For many years, it was common practice to use a lead and aligator clip in
place of a roller inductor. Continuously variable and cheap.

"-=jd=-" wrote in message

The variable inductor is my stumbling block. I want that continuously
variable functionality, but without dropping $100 - $200 for a new/used
inductor. I'm thinking about trying to build one - but that's all I'm
doing... just thinking...

-=jd=-
--
My Current Disposable Email:

(Remove YOUR HAT to reply directly)

Take the batteries out. Put your (unconnected) plug into the socket. Check
for continuity between its outer contact (barrel) and the negative battery
terminal. Many radios have jacks with plastic external rings but there is a
ground terminal inside.

"Dave" wrote in message
...
Just a quick note: it actually does have an external antenna input, I just
don't know what type of plug to stick into it. Plastic ring with metal
contact inside, looks like 1/8" mono would do it, but how would I ground
it?
Negative battery term?

Thanks,

Dave

You don't in this newsgroup (shortwave). This is a text only group.

"Yodar" wrote in message
m...
I just tried to send a post with a schematic for a simple antenna tuner
and the diagram was cut out...how do I add it?

"-=jd=-" wrote in message
. ..

I'm thinking a bead (say, 1/2") threaded on a rod (brass for both bead and
rod?), positioned so that the bead can be lifted just slightly, then slid
along the coil - but when you release the bead, there's a bit of tension
pressing it against the coil. I thought about the gator clip method, but
I'm
thinking it might be easier to fool with if I had something I could adjust
without taking my focus off the radio.

Then again, alligator clips and leads are a more widely available than the
pseudo roller inductor parts rattling around in my head...

-=jd=-


I'll suggest you try the alligator clip and wire first. It will be alot
easier to do any modifications. Also, you might find the whole experiment
isn't particularly helpful in your situation. If so, you might as well find
out right away.

Frank Dresser

The bead on a wire idea works. It has been used frequently in crystal
radios.

"-=jd=-" wrote in message
. ..
On Fri 09 Apr 2004 12:40:57p, "CW" wrote in
message :

For many years, it was common practice to use a lead and aligator clip
in place of a roller inductor. Continuously variable and cheap.


I'm thinking a bead (say, 1/2") threaded on a rod (brass for both bead and
rod?), positioned so that the bead can be lifted just slightly, then slid
along the coil - but when you release the bead, there's a bit of tension
pressing it against the coil. I thought about the gator clip method, but
I'm
thinking it might be easier to fool with if I had something I could adjust
without taking my focus off the radio.

Then again, alligator clips and leads are a more widely available than the
pseudo roller inductor parts rattling around in my head...

-=jd=-
--
My Current Disposable Email:

(Remove YOUR HAT to reply directly)

Good advice. No need to over design something if your not sure it will work.
"Frank Dresser" wrote in message
news:NTBdc.1512$K_.34795@bgtnsc05-

I'll suggest you try the alligator clip and wire first. It will be alot
easier to do any modifications. Also, you might find the whole experiment
isn't particularly helpful in your situation. If so, you might as well
find
out right away.

Frank Dresser

"Dave" wrote in message
...
The antenna does indeed seem to be working great, and the radio is not
operating too shabily either as it is only the "background noise" I am
trying to reduce. I hooked a 100 mH RF choke up to it with good results,
and am planning on adding another one or two similar devices in an effort
to
cut down on higher frequency interference. Question: how would I ground
this antenna?

Uh, you don't ground the antenna. You ground ground. :-) The ground is like
a "return" path for the current induced in the antenna by the radio wave.

I have a grounding rod right outside the window, but don't
know what to hook it too. The negative battery terminal?

Probably. Any handy chassis ground will be fine.

This radio does
have an external antenna input, but that has a plastic ring around the
outside. Open to suggestions.

The radio might be grounded through the power cord, if it's a 3-prong.
Otherwise, just a wire from the radio's chassis to the ground rod, or
even to one of the mounting screws of a grounded outlet.

