I'm really new to SWL and obviously have a lot to learn. So I'd like to try
to understand what I need to receive what radios like the Grundig 400PE and
Sangean 803A are capable of receiving. I use both, but find the Sangean more
"fun" because it has a tuning knob. There is something about a tuning knob
that feels better than a button to go to a frequency. Perhaps its because
its more like that old radio I used to play around with when I was a kid
back in the early 50's.

In any case, since its winter here in Illinois I have put off any attempt to
put an antenna outdoors. The situation is this: aluminum sided home, shack
in the basement about four feet from my laptop computer. About 15 years ago
I ran an RG59U cable from the attic to the basement; its been unused for
most of those years, but recently I ran a 40 foot length of #14 single
stranded, insulated copper wire lengthwise in the attic. It is stapled to
the rafters about three feet down from the peak. I soldered the center
conductor of the RG59U to the end of the copper wire. The cable runs down 25
feet vertically to the basement and is connected to the whip antennas of the
radio with an alligator clip, since the radios do not accept the same plug.
(The wire in the attic runs essentially NNE to SSW and the downlead cable is
soldered to the NNE end of the wire. the SSE end takes a right angle with
the last 6 feet of wire. So it takes the following shape:

|
|------------------------------------- (Downlead
side) NNE

This setup left me able to receive more than I could with about 25 feet of
multistrand, speaker wire tossed out the basement window and anchored up in
a tree next to the window, but it is noisy. Lots of static, but turning off
various things (computers, fluorescent lights, dimmers, etc.) doesn't seem
to reduce the noise. I noticed that when attaching the antenna to the whip,
I was getting pretty good reception and less noise when the alligator clip
was about two inches from the whip. For some reason I decided to wrap about
50 loops of the #14 insulated wire around a piece of 1 1/2 inch PVC pipe
and bare one end of the coil for attachment to the alligator clips. I
slipped the coil over the whip, attached the clip to the bare portion of the
wire forming the coil and I get pretty decent reception with less noise that
with the clip attached directly to the whip. Clipping the alligators to the
insulation on the end of the coil I get even less noise, and still pretty
decent reception.

Why does this work? Is there anything else I can do with the current setup
to improve things? Until spring arrives I'm not even going to think about an
outside antenna. What mistakes did I make? How is the current setup going to
limit reception on various bands? How will it improve reception relative to
just the whip (which is kind of useless in the basement, anyway)?

Did I do anything right? Did I do anything wrong? I see SWL as essentially
experimenting with antenna configurations. Is this a valid way to look at
it?

Harlan

On Sat, 3 Jan 2004 23:45:31 -0600, "H Davis" hdavis@(no
spam)ntsource.com wrote:

Hi Harlan,

This seems to be a significant clue:
since the radios do not accept the same plug.

snip

This setup left me able to receive more than I could with about 25 feet of
multistrand, speaker wire tossed out the basement window and anchored up in
a tree next to the window, but it is noisy. Lots of static, but turning off
various things (computers, fluorescent lights, dimmers, etc.) doesn't seem
to reduce the noise. I noticed that when attaching the antenna to the whip,
I was getting pretty good reception and less noise when the alligator clip
was about two inches from the whip. For some reason I decided to wrap about
50 loops of the #14 insulated wire around a piece of 1 1/2 inch PVC pipe
and bare one end of the coil for attachment to the alligator clips. I
slipped the coil over the whip, attached the clip to the bare portion of the
wire forming the coil and I get pretty decent reception with less noise that
with the clip attached directly to the whip. Clipping the alligators to the
insulation on the end of the coil I get even less noise, and still pretty
decent reception.

Why does this work? Is there anything else I can do with the current setup
to improve things? Until spring arrives I'm not even going to think about an
outside antenna. What mistakes did I make? How is the current setup going to
limit reception on various bands? How will it improve reception relative to
just the whip (which is kind of useless in the basement, anyway)?

Did I do anything right? Did I do anything wrong? I see SWL as essentially
experimenting with antenna configurations. Is this a valid way to look at
it?

Harlan

You are on the right path. However, as to the "clue" above. I am not
familiar with the specific models, but I have every suspicion that the
whip antenna is for FM only, and AM/SW is achieved through either a
ferrite bar antenna inside, or an external connection, or both. Your
windings are not really coupling into the whip but rather this
internal antenna, and they are still too far apart. However, barring
a more detailed description, this is just a guess.

