[Boatanchors] Thanks all, Balun need filled (at least temporarily)

[Phil KO6BB]

Earlier I put out a request for ideas on matching, at least somewhat a 
ladder line fed dipole to a couple receivers, and I received some good 
ideas from folks on the list, including construction methods.  The 
primary requirement was 'cheap' as this particular requirement doesn't 
entail transmitting.

After getting a couple good ideas I decided to check my somewhat meager 
junk-box for parts.  This yielded a small plastic project box with two 
banana jacks on one side and various and sundry holes drilled in it. 
I'd rescued it from a "freebie" box at a local hamfest a long time ago. 
  Digging further I located some old, very tarnished (silver) BNC jacks 
that I'd reclaimed from something a long time ago. I was able to clean 
one up nicely. and mounted that in the box.

Now, I just needed the balun transformer.  I only had one toroid core of 
  unknown properties, but which I believe I'd recycled from an old 
computer power supply.  I didn't figure that would be very suitable for 
HF.  But digging in a small drawer containing various and sundry coils I 
ran across a long skinny single tubular type toroid (perhaps 3/4 inch 
long) that had two windings on opposite sides.  One had three turns and 
the other six.  Hmm, now where did this come from?  Then I remembered 
that I had scrapped out a smoked HF FET pre-amp a couple years ago and 
it came from that, I believe as an output coupling transformer.

Hey, it can't hurt to try it and see what happens.  So, I put it in the 
box with the six winding side feeding the banana jacks and the three 
turn side feeding the BNC connector.  I also put a 10K resistor from 
each of the banana jacks to the ground of the BNC connector to drain any 
static buildup from inclement weather.

NOT a true balun, but at least it matches and isolates the antenna somewhat.

The only thing left to do was to test it out.  In testing it with the 
two receivers that it was to be used with (The Zenith Royal 7000 
transoceanic and the Realistic DX380) the results were VERY positive.

1.  The Zenith Royal 7000 TO has NEVER responded well to connecting an 
external antenna to it's external antenna jack.  It always just barely 
made any difference over the internal whip antenna.  It usually helped 
overcome some local noise on the broadcast band, but rarely made any 
difference on shortwave (and that's trying the different antenna 
connections on back of the radio).  Although over 40 years old this is 
my radio of choice for SWLing because of it's tone.

NOW, connecting the antenna to the external antenna terminal makes a BIG 
difference on shortwave, little difference on MW.

2.  The DX380 (Sangean ATS808).  External antennas connected to it's 1/8 
inch antenna jack has always helped this set, often overloading it on MW 
unless the attenuator is turned on. Using the new coupling transformer 
the antenna helps the radio quite a bit on shortwave, NOT on mediumwave.

My observations:

On Shortwave this coupling transformer helps a LOT, it's quieter than if 
I just feed the ladder line directly into the radios (unbalanced feed). 
  It does NOT work very well in the mediumwave band.  I feel this is 
probably due to insufficient inductance in the windings, no room in the 
core to add more turns. (I think that old pre-amp I scrapped tuned from 
80 to 6 meters if I recall correctly).

But it'll do until I find another toroid core and wind a different 
transformer. . .

-- 
73 de Phil,  KO6BB
http://ko6bb1.multiply.com/ (My OTR Blog)
http://cbsmysterytheater.multiply.com/
http://www.qsl.net/ko6bb/   (Web Page)

RADIOS:
Yaesu FT-2000 Xceiver for "hamming" and LF Beacons.
Zenith "American" Royal-7000 Transoceanic Portable.
Radio Shack DX-380 digital portable.

ANTENNA: 88' Long balanced dipole.