lu6etj wrote in
:

....
For monoband applications we can get more Z from a coaxial choke
making the winding for autorresonance. K1TTT have a good data table.

Time ago I want test differents antenna to lift with a kite and I
found =
http://www.io.com/~n5fc/rfd.htm, the idea seems to me interesting
enough to make some test that are descibed here =

http://www.solred.com.ar/lu6etj/tecn...ga_revisada-en
.htm

from here I think of another use of de "coaxial trap" to get more Z
from coaxial winding specially in monoband antennas, I named de
critter "The Trap balun" =

http://www.solred.com.ar/lu6etj/tecn...a_balun-en.htm

4NEC2 simulations and real field test show me both approachs works
fine :)

How did you arrive at the value of Q (=100) used in the modelling. Was it
measured, or guessed?

Based on some experimental work, I expect that the effective RF
resistance of a closed space solenoidal coil of braided coax is much
higher than the same straight length a copper cylinder.

BTW, if you want to make a more compact self resonant trap on the lower
HF bands, wind the coil in two layers. The article at
http://vk1od.net/antenna/7MDipole/7MDipole.htm shows a pic of a two layer
7MHz self resonant balun made with IIRC about 6 turns per layer of RG6.

Owen

On 14 sep, 17:34, Owen Duffy wrote:
lu6etj wrote :

...





For monoband applications we can get more Z from a coaxial choke
making the winding for autorresonance. K1TTT have a good data table.

Time ago I want test differents antenna to lift with a kite and I
found =
http://www.io.com/~n5fc/rfd.htm, the idea seems to me interesting
enough to make some test that are descibed here =

http://www.solred.com.ar/lu6etj/tecn...ga_revisada-en
.htm

from here I think of another use of de "coaxial trap" to get more Z
from coaxial winding specially in monoband antennas, I named de
critter "The Trap balun" *=

http://www.solred.com.ar/lu6etj/tecn...a_balun-en.htm

4NEC2 simulations and real field test show me both approachs works
fine :)

How did you arrive at the value of Q (=100) used in the modelling. Was it
measured, or guessed?

Based on some experimental work, I expect that the effective RF
resistance of a closed space solenoidal coil of braided coax is much
higher than the same straight length a copper cylinder.

BTW, if you want to make a more compact self resonant trap on the lower
HF bands, wind the coil in two layers. The article athttp://vk1od.net/antenna/7MDipole/7MDipole.htmshows a pic of a two layer
7MHz self resonant balun made with IIRC about 6 turns per layer of RG6.

Owen- Ocultar texto de la cita -

- Mostrar texto de la cita -

I do not remember Owen, I believe Q 100 was a number for the text
example, calculated Q on 7 MHz for ideal coil was about 400 and
measured real coaxial made coil with a GR-1606 A near 200. at that
time I did not think to use RG6, It is more light than RG58, isn't it?
Seven turns of RG 58 on 63 mm diameter with parallel condenser it was
very light, enough for the purpose, Rokkaku lifted 40 m "syringe"
antenna flied very well.

R, to two layers choke. Well... frankly to me common mode radiation it
is not something I lose sleep, I have not troubles in my shack and I
was not very lucky in all attempts to reduce nasty modern suburban
noise with baluns + chokes + grounded points, so many noisy companies
and neighbors cables around :( antenna height showed much better
results.

73

Miguel LU6ETJ