Do your receivers have any kind of jack that is not audio or power?
Chances are that is an external antenna connection, especially if
there is a switch nearby. If so, that is the proper way in with your
wire antenna and it will make a significant difference. I say this
because it sounds like the noise is from your having the gain set all
the way up, and what would be strong signals are competing with weak
noise. The reason why the strong signals are not booming in, is you
haven't made a good connection. The other possible answer is that you
are in fact deep in a very noisy environment and your antenna is doing
the best it can.

73's
Richard Clark, KB7QHC

Richard:

Perhaps I led you astray with that comment regarding different plugs. I
should have said that both radios have external antenna plugs, but they
require different types of plugs. The Grundig takes a 1/8 inch mono plug
such as the type usually used for mono earphones. The Sangean takes a
different plug from what I understand, so I decided to compromise and use
the clip and attach the external antenna via the alligator clip rather than
try to switch plugs each time I want to switch radios. By the way, both
radios use the whip and/or the external antenna for SW. If I don't have
access to an external antenna, both radios require the full extension of the
whip for SW.

Richard, in reading all I can about the subject of using alligator clips or
plugs for the external antenna, I got the impression that the clip would
yield a good connection if you couldn't use the plug. I think what you are
telling me is that isn't the case. Of course, it stands to reasons that if
the radios have a provision for plugging in an external antenna, that would
be the ideal connection.

Thanks for commenting, Richard; this is a great forum to learn from others.


Harlan





"Richard Clark" wrote in message
...
On Sat, 3 Jan 2004 23:45:31 -0600, "H Davis" hdavis@(no
spam)ntsource.com wrote:

Hi Harlan,

This seems to be a significant clue:
since the radios do not accept the same plug.

You are on the right path. However, as to the "clue" above. I am not
familiar with the specific models, but I have every suspicion that the
whip antenna is for FM only, and AM/SW is achieved through either a
ferrite bar antenna inside, or an external connection, or both. Your
windings are not really coupling into the whip but rather this
internal antenna, and they are still too far apart. However, barring
a more detailed description, this is just a guess.

Do your receivers have any kind of jack that is not audio or power?
Chances are that is an external antenna connection, especially if
there is a switch nearby. If so, that is the proper way in with your
wire antenna and it will make a significant difference. I say this
because it sounds like the noise is from your having the gain set all
the way up, and what would be strong signals are competing with weak
noise. The reason why the strong signals are not booming in, is you
haven't made a good connection. The other possible answer is that you
are in fact deep in a very noisy environment and your antenna is doing
the best it can.

73's
Richard Clark, KB7QHC

On Sun, 4 Jan 2004 03:24:30 -0600, "H Davis" hdavis@(no
spam)ntsource.com wrote:

Richard:

Perhaps I led you astray with that comment regarding different plugs. I
should have said that both radios have external antenna plugs, but they
require different types of plugs. The Grundig takes a 1/8 inch mono plug
such as the type usually used for mono earphones. The Sangean takes a
different plug from what I understand,

Why don't you go to Radio Shack, and get the two kinds of plugs you
need, and then attach both to the center conductor of your coax, using
a little hook-up wire and solder. Then just plug the antenna directly
into each radio. You seem to be getting too many variables from
clipping onto your whip.

It's also possible the proper plugs came with each radio, no need to
go to Radio shack.

Learning about plugs is a part of SWLing :-)


Bob
k5qwg

"H Davis" hdavis@(no spam)ntsource.com wrote in message
...
I'm really new to SWL and obviously have a lot to learn. So I'd like to
try
to understand what I need to receive what radios like the Grundig 400PE
and
Sangean 803A are capable of receiving.

For the Grundig, which I own one of, it is an amazing little radio, and the
double-hetro design makes the receiver as wide-open a front end as possible
to receive almost everything. The down side to the radio is that it is
_easily_ overloaded with signals from any kind of antenna longer than the
recommended 20' or so provided with the unit. I have found that the Grundig
400PE operated with it's stock whip antenna fom a second floor room will
receive almost anything that the best receivers with any antenna can. Bear
in mind it is a wide-open front end with _lots_ of noise, but it doesn't
miss much either. I think that the Sangean has very similar characteristics
and ablities. I suggest enjoying them both as they were designed, and not
expecting any kind of external antenna design making a significant
improvement on their performance.

Jack
Virginia Beach Va

On Sun, 4 Jan 2004 03:24:30 -0600, "H Davis" hdavis@(no
spam)ntsource.com wrote:

Richard:

Perhaps I led you astray with that comment regarding different plugs. I
should have said that both radios have external antenna plugs, but they
require different types of plugs. The Grundig takes a 1/8 inch mono plug
such as the type usually used for mono earphones. The Sangean takes a
different plug from what I understand, so I decided to compromise and use
the clip and attach the external antenna via the alligator clip rather than
try to switch plugs each time I want to switch radios. By the way, both
radios use the whip and/or the external antenna for SW. If I don't have
access to an external antenna, both radios require the full extension of the
whip for SW.

