Erik: Thanks for the well-thought out reply, you make excellent points. Comments below....
--- In digitalradio@yahoogroups.com, list email filter <[EMAIL PROTECTED]> wrote: > > Wow, Brian, there's a lot of very good information in your post, my > problem is that there is so much good fact, that it would be easy, too > easy, to accept it all at face value. In my mind, I have a few issues, > and I'll address them in line, though I really do think that parts your > post should be the basis for a faq entry or a wiki or something. > > Comments below: > > 73, > > Erik > N7HMS > IRLP Node 3804 445.975 Simp PL103.5 > > Emails sent directly to this address instead of going through a yahoo > group are automatically processed as junk mail, so I never see them. If > you want to email me directly, try 'mycall' at 12bars dot com, thanks. > > > Brian Kassel wrote: > > Guys: > > > > I have found that *MANY*, but not all, so-called Wide signals on PSK > > modes are caused by several things being overlooked at the *RECEIVE* end > > of the QSO. If adjusted properly, most newer radios should handle > > 50-100W signals providing of course that the transmitted signal is > > indeed clean to start with. > > Agreed, if you're saying well adjusted and operated modern receivers > should handle being in reasonably close proximity to adjacent stations > running 50 - 100 watts. That is not the issue, though, the issue is the > need to run 50 - 100 watts (actually the issue I had was someone running > 400 watts, but lets not let that interrupt the discourse) to maintain > reliable communications. > > > > > There are indeed plenty of "bad signals on the air, but just running > > higher powers, or big antennas is not the cause by itself. > > > > Absolutely agree here, I know I can put out a terrible signal with my > IC-703 at 2 watts into an MP-1, I can also put out a perfect signal with > the same setup, and work stations 1,000's of miles away. > > > Try to: > > > > Turn of AGC if possible, use RF gain to adjust signals. This will allow > > your receiver to have greater dynamic range. > > Use a Notch filter if available. > > Turn off the preamp, switch in the attenuator, especially on bands > > below about 30M. > > Absolutely agree, this is the part that really should be in a faq or > wiki. I'm not real keen on the attenuator bit, but then that could just > be my experience with the attenuators in my rigs, I find that I get > better printing if I let the computer audio software handle this, but > then it could be my rigs. > > > If the above doesn't work, try a better sound card. When strong > > signals are encountered, this is where the more inexpensive models start > > to "fold up". > > Why is that folks will spend many thousands on a fine rig, only to use a > > $15 sound card? > > In Digital modes, the sound card is an integral part of the RX chain. > > > > Sorry, this is where I really have to take issue. I can see why you > think so reading a little ahead into your post. About the only amateur > radio application that the generic modern sound card is not up to the > task of handling is SDR. This is especially true when working with > modern up to date software. About the only deficiency inherent in the > common hardware is the problem of receive and transmit audio not being > precisely aligned with each other. I honestly can't think of a modern > version of any digital mode software that doesn't have an alignment or > sound card setup functionality that either manually or automatically > takes care of this deficiency for the operator. It is however very > important that you go through the alignment process if your software of > choice doesn't do it for you. If your software can't adjust for this, > upgrade your software. The base software requirement for digital mode > operation is a nominal sample rate of 11025 samples per sec. It's all > the current software can take advantage of, and unless you are using a > sound card as part of a sdr receiver, any fancier or more advanced > features are just not taken advantage of by any of the software we use. > That said, there are always some exceptions, certain old laptops and > motherboard built-ins do have problems, strictly speaking, these issues > are a matter of integration into the motherboard and the OS, not an > issue with the base audio hardware's capabilities. > > The bottom line, is that unless you are planning to run an sdr receiver, > any modern < $20.00 add-on sound card that is supported by your > operating system of choice will do a fine job. I probably didn't quite go into enough detail on this point. Certainly reading the recent QST article that compared various popular sound cards shoes that there is indeed not much difference as far as sensitivity and other parameters. I think though from the standpoints of dynamic range and overload, the so-called "professional" cards fare somewhat better. However all things considered, money is much better spent in the RF RX side. I must note that since switching to the SDR-1000/Delta 66 route, about 6 months ago, I have NEVER seen a signal overload the system to the point that I couldn't deal with it easily. It is extremely rare that I have to switch in any additional filtering narrower the 5 KHz. waterfall for a truly clean signal. Of course, having said that, band conditions have been dismal, not many strong signals to deal with. I still must maintain that any clean signal, unless truly super strong, should be able to be dealt with in about any modern receiver, IF adjusted properly. > > > Please realize that distortion can occur in either the TX or the *RX* of > > any signal. Many hams don't realize that this basic fact about analog > > signals. Typically, in many cases, the cause of a wide appearing signal > > is in the transmitter. I get wide reports frequently. However, I > > monitor my output with a spectrum analyzer, and have done on the air > > tests to confirm that my signal is not running worse than -20 IMD, > > often much better than that. In fact it usually runs better than -25 > > DB. I run the SDR-1000 software defined radio at 5W (well below the > > 100W rating), a D-44 professional sound card, and an Ameritron > > ALS-500M amplifier (rated at 600W out) to get 50 -100W out. This is > > much more power than most PSK signals, so my signal tends to be much > > stronger, especially on bands where I use my 55' high beams. You drop > > any signal down, either by reducing he RF gain, or putting in some > > attenuation, or even a notch filter is you have that capability. This > > distortion occurs most often as you might expect in low end sound cards, > > like those installed on mother boards etc. > > Very nice, in many ways, your operating practices are what we should