Portables and Antennas
 

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

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

Remember, also, that in addition to an external antenna jack, which means
the radio was specifically designed with the idea that it might be used with
an external antenna, the Satellit 700 also had that manually adjustable RF
gain control to deal with any possible front-end overloading of the antenna.

Based on my experiences with more than one each sample of Grundig Satellit
700, Satellit 500, Satellit 400, Sony ICF-2010 and ICF2001, Sangeans
ATS-803A, ATS-390 and their Radio Shack brand equivallents, and Philips
D-2999, and Panasonic RF-3100, RF-2900 RF-4900, and RFB-600, I would rate
the Satellit 700 to be the best of that entire lot for receiver performance,
ability to handle external noise interference, and audio quality. On some
bands, it might be only marginally better than some of the other models
mentioned. I don't think you'd have to worry about damaging a Satellit 700
by hooking up any length of antenna to its external antenna jack, or even by
clipping a long wire antenna lead directly to its telescopic whip antenna,
as long as you observe that already mentioned caveat about lightning, etc.

Reply to:
Brent Reynolds, Atlanta, GA USA

Seconding this msg:
Unless Lightning strikes the antenna or hits nearby,
No amount ( Up to thousands of feet; or miles, I suppose )
of antenna will have any adverse effect on your set.

I suppose if you live in the desert, with persistant winds, you might ground
the antenna to protect against static charges..

If there is a Very Strong Signal nearby, it will possibly
show up in multiple locations on the dail..

- Thats It ! ! !

- Conversly, having lots of antenna may help pick up Very very faint signals,



In article ,
(Gary) writes:


(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

You won't damage the radio by using a 75-feet wire antenna UNLESS
lightning strikes or is close enough to cause strong static. The
added signal strength, which might not be as much as you expect it to
be, will not damage the radio. If the signal overloads, you will
merely hear the signal where is doesn't belong, or it may be very
distorted