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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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.