Topband: LU5OM shortened dipole (inverted vee) doing a nice job
lennart.michaelsson at telia.com
Mon Jul 24 11:41:22 EDT 2017
Way back in time - 1982 - I had my first QSO with Mike which actually was the first QSO on 160 between SM and VK.
Still recall his pounding signals. Since then we had a lot of QSO:s , always with good signals. RIP Mike!
Från: Topband [mailto:topband-bounces at contesting.com] För Guy Olinger K2AV
Skickat: den 24 juli 2017 16:22
Till: Steve Ireland <vk6vz at arach.net.au>
Kopia: TopBand List <topband at contesting.com>
Ämne: Re: Topband: LU5OM shortened dipole (inverted vee) doing a nice job
The inverted L has some quirks that if not managed can impact performance.
They don't do well if the bend is supported by a tower, or if there are nearby "weed" parasitic elements from 40 and 80 dipoles/vees lacking the blocking to isolate them on 160. L's don't do well if there are trees inside the bend. Also an L over radials will have quite a bit more current in the radials beneath the horizontal. This unbalances the efficiency of the radials as normally found beneath a T or straight vertical.
Comparing an L to an inverted vee on top band is a pretty murky subject.
Some would say that arrival angles via grey line propagation can be quite high, and thus a high angle antenna might be a lot more useful if grey line is a frequent mode. There is also a useful NVIS mode that is rarely touted for DX, but would come into play comparing vee's to whatever if shorter distances are important.
73, Guy K2AV
On Mon, Jul 24, 2017 at 9:36 AM, Steve Ireland <vk6vz at arach.net.au> wrote:
> One of the great myths about 160m is that low angle radiation is
> always needed to work DX on the topband. The other is that almost any
> kind of vertical antenna will always beat a relatively low (in terms
> of a
> wavelength) horizontal one for 160m DXing. It all depends on where
> you live.
> The best advice I was ever given on antennas was by Les Moxon G6XN,
> who suggested that some locations predominantly suit a particular type
> of polarisation and one should always try both. Even better, if
> possible, have both a horizontally polarised and a vertically
> polarised antenna for your favourite low-band – and switch between them regularly.
> In Western Australia, our ground conductivity is so poor that on 160m
> even vertical antennas over as full-size ground screen lose so much
> signal in the far-field that a ‘cloud-warmer’ dipole under a quarter
> wave length high will outperform them. This situation isn’t helped by
> the south-west of WA having a geomagnetic latitude that suits
> horizontal antennas at least as well as vertical ones.
> Mike VK6HD, Western Australia’s greatest topband DXer with around 260
> countries confirmed, found a simple inverted vee dipole about 100’
> high generally outperformed his quarter-wave inverted-L with an 80’
> vertical section over 132 quarter-wave radials.
> Similarly, in VK6 I have tried a heap of different vertical antennas,
> over a variety of high-quality elevated and buried radial systems, and
> have always come back to using dipole antennas, of a similar height to
> that used by Mike and my friend Phil VK6GX. In my case, this has
> resulted in 236 countries confirmed.
> If you have losses in the far field from poor soil conductivity, all
> the radials in the world and a full-size vertical can’t fix this. ;-)
> Vy 73
> Steve, VK6VZ/G3ZZD (topbander since 1971)
> I wondered about the inverted-L. My guess is that it had a poor ground
> 73, Mike
> On Jul 17, 2017 9:22 AM, "K1FZ-Bruce" <k1fz at myfairpoint.net> wrote:
> There are always exceptions.
> A few years ago there was someone that had a inverted V that worked
> well for DX.
> It was found that it was feed with open wire feeders that acted as a
> vertical antenna with top loading.
> If your antenna works well be happy. Ham radio is a great hobby.
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