On 5/4/10 05:03 , Brian Gregory [UK] wrote:
wrote in message
m...

How laughable.

Who buys into the whole "active antenna" thing? Some of my best SWLing has
been with a 5 or 6 foot hunk of wire laying on the floor.

Put your effort into a getting a good alignment. That will do you far
better than these red herring gadgets that are just like a shiny lure to a
sucker.

When you amplify, you amplify EVERYTHING...noise, distortion and often
these gadgets inject products into the mixer that screw up your IF
tracking, reducing the inherent performance of your receiver.

Quit looking for a "magic pill" and get back to basics: 1. Good alignment.
2. Wire antenna in unobstructed free space.

That's all you need.




You're basically right that the TinyTenna can't achieve miracles.

But what do you mean (or think you mean) by
a) Alignment.
b) IF Tracking.


A series of tuned circuits, such as those found in a
superheterodyne receiver are said to be in alignment when all paths
are tuned to the correct frequencies. Correct alignment raises
output of desired signals, while reducing noise floor. A receiver in
proper adjustment-- proper alignment -- will perform often
remarkably better on the same antenna, in the same location as the
same model receiver out of alignment. Often by only a very small
amount.

IF tracking is the property of two variable tuned circuits to
produce a single output frequency across their entire range.

Forgive me if this is something you already know. A gross
oversimplification, here, if you don't, will explain.

IF, or intermediary frequency, is a property of a superheterodyne
receiver that improves selectivity, improves rejection of undesired
signals, and produces a single, easily manageable signal for
detection. IF is produced by mixing the incoming desired signal with
a locally generated signal of a frequency above the desired signal
that is a fixed difference from the desired incoming signal.

By mixing these two frequencies, the intermediary frequency is
generated the frequency of which is the exact difference between the
incoming and the locally generated frequency. There is also a
frequency generated that is the sum of the two mixed frequencies,
but that is rejected by the tuned intermediary frequency circuits
which are tuned to a single fixed frequency.

In order for the intermediary frequency to pass through the tuned
IF circuits, the intermediary frequency needs to be the same as one
tunes incoming signals across the dial. That means that the mix
frequency needs to vary along with the incoming frequency to remain
precisely higher than the incoming frequecy by the amount of the IF.
This is referred to as tracking. One signal tracks the other to
retain the proper relationship as the tuning dial is moved.

Implements, like the Tiny Tenna, in some inexpensive receivers,
can, if overloaded, produce their own mix frequencies that, in turn
mix with incoming and locally generated frequencies to yield un
expected mix products that produce variations in the intermediary
frequency. In some receivers, a very strong signal alone can cause
the IF to shift.

So, what the poster was referring to is proper adjustment of
tuned circuits within the receiver, and the injection of instability
by frequencies created by cheap active antennae disturbing the
frequencies that must pass through those tuned circuits.

Again, apologies, if your technical understanding exceeds these
oversimplified descriptions.