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Old October 18th 09, 06:26 AM posted to rec.radio.shortwave
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Posts: 17
Default type/length of wire and connectors for external antenna?

Thanks again, everyone.


But can I damage G5 with an external wire? If so I'll use the whip
inductor. Please advise....


Yes, you can, as most of these portable recievers do not have strong
input protection, *nearby strikes can damage the input. *Don't make
the wire longer then necessary and remove the mini plug from the radio
in case of natural photo flash. You might add the inductor or resistor
to lower the risk on damage because of built-up of static
electricity.


Wim (or anyone),

So, an early post stated "the longer the better" but you say not so
long. What is a good length to try? I assume I'll want to experiment
with longer and shorter. Bought 24 gauge speaker wire, 100 ft. for
$6.50 at Home Depot. But I'm nervous now, I don't want to do anything
until I understand.

I presume you mean, disconnect the antenna during storms with
lightening flashes. OK.

So, I'm thinking there are three kinds of potential damage from a long
wi static, lightening, and overload from a strong signal.

There are four ways to connect the antenna that I've encountered:
miniplug into antenna out, alligator clip to whip, bare wire wrapped
around whip, and inductive coupler (insulated wire wrapped around tube
placed over whip). (Leaving the balun out for the moment)

Am I right that too strong a radio signal (from too long a wire) can
hurt the radio? I presume this is true anytime too strong a signal
reaches the inside electronics. But my brother tells me the whip is
connected to an internal amplifier that the antenna input jack is not
connected to. So maybe the antenna input jack is safe in terms of
overloading signal from the long wire. And maybe the inductor can also
induce too strong a signal in the antenna which is then amplified,
causing damage, is this so? So, connecting the wire via the antenna
out jack and miniplug is safe with regard to overload, but inductive
coupler, alligator clip on whip, and bare wire wrapping around whip
(i.e., all connections to whip) are not. True?

As for lightening, it seems all connection methods are dangerous. For
static, all but the inductive coupler are dangerous. Right?



Using a special transformer as mentioned in other postings gives you
more signal output in case of short wires. So you can have a shorter
wire (for example when you have limited space). I do not share the
opinion that these transformers *reduce interference significantly.

When you live in a residential area, you probably don't need this as
noise will be dominant with moderate wire lengths. * More signal does
not always mean better reception as noise will raise also.




If I can figure out how to safely connect the antenna to the radio,
then is a good way to solve this noise issue to use a very long wire?
Or will it just pick up more residential EMG noise? I am in a
residential area, I have apartment buildings on two sides, 100+ feet
away, house on third side.

Maybe tuning to wavelengths is the only way to get a wire to elevate
signal above noise.

Thanks very much!

Jim
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Old October 18th 09, 06:12 PM posted to rec.radio.shortwave
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First recorded activity by RadioBanter: Mar 2008
Posts: 329
Default type/length of wire and connectors for external antenna?

Hello Jim, I put my comment between your text

On 18 oct, 07:26, JimK wrote:
Thanks again, everyone.

But can I damage G5 with an external wire? If so I'll use the whip
inductor. Please advise....


Yes, you can, as most of these portable recievers do not have strong
input protection, nearby strikes can damage the input. Don't make
the wire longer then necessary and remove the mini plug from the radio
in case of natural photo flash. You might add the inductor or resistor
to lower the risk on damage because of built-up of static
electricity.


Wim (or anyone),

So, an early post stated "the longer the better" but you say not so
long. What is a good length to try? I assume I'll want to experiment
with longer and shorter. Bought 24 gauge speaker wire, 100 ft. for
$6.50 at Home Depot. But I'm nervous now, I don't want to do anything
until I understand.


As you are in a residential area, start with about 20 ft. there may
be some bends in the wire (for example some part horizontally, some
vertically. I checked the I-manual. The receiver has a DX/LOC switch.
When you are listening to a weak station and the clearness doesn’t
reduce when switching from DX to LOC, your wire is long enough (maybe
somewhat to long for that particular frequency band).


I presume you mean, disconnect the antenna during storms with
lightening flashes. OK.


Correct.


So, I'm thinking there are three kinds of potential damage from a long
wi static, lightening, and overload from a strong signal.


OK, If there is no DC bath between the inner conductor and the shield
of the cable, you can have build-up of static charge that may damage
the input circuitry. Strong overload (due to strong stations) will
very likely not damage the input, but may result in bad reception of
signals at certain frequency bands.


