Guido wrote: > cheap, > require no aliasing LC filter, > standard I2C interface, > multiple clock outputs, > less spurs, > all at the cost of phase noise (unsure if it makes a bad receiver). > > Guido
Guido warned me about the likely phase noise problems with the Elektor SDR receiver when he emailed me a copy of the Elektor article, and other files, that I asked for. As did several other people, to whom I was also grateful as everyone included something new to the files and information that everyone else had provided. :-) In my experience there are several different types of receiver. One type is the technically pure one which should be the aim of all Amateurs, but is not always recognised or accepted. Other types are the ones that, maybe despite being technically good or bad, are just 'liked' by people who own them and the third are the ones that are either good or bad, but are just not liked by the users... My arguement is that we presently have many makes and models of transceiver which we all pay alot for, and so are convinced we bought the 'right' one and wont take kindly to anyone who tells us that our transceiver is, perhaps, not as good as it should be. I listened to the presentation to the RSGB HF Convention on the new K3 transceiver, after I had seen the presentation on SDR earlier in the day, and several things occured to me during both of those presentations, even during the one by Simon Brown (HB9DRV) on digital modes programs (which I freely admit to having a vested interest in as I am a beta tester for Ham Radio Deluxe/DM780 and a moderator on the HRD Forums) in that receiver performance has always seemed to me to be a critical element of an Amateur station, after the antenna/aerial, of course. However, with the rise of the microprocessor controlled, multi band, wide recieve bandwidth, gear from the 1980s and 1990s the role of IMD, phase noise, selectivity, sensitivity and associated problems with the interaction of each have been pushed back in favour of being able to have several hundred memories, dual VFO and dual receivers, PC control, etc., etc. Why have we managed to get to a position where it seems that every commercially made Amateur HF receiver has to have the pre-amp switched on to have any reasonable front end gain, is a debating point that is probably not on topic here, but is relavant. The latest variable is now the PC soundcard, as in built in, USB, Firewire or separate card connection. Many people use the built in soundcard, ignoring (or maybe even not knowing the limitations) others use commercial add on cards, either USB or 'hard wired' and still fewer use commercial grade audio cards. Many still suffer from poor earthing practice, which only adds to the problems... The other issue is, what are all these transceivers doing to the RF spectrum around them when they transmit? Even some SDR transceivers, it would seem, are not as clean as you would like them to be if they are within, say, 200kHz of the signal that you want to receive. I still see posts from people who use un-isolated audio lines on either audio in or out from the radio or sound card. These same people then say that they "cannot detect a problem on their transmission". Yes, on your local IMD meter (if you have one) you don't always see a problem, but look 10k, 20k, or even 100k out and the Elecraft people, and others with good test gear, may well show you where you are causing problems you did not even know existed. We, as Amateurs, seem hung up on the RFI generated by various other bits of kit, and even that which might come along if certain modes of delivery of data into the home go ahead. But, how much extra are we all pumping out to give problems to other Amateurs, let alone people overdriving their PAs? So, as I drove home from the HF Convention (the first I'd ever been to, being more a VHF/UHF/SHF enthusiast) I reflected upon the following, as far as SDR radios go at the moment. Despite the hype, how much better are some SDR receivers/transceivers than 'traditional' radios? Will the K3 out perform the SDR5000 and, if it does, will owners of the SDR5000 admit it? Will people stop buying top of the range Yaesu/Kenwood/Icom non-SDR transceivers based upon the presented facts, from Elecraft, that these manufacturers radios may be adding to the RFI encountered by all other Radio Amatuers and vice versa? Especially as the K3 is not an SDR, but claims better figures on RX and TX than almost every other transceiver on the Amateur market. Even then, will people who have bought a radio (top of the range or not) accept that they are adding to the RFI problem? I know that these last points are way Off Topic here because it strikes at every Amateur who has ever bought or built a transmitter/receiver/transceiver, as it shows that we all interfere, to some extent, with each other. But, some interfere more obviously than others. LOL Dave (G0DJA)
