RadioBanter - View Single Post

October 23rd 04, 06:47 AM

In article ,
(bpnjensen) wrote:

(RHF) wrote in message
m...

Good information snipped

STARMAN,

Isn't Type 43 the recommended as a Balun "Core Material" ?

Why isn't Type 61 also a 'suggested' Balun Core Material ?

NOTE: Matching Transformer = Balun = UnUn

True Story: A while back I bought a Grab Bag of Feritte Cores on
eBay. Some of them had a #20 Enameled Wire wrapped on them with 36
Turns. They were about 1" OD x 1/2" ID x 1/2" H. So I thought, why
not try them as an Matching Transformer on an 'old' Telephone Two
Wire Service Line (pre-1950s) that runs overhead about 75 Ft from
the Power Pole to the House. Being lazy I simply wrapped a Twelve
Turn (12T) Secondary and wired it up with a #22 Magnet Wire from a
RadioShack 'three pack' Catalog # 278-1345 ($5). Well 36:12 Turns
worked good for AM/MW and up to 7 MHz but the Signal Levels fell
off after 7 MHz. So then I tried Reducing the Primary to 30 Turns
and the Secondary to 10 Turns. Again the AM/MW Band was good and
the Shortwave coverage went up to 23 MHz. Not being one to settle
for 'good enough'; I then tried Reducing the Primary to 24 Turns
and the Secondary to 8 Turns. Well the AM/MW Reception went down
and the Shortwave Bands reception picked up to the CB Band. So it
seems that the 'majic' 30 Turns and 10 Turns worked the best for my
needs using this ?Core?.

RHF - it sounds like you did not know what the material for this core
was (43 vs. 61 or other) - right? Is it possible that the frequency
range is more dependent on the number of turns (inductance?) than the
actual material? This is not a trick question...

Well, actually in a way it is a trick question. Inductors and
transformers are complex devices. Small differences in construction
will have a large effect on performance. How you connect it will change
its performance. Where (in frequency) you make measurement will affect
the results. I mention this because you want it to work from .5 MHz to
30 MHz.

--
Telamon
Ventura, California