[PCR-1000] NOAA APT reception

[R. J. Grasser]

Peter,

NOAA 12/15 send APT (AM modulation, 15 Khz bw) on 137.500 Mhz.  NOAA 17 is
on 137.620 Mhz.  All 3 also xmit a very low power "pilot beacon" carrier on
different frequencies.

Since I dont know where you live, I cannot comment on what kind of signal
strength you can expect to see.  The antenna I use is a 6 Db gain vertical
colinear that just barely resonates at 137 Mhz.  I regularly see 10 over 9
RST on high angle passes with this configuration.

You might be desensing your frontend by demodulating out-of-band signals
that you dont actually see/hear, but cuts the rcvr sensitivity radically.

Also, all discone antennas are not "born equal".  One of the most popular
ones here is the Radio Shack 20-043, which claims to be broadbanded but is
not.  It needs to be "trimmed" for a specific 50 Mhz bandwidth.  Field tests
at a military antenna calibration facility shows up to 12.5 Dbm of loss at
many points in their claimed frequency spectrum.  Definitely not worth the
selling price.

A better choice for 30 Mhz thru 1.3Ghz is  the ST-2 from Antenna Warehouse.
While it has no practical gain, it also only has 0.03 Dbm of loss at certain
minor points over the entire spectrum.  The ST-2 is an unconventional design
using multiple vertical interactive fan-dipoles on a single frame.  It is a
BIG antenna that needs 12 feet of free space, and has considerable wind
resistance.

For coverage from 100 Khz thru 54 Mhz, I use the H-800 active helical
monopole that has a typical gain of 15 Db over the entire band.  This
antenna is manufactured by LF Engineering Inc, and can be purchased
directly.

I also use an MFJ-1045C rcvr preselector since the PCR-1000 frontend is so
broadbanded that it will demod all sorts of images, harmonics, spurs, etc if
left on its own.  It covers 1.0 to 54 Mhz.

To minimize coax loss, I use RG8U below 100 Mhz, and LMR-400 semi-rigid coax
above 100 Mhz.  LMR-400 is very difficult to work with. :-(

This system works well for me, but I see some room for future improvements
when the budget is available :-)

FYI: the best APT software is WXTOIMG from NZ.  Its free, and on the web.

Regards, RJ (rgrasser at frontiernet.net)
----- Original Message -----
From: "peter.tesar" <peter.tesar at centrum.sk>
To: "Discussion of PCR-1000 by Icom" <pcr-1000 at mailman.qth.net>
Sent: Tuesday, November 02, 2004 4:20 PM
Subject: Re: [PCR-1000] NOAA APT reception


> Mike,
> now I remember that neither S-meter nor BandScope had shown signal.
> Therefore I am afraid that other output will be deaf too.
> Peter Tesar.
>
>
>
> mikea wrote:
>
> >On Tue, Nov 02, 2004 at 08:24:59PM +0100, peter.tesar wrote:
> >
> >
> >>Hallo,
> >>I have a problem in regard to the reception of APT of NOAA satellites by
> >>Icom PCR1000.
> >>
> >>I receive the APT of NOAA satellites (137.XX MHz) using my 30-years old
> >>analog East-German "RFT" selective microvoltmeter without problems. I
> >>use a  discone antenna (I know that it is not very suitable for that
> >>kind of reception, but for the first experiments I think it is
> >>sufficient). The signal is usually strong and clear when the satellite
> >>is high enough and I can hear the typical sound of APT transmission.
> >>
> >>Several weeks ago I have bought a PCR-1000 receiver. I expected that
> >>with this radio I will be able to receive the pictures from NOAA.
> >>However, I was very disappointed when I tried to tune NOAA satellite on
> >>this radio. I heard almost nothing, even when the signal on RFT receiver
> >>was very strong. I have tried all available banwidths and modulations
> >>without success. Only in USB I have heard a very, very weak signal,
> >>which slowly changed with Doppler-shift.
> >>Otherwise the sensitivity of my PCR-1000 is OK, because stations on
> >>airband (135 MHz) and 2m amateur band (145 MHz) are well audible.
> >>
> >>On the internet I have found a lot of good references regarding to APT
> >>reception with PCR-1000.
> >>
> >>So, I am helpless, where can be the problem.
> >>
> >>
> >
> >Try using the other output jack -- I'm not where I can see mine, and
> >so can't give you the exact name. It's wideband output, and more
> >suited to data transmission.
> >
> >
> >
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