IW5EDI Simone - Ham-Radio

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Wonder Whip Antenna

Posted: 13 Jun 2019 12:09 AM PDT
http://www.iw5edi.com/ham-radio/3313...r-whip-antenna



The Wonder Whip?




A £10 QRP Portable Multiband Antenna for HF, VHF and UHF




A variation on the “Miracle Whip� and “Wander Wand�.




The Wonder Whip

















Context




I
enjoy low power, portable operations, from various headlands on St
Mary’s and also from some of the more remote off-islands around my home,
on the Islands of Scilly. My Yaesu FT857D acquires its RF signals from
an ad-hoc antenna system, based around; a telescopic fishing pole,
various bits and pieces of wire, a lightweight MFJ-901B ATU for HF; and a
SOTA beam for 144MHz operations. Many of the locations I visit are
remote, rocky and without topsoil. In many circumstances, it is almost
impossible to erect any form of antenna. Often the soil is only
millimetres thick and it is not possible to guy the telescopic pole.
Vegetation is low lying and making attachments to the granite rocks, to
gain height, is not really feasible. I wish to combine my interests in
amateur radio with my desire to operate from the picturesque locations
these islands have to offer.




Existing Products




There
are several commercial solutions to my problem: Miracle Whip, Wander
Wand, Buddistick, ATX Walk-about and various Maldol and Diamond
systems. Reviews of these products suggest that they all work well,
within the limits of a very short antenna and radiating elements. It is
notable that many of the reviews, highlight the lack of any facility to
attach a counterpoise. These ready made, commercial solutions, come at a
high economic price. Against the background of what I need, I have set
myself the task of designing and constructing a portable multiband QRP
antenna system. The main constraints are economic, my limited antenna
design expertise, the availability of materials (no radio shops in the
Atlantic!) and my very limited test equipment.




The Autotransformer – Miracle Whip




Trawling
through the Internet I discovered an article by Robert Victor, VA2ERY,
who described his investigations with an autotransformer, as a solution
to achieving multiband, QRP, portable, HF operations. Briefly, he
describes methods of transforming impedance, using a transformer rather
than a loading coil to match a short whip over a wide range of
frequencies. The autotransformer may be considered as a double wound
transformer; the bottom, primary part being connected to the rig, whilst
the secondary is connected to the whip. The impedance transformation is
the square of the ratio between the secondary and primary windings.
The tapping point varies the ratio between the secondary and primary
windings and establishes an impedance transformation. The article can be
read in full in QST, July 2001 © ARRL.




The
VA2ERY design is a continuously variable autotransformer, based on a
coil transformer of 60 turns with the impedance ratio selected by a
wiper sourced from an “Ohmite� rheostat. Clearly there are considerable
manufacturing difficulties in producing and winding the transformer core
and the need for accurate construction and placement of a wiper
mechanism.




Using
VA2ERY’s autotransformer concept as a starting point, I experimented
with a compromise design which would allow me incremented tuning (rather
than continuously variable), with the advantage of less rigorous
mechanical complexity. After some experimentation (trial and error) my
final design employs a 36mm outside diameter, ferrite ring and is wound
with
48 turns of either 16, 18
or 20 gauge copper wire. The core is tapped at every second turn.
Fine adjustment is achieved by altering the length of the whip.




23 TAPS



The above toroid is a 36mm diameter RSGB sourced ferrite, wound with 48/47
turns of 16SWG enamelled copper wire. With 16SWG wire, it is a little tight
to wind the toroid and you may prefer to use a smaller diameter wire,
to facilitate easier windings.
Additionally, you may prefer to form small twisted loops to the windings
(see below) to make a more mechanically robust soldered joint.



46 POINTS OF TUNING




To allow finer tuning, particularly, for 7MHz through to 1.8MHz the
23 TAPS diagram may be amended as follows:



inserting an additional single tap at the point marked B;connecting the
whip to the pole of a S.P.D.T. switch (single throw, double pole
switch);connecting points A and B to the relevant Throw contacts of the
S.P.D.T.;switching between A and B, reduces the inductance, and effectively
gives access to the turn between each physical tap.








