RadioBanter - View Single Post

D Peter Maus · January 18th 07, 05:56 PM posted to rec.radio.shortwave

wrote:
D Peter Maus wrote:
Diversity reception has been a well established practice since the
early days. Hallicrafters produced a diversity receiver, which was
actually two receivers diplexed into a single audio stage, fed by
separate antennae.

May have been a bit of overkill. Separate antennae, if electically
isolated from one another, diplexed into a single input can produce
similar results: reducing selective fading before it reaches the receiver.

When I lived in Rockford, I rented a two bedroom home on a private
estate west of town. The rental property included several acres on a
hilltop, and access to the private lake on the estate.

Of course, I went antenna crazy. And using multiple antennae into the
BC-794, was able to mitigate a good deal of the selective fading
throughout most of the HF spectra.

Each antenna was connected to an RF preamp with a gain of 2-6db. The
outputs of the preamps were combined through resistive pads (for
isolation) into the RF input of the BC-794. The result was nothing
short of amazing, with fading distortions dramatically reduced, and
program listening, was quite pleasant. Even my wife was no longer
critical of SW listening.

Make no mistake, it wasn't FM quality. But it was fine wideband (when
conditions permitted) AM quality. And though there WAS some latent
fading remaining, it was, by far, less objectionable, and often barely
noticeable than a single antenna on the same receiver.

Diversity, at least in this case, is something to be implemented with
affirmative action.

I will have to try this tonight!

I have 2 very nice active dipoles seperated by about 100'. Right now I
am using
a "phaser" to "rotate" the beam/pattern. It will be very easy to
coulple them via a
Mini Circuit power divider/combiner!

Thanks for the hint. I had always assumed you needed "fancy"
electronics to
do this.

Terry

You rarely need 'fancy' electronics to experiment. And as I recall
(I'll have to dig out my notes on this--I did a lot of experimenting,
there, due to the RF quiet...including using an AK Model 30 as a high
fidelity air monitor for airchecking...LOVE those infinite impedance
detectors) it really was this simple.

But reading Steve's comment about switching and AGC in diversity
reception, I'm thinking there may have been an additional stage in my
installation. Though I don't specifically recall this. I do recall that
the AGC was swithed off, and the RF gain was manually set.

But, it was 30 years ago, after all. I'll have to dig out my notes.

Regardless, there is nothing to be lost in the attempt. And if you
find something that works, that streamines what I did, please share the
wealth.