On 2/17/2011 4:46 PM, Michael Tondee wrote:
I was going to say, same reason people still use CW hi hi...but I
must admit CW is a lot more reliable from of QRP level communication
than AM is. Anyone tried a 1500 on AM yet??
73,
Michael, W4HIJ
I've heard a couple on AM, and they sound fine. And while AM is not as
good for QRP as cw (or JT65!) it does do surprisingly well. For the
last few weeks there's been an AM QRP net running in the northeast on
Sunday afternoons and doing quite well. It was started off by some
folks getting interested in the Retro75 kits, but has expanded to all
kinds of tube and solid state rigs at this point including some
throttled down flex units.
AM doesn't suffer quite as bad as the numbers make it out to since
they usually compare only one sideband. But in practice, with a proper
receiver you receive both sidebands and combine their energy back into
the recovered audio and get the advantage of spectral diversity in
case one sideband is taking hits. There is still a lot of power going
into the carrier with no intelligence, but OTOH, it does tend to quiet
the frequency between words.
As far as SSB with a pilot carrier sounding as good, I remain to be
convinced. I think it depends on how you generate the SSB. Mechanical
or crystal filters seem to do something to the audio in the passband,
probably relating to the phase shifts needed to get the steep roll
offs at the edges, that seems to affect how the audio sounds - and I'm
no audiophile. Of course there are phase shifts in the receiver filter
as well, and some folks prize the R390 and Drake receiver because of
their LC IF filters over the 390A with the mechanical filters and the
later Drakes with crystal filters because of their sound. People who
use phasing exciters seem to have nice audio, and whatever 'magic' is
used to generate AM in the Flex does a very nice job also.
When I built large HF systems with Harris RF Communications in the
70's we had 1kw and 10kw transmitters that were capable of SSB, 4 ISB,
full carrier AM, and pilot carrier (-26db) AM for use with the RF550
receivers with synchronous detectors. They sounded good, but not as
good as a nice plate modulated AM signal, or a Flex.
No matter what equipment you use, AM is fun. One thing I especially
like about it is that it puts me in contact with folks who have often
followed a similar path through ham radio - starting off in the era of
AM and tubes, and with people who very often build and modify their
own equipment and who really know what's going on inside of the box.
It's a nice community. Plus it just plain sounds good. There's a time
and place for punchy, 'space shuttle' audio with minimal bandwidth,
but when I just want to hang out and chat with friends, I find it
fatiguing and eventually annoying. I much prefer AM or FM for relaxed
casual conversation.
I purchased my Flex 5000 specifically with AM operation in mind. I
like all modes, but good AM performance was on my requirements list
and the Flex 5000 does a pretty good job at delivering.
73 de Kevin, WB2EMS
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[email protected]
http://mail.flex-radio.biz/mailman/listinfo/flexedge_flex-radio.biz
This is the FlexRadio Systems e-mail Reflector called FlexEdge. It is used for
posting topics related to SDR software development and experimentalist who are
using beta versions of the software.