Materials




Telescopic Whip Maplin LB10 HQ 10-section 1.31 metres Ferrite ring
Fair-rite FT140-43 or RSGB
36mm Rotary switch Maplin N89BX
12 way (2 off) Black Knobs Maplin
KB4 Antenna wire
16, 18 or 20 gaugeS0239 Sockets (2
off) Binding post 4mmEnclosure
Floppy disk box(Additionally I have included a 3/8th socket for mobile
whips)




Construction



FIGURE 1




From Figure 1 it should be possible to assemble the various elements of the
design, however the toroid requires further explanation. The toroid core
is wound with 47/48 turns of 16-gauge antenna wire (see note above about
smaller diameter Cu wire). The core is tapped at every second turn.
Because 24 pole, 1 way rotary switches are not readily or economically
available, two 12 pole rotary switches are used. The 12th pole of the
first rotary switch is connected to the centre rotor connector of the
second switch, to give 23 positions of adjustment. The 23 wire connectors
to the toroid are directly soldered to the windings. This was achieved by:
a, cleaning and “tinning� the relevant core winding; b, forming a small
“tinned� loop to each connecting wire; c, positioning each wire on the
tinned core winding, applying the heated soldering iron, which will melt
the two tinned surfaces to fuse a secure joint. This process requires
patience and care. The telescopic whip is 10mm diameter at the base, with
a 4mm hole to accommodate the antenna wire. I modified an PL259 connector
by drilling out the cable entry connector to 10mm interference fit, into
which I screwed the telescopic whip. The whip is secured to the PL259
connector by finally soldering the antenna wire into position. The green
4mm post identifies the socket for the earth/counterpoise. A counterpoise
may assist in lowering the SWR on some frequencies, particularly, below
14Mhz. Above 14MHz the use of a counterpoise does not seem to make any
significant difference to on air reports I disconnected my CP, halfway
through a QSO on 18MHz and the other station reported no change in signal
strength. I use approximately 10 Metres of 1.5mm diameter wire for all
situations. Results suggest that a quarter wave length for the required
operating frequency will work satisfactorily.








Prototype – before the “paint job�




Operation




The antenna is tuned by selecting
the required band on the radio, and then rotating the two rotary
switches on the ATU until the highest background noise or signal is
achieved. The antenna peaks on receive and this will provide a good
starting point for transmitting. Set your rig to a low power setting (5
watts) and transmit while observing the SWR meter. Rotate the rotary
switch knobs until the SWR is optimised at the lowest level. Fine
adjustments to the SWR may be made by altering the length of the
telescopic whip (not whilst transmitting).




VHF and UHF operation is
performed by selecting position one on the control knobs and
adjusting the antenna to a quarter wave length.




Horizontal polarisation, particularly for SSB 144MHZ operationÂ* is
achieved by turning the antenna on its side.








Performance




My subjective feeling is that receive performance is first rate. S meter
readings appear very respectable.





Transmit SWR results, using a 5 Watts carrier
(23 Taps, without a counterpoise):




432MHz
1.5.1144MHz
1.5:150MHz
1.128MHz
1:124MHz
1:1 21MHz
1:7518MHz 1:114MHz 1.5:110MHz 1.5:1
7Mhz
3:13.5MHz 8:1




SWR results, 5 watts carrier with
(23 Taps with a counterpoise):




28MHz
1:124MHz
1:1 21MHz 1:118MHz 1:114MHz
1:110MHz 1:1 7Mhz
1.5:13.5MHz
6:1




SWR results, 5 watts carrier (46
Virtual Taps with counterpoise):



7Mhz
1.3:13.5MHz
3:11.8MHz
4:1




On Air Reports




Does it work well? Emphatically YES.




My
first
portable contact on 40 metres, using 10 Watts, was on Sunday 29th
January 2006. Jan, at GB2IWM, gave me a 53 signal report on 7.057MHz.




SM4YPG, Lars, north of Stockholm reported, on the 31st January, 4/7 to 5/7.
I was using just 5 watts.




On
Wednesday 1st February I contacted AC5N, /Portable from Star Castle
G/008/C. Terry, in Oklahoma, USA, on 21MHz, using 15 Watts, reported 59
on his QSL card! A distance of 4400 miles using just 15 Watts into a 51
inch telescopic whip!




Early results are encouraging and I am hopeful that this little box of
tricks, and my 51-inch telescopic whip, will serve me well on my next
“pedestrian portable expeditionâ€� to the remote corners of the islands.Â* My
initial enthusiasm is, however, tempered by realism, I have little
expectation of making ground breaking DX. But if I can bridge the gap
between Scilly and the Mainland and enjoy the occasional QSO when
conditions permit, I will be happy. If not, well there is always the view




Article by M1IOS John originally available at
myweb.tiscali.co.uk/m1ios/html/wonder whip.htm




© M1IOS, John Goody January 2006

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