On Jun 28, 3:32 pm, wrote:
On Jun 28, 12:44 pm, Cecil Moore wrote:





wrote:
By using a vertical wire of a suitable magic length (7.2, 8.8 or
11.8m) supported by the fishing pole, I can get the LDG tuner to
provide a good match on all Amateur bands from 80m upto 6m as the
impedance presented to the tuner is just within it's (slightly
limited) matching range.

When a vertical monopole length is much longer than
5/8WL, the take-off-angle increases and much of the
radiated RF is lost into space on the higher
frequencies.

For instance, on 6m using the 7.2m monopole, the
take-off-angle is ~56 degrees.

7.2m is ~5/8WL on 12m, not good for 6m-10m.
8.8m is ~5/8WL on 15m, not good for 6m-12m.
11.8m is ~5/8WL on 17m, not good for 6m-15m.
--
73, Cecil http://www.w5dxp.com

Hi Cecil,

Thanks for this, I must admit I hadn't considered the affect on
radiation angle.

I guess I'm prepared to trade this on 10m and 6m if it's going to
result in a reduction of less than say 10dB useful gain, just for ease
of operation. Epecially as both these bands tend to be either 'open'
or 'shut' with not much in-between. Just so I can get a feel for
this, what sort of magnitude are we talking about in terms of
elevation angle vs dB's

Alternatively could I coil a portion of the vertical to create
something aproximating to a 6m colinear which may help the situation
on the worst band without affecting the matching range too much on the
other bands.

Just to get this in proportion, If I've got sufficient space and time
(and the weather is good) I can roll out a ZS6BKW version of the G5RV
using the 10m pole as a support to create an inverted V (which works
very well as a general all rounder). The vertical is meant to be a
quick, cheap and cheerful, 'let's grab some QSO's' during the lunch
hour antenna, so any suggestions for alternatives which permit quick
band changing would be welcome.

Looks like I'll have to bite the bullet and start getting used to
modelling with NEC or similar.

UKM- Hide quoted text -

- Show quoted text -

Hi Again,

OK I just found this which answers most of my questions.

http://www.moonraker.com.au/techni/patterns.htm

Looks like some form of loading coil say 60% up may be the way to go.

As before suggestions welcolmed.

UKM