In the 1980's and 1990's there were rigs that allowed switching the IF filters indepedently of turning on the BFO and had 5-6 kHz bandwidth AF amplifiers for decent shortwave broadcast reception. I haven't bought a commercially made rig since the new millenium but I've seen this feature mentioned in at least one data sheet. A 10-12 kHz bandwidth for SSB would have been unlikely in an amateur rig in the past but should become more common as DRM software requires a 12 kHz output for a soundcard.
The current designs by KK7B (mini- and micro- T2 and R2) use NE5532 op amps, which are certainly linear to 20 kHz, and 2N3904 preamps. The 2N3904 has an Ft of 300 MHz and it was linear to at least 50 kHz in home-brew equipment that I have made with almost identical circuitry. These kits would require modification, but they are inexpensive. I'd say that the SDR-1000 is fairly well known now. 73, John KD6OZH ----- Original Message ----- From: jgorman01 To: digitalradio@yahoogroups.com Sent: Thursday, May 03, 2007 20:47 UTC Subject: [digitalradio] Re: FCC regulations (was Digi Voice) Shifting the bfo in a crystal filter rig does not change the bandwidth, it only changes the frequencies passed. That is, going from 300 - 3000 Hz (2.7 kHz bandwidth) to 100 - 2800 Hz (2.7 kHz bandwidth). Some ESSB folks do this so they can emphasize the bass but they do so at the expense of high freq response and also moving the opposite sideband up the attenuation curve of the filter resulting in less opposite sideband suppression. I doubt many rigs allow you to enable the NBFM in SSB mode since the circuitry for each mode is entirely different. Also, the rigs you are talking about don't have audio amplifiers that would support this kind of bandwidth without modification. The T2/R2 combo's wouldn't only require modifications to the audio filters but also to the audio stages. Those amps don't have the linearity to support a 20 kHz bandwidth. Granted the SDR radios may be able to do this kind of bandwidth. They are the only radios I know of that could possibly do so out of the box. Basically, there aren't any well known commercial rigs available to do this bandwidth using sound card modems. Jim WA0LYK --- In digitalradio@yahoogroups.com, "John B. Stephensen" <[EMAIL PROTECTED]> wrote: > > In J3D you just need more subcariers. Up to a 5 or 6 kHz bandwidth, many transceivers will let you offset the BFO far enough to use a sound card modem. At one point WinDRM had a 5 kHz wide mode. There might be some tansceivers that would allow a 12 kHz bandwidth if you can enable the NBFM filter in SSB. Many shortwave receivers now allow this as they are designed to receive 5-10 kHz wide DRM broadcasts using a PC to demodulate the 12 kHz IF. > > For 20 kHz bandwidths you'd need a software-defined radio like the SDR-1000 or Soft Rock 40 where all the signal processing is done in the PC. The T2 and R2 radios described in QST 10 years ago would also be ideal for this use as the audio filters can easily be widened. There were hams working on wideband HF modes but I don't know what effect the ARRL pushing a 3 kHz limit has had. They did endorse 16 kHz bandwidth OFDM on 10 meters. > > 73, > > John > KD6OZH > > ----- Original Message ----- > From: jgorman01 > To: digitalradio@yahoogroups.com > Sent: Thursday, May 03, 2007 13:04 UTC > Subject: [digitalradio] Re: FCC regulations (was Digi Voice) > > > After giving this some thought I wonder what HF rig would you use with > 20 kHz bandwidth and what mode? What design criteria would be needed > to use this, especially in J3D? > > Jim > WA0LYK > > --- In digitalradio@yahoogroups.com, "John B. Stephensen" <kd6ozh@> > wrote: > > > > If I'm at the low end of an HF band, I can now send send text > (RTTY), data or images using PSK31. If I'm at the high end of the > band, I'd like to send text, voice, data or images in a 20 kHz > bandwidth on wider bands or 8 kHz on narrower bands. Right now data > and text are limited to the lower portions of each band where wideband > emissions would be a problem. If I'm on a VHF band I'd like to see a > 200 kHz bandwidth limit for portions of each band rather than the 20 > kHz limit. On 70 cm I'd like to eliminate the 100 kHz bandwidth > restriction on data and make it at least 6 MHz. > > > > I have operated HF digital modes on 40, 20 and 10 meters in the > past, but my experments with wideband digital modes have been > restricted to 6 meters and 70 cm. > > > > 73, > > > > John > > KD6OZH > > > > ----- Original Message ----- > > From: mrfarm@ > > To: digitalradio@yahoogroups.com > > Sent: Wednesday, May 02, 2007 14:51 UTC > > Subject: Re: [digitalradio] Digi Voice: No Bandwidth Limit > > > > > > There has been some criticism of the U.S.'s supposedly backward ways > > with amateur radio bandwidths, and other countries (practically > everyone > > else?) being so advanced in this area. > > > > If it is true that others are not being held back, what actual new > > wideband HF modes have been developed that we can not use in the U.S.? > > > > How many are actually using these new modes? If not, why are you not > > doing so? > > > > Or is all this criticism being levelled at the U.S. without any > substance? > > > > 73, > > > > Rick, KV9U > > > > John B. Stephensen wrote: > > > My comment was in regards to a question about why the rules need > to be > > > changed. They do because you can't mix voice, image and data on one > > > frequency in the HF bands. The defect in the ARRL proposal for > > > regulation by bandwidth was the 3 kHz limit that they chose for > HF. I > > > argued for 25 kHz and then 9 kHz as time went by, but with no > effect. > > > There are also limits on data bandwidth of 20 kHz in the VHF > bands and > > > 100 kHz in the 70 cm band that need to be changed. > > > > > > There is no bandwidth limit in the HF RTTY/data segments as > > > 97.307(f)(2) is only referenced in the table in 97.305 for the > > > phone/image segments. I agree that digital phone has no bandwidth > > > limit, but image does. > > > > > > 73, > > > > > > John > > > KD6OZH > > > > > >
