Hello,

I listen on a SAT 700 and want to try and catch more DX in the SW bands. I am
told that if I put too much wire on it I can damage the radio due to the fact
that it has no dynamic control. Is there a device I could buy that would allow
me to put a longwire up and then regulate how much signal the receiver is fed?
Does this even make sense?

Thanks,

neil

BCcubed wrote:

Hello,

I listen on a SAT 700 and want to try and catch more DX in the SW bands. I am
told that if I put too much wire on it I can damage the radio due to the fact
that it has no dynamic control. Is there a device I could buy that would allow
me to put a longwire up and then regulate how much signal the receiver is fed?
Does this even make sense?

Thanks,

neil

To much signal strength from the antenna won't damage the radio but it
might cause overloading problems known as intermodulation or intermod's.
This happens when the dynamic range of the receiver is not sufficient to
handle very strong signals, which can happen with a long antenna. The
symptom of overloading is hearing many spurious signals on frequencies
and bands where they don't belong. For example, you might hear an
international broadcaster on a frequency which they are not actually
using and is not located in an international band. The solution is
either to make the antenna shorter until you don't hear these intermod's
or use a passive preselector between the antenna and receiver to tune
out the spurious signals. The latter method is preferred because you
won't loose much sensitivity to weak signals when using a preselector.


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BCcubed wrote:
Hello,

I listen on a SAT 700 and want to try and catch more DX in the SW bands. I am
told that if I put too much wire on it I can damage the radio due to the fact
that it has no dynamic control. Is there a device I could buy that would allow
me to put a longwire up and then regulate how much signal the receiver is fed?
Does this even make sense?

Thanks,

neil

Here are two options.

First, a step attenuator - these will allow you to dial in various
amounts of attenuation - if you found one that ranged from 0db to 50db
you'd probably have more range than you needed. Odds are you could
leave it parked on a few db of attenuation for most of the time, and
tweak it if you were going after something particularly weak, or strong.

A dirt cheap attenuator that isn't calibrated can be made with a simple
potentiometer (like a volume control) with the antenna hooked on one
end, ground on the other, and the wiper connected to the antenna jack of
the radio. The part is likely to cost about $3 and while it's an
electronic part, you might even find it at Radio Shack.

Second - you could use a passive preselector - you'd need to adjust this
every time you tune to a new frequency.

The preselector is sort of like an attenuator with a tunable notch that
will let the frequency it's tuned to pass through with little attenuation.

It's a more flexible tool - but it's also an extra knob to twiddle when
you change the station - some people like that - others don't.

The preselector is sort of like an attenuator with a tunable notch that
will let the frequency it's tuned to pass through with little attenuation.


Just the opposite- a tunable passband as opposed to a notch (band reject)\

It's a more flexible tool - but it's also an extra knob to twiddle when
you change the station - some people like that - others don't.

Dale Parfitt wrote:



The preselector is sort of like an attenuator with a tunable notch that
will let the frequency it's tuned to pass through with little attenuation.



Just the opposite- a tunable passband as opposed to a notch (band reject)\


Had the right idea but the wrong word. Was distracted by one of my cats
who learned how to use the pull string on a talking toy while I was
writing it.

Is this true?

Why was I told that I could break my radio?

If this is so I don't necessarily need a R8B. I can use my SAT 700 with a
passive preselector and a nice 75' square longwire and do some serious DXing.

Help.


Neil

(BCcubed) wrote in message ...
Is this true?

Why was I told that I could break my radio?

If this is so I don't necessarily need a R8B. I can use my SAT 700 with a
passive preselector and a nice 75' square longwire and do some serious DXing.

Help.

There's a lot more to serious DXing that sensitivity and antenna. The
Satellit 700 has a fair to poor dynamic range while the R8B dynamic
range is good to excellent. Another factor is blocking - the 700 is
fair while the R8B is excellent. What it all comes down to is this -
portables are made to be used with their internal antennas and
desktops are made to be used with outdoor or external antennas with
higher gain. You can't do serious DXing on the 700 with an external
antenna because when you amplify the weak signals you are also
amplifying the strong signals next to it. Blocking is the ability to
resist desensitization by powerful nearby signals. Poor or fair
blocking will take the strong signal you don't want and actually
desensitize the signal you do want. Portables just aren't built for
serious DXing. For serious DXing you also should have passband offset
and a good notch filter. The R8B has both.

Without the expense of the R8B, the next best thing is something like
the SW8, or the Grundig Satellit 800. While missing some of the
features, they both are made to work well with an external antenna.

The new Eton E1, which is supposed to come out this summer, will be
the only current model portable with passband offset, but still no
notch filter. It will be interesting to see test results of this new
model to see how it performs compared to other portable and desktops.

One thing many Satellit 700 users don't know about is that the receiver
already has a tunable preselector. One of the worst things about the
Satellit 700 is the English language translation of the user's manual, which
does not mention or explain the preselector feature.

Tune to a specific frequency, preferrably one you know is not one of the
stronger signals you can catch at your location. Next, press the
stereo/mono button and hold it in. While holding that button in, rotate the
tuning knob. You notice the strength of the received signal getting
stronger or weaker as you trun that tuning knob. When you have peaked the
strength of the signal to its maximum, stop turning the knob and release the
stereo/mono button.
Also, make sure the DX/Local switch is in the DX position for best reception
of weaker signals.

Hey JBR

I do know this and have used this function. My question had to do with
damaging the radio by stringing a 75 foot square of wire 12 above the ground
and using the ext. antenna on my SAT 700 to DX without hurting the radio.

Until I can get a better radio I was hoping to find some way to modify this one
to perform better.

neil

(BCcubed) wrote in message ...
Hey JBR

I do know this and have used this function. My question had to do with
damaging the radio by stringing a 75 foot square of wire 12 above the ground
and using the ext. antenna on my SAT 700 to DX without hurting the radio.

Until I can get a better radio I was hoping to find some way to modify this one
to perform better.

neil

Use two wires. One long, one short. IE: a 75 ft wire, and also a 20 ft
wire, or whatever. Experiment with the length of the short one to get
the desired signal level when listening to the powerhouses that could
overload you, or if you are suffering a problem from a powerhouse on a
different frequency. Can ever be strong MW signal related in some
cases... But if that radio has a preselector as you say, that will
help reduce out of band crud a bit..Always use that.. The long one
would be the preferred weak signal antenna unless you started
overloading. In that case, switch to the shorter one, or the whip.
This would be one method that could be used that really doesn't cost
anything except some wire. A step attenuator can be built fairly
cheaply. I prefer rotatable small loops for most MW listening. Those
can greatly help the MW performance over a long wire. There is a big
difference between the SAT 700 and a Drake R8B in nearly all aspects.
Make no mistake. But with some wire length adjustments, you could do
fairly well with what you have. There is no way you can damage the
radio from overloading it, unless maybe you had a transmitter so close
to be nearly connected to it.. :/ And many radios are protected from
that with back to back diodes, or whatever. Don't worry about that.
Whoever told you that is confused about "overloading"...It's a
performance issue, not damage. BTW, one asked about a tuner...Yes, a
tuner can help in many cases to "clean up" a radio. It won't attenuate
what you are listening to, and you could still overload on a station
you are actually tuned to, but it will reduce the level of out of
band signals. With many lower end radios, it's quite possible to see
an improvement in overall s/n ratio. Will have little if any effect on
a well designed radio that is already clean though. IE: You would
likely see less improvement when using a tuner with a R8B or other
medium quality radio, than you would a lesser radio. With an already
"bulletproof" radio, all a tuner would do is add a bit of loss...:/
MK