of wire usable for an end-fed antenna that didn't
present the tough-to-tune, high-impedance load on a select set of bands. In
short, he proposed selecting an end-fed wire length in the 1/8 - 3/8 or 5/8
- 7/8 wavelength range, avoiding 1/2 wavelength (or multiples thereof).
In the article "Taming the End-Fed Antenna" ("The Antenna File", RGSB, pg
118) he looked at this issue by plotting various 1/2 wave lengths and
proposed the following end-fed wire lengths:
- 26.5m (86.9 ft) for 160 - 10M use
- 15m (49.2 ft) for 80, 40, 20, 17, 15, 12, 10M use
- 10m (32.8 ft) for 80, 40, 30, 17, 15, 12, 10M use
You can set up a spread-sheet and calculate wire lengths by increments of
1/8 wave, using band centers (or your desired band segment) as a starting
point. Look for wire lengths that don't fall on the 1/2 wave wire length.
For example, a 15m wire is about 3/8 wave on 40M, around 6/8 wave on 20M and
9/8 wave on 15M.
Steve
Aa8af
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED]
> Sent: Wednesday, January 04, 2006 4:02 PM
> To: elecraft@mailman.qth.net
> Subject: [Elecraft] T1 Antenna Considerations
>
> Hello
> I have just received my T1 kit and i notice that under the
> above heading in the owners manual under random-wire antennas
> it states(avoid lengths close to a multiple of 1/2
> wavelength on any band) please can someone explain why this
> is important,also i wish to use this tuner on the following
> bands 20/15/10m so a suggested wire length would be
> appreciated I only have 40ft of space to play with.
>
> Thank you.
>
> Mick M1MGD K2#4785 K1#1532
> G-QRP 11355 ARCI 12343
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