Re "I think that rigs like the SDR-1000 would work and I'm sure that
ICOM, Kenwood, YAESU and Alinco would build them."
One could certainly use the SDR-1000 hardware a foundation for
broadband communication at HF, but this is not a product aimed at
the average amateur. On what grounds are you so sure that Icom,
Kenwood, Yaesu, and Alinco would build similar rigs? All seem to
struggle with basics like transceiver-to-PC communications. Creating
a resilient SDR platform whose software would be understandable and
modifiable by its users seems several generations beyond their
current capabilities.
73,
Dave, AA6YQ
--- In digitalradio@yahoogroups.com, DuBose Walt Civ AETC CONS/LGCA
<[EMAIL PROTECTED]> wrote:
>
> Hi Tim,
>
> See below.
>
> Walt/K5YFW
>
> -----Original Message-----
> From: digitalradio@yahoogroups.com
> [mailto:[EMAIL PROTECTED] Behalf Of Tim Gorman
> Sent: Wednesday, November 30, 2005 6:46 PM
> To: digitalradio@yahoogroups.com
> Subject: Re: [digitalradio] Re: How Safe is Amateur Radio
>
>
> Walt,
>
> Good answers.
>
> Couple of comments.
>
> On Wednesday 30 November 2005 16:25, DuBose Walt Civ AETC
CONS/LGCA wrote:
>
> >
> > It isn't the high-ranking government officials that drive
> > policy...its the GS-12s, 13s and 14s. The are the ones
> > who brief the GS-15s and SESs who if they like what the GS-
15s
> > say forward the "brief" to the agency head who determines if
he/she
> > wants to send it to their congressional liaison.
> >
>
> I know the state level Natl Guard here isn't interested in the ham
bands.
> They
> have at least 6 racks of HF radio's in the State EOC with data
capablity
> already set up on gov't frequencies. They have all kinds of VHF
and UHF
> capabilities. There is nothing the amateur bands offer them they
want or
> need.
>
>
> True in most states. In Texas during Hurricane Rita the
Natl Guard
> had a 10-25 watt
> VHF repeater out at Kelly-USA. They used 2 antennas on 10
ft poles
> separated by about 30 ft.
> The repeater was in a pretty yellow fiberglass box between
the two
> antennas.
>
> They have lots of hardware and few frequencies and some
knowledge.
>
> I was chief of communications during Desert Shield for the
Theater
> Aeromedical
> Evacuation System. We had loads of HF gear...500 watt
portable
> stations. And as
> I indicated earlier, perhaps 22 frequencies to operate on.
>
> When back home in the states, for training and civil
emergencies, we
> had 2 frequencies
> per military communications region...there are two regions
in the
> U.S. Our region
> frequencies were at 8.5 Mhz and 11.2 MHz. We also had 2 or
3 VHF
> frequencies for Conus
> use but never could get them approved in Saudi so used a
couple of
> Army frequencies.
>
> >
> > And you never have explained how unmodified commercial amateur
> > transceivers with ~3.5 kHz passbands are going to handle 16 kHz-
wide
> > audio signals from a soundcard.
> >
> > I don't think many of the HF transceivers used today can be
modified
> > for wide signal bandwidths. Only those with changeable
filters and
> > probably with DSP IFs would be able to accomplish the change.
> >
> > Certainly SDRs will and also some of the very latest gear
from the
> > Pacific
> > Rim will...but not my IC-735.
> >
>
> It's not just the IF chains, it is the audio chains also. Most
amateur rigs
> also have low pass filters in their transmit audio chains of some
kind or
> another and many even have transmit tone controls built into the
ckt boards
> that most people never find because they aren't front panel
adjustable (icom
>
> has several rigs with this). Most receiver audio chains are so low
fidelity
> that getting a 5khz bandpass is a problem, let alone anything
approaching
> 15khz. That would require an audio chain equivalent to that found
in a good
> stereo system. Audio amps, be they tranmsit or receive, with 15khz
> bandwidths
> or higher that have good amplitude linearity and controlled phase
shifts are
>
> not trivial to build. Something as simple as a product detector
could be a
> problem at this bandwidth.
>
> Very true. I think that almost everything from the IF on
down would
> have to be
> done outboard.
>
> I suspect you are talking about a whole new set of equipment that
would be
> needed to set up a usable transmitter/receiver link. It may, in
fact, have
> to
> be constructed instead of purchased.
>
> I think that rigs like the SDR-1000 would work and I'm sure
that
> ICOM,
> Kenwood, YAESU and Alinco would build them.
>
> Has anyone ever looked at the phase shifts in a 16khz wide IF
filter? I
> would
> expect the phase shifts at the upper and lower ends could be
significant.
> Would the soundcard have to pre-distort the transmitted signal to
> compensate?
>
> I know that this has been discussed on some of the technical
list
> but those
> who deal regular ally in that arena.
>
> Walt/K5YFW
>
>
> tim ab0wr
>
>
>
>
>
>
> Need a Digital mode QSO? Connect to telnet://208.15.25.196/
>
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