"DrYattz" wrote in message
...
My 15 year old son is exploring shortwave radio, and has purchased a
Realistic DX-394a. We're experimenting with various antenna
configurations, now trying an inverted L. The layout so far can be
seen at:

http://i258.photobucket.com/albums/h...t/antenna2.jpg

So, a single strand wire crosses the yard at a height of about 14-18
feet, stretched east-west, insulated at each end, and another length
of wire connected to it drops to below a window, then passes through
the wall and to the Hi-Z antenna input. (The diagram shows a
lightning arrestor, but that isn't attached yet.)

But it seems to offer little or no advantage over the little
telescoping antenna. In fact, the best reception is when we touch the
antenna lead wire to the telescoping antenna. Do you suggest:

1) an antenna tuner?

2) coaxial cable running from the radio (Lo-Z input) to the end of the
75 foot run?

3) a north-south run?

4) a completely different configuration?

5) anything else?

Rees Chapman
winwinsit at gmail period com

I found the manuals and the schematic online but I still need to engage in
guesswork. Work with me.

You said best reception is obtained by touching your lead-in to the
telescoping antenna. Would you believe there is one and only one component
betweent the ANT HI-Z jack and the termination of the telescoping antenna?
it's a15 pF coupling capacitor. I guess it's bad .

Its reference designation is C179. There is another component in the
circuit, a 100K static drain resistor, R190, connected to ground. Resistors
rarely short out, so I won't guess that; besides, if it were to short, it
would hamper reception with the telescoping whip.

Connecting your outside antenna to the telecoping whip with a clip lead may
be OK, now and forever. I'd like to see you do it through a 15 pF
capacitor, if possible. This project/repair may end here.

If you want to proceded with troubleshooting, connect your antenna to the
ANT HI-Z jack. Open the case and move the body of the ANT HI-Z jack while
listening. Wiggle it gently. The solder joint to the PC board may have
cracked. I've seen about six of these failures with consumer equipment.
Sometimes an easy fix, sometimes a PITA.

If you can locate the junction of C179 and R190, touch your antenna lead to
that point instead, still while listening. There is no voltage there and
you can't be hurt. (It's like touching the telescoping whip, actually.)
R190 is a few milimeters in from the ANT HI-Z jack on top of the board.
It's an easy reach. I can't tell you which end is which. If you touch the
ground end first, nothing will happen, if you touch the correct end first
(and the ANT HI-Z jack is bad) you will hear signals. If you don't hear
them, it's probably C179 that's bad.

Maybe I've gone too fast and confused you. Read it again and/or get back to
me.

I guess one other option is to try your other connection for an external
antenna, labeled "ANT LO-Z". What does that do for ya? If you were to
change your antenna to a coaxial-fed dipole, the ANT LO-Z would probably be
a good match at most frequencies. If you are already "experimenting with
various antenna configurations," you ought to try that one, too. The
attenator switch, ATT 0dB - 20dB, is in-line with that path; work the
switch a few times to be sure it's free of corrosion enough for good
contacts.

Feedback to me would be nice. A Nobel Prize would be a bonus.

"Sal"
(KD6VKW)