all > strive for. Except of course for the 50 - 100 watts output... I > certainly can't concede my base premise that easily. ;) > > > > > I don't wish to start any wars, just want you to understand some of > > the other possible causes of these stronger signals. > > > > No wars here either, yours is the most reasonable and well thought out > post in opposition to a somewhat modified version of my original thesis, > and I personally appreciate both the time you took to compose it, and > the fact that you posted it. It opens up the discussion to cover some > 'more interesting' ground. > > > Sorry guys, I don't see why any operator should apologize for having a > > strong, but clean signal. > > > > This is where you and I really differ, I do see why an operator should > apologize for having a strong signal. If its just strong enough to do > the job, that is perfect, no apology necessary. If its stronger than > needed to do the job, but within a range that is reasonable to > compensate for expected VARYING conditions over the course of the qso, > thats all right as well. If its stupidly too strong, I do think a > modification of operating procedure is in order. > > The honest fact, is that the FCC agrees with me on this. The following > are quotes from a recent enforcement action inquiry, where a station has > a complaint against it for: > > '...extremely poor signal quality and "splattering" apparently cause by > improper adjustments or a defective gain control and unnecessary use of > a power amplifier...' > > in his notice to this particular station, W. Riley Hollingsworth quotes > the following: > > '...Section 97.313 of the Commission's rules, 47 C.F.R. S 97.313, > requires Amateur stations to use the minimum power necessary to carry > out the desired communications.' > > and > > '...Section 97.307 of the Commission's rules, 47 C.F.R. S 97.307, states > that no Amateur station shall occupy more bandwidth than necessary for > the information rate and emission type being transmitted, in accordance > with good amateur practice.' > > I don't know how any of us would choose to read the above, but I > seriously doubt a reasonable and knowledgeable amateur such as yourself > would read the above and not take issue that a station (with a > phenomenal antenna system) is using "the minimum power necessary to > carry out the desired communications", when they are running 400 watts, > and everyone else is running 40 or less. It's pretty hard to say > they're operating "in accordance with good amateur practice", isn't it? > I know I certainly wouldn't risk my operating privileges, equipment > forfeiture, and fines, just to be able to swing a big stick when one > isn't needed. > > I find it interesting that one of the things no one has done so far, is > question "Why don't you need as much power for psk31 as you would for a > ssb voice qso under the same conditions?" Folks, the answer to this is > not magic, it's simple physics and mathematics. The key is the power > density over the bandwidth of the signal. Your psk signal is only 31 Hz > wide, and disregarding system losses due to hardware, feedline, and > antenna efficiency, 100% of your 20 watts of power on ssb is put into > that 31 Hz of bandwidth. Even at 20 watts, thats a lot of punch (psk31 > really is a mode with a built-in software linear), your same 100 watt > barefoot transceiver is doing a phenomenal job (and your compressor is > probably set a little too high to comfortably listen to) if it manages > to get 70 watts out during your voice peaks, and that 70 watts is spread > across the entire 2kHz bandwidth of your signal on voice. Bluntly, when > comparing signal power density; under the same propagation conditions; > full barefoot power on voice ssb, is a whisper, and 20 watts on psk31 is > a SHOUT. Taking the comparison one step further, 400 watts out on psk31 > is a rather obscene tantrum. If you were to attempt the same power > density on voice ssb, you would need to be putting out several times the > legal limit. Yes, lot's of room for wide interpretation here. In a regular rag chew type of QSO, one should ALWAYS reduce power to a reasonable level. I do that here actually. Problem is in a contest situation, QSO's don't last long enough to make the change easily. One guy who is relatively local may require only 1W, a DX station that calls immediately after may require 50W or even 100W to complete a QSO. Two stations running 50W may be able to make a QSO, while at 10W they would not know that each other even exists. In these times of dismal band propagation, every DB counts in a contest environment. Of course I realize that maybe 1 in 100 contesters would ever take the time and effort to adjust their power. That's really too bad, but a fact of life. Most contests have a QRP, low and high power category. In almost all cases, more points or multipliers are awarded for running lower power. In this way operators are rewarded. I have been a QRP addict for many years, and enjoyed running QRP in various contests. I will probably return to that operation more frequently when the sun spots return. I had an APLINK gateway station in the late 80's and early 90's. I came up with a simple circuit that reduced the TX power automatically based on the errors indicated on the LED of the PK-232 controller that I was using at the time. It worked very well and gave amazing indications at just how very low power, 5W and below, that would be required to maintain a link. Of course since PSK modes are not ARQ types, this idea would not be all applicable for the PSK modes I think that some good compromises could be made though. If each operator would be mindful of band conditions, and the type of operating that they are doing at the moment, they should be able to adjust power to some extent, probably not each for QSO though in a typical contest operation. Being unable to control or even effectively enforce the power rule, probably the only alternative, realistically, is to optimize, and learn how to deal with the stronger signals. Of course if a truly dirty signal, and there are many, are encountered, one should not hesitate to point them out to the operator. As Fess Parker, who played Davy Crockett in the 50's used to say: "Be sure that you are right, and then go ahead." ;) > > > > Brian K7RE > > > > BTW, Brian, you live in a very beautiful place, I used to have family in > Spearfish, last time I was there I was passing through on my way to > Sturgis, back in '77 or '78. Does the water still freeze from the > bottom up? HI! I never really checked, but we still hold the world all time record for the fastest temperature changes ever officially recorded. ;) Again, thanks for the very FB comments, Erik Brian K7RE >
