> Rein PA0R wrote > When I am camping in the south of Spain through the winter, > every sunday morning our our 30m pskmail link to Sweden > is covered up by splatter from french SSB stations. > Pskmail makes use of the gaps in the conversation
Hi Rein, I am curious about the "splatter". Normally, splatter refers to unusually high spurious signals that are emitted by an improperly adjusted SSB voice transmitter. The splatter is the spurious signal(s) adjacent to the main normal SSB voice signal channel, usually a result of poor linearity in the transmit amplifier chain. When one is not tuned to the transmitting SSB station's channel, their splatter normally shows up as a popping sound during voice peaks or sibilance excursions. Many of the FEC or ARQ digi modes can deal with low amplitude splatter. 2kHz bandwidth Olivia might be one of the more resilient modes for FEC work. Of course, almost any ARQ might work fine, such as PSK-ARQ. But, perhaps you are dealing more with a co-channel undesired SSB signal, or an overlapping channel SSB signal? If such is the case, then it isn't really splatter, is it? If the objective is to get a digital data signal through during a co-channel simultaneous SSB voice QSO, then one might wonder if QSY or QRX could be the preferred technique, rather than QRM-anti-QRM :) In any case, if a voice SSB station happens to be operating on one's favorite digi data channel, perhaps "patience" is the best mode of operation. But, sometimes there are situations when one must simply get the message through, and the interference is not mutual. Such is the problem on the 7MHz band, where stations in many parts of the world often operate between AM broadcast carriers, but within the AM audio sidebands. In USA, there is a very narrow automatic subband on 7MHz at 7100-7105kHz. It also happens to be adjacent to a strong AM broadcast station at 7105kHz, and it has a powerful audio Lower Sideband directly co-channel with the segment. Most of the hams successfully using this segment are using ARQ modes, but the communication still suffers or slows down, because the messaging and signalling often takes many repeats. I'm sure a lot of us have seen mini mode wars erupt spontaneously, especially on 7MHz, due to the disparate bandplans and allocations throughout the world. It isn't uncommon to see a CW station fire up on top of a digi texting QSO in the 7025-7045kHz area of the band, or vice-versa. We see a lot of digi texting ops in USA fire up directly on top of SSB QSOs in the 7060-7085kHz area. Often, these are situations where SSB QSOs with different languages are in progress. Perhaps it is in our nature for humans to ignore other languages that are not our own, and there is a parallel to this with ignoring "other modes" which we can't or don't want to take the time to decode. The 7MHz band in South America has been entirely taken over by unlicensed SSB voice stations mostly operating in USB. 7000kHz is like a continuous zoo, similar to the cacophony of the CB trucker channel on a big highway. In order for hams to have any effective use of the 7MHz band there, one must operate in country-wide nets and maintain large group QSOs on SSB, with "the wagons circled" in the area of 7070-7100kHz. 10MHz is a more difficult problem, because hams are secondary users of this shared band. How are hams to know which stations are the real primary users, and which ones are pirates? This is a huge problem on a number of ham bands in the tropical and equatorial areas of the world. Here in Asia, due to the vast number of languages and dialects one can hear on the air, it is almost impossible for the average ham to sort out whether they are hams or not, and whether one must yield to all of them. I'm sure it is similar for you in Spain, with its proximity and excellent propagation to Africa and all of Europe. Bonnie VR2/KQ6XA
