[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: KLM 14C



Hi Ron, VE7YC

I believe that your KLM 14C is a crossed dipole antenna for 2 meters with
the horizontal and vertical elements spaced 1/4 wave free space along the
boom.

If this is correct both driven elements should be folded dipoles and your
baluns that looks like new are 1/2 electrical wave i.e. 1/2 free space wave
x the velocity factor of the coax cable used for it.

If the jacket of coax of your balun is yellow than it is a teflon coax with
velocity factor 0.695 and you shoul read  RG-303/U on the jacket of it
and it's characteristic impedance is  Zo= 50 ohm

The lenght of the above balun 1/2 electrical wave long should be 71.89 cm
or 28.3 "

Be carefull that the coax balun leads are connected to the lugs at feedpoint
of  each folded dipole and the strap of the coax braid is connected on
mounting stud wich is grounded to the boom.

In this conditions the unbalanced impedance of each driven element
between one lug of the folded dipole and the ground at feedpoint is
50 ohm nominal

Now you need to transforme the 50 ohm impedance of  each folded
dipole at feed point in to 100 ohm and than connect both 100 ohm
impedances in parallel to get again 50 ohm resultant impedance to be
connected to your transmission line with Zo=50 ohm

The above impedance transformation is accomplished using a 1/4 electrical
wave of coax cable having characteristic impedance Zo= 75 ohm and
a suitable teflon cable is RG 302/U with velocity factor 0.695 so that for
145 MHz its lenght is 35.9 cm or 14.15 "

If you don't have RG 302/U for the moment use normal RG-59/U with
impedance Z0=75 ohm and velocity factor 0.66 so that the lenght of the
1/4 electrical wave is 34 cm or 13.44"

The above lenghts are those measured at the end of the braid and the lenght
of the inner conductor must be as short as possible to connect the terminals
to the lugs and to ground at feed point of each folded dipole.

To prepare the above cables  follows the same technique used by KLM for
the balun.

Now you have built a phasing harness but you don't have a relay on it to
select RHCP or LHCP so that it is best to connect the dipoles to get only
RHCP for the moment.

Put your self rear of  boom and orient vertical the dipole closer to the
satellite and the horizontal the dipole close to you.

Connect one of the 75 ohm 1/4 electrical wave to the vertical dipole in such
a way that the inner conductor is connected to the upper lug of the vertical
folded dipole and the strap of the braid to the same ground of  balun i.e.
to the boom.

Connect the other 75 ohm 1/4 electrical wave to the horizontal dipole in
such a way that the inner conductor is connected to the right lug of the
horizontal folded dipole as seen by you from rear of reflector and connect
the strap of the braid to ground.

Now the open ends of each 75 ohm 1/4 electrical wave will show an impedance
of about 100 ohm

Connect both the open ends in parallel to a suitable N connector with both
inner conductors to the central pin and both braids to the flange of it.

The VSWR should be acceptable depending on the accuracy the coax are cutted
and prepared and the actual polarization is RHCP

I hope this helps

Best 73" de

i8CVS Domenico


----- Original Message -----
From: "Ronald A. Stunden" <ve7yc@shaw.ca>
To: "Amsat" <amsat-bb@amsat.org>
Sent: Saturday, May 21, 2005 5:59 PM
Subject: [amsat-bb] KLM 14C


> Is KlM still alive?? can't seem to find them on the Internet. I am in
> need of  either the matching harness or the dimensions for it. I have an
> antenna with the baluns that looks new but no harness. I would think its
> 1\4 wave?? However that doesn't seem to work.. Any Ideas.  Thanks Ron
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> Not an AMSAT member? Join now to support the amateur satellite program!
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home