Re: [IRCA] Re: Radio Marti 1710

["Robert Foxworth" <rfoxwor1@xxxxxxxxxxxxxxx>]

> Glenn Hauser wrote:
>
> > No, as I have explained several times before, if the receiver IF is
450 kHz,
> > here`s how the image works: 1710 x 3 = 5130. 5130 + (2 x 450) =
6030, a regular
> > R. Martà frequency (Glenn Hauser, DX LISTENING DIGEST)
>
> That's kind of convoluted. I can't imagine how the signal would go
> through that kind of mathematical process in the receiver.
>
> This makes more sense:
> 6030 - (2 x 2160) = 1710, where 2160 is the local oscillator freq when
> the radio is tuned to 1710 (2160 - 1710 = 450).
>
> The LO apparently needs to be LPF'd to get rid of harmonics.
>
> -- 
> Mike Westfall, N6KUY, WDX6O

Either math sums up correctly but Mikes makes more sense as it is
the harmonic of a real signal, and not a harmonic of a virtual "signal"
such as that to which the receiver is tuned. IOW, 5130 should not exist
in
the receiver as RF, but 4320 (2x2160) certainly will exist as RF.

Several years ago (1997 or 8) when listening from New York on a DX-375
late at
night. I once heard Marti on 1710. I heard RHC from Havana on 1700, and
I
heard a station then traced to 5970,  on 1690. While in Ireland in 1997
I once heard a
DW program in German when tuned to 1683 but it sounded mis-tuned. A
possibility
would be 5945 (4 kHz low) but I actually do not know if DW ever used
that freq
in Europe or not. I think I am the only Dxer to ever report three such
artifacts at once,
on the same RX and at the same time.

Mike's math works as so:

6030 - (2x2160) = 1710
6000 - (2x2150) = 1700
5970 - (2x2140) = 1690

This is probably unprovable today as 1710 is the only remaining
frequency
that is unoccupied by real signals. Back then, all those freqs were
vacant. The
rx behaves as if there was a bandstop filter in place that works well up
to about "1680" (it may actually be different) which just allows the
very top
end of the band to bleed through.

The real mystery is why it is only noticed occasionally and not nightly.
What needs to be done is to identify the triggering factor that makes
this happen.

I must have posted about this a half dozen times by now, but generally
on another list.

I would suggest, when this appears again, also looking for a RHC Habana
"signal"
on 1700 but this is probably quite hard to separate from the other SS
now.

Bob


_______________________________________________
IRCA mailing list
IRCA@xxxxxxxxxxxxxxxx
http://dallas.hard-core-dx.com/mailman/listinfo/irca

Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers

For more information: http://www.ircaonline.org

To Post a message: irca@xxxxxxxxxxxxxxxx