There are four ways to connect the antenna that I've encountered:
miniplug into antenna out, alligator clip to whip, bare wire wrapped
around whip, and inductive coupler (insulated wire wrapped around tube
placed over whip). (Leaving the balun out for the moment).


In my opinion, the insulated wire wrapped around a tube place over the
whip, looks like inductive coupling, but is capacitive coupling (no
direct electrical connection between wire and whip). This method of
coupling reduces the coupling for low frequency. By varying the number
of turns you can figure out the best coupling to your receiver. That
means sufficient signal from the antenna to overcome the receiver
noise, but not too much to get intermodulation (overload) problems.


Am I right that too strong a radio signal (from too long a wire) can
hurt the radio?


I think not, see text above.

I presume this is true anytime too strong a signal
reaches the inside electronics. But my brother tells me the whip is
connected to an internal amplifier that the antenna input jack is not
connected to. So maybe the antenna input jack is safe in terms of
overloading signal from the long wire.


Depends on type of receiver, I don't know the inside of the G5.

And maybe the inductor can also
induce too strong a signal in the antenna which is then amplified,
causing damage, is this so? So, connecting the wire via the antenna
out jack and miniplug is safe with regard to overload, but inductive
coupler, alligator clip on whip, and bare wire wrapping around whip
(i.e., all connections to whip) are not. True?


Many portable receivers show overload problems when connecting long
wire (for example 100ft) directly to the whip (electrically
connected). By wrapping the insulated wire around the whip, you reduce
the coupling (especially for the low frequency ranges like AM and LW),
hence reducing change of overload.


As for lightening, it seems all connection methods are dangerous. For
static, all but the inductive coupler are dangerous. Right?


Depends. When the wire is insulated from the antenna (what you call
inductive coupling), static charge may build-up until it reaches the
ultimate strength of the insulation. When exceeded, your whip might be
subjected to static discharge.

You can bleed the static charge by providing a DC path to ground.
Mostly when the bare antenna wire touches the building construction
(wood, concrete, etc), static charge will not build-up.


Using a special transformer as mentioned in other postings gives you
more signal output in case of short wires. So you can have a shorter
wire (for example when you have limited space). I do not share the
opinion that these transformers reduce interference significantly.


When you live in a residential area, you probably don't need this as
noise will be dominant with moderate wire lengths. More signal does
not always mean better reception as noise will raise also.


If I can figure out how to safely connect the antenna to the radio,
then is a good way to solve this noise issue to use a very long wire?
Or will it just pick up more residential EMG noise? I am in a
residential area, I have apartment buildings on two sides, 100+ feet
away, house on third side.


You may try this. When you have a significant part of the wire
outside, away from electronics, that will improve reception, but be
aware of overload as mentioned earlier (so use the capacitive coupling
with the insulated wire wrapped around the whip). Note that this is
not my favorite solution (I prefer the coaxial feed and have all
antenna parts away from electronics).


Maybe tuning to wavelengths is the only way to get a wire to elevate
signal above noise.


Sorry Jim, I don't understand what you mean.

Thanks very much!

Jim


I hope my response is not too confusing.

Best regards,

Wim
PA3DJS
www.tetech.nl
without abc, you have a valid address.
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Old October 18th 09, 06:25 PM posted to rec.radio.shortwave
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First recorded activity by RadioBanter: May 2009
Posts: 313
Default type/length of wire and connectors for external antenna?



Am I right that too strong a radio signal (from too long a wire) can
hurt the radio?



Depends on the radio. The input gain device may be adversely
affected by too strong a signal. Being driven into saturation can
result in failure of some devices. This was a problem with some Sony
radios. It was a problem on a few inexpensive radios. It was a
problem on a number of early solidstate radios.

Today, receivers have overload protection before the first active
device. Sony installed diodes before the front end of their affected
devices. And most input devices used today have sufficient headroom
in circuit to prevent front end overload in all but the most extreme
cases. Buffers, and IF amps will more quickly overload than many
front ends, today.

But if you're talking about SW, unless you're near Antigua, or
living in Western Europe, you're not likely to encounter signals
strong enough to cause overload problems. A few domestic SW players,
if you're close enough. But not nearly what it used to be.

So, depending on your location, your concern may be a non-issue.

That said, it's something that's worth bearing in mind.


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