Posted by
n6wg on
Apr 08, 2005; 12:17am
URL: http://elecraft.85.s1.nabble.com/Balun-question-tp376719p376720.html
Hi Vic
You can use your MFJ to measure the impedance of the balun. Connect one of
of the balun (short both wires together) to the center of the MFJ coax
connector
and the other end, shorted together, to the shell of the connector.
Use the MFJ to measure the impedance of the inductor formed at the frequency
to be used, say 1850 kHz. If the impedance is 5 or more times the 50 ohm
line impedance, you have a good balun for 160m. If that is the only band
you
expect to use it on, you are done.
If you expect to use it over more bands, say 80 and 40m as well, tune the
MFJ
to those bands also and make the same neasurement. With a good core, the
impedance
should hold through these bands as well, or even be higher.
Good luck and 73
Bob N6WG
-----Original Message-----
From:
[hidden email]
[mailto:
[hidden email]]On Behalf Of Vic Rosenthal
Sent: Wednesday, April 06, 2005 3:39 PM
To: Elecraft Reflector
Subject: [Elecraft] Balun question
I made a simple 1:1 receive-only balun for 160 meters by winding 9 bifilar
turns
of no. 24 enameled wire on an FT37-77 toroid. I connected a 50-ohm resistor
to
the output and my MFJ antenna analyzer to the input. On 1.8 MHz it shows a
resistance of 50 ohms, an inductive reactance of 1 ohm, and an SWR of 1.0:1.
My question is, did I make a 'good' balun? Are there other tests I should
do?
It's job will be to isolate a receiving loop antenna from its feedline, to
keep
the nulls deep and reduce noise pickup.
The RANT feature of the K2's 160-meter option has made it possible for me to
use
a ferrite loop which is only 21 inches (53.3 cm) long and has a s/n ratio
much
better than my inverted L transmitting antenna, even without the balun.
I'll
put details on my website after I finish testing it.
--
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco_______________________________________________
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