OK, Dave. No, I had not read Rick's report to ARRL. Thanks. Dave Bernstein wrote:
> The asymmetric propagation case is impractical to address, whether > the stations involved are attended or unattended; fortunately, its > not common. The case we can address is that of the unattended station > that could, if suitably equipped, detect an already busy frequency > and thereby avoid QRMing an ongoing QSO. Let's hope it is not abused when people know that the automatic station stops when they sit on top of it. > The busy frequency detector in SCAMP was a first-cut "see how it > works" implementation -- yet expectations were exceeded. From my > email exchanges with Rick, it was clear that there remains plenty of > opportunity for improvement. > > Appended below is Rick's post to the ARRL bandwidth committee, in > which he characterizes SCAMP's busy detector. This was originally > made available on the SCAMP reflector, to which you may not have > access. > > 73, > > Dave, AA6YQ 73's Jose, CO2JA > > Rick Muething KN6KB's post to the band width committee: > > > I want to take this opportunity to update the bandwidth committee on > recent progress made in the testing of a new digital mode called > SCAMP (Sound Card Amateur Message Protocol). This sound card mode > incorporates integrated ARQ (Automatic Retry reQuest) and dynamic > encoding levels to deliver error-free digital data at respectable > speeds (3-4 Kbytes/minute) over 1.9 KHz HF channels. One objective is > to provide performance comparable to Pactor II and III using low > cost sound card/PC technology and standard voice grade radios (HF and > VHF). > > On March 19, 2005 we began initial beta testing of SCAMP with Winlink > 2000 with the exchange of test messages on 17 meters from the client > program Paclink SCD W5SMM (Vic Poor) to WL2K SCAMP Server KN6KB. > This will be continuing for the next few months using KN6KB's SCAMP > Server and one or two additional WL2K SCAMP Servers in selected > areas. This marks the the third phase of on-air SCAMP testing which > started in November 2004 ( > http://www.arrl.org/news/stories/2004/12/07/6/?nc=1 > <http://www.arrl.org/news/stories/2004/12/07/6/?nc=1> ) > > Since SCAMP is a "wide band" digital mode (1.9 KHz) SCAMP servers are > operating only in the narrow HF forwarding sub bands shared with HF > Packet, Pactor III and other automatic/semiautomatic wide band modes. > These sub bands were envisioned many years ago as a compromise to > permit unattended HF forwarding between HF packet stations. Clearly > the abundance of new digital modes including digital voice, data and > images has exceeded the narrow limitations of these sub bands (only > 5-10 KHz on some bands) > > The SCAMP clients and servers also incorporate an effective channel > busy detector to significantly reduce QRM from either the careless > operator or the hidden transmitter (3rd station not heard by the > station manually initiating the connection but detected by the > automated server). > > While there is and continues to be much comment from groups that > would like to banish all automated (full or semi) transmissions these > automated modes have proven to be a very useful and popular. These > modes have also proven to serve best and be most efficient and > reliable in times emergency when sufficient control operators are not > always be available. > > The attached screen capture GIFs from the WL2K SCAMP server show that > while not perfect the state of the art in automated busy detectors > has improved considerably. > > The following GIFs were all made at fairly weak signals...Signals > barely moving the S meter above the background noise. The SSB signal > is about 1 S unit over the noise. > > Clear channel display (reference) Weak CW (about 1000 Hz on the > display) PSK 31 signal at about 1000Hz with a weaker CW carrier below > Pactor II signal near the bottom of the Pass band Pactor III signal > showing mode transitions SSB voice at about 1 S unit over the noise > > There is no question that the integrated use of these types of busy > detectors can substantially mitigate QRM from automated or semi > automates stations even in difficult "hidden transmitter" scenarios. > > This combined with reasonable partitioning by bandwidth (clustering > like bandwidth signals in band segments) will allow a peaceful co > existence of the myriad of modes now in use in amateur radio > including the semi automatic transfer modes now so popular. It will > also foster an environment to experiment with and expand the use of > digital technology...an important aspect of keeping Amateur radio > healthy. > > I think it is also important for the committee to consider that the > US is only one country and that several other countries have adopted > a policy of minimal regulation of bandwidth and modes. Canada for > example permits all HF digital mode < 3 KHz (1 KHz on 30 meters) with > virtually no restrictions as to mode, or automation level. > > I would suggest the committee consider the following in developing a > band plan to submit to the FCC. > > 1) Generally minimize the complexity of band restrictions by > mode,bandwidth and level of automation. The Canadian model is a good > example of such simplicity. > > 2) Allow semi automatic operation while encouraging the use of > technologies like smart busy detectors that reduce QRM both for the > manual and automatic station. > > 3) Use a simple metric (e.g bandwidth) to segregate modes if required > yielding a regulation that is flexible and viable for many years to > come. > > 4) Move with leadership toward a fast resolution of the current > antiquated band plan and propose it for fast track adoption with the > FCC. > > > Thanks for your consideration. I am at your disposal to answer any > technical details of the SCAMP effort and its implementations. > > 73, > > Rick Muething KN6KB > > --- In digitalradio@yahoogroups.com > <mailto:digitalradio%40yahoogroups.com>, "Jose A. Amador" > <[EMAIL PROTECTED]> wrote: >> >> >> Dave, >> >> Well, I was aware of SCAMP, but maybe not well informed about the > results. >> I have never seen it in action, as I was not one of the beta > testers. >> >> Nevertheless, it is a formidable task, and I know that Rick did > work >> hard on it. >> >> But as SCAMP has not been in public distribution and not released > after >> the tests, it is still only hope, as far as I can see. Besides what >> Rick and > team >> did, I know of no other similar efforts. >> >> And you are right, the perfect is the best enemy of good. But even > then, >> good operating practices are needed, as assymetric conditions will >> not > disappear >> and people with good detectors may be run over by those who don't >> use them or > defeat them. >> >> So, let's wait and see, hoping for the best. >> >> 73, Jose >>