One question that is unanswered: is there a switch near either of
those input jacks? Might be labeled local/dx.

Richard, in reading all I can about the subject of using alligator clips or
plugs for the external antenna, I got the impression that the clip would
yield a good connection if you couldn't use the plug. I think what you are
telling me is that isn't the case. Of course, it stands to reasons that if
the radios have a provision for plugging in an external antenna, that would
be the ideal connection.

Thanks for commenting, Richard; this is a great forum to learn from others.


Harlan

Hi Harlan,

The variation of where you clip it to the whip suggests the whip is
not directly connected to the SW path (because it simply doesn't go
there, or this switch I have supposed, is in the wrong position, or
both).

Anyway, I will offer a list of stations I can get here, in Seattle,
that come in full tilt boogie. If you couldn't duplicate this
experience, you have a switch/path problem (and I doubt both sets
would suffer identically unless your wire was broken one foot from the
clip).

Anyway, in the form of a quote, my ad-hoc log:

Our time 9 AM (1600 UT) for an hour
on 11650 KHz (or 11.650 MHz)
Radio Australia (noted by its interval signal of "Waltzing Matilda").

10 AM (1700 UT)
on 11710 KHz
Japanese Language program

10 AM (1700 UT)
on 11750 KHz; 11795 KHz; 11945 KHz; 11995 KHz
Far Eastern music mixed with other signals (less so at 11945)

10 AM (1700 UT)
on 11880 KHz
Radio Australia

10:30 AM (1730 UT)
on 9505 KHz; 11970 KHz
Swing music and talk about genetically modified corn in corn chips from Radio Japan (NHK)

10:45 AM (1745 UT)
on 17605 KHz
French language program

11 AM (1800 UT)
on 17640 KHz
Far Eastern music program

11:30 AM (1830 UT)
on 17705 KHz
Spanish language program

11:30 AM (1830 UT)
on 17785 KHz
French language program (probably VOA)

12 PM (1900 UT)
on 17860 KHz
German language program (DW)

12 PM (1900 UT)
on 17870 KHz
French language program (Radio Canada)

12 PM (1900 UT)
on 17895 KHz
Mixed music program (VOA)

12 PM (1900 UT)
on 21590 KHz
Interview program about helicopters (Radio Netherlands)

12 :30 PM (1930 UT)
on 117850 KHz
Far eastern music

======== Now at a later time, in the evening he

8 PM (0300 UT)
on 5950 KHz
news in english from Radio Taiwan

8 PM (0300 UT)
on 5960 KHz
Japanese language program (NHK)

8 PM (0300 UT)
on 5975 KHz
health program from BBC

8:30 PM (0330 UT)
on 5950 KHz
news in Spanish from BBC

8:30 PM (0330 UT)
on 9450 KHz
program in Russian (possibly Radio Moscow or VOA)

8:30 PM (0330 UT)
on 9460 KHz
program in mid eastern music

8:30 PM (0330 UT)
on 9575 KHz
news in english for western pacific from VOA

8:30 PM (0330 UT)
on 9590 KHz; 9640 KHz
news in German (CBC, Radio Canada)

8:30 PM (0330 UT)
on 9640 KHz
program in German (possibly DW)


73's
Richard Clark, KB7QHC, WPE0EPH

On Sun, 4 Jan 2004 11:55:43 -0500, "Jack Painter"
wrote:

The down side to the radio is that it is
_easily_ overloaded with signals from any kind of antenna longer than the
recommended 20' or so provided with the unit.

Hi Jack, Harlan,

This is very significant. I should have thought of this too.

This is the hidden sensitivity killer because a nearby AM stations's
signal going in these style of front end will develop AGC that
absolutely de-sensitizes the SW bands. You don't hear the signal at
the speaker, but the receiver hears it at the antenna (quite loud).

Put a cheap antenna tuner between your sets and the antenna to prevent
this. Or simply build a cheap high pass filter (antenna through cap
to set, AND with antenna through coil to ground). If you make the cap
variable, you can peak SW reception in a couple of bands. If you also
tap the coil, you can switch its value and peak in most bands (thus a
tuner). The tuner will short out the local power house that is
swamping your sets and allow the SW through to a more sensitive
condition. The cheapest, simplest (two or three control) Ham tuner
will do.