And thanks for the input RE purchasing a
new/used tuner.

dave

As you seem to have mentioned, you have lots & lots of signal
strenth, so you actually might want to make your antenna even _less_
sensitive. What it sounds like you're looking for is selectivity,
and you do that with tuned circuits. Or you did back when I was
learning this stuff. ;-)

Hope This Helps!
Rich

"Dave" wrote in message
...

As you seem to have mentioned, you have lots & lots of signal
strenth, so you actually might want to make your antenna even _less_
sensitive. What it sounds like you're looking for is selectivity,
and you do that with tuned circuits. Or you did back when I was
learning this stuff. ;-)

Hope This Helps!
Rich



Yes, a tuned circuit, I am thinking. There is currently much more signal
than I need. Is an antenna tuner what I am looking for?

I hooked up 300 microhenries worth of RF choke, which reduces the entire
signal just a hair, but that is enough to knock the noise level down
considerably. I am not yet sure, but this *may* be all I need. BTW, did
some fiddling withe the anchor of the random wire, and decided it is more
like 45 - 50 feet total. I am planning on moving it, however, and placing
it under the eaves and off to the side of the aluminum rain gutter, which
may deflate it some. Right now I have signal to waste. That may change.

Thanks for the input. Working with RF is new to me.

Actually, if you've got good electrical conductivity, the aluminum
rain gutters themselves might make a passable antenna. Ground _one_
of the downspouts at the bottom end, and experiment with different
pickoff points along the length of the gutter. An antenna has
different impedances at different points along its length, based on
the wavelength of interest. And you'd add inductance and capacitance
as needed to make the whole thing resonant at the freq. you want.
(that's the philosophy of an "antenna tuner.")

It really wouldn't do any harm to look up some books on antennas
and stuff, like "The ARRL Antenna Book", and talk with practically
any radio amateur - those guys do this stuff all day long.

Cheers!
Rich

i have that receiver. the amp connected to the whip is hot as a
firecracker and it overloads very easily. (the external ant jack isnt
much different!) use the antenna jack instead of the whip for a
connection. even then it wont handle that much wire. try laying your
wire right on the ground. i use a "snake" antenna with several sangean
radios with excellent results. even the low gain properties of an on
ground antenna is too much for this radio if its too long.

Dave wrote:

"starman" wrote in message


It sounds like you need a passive preselector rather than an antenna
tuner, if your receiver can't handle the strong signals on the antenna.
Are you hearing stations outside the bands where they are actually
located? Is there a lot of noise from many stations all over the
shortwave range.


I am picking up a few very weak signals out-of-band, and there is only
background noise on the DX setting. The RF choke seems to have done a nice
job of cleaning up most of the hash and trash in the background. I would
like to enhance the signal I am actually looking for, however. During
periods of good propogation I have ocassionally picked up Voice of Korea
transmissions aimed at Central and South America, and I would like to load
the dice in my favor if I can.

I really think you should try a passive preselector. It will reject the
strong out of band signals which cause intermodulation products while
peaking the weak stations. The choke helps but it also reduces the
receivers sensitivity to the signals you want to hear. The preselector
does the opposite. I used a preselector with my Sony-2010 and an
inverted-L antenna. It worked great. Without the preselector the 2010
would overload and produce a lot of spurious signals throughout the
shortwave spectrum.

It's pretty easy to build a passive preselector that will cover the
range of 3-30 Mhz with two coils. The larger coil will tune the range of
about 3-7 Mhz and the smaller one 7-30 Mhz. It's best to use ferrite
cores in the coils for the best selectivity or 'Q'. Of course you'll
also need an air variable capacitor like 10-365/pf and a simple rotary
switch to select the coils. The circuit is a parallel (tank) design
which is connected between the antenna input of the radio and ground,
along with the antenna itself.

If you're not into building, you can buy a passive preselector at:

http://www.grove-ent.com/MFJ1046.html

Here's an interesting article on antenna tuners:

http://www.nyx.net/~dgrunber/tuner.ssi


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