Looking for feedback from all Makes and Models about: AM Mode Synchronous Hf
reception.
I have yet to have any peice of equipment that has everything just the way I
want it - I agree with Morel, 4X1AD, that there are no perfect rigs. Even
though I am very pleased with my FT-1000MP ( serial number - 7C170105
1/97 - CPU Version 1.30 - Menu 9-8 Date 970214c2 2/14/97), there are a few
things I would like to see improved. Top of the list for me is the AM mode
of operation. I love shortwave, all modes and do a lot of AM shortwave
broadcaster listening.
Never before have I had AM synchronous Tuning (page 29 in the user manual)
and I was really looking forward to what it would bring to my listening
pleasure. Per the manual, synchronous tuning reduces the distortion caused
by carrier fading by receiving the signal in LSB while reinjecting a
unfading carrier. In the past I would simply use sideband to tune in the AM
station and choose the side that was the cleanest. Synchronous tuning does
lock onto the carrier and allows tuning around the signal abit with out
losing zero beat.... Okay, well and good, but I simply dont find fading
issues to be that improved in synchronous mode much more if at all over non
synchronous mode...even with different filter selections ( I normally stay
in the widest filter). I have running many comparasions with the both
receivers tuned to the same station, same AM mode, same filters, but one
receiver non synchronous and the other synchronous. Using stereo headphones
and the menu option 4-8 set to the stereo 2 option (gives full main rx audio
to the left ear, and full sub rx audio to the right ear with no mixing), I
generally still get audio when I have a fade out with the synchronous mode
side. I still find my self frequently going to upper or lower sideband to
improved fading distortion in the audio, even when using the 2.4khz filters.
I had expected better than this. To me this is a performance expectation
issue, not a bug or flaw report issue.
Part of the problem with the above is aggravated by a second AM mode issue,
and the bigger one in my experience. Hum in the AM mode audio that changes
with the the signal strength and is particularly an issue with rapid
fading.... enough to destroy the received audio intelligibility. The hum in
90 plus percent of the cases is not in the audio when listening to a AM
signal in sideband mode, so it is not a station sourced hum.
Oddly enough I have discovered that this hum issue varies with the antenna
used. I have tuned in the same signal on a Icom R10 handheld general
coverage receiver and the hum changes on it the same way as the FT-1000MP
with antenna changes..... so I am confused.... hi hi
It is possable that I am looking at computer noise sourced issues as I do
have a in house lan...... interaction with the switching power supplies may
be modulating the detected carriers and influences even the hand held. One
of the tests I will be doing is killiing everything in the house one day,
and putting the FT-1000MP on to a car battery. Even as a kid I had learned
that portable battery operated radios were influenced by antenna's brought
into the house for use by other radios, and that today's digital world is a
mixing nightmare for various noise sources. I wouldnt be surprised that a
phase mixing problem exists internal to the FT-1000MP
Plans are to study the circuit for the AM system and the service manual,
look for possable modifications, eliminating the switching power supply
issue, and testing the 70MHz I.F. amplifier from inrad
http://www.qth.com/inrad/ ) . I have the Inrad amp on order and expect it
any day now.
While pursuing that path, I may also play with the audio frequency response.
I have some high frequency hearing loss from the Air Force, and it is not
unusual for me to add highs and roll off lows in most of my audio equipment
to compensate.... hi hi
I am looking forward to any feedback from other users of the FT-1000MP, and
even other makes and models that exibit similiar traits. Please post to the
FT-1000MP reflector. Go to: http://www.jehosophat.com/1000mp/
to subscribe and browse past archive messages about this radio.
73 from Bill - WD8ARZ
wd8arz@null.net
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