Can anyone point me to a site that shows how to build a multi freq hf
vertical, thanks in advance
LUSHY
VK3HDL
Victoria

"Lushy" wrote Can anyone point me to a site that shows how to build a
multi freq hf
vertical, thanks in advance.

-------------------------------------------------------------

You can do no better than to begin with a bottom-fed, bottom-tuned, vertical
or sloping wire, or pole or mast as high as you can manage.

For short vertical antennas of any sort a fairly good ground is needed. If
you have an agricultural or reasonably fertile garden soil with occasional
rainfall then a modest array of half-a-dozen shallow-buried ground radials
may be sufficient. Radial length need be no longer than antenna height.
Increase number of radials till you find there's no improvement in received
signal strength. Not much point in having more than 20 or 30 radials.

If you have one, you best ground radial is your domestic incoming water main
pipe.

If you have any more wire to bury in the ground then prefer to increase the
number of radials rather than length.

If you can't increase height or length of antenna any more then a top
capacitance hat can be very useful. Or take the wire sideways. Do NOT
attempt to insert a loading coil for a particular band - it will no longer
be multi-band.

If you can provide height only by taking a wire up the side of your house to
a pole on the chimney then DO IT.

A simple vertical or sloping high wire is multi-band. It is impossible for a
lower ground-mounted commercial antenna, festooned with coils to improve
upon it.

Whatever short vertical antenna you select you will need a tuner somewhere
between bottom and the transceiver. Concentrate on THAT! A home-brew with
crocodile clips can be more versatile than any expensive commercial job.
----
Reg, G4FGQ

Reg Edwards wrote:
You can do no better than to begin with a bottom-fed, bottom-tuned, vertical
or sloping wire, or pole or mast as high as you can manage.

But don't allow the vertical radiator to be longer than 5/8WL
on the highest frequency of interest.
--
73, Cecil http://www.qsl.net/w5dxp



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Reg Edwards wrote:
You can do no better than to begin with a bottom-fed, bottom-tuned,
vertical
or sloping wire, or pole or mast as high as you can manage.

But don't allow the vertical radiator to be longer than 5/8WL
on the highest frequency of interest.
--
73, Cecil http://www.qsl.net/w5dxp

------------------------------------------------------------

Cecil, The difference between 3/4-wave and 5/8ths wave insofar as low and
medium-angle stuff is concerned is not worth thinking about. It is
unnoticeable in normal use. You ought NOT to go around unnecessarily
frightening people into hacking the tops off perfectly good antennas.
---
Reg

Reg Edwards wrote:

W5DXP wrote:
But don't allow the vertical radiator to be longer than 5/8WL
on the highest frequency of interest.

Cecil, The difference between 3/4-wave and 5/8ths wave insofar as low and
medium-angle stuff is concerned is not worth thinking about. It is
unnoticeable in normal use. You ought NOT to go around unnecessarily
frightening people into hacking the tops off perfectly good antennas.

I wasn't thinking about a 3/4-wave, Reg. I was thinking more about two or
three wavelengths long where most of the radiation is high angle when low
angle is what one needs on the higher frequencies. You said to make the
vertical "as high as you can manage". So don't make it longer than 3/4WL.

However, a 3/4WL vertical has its maximum gain at a take-off angle of
46 degrees. A 5/8WL vertical has its maximum gain at a take-off angle
of 16 degrees. At 16 degrees, the 5/8WL vertical has about 3dB gain
over a 3/4WL vertical.
--
73, Cecil http://www.qsl.net/w5dxp



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Lushy wrote:
Can anyone point me to a site that shows how to build a multi freq hf
vertical, thanks in advance

The easiest system is to cut the vertical for 5/8WL on your highest
frequency of interest and feed it at the base with an SGC-230 autotuner.
--
73, Cecil http://www.qsl.net/w5dxp



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Cecil Moore wrote:
Lushy wrote:
Can anyone point me to a site that shows how to build a multi freq hf
vertical, thanks in advance

The easiest system is to cut the vertical for 5/8WL on your highest
frequency of interest and feed it at the base with an SGC-230 autotuner.

Agreed - for example, about 10m (33ft) high will nicely cover
7-10-14-18MHz. You're only highly dependent on grounding at 7MHz or
below.

But as you rightly say, beyond 5/8 wavelength the high-angle lobe grows
very rapidly and the low-angle lobe shrinks rapidly too. By 21MHz, a 10m
high vertical is noticeably beginning to "lose it", for example in terms
of cracking pileups.

It's only a few dB, but if you "need" to work certain specific stations
- like DXpeditions and contest multipliers - then those few dBs make a
big difference to how long it takes. On the higher HF bands, stations
with verticals are already one layer below the stations with beams, so
unless your vertical is the best it can possibly be, you'll be at the
bottom of the second layer too.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
Editor, 'The VHF/UHF DX Book'
http://www.ifwtech.co.uk/g3sek

On Thu, 2 Oct 2003 08:24:10 +1000, "Lushy"
wrote:

Can anyone point me to a site that shows how to build a multi freq hf
vertical, thanks in advance
LUSHY
VK3HDL
Victoria




See

http://www.cebik.com/radio.html


Bob
k5qwg