I'm hearing a shortwave broadcast on MW
 

Chances are it is an image signal beacause RHC is broadcasting then.
The combination of a modestly priced but very sensitive receiver and
big antenna means you are probably getting repeat signals all over the
dial. Because the 350 is an analog receiver with a digital display my
guess is that the receiver is actually tuned to 1700 +- 10.

Try listening to these RHC frequencies to see if the signal is the
same.
6000, 6060, 9550, 11760

It's a nice radio in many respects, but it has limitations that are a
fuction of it's price. More than one review I have read complain about
multiple images, poor dynamic range, etc. Get rid of that long antenna
and use the RF gain to control signal strength.



Honus wrote:
It's Sunday here in Seattle, 0530 UTC and I'm picking up Radio Havana
Cuba
on a Grundig S350 with a 70' random wire antenna tuned to ~1697 KHz.
(The
signal drifts a tiny bit, between 1696 to 1698.) I've tried to do my
own
research and see if perhaps they broadcast on MW as well as SW, but I
can't
find any indications that they do. They're also frequently mentioning
that
it's a shortwave broadcast...so through what bit of electronic
inadequacies
on the part of Grundig am I hearing this on MW? I understand images
to a
degree, thanks to r.r.s. Is this a related issue? Thanks in advance.

On 7 Mar 2005 06:22:45 -0800, wrote:

Chances are it is an image signal beacause RHC is broadcasting then.
The combination of a modestly priced but very sensitive receiver and
big antenna means you are probably getting repeat signals all over the
dial. Because the 350 is an analog receiver with a digital display my
guess is that the receiver is actually tuned to 1700 +- 10.

Try listening to these RHC frequencies to see if the signal is the
same.
6000, 6060, 9550, 11760

It's a nice radio in many respects, but it has limitations that are a
fuction of it's price. More than one review I have read complain about
multiple images, poor dynamic range, etc. Get rid of that long antenna
and use the RF gain to control signal strength.



Honus wrote:
It's Sunday here in Seattle, 0530 UTC and I'm picking up Radio Havana
Cuba
on a Grundig S350 with a 70' random wire antenna tuned to ~1697 KHz.
(The
signal drifts a tiny bit, between 1696 to 1698.) I've tried to do my
own
research and see if perhaps they broadcast on MW as well as SW, but I
can't
find any indications that they do. They're also frequently mentioning
that
it's a shortwave broadcast...so through what bit of electronic
inadequacies
on the part of Grundig am I hearing this on MW? I understand images
to a
degree, thanks to r.r.s. Is this a related issue? Thanks in advance.

An MFJ-956 between the radio and the antenna may help.

Honus wrote:
And now I'm hearing a memorial to Gene Scott on 1615 (MW, of course) at 0555
UTC. It's identical to the broadcast that I'm receiving clearly on 5755
(KAIJ, TX)

You're receiving the 5755 transmission on 1615 because of the third
harmonic of the radio's local oscillator. (i.e. they are NOT actually
transmitting on 1615)

When you tune to 1615, the radio tunes an internal oscillator to
2070KHz. This 2070KHz signal is mixed with the 1615KHz signal (if there
was one). You get four outputs: 1615, 2070, 2070+1615=3685KHz, and
2070-1615=455KHz. The selective circuits in the intermediate frequency
amplifier only pass the last signal at 455KHz, and that's what you hear.

But the internal oscillator is not perfect. It generates "harmonics" on
multiples of the frequency to which it's tuned. 2070KHz,
2070x2=4140KHz, 2070x3=6210KHz, 2070x4=8280KHz, etc... (they get weaker
as the multiplier increases)

If any of these multiples can mix with a signal to generate 455, then
that signal will be heard as well.

And in this case, it can. 6210-5755=455. The KAIJ signal will mix with
the 3rd harmonic and will be heard.

Your reception of Cuba on 1697 is probably from the same phenomonon. I
note that when tuned to 1697KHz, the local oscillator is on 2152KHz.
2152x3=6456, and 6456-6001=455. So if Radio Havana was broadcasting on
6001KHz, you'd hear it on 1697. Monitoring Times does list Radio Havana
as being on 6000KHz at 0530z.
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com

That's the preselector I believe. Yes, it could help, although in my
experience just reducing the antenna size will help too. Those little
radios usually work pretty well on the whip alone.

wrote in message
ups.com...
Chances are it is an image signal beacause RHC is broadcasting then.
The combination of a modestly priced but very sensitive receiver and
big antenna means you are probably getting repeat signals all over the
dial. Because the 350 is an analog receiver with a digital display my
guess is that the receiver is actually tuned to 1700 +- 10.

Try listening to these RHC frequencies to see if the signal is the
same.
6000, 6060, 9550, 11760

It's a nice radio in many respects, but it has limitations that are a
fuction of it's price. More than one review I have read complain about
multiple images, poor dynamic range, etc. Get rid of that long antenna
and use the RF gain to control signal strength.

I've heard the same reviews. Now I actually know what they mean. g The
long antenna really helps, though; I'm loathe to give it up.

"David" wrote in message
...

An MFJ-956 between the radio and the antenna may help.

I'm going to have to look into that. I'll dig through google as well, and
see what the other denizens of r.r.s. have had to say about it. Thanks.

"Doug Smith W9WI" wrote in message
...
Honus wrote:
And now I'm hearing a memorial to Gene Scott on 1615 (MW, of course) at
0555
UTC. It's identical to the broadcast that I'm receiving clearly on 5755
(KAIJ, TX)

You're receiving the 5755 transmission on 1615 because of the third
harmonic of the radio's local oscillator. (i.e. they are NOT actually
transmitting on 1615)

I suspected as much, but the coincidence of the harmonic coming in so close
to one of their other broadcast freq's made me wonder a bit. That and the
fact that I've never picked up harmonics from SW in the MW end of my dial. I
usually come across them 910 KHz away from the true frequency. Thanks for
all of your help explaining this to me. I snipped it in this reply, but I've
saved in my mailbox and I'll be sure to study it in more depth.

Are you actually hearing more stations with the longer antenna? If so
make sure you are not dxing images (I've done it!). If the signals are
just louder I would disconnect the antenna and increase the volume.

The MFJ preselector could also help, although it might cost as much as
the radio.

Honus wrote:
It's Sunday here in Seattle, 0530 UTC and I'm picking up Radio Havana Cuba
on a Grundig S350 with a 70' random wire antenna tuned to ~1697 KHz. (The
signal drifts a tiny bit, between 1696 to 1698.) I've tried to do my own
research and see if perhaps they broadcast on MW as well as SW, but I can't
find any indications that they do. They're also frequently mentioning that
it's a shortwave broadcast...so through what bit of electronic inadequacies
on the part of Grundig am I hearing this on MW? I understand images to a
degree, thanks to r.r.s. Is this a related issue? Thanks in advance.




When your S350 is tuned to 1697.666666666..., the local oscilator is
running at 2151.66666666....

RHC on 6000 kHz is mixing with the 2nd harmonic of the local oscillator
(which is at 4303.3333333...)

6000 - 4303.333333... = 1696.6666666...

It's a common problem with cheap portables.



--
Mike Westfall, N6KUY, WDX6O
Los Alamos, NM (DM65uv)
Online logbooks at http://dxlogbook.gentoo.net
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