ZS6BNE's Blog

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RaDAR - 160m end fed half wave antenna building instructions

Posted: 03 Jul 2017 06:21 AM PDT
https://zs6bne.wordpress.com/2017/07...-instructions/


Antenna building instructions / article for Radio ZS

This is about the easiest way to build a 160m antenna. Its up to you to get
it as high as possible. An inverted L shape is good, even vertical if you
can but if you have no other choice get it off the ground if only a few
meters high. Youll still have some NVIS (Near Vertical Incidence Skywave)
fun with really good signals after dark!



Firstly, youll need a 100 meter length of copper wire that will be strong
enough and good enough and the ideal for this is a 100m roll of 1.5mm
electrical house wiring wire from your nearest electrical outlet. It will
cost around R200.00 If you want everyone to see your wire, choose red or
green / yellow but if not, choose black.



Unroll the wire making sure there are no kinks, loops or tangles. Take your
time and enjoy the sunlight! Once unrolled, measure off 20 meters and cut
the wire leaving hopefully a length of 80 meters behind. The 80 meter
length of wire will be your radiator and the 20 meter length will be your
counterpoise. Youll need the counterpoise otherwise RF will be looking for
a path to ground in all the places where it shouldnt!



Good news, youll only need a short piece of coax from your rig to the magic
box. Inside the magic box youll have a toroid with a few turns of wire
around it. Youll also need to find a variable capacitor which may be the
most difficult obstacle. Find one that is around 200 pF or more. The vane
spacing is usually not critical unless you want to use a few hundred Watts
where youll need wider spacing otherwise you may encounter arcing between
the plates.

We are going to feed the antenna from the side, not in the middle like a
dipole or inverted vee. That means we need to match the rigs 50 ohms to the
antenna which is 2750 ohms or more. Thats easy of course using a low pass
filter and it will supress some unwanted harmonics too!



My friend Pierre ZS6A, drew up an interesting table of suitable inductance
values for various bands and feedpoint impedances.



From the table we see we need an inductance of around 32uH if the feedpoint
impedance is around 2750 ohms. If its higher well need a little more
inductance but its impossible to know exactly what the feedpoint is. An
inductance of 32 uH worked well for me and a 200 pF variable capacitor was
sufficient too.

You will need a suitable toroid. I had a T157-2 in my parts box and used
that. This is a red toroid suitable for HF frequencies. An excellent
website on determining what toroids you have available in your box can be
found atÂ*http://toroids.info/

There is also an online winding calculator which you can use to see how
many turns you need to make on your toroid to get the required inductance.

There is an excellent program you can download from the Internet to your PC
to make calculations on your toroid inductances. It can be downloaded
fromÂ*http://www.electronicecircuits.com/d...%20program.zip

This program gives you additional information like the affects of power on
the toroid. For QRP 5 Watts, the voltage on the toroid would be V = SQRT (P
x Z) and with a feedpoint impedance of say 3000 ohms, 5W would look like
this. Id loose 300 mW through the toroid which isnt that bad at all!



At 100W the T157-2 would start to take a little strain as far as heating is
concerned but thats quite normal! An odd 7.4 Watts are lost through the
toroid. Tradeoff . lots of coax feeding the wire in the middle like in a
dipole with the logistical complexities of a very large dipole or the end
fed. The end fed offers many alternative options.



Note the 20 meter length of wire is connected to the earth side of the
capacitor make that the rotor then the control shaft is also at earth
potential so there is no chance of getting a RF burn while tuning. Of
course thats the same potential of the rig via the coax braide.

Â*Â*Â*Â*Â*Â*Â*Â*Â*Â*

Tune for minimum SWR. Its pretty easy to get 1.1:1 with this setup but dont
leave the counterpoise unconnected! The counterpoise can simply lie on the
ground.

Note, I built mine into an old modified MFJ945e antenna tuner with built in
cross needle SWR meter. It can be much simpler, the toroid and capacitor in
a suitable little plastic box.

At the far end (80 meters away) , terminate the wire on an electric fence
insultaor and tie down with a nylon rope. The ends are at a high voltage
low current point.

Enjoy 160m, there are quite a few ham radio operators in ZS who would love
to have a QSO with you!



73 de Eddie ZS6BNE








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RaDAR - The RaDAR One Hour Sprint design phase

Posted: 03 Jul 2017 02:44 AM PDT
https://zs6bne.wordpress.com/2017/07...-design-phase/


There are three, four hour full RaDAR challenges, that take place
internationally each year. The idea behind the RaDAR One Hour Sprint is to
promote the use of CW (Morse code) and to attract newcomers to this awesome
method of communicating over radio.





I was thinking monthly but weekly sounds better. It could coincide with the
CW Proficiency badge system submitted to the SARL council earlier this year
which was accepted in principle. Say every Saturday at around 16:00 to
17:00 local time on 40 meters. If you miss the schedule then its only a
week to wait and then you can try again.

Frequencies between 7.020 and 7.030 with special regard to Pixie
transcievers on 7.023 MHz.

The RaDAR sprint QSOs can take place using a rubber stamp method which
could help newcomers, like the young Hammies to overcome their fears and
build confidence using the morse code on the air. Similar guidelines to
Morse Runner which is the proficiency testing medium.

All communications using a hand key and speed around 12 w.p.m. (Level 1)

Station legend :

A Fixed station at home or in another building

B Portable station

C Motorized mobile station

D Bicycle mobile station

E On foot / Canoe station

F Wheelchair station



The QSO format could be such

Calling CQ CQ RaDAR de ZS6XYZ Â* Â* Â* Â* Â*(Can be repeated)

Reply ZS6XYZ de ZS5ABC 599 A Â* Â* Â* Â*Â* Â* Â*(Answer the CQ station, RST 599,
Im a Fixed station)

Query QRZ ? de ZS6XYZÂ* Â* Â* Â* Â* Â* Â* Â* Â* Â* Â* Â* Â* Â*(If the station was not
copied correctly)

OR

Confirm ZS5ABC de ZS6XYZ 559 E TU Â* (Confirm the calling stations
callsign, RST 559 , Im on foot or in a canoe , Thank you)

And thats the QSO made and can count towards QSO credits for the
proficiency badge.

SeeÂ*https://zs6bne.wordpress.com/2017/02...-cw-operators/

We can start this weekend and Ill have it approved for the Blue book in
2018.



73 de Eddie ZS6BNE