73's
Richard Clark, KB7QHC

Harlan:

You have made two minor missteps, but they have major repercussions. They
are due to some fundamental misunderstandings of radio technology, as with
almost all beginners. Fortunately, both are simple fixes.

First, by not properly connecting the shield of the coaxial cable, it
becomes an unwanted part of the antenna, and its proximity to stuff in the
house is picking up noise. Since the house is (sort of) shielded, it is
also likely to not picking be up any useful signals. The shield of the coax
needs to be "terminated", that is, connected to the correct *something* on
both ends.

Second, the input circuits of portable radios are a compromise. They are
optimized for the whip where it is internally connected, but a different
circuit is connected to the antenna input jacks to accommodate the stronger
signals which will come from a *better* antenna. Connecting the *better*
antenna to the whip simply detunes and overloads the front end. It will
accept some higher level signal, and this occurs when approaching the whip
with these various attachments to the end of the coax, but a the ability to
accept a direct connection of a good antenna to the whip is simply not
provided for in the design.

Now, changes needed. You could make the two headed plug as Bob suggests, or
get the appropriate adapter for one of the radios so one plug will fit
either. I am at a loss to imagine what is different, unless one is 1/8" and
the other 3/32", and if so there indeed are adapters. Now, make sure the
shield of the coax is connected to the second terminal in the plug, which
will be coupled to the radio common inside the radio. If necessary to
physically install the tiny plug on the RG-59, short pieces of insulated
hook up wire can be used, just be sure to connect the shield to the sleeve
of the plug, and the center conductor to the tip.

Then, go up to the attic with another 40 feet of wire. Connect it to the
shield up there, and stretch it out as much as possible away from the
existing wire. If the attic is small, a more effective installation might
be to zig-zag both halves of the dipole so it is nearly balanced in
configuration. Don't worry about the wire being straight, the electrons
won't care.

These two changes should couple a cleaner signal into the intended high
level input of each receiver.
--
Crazy George
Remove N O and S P A M imbedded in return address

H. Davis wrote:
"How will it improve reception relative to just the whip (which is kind
of useless in the basement anyway)?

Your coax can be used as a transmission line, instead as part of the
antenna, to bring above ground signals into your basement while
shielding against noise inside your house if connected to a balanced
antenna somewhat removed from noise sources. Noise will appear as
common-mode in many cases balancing out in a coupling coil.

For a receiving antenna, a small inexpensive toroidal ferrite core
appropriate to the frequency of your receiver may be used on which to
wind a primary of an antenna coupling transforner. The secondary will be
the whip antenna itself.

The 19th edition of the ARRL Antenna Book shows a noise bridge for 1.8
to 30 MHz on page 27-24. The bridge generator is connected to the bridge
detector (receiver) and to the unknown impedance (antenna) via a
broadband toroidal transformer. This core would be right to couple coax
to a whip antenna except for its size and shape. It is a small binocular
core. All that`s needed to couple to a receiver whip antenna is a
ferrite ring with enough diameter for 3 or 4 turns of # 30 or so
enameled wire leaving enough hole space to be impaled over either of the
two whips.

The core used in the noise bridge is an Amidon BLN-43-2402. The material
is obviously apropriate for 1.8 to 30 MHz. I don`t have an Amidon
catalog handy but for sure the material is available in a simple ring.

Simply wind the coil around the ring and connect it your coax. Connect a
balanced antenna to the other end of the coax. The antenna should be
placed away from noise sources and placed in the field of desired
signals. Slip the ring over the whip of the receiver you want to use
with an external antenna. That`s it! You may need a balun at the
balanced antenna for minimum noise.

The whip forms a complete circuit through its capacitance to the earth
and to the radio circuit board or chassis. It is a 1-turn secondary on
the toroidal antenna transformer. Its operation is akin to an a-c
clamp-on ammeter.

This system has been used to couple a transmitter to a grounded
transmitting tower. For transmission, air was used for the core of a
large toroidal coil surrounding the tower. To tightly couple the coil to
the tower, the coil`s reactance was tuned out with a series variable
capacitor. This has a disadvantage of the tuned circuit type. It has a
narrow bandpass. For reception, you likely don`t need tight coupling as
gain is usually surplus in your receiver. You need signal to noise
ratio.

Toroidal coupling systems are not found in standard broadcasting
stations because the large toroid would be expensive, and difficult to
construct and insulate. It would also slice away the medium-wave
higher-frequency sidebands, limiting audio frequency response of the
station.

Untuned, the toroid coil coupling is tight enough for a high gain
receiver and bandwidth is sufficient for a 1.8 to 30 MHz noise bridge or
receiver.

Best regards, Richard Harrison, KB5WZI