Как организована работа кварцевых&DSP фильтров в К3.
Let's suppose the only crystal roofing filter you have installed is 2.8 kHz wide. You put the rig into CW (or data) mode, then dial the DSP bandwidth down to 400 Hz. Everything will be fine -- unless an extremely strong signal appears "outside" the DSP's passband but still "inside" the crystal filter passband. This can cause what's called "pumping," meaning activation of the AGC or desensing. Many transceivers with IF DSP don't have the ability to do anything about this, so they get "trashed" on receive. Such transceivers typically have only a 3 kHz (or wider) roofing filter, allowing strong signals to cause trouble. The K3 has roofing filter bandwidths as low as 200 Hz, giving you a means to completely eliminating problems with nearby signals. If installed, these will be automatically selected as you narrow the DSP's bandwidth using the shift/width/hi-cut/lo-cut controls. Or you can select them manually.
Предположим что у нас установлен только один кварцевый руфинг-фильтр шириной 2,8кГц. Мы работаем CW или "цифрой", и при помощи DSP сужаем полосу до 400Гц. Все будет прекрасно до тех пор, пока рядом не появится мощный сигнал вне полосы DSP, но в полосе руфинг-фильтра. Это приведет, что называется "накачиванием" (или как у нас - приемник начинает "дышать", "затыкаться") т.к. начинает работать система АРУ. Многие трансиверы с IF DSP ничего не могут сделать с этим. Такие трансиверы имеют 3кГц руфинг (или шире), позволяя мощным сигналам доставлять вам неприянтости. К3 имеет узкие руфинги вплоть до 200Гц,, что позволяет решить проблему мешающих сигналов. Если у вас установлено несколько руфинг-фильтров, они будут выбираться автоматически, в зависимости от выбираемой при помощи DSP полосы. Или вы можете выбрать любой р.фильтр вручную.
As you adjust the DSP's WIDTH control (or hi-cut/lo-cut), firmware automatically selects that crystal filter which is closest to your selected DSP passband. This means you don't have to worry about manual crystal filter selection at all, normally -- let the K3 do the work. The five filter icons (FL1-FL5) will indicate which crystal filter it has selected. You can continue to narrow the DSP bandwidth all the way down to 50 Hz in every mode, and the K3 will dutifully select the best installed crystal filter. Slight differences in filter passband loss are taken into account as well.
Как только вы установите нужную ширину ручкой DSP-фильтра, программа автоматически выберет тот кв.фильтр, который максимально близок к выбранному DSP-фильтру (оригинальное решение, не правда ли?). Это позволяет вам не беспокоиться о ручном выборе нужного фильтра, программа К3 все сделает за вас. На дисплее будут отображаться пять положений FL1...FL5 позволяя видеть который из пяти кв.фильтров выбран. Вы можете продолжить сужать полосу при помощи DSP вплоть до полосы в 50Гц для любой модуляции.
If you have a number of roofing filters, you'll have a three-point filtering system with ultimate rejection that's basically infinite (roofing filter, DSP IF, DSP AF). Anyone who has suffered AGC pumping, desense or other problems when using wide roofing filters will notice the different the first time they use the K3 in crowded band conditions. You can select crystal filters manually if you wish using the XFIL button. When you do this, the DSP passband is set to match the selected crystal filter's passband. You can then alter it with WIDTH or HI-CUT/LO-CUT from there.
There are two other controls of interest that really simplify operation:
NORM -- This normalizes the overall system passband (crystal filter and DSP filtering) to a per-mode value, e.g. 2.7 or 2.8 kHz on SSB. This is a quick way to get back to initial conditions; it also removes any SHIFT.
I/II -- This toggles between two "presets", i.e. two previously-established combinations of DSP control settings and crystal filter selection. If you have two settings you typically use (wide/narrow for CW tuning), toggling between the two presets makes it very fast and easy. In CW mode, I usually have preset I set for 400 Hz, and II set for 100 Hz.
All of the DSP/filter settings are per-mode and per-VFO. So if you have the subreceiver installed, you can for example listen to CW at two separate bandwidths in the two receivers. The audio can be mixed, or one receiver's audio routed to the left earpiece/speaker and the other to the right. This is why we wanted two high-performance receivers with identical filter complements: versatility.
The future optional variable filters will in effect give you 4 to 8 filters in a single slot. Since crystal filters are selected automatically as you adjust the DSP controls, you can think of the variable-passband filters as DSP-tracking crystal filters -- unique to the K3.
he K3's DSP subsystem has extremely high fidelity and low IMD. Until signals reach a fairly high level, the DSP's own filtering could handle the entire job. The roofing filters, if installed, will remove very strong signals outside the communications bandwidth being used. There's also pre-DSP hardware AGC that comes in at a high level to protect the A to D converter when very strong signals are present in the crystal filter passband.
О коммутации антенн в К3.
The settings for ANT1 and 2 are stored on a per-band, per-general purpose (GP)-memory basis. Also stored is up to a 5-character text label for each antenna. So, when you change antennas, it'll tell you whether you're on the "YAGI" or the "VERT", etc. The antenna name is also flashed briefly whenever you change bands, as a quick reminder that's more meaningful than just "1" or "2".
Настройки для АNТ1 и АNТ2 запоминаются для каждого диапазона(как и в К2). Так же запоминается текстовая информация (5 знаков) для каждой антенны. Т.е. когда вы переключаете антенны, надпись подскажет когда вы включили "YAGI" а когда "VERTICAL", и.т.д. Также название антенны будет мигать каждый раз, когда вы переключаете диапазоны, давая более полноe представление о антенне чем просто цифры 1 и 2.
И главный и Sub-приемник одновременно могут использовать одну и ту же антенну, или в различных сочетаниях ANT1/ANT2/RX-ANT.