[Hallicrafters] SX-28 sensitivity on 10-15 meters?

[Glen Zook]

A cheap thing that often helps is to install a TV type
balun.  The older receivers have a nominal antenna
impedance of between 300 and 400 ohms.  Feeding the
antenna directly with 50 ohm coax often results in a
serious loss of signal.

Take loose the connection between one of the antenna
terminals and ground then install the balun.  Run the
coax into the jack.  The fact that most antennas use
50 ohm coax instead of 75 ohm doesn't really have much
effect.  Also, the impedance matching to 300 ohms is
also only nominal.  The impedances of the TV type
baluns is only approximate but they definitely have a
"good" effect on the older receivers.

Depending on the individual receiver and even the band
on the receiver, I have seen this use of a TV balun
improve things between 6 dB and over 20 dB!  For more
information you can read the text of the article on
this that was published in Electric Radio a couple of
years ago.  That article is reproduced on either of
the websites at the end of this message.

If it is necessary to use a preamplifier such as those
manufactured by Ameco, the balun will match the output
of those to the receiver.  I have used the Ameco
preamplifiers on various receivers and they do help. 
However, you do need to make sure that you don't
overload the input to the receiver.

Glen, K9STH

--- Gary Pewitt <gpewitt at execpc.com> wrote:

try something like an Ameco nuvistor cascode pre amp
or 
> equivalent. 

=====
Glen, K9STH

Web sites

http://home.attbi.com/~k9sth
http://home.attbi.com/~zcomco

__________________________________________________
Do you Yahoo!?
Yahoo! Web Hosting - establish your business online
http://webhosting.yahoo.com