[BC] Sangean HDT-1

[Mark Humphrey]

You might want to try using the conventional L and R outputs of the
HDT-1 with an inexpensive stereo generator, such as the $212 "Digilog"
card:

http://www.fm-transmitter-modules.com/bw-broadcast/digilog-stereo-encoder/10/product

Over the years, I've done lots of work with translators and found they
often produce better results if the incoming signal is taken down to
discrete L and R and run through 15 kHz low pass filters (or some
high-frequency blending -- which may be an undocumented feature of the
HDT-1) before regenerating the stereo.   In a less-than-perfect
receive situation, the composite signal usually carries significant
noise above 53 kHz, which can cause multipath distortion to become
more noticeable.  Within a couple of miles of the translator,
automatic blending circuits in car radios are "fooled" by the high RF
signal strength and will not act to reduce excessive L-R hiss.

Years ago, while driving through upstate PA, I came across a
noncommercial "repeater station" that was using a Belar FMM-2 mod
monitor (with RF amplifier) as a composite relay receiver.  A nice
idea in theory, but the input signal just wasn't clean enough to allow
this configuration.   The composite output of the the monitor was fed
directly into the exciter, avoiding the need for a on-site stereo gen
or processing, but also allowing all sorts of wideband noise to be
rebrodcast.   Not only was the stereo signal/noise ratio poor, but
reception was horrible back in the hills (the region which this
facility was intended to fill) due to the accentuated multipath.

Mark



On 10/7/07, ChuxGarage at aol.com <ChuxGarage at aol.com> wrote:
> Has anyone figured out how to get a composite (MPX) output from a Sangean
> HDT-1?  Regardless of your views about HD Radio, this is one heck of an analog
> tuner.  It would have lots of applications in translator service if you could
> figure out how to get a composite signal out of it.
>
> The HDT-1 has another nasty trait: In the event of a power failure, it
> reverts to the "off" position.  I can figure out how to fix that using a simple 555
> timer chip to turn it back on.
>
> The lack of a MPX output is a problem, since I use some Rio Radio RDS
> decoders to shut down things if the RDS signal is lost. That's easy to do with
> receivers like a Fanfare, but the Sangean actually seems to reject adjacent channel
> RF problems better than the Fanfare with Microwave Filter bandpass filters in
> place.  That's impressive, since the Fanfare is a great tuner.  The Sangean is
> about 10% of the cost of the Fanfare and the appropriate filters.  Any
> suggestions?
>
> How's the Inovonics translator receiver?
>
> Chuck Conrad
> www.kzqx.com
>
>
>
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