Re: [Elecraft] Price Comparison and Comment
Keep up the good work Bill!! May I second you request for comprehensive IMD / BDR test results. Crystal filters, particularly ladders, do have a habit of coming back to bite unless their linearity, or lack of, is taken into account while setting Gain Distribution et al during the design activity. I sometimes wonder whether the use of wide SSB filters e.g 2.7 kHz in our ham community is due to poor narrower filter design, and the reulting group delay characteristic. This in turn can result in a SSB voice signal having a raspy sound. In my opinion based on observation and use, 2.1 kHz is enough for very good soundimg audio IF things are set up properly (carrier position, modulator AF drive, ALC, mic, etc, etc), leaving more spectrum for others to use. 73, Geoff GM4ESD On Friday, May 04, 2007 at 7:59 PM, Bill Tippett wrote: SSB - 2.7 kHz unless you want ESSB (not sure how high that goes these days but IMHO we should be trying to minimize communications bandwidths rather than playing broadcast disc jockey (my personal opinion!). Those folks should go to 29 MHz FM if they want to do that. . snip A roofing filter's purpose is simply to minimize spurious artifacts from being created *inside* the RX by external signals. It does NOT create the ultimate selectivity (which is determined by the DSP filter at the 2nd IF). Please read the last sentence again! Here's a simple summary: snip ...roofing filter prevents very strong signals from creating spurious (i.e. *NOT REAL*) signals which will then appear inside the DSP. snip The number of poles (i.e. shape factor of the filter) can affect IMD/BDR issues inside the RX. For this reason hopefully Elecraft will provide actual IMD/BDR measurements with each option to help answer the following questions: 1. Is the optional 8-pole 2.8 kHz better than the stock 5-pole 2.7 kHz (by better I mean resulting in better IMD/BDR performance which is the primary purpose of a roofing filter). snip The variable BW filters are interesting but I would not consider them until we have some actual results for IMD/BDR. They are NOT providing ultimate selectivity as they do in the case of the K2, which seems to be confusing many folks. 73, Bill W4ZV ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Price Comparison and Comment
--- Don Wilhelm [EMAIL PROTECTED] wrote: Bill, All of what you say is true *EXCEPT* for one item - and that is the AGC. [...] Now, if the signal you are trying to copy is an S-1 or S-2 level and an S-9 signal comes into the roofing filter passband (again it may be out of the DSP passband and will not be heard), the receiver gain will be reduced and you will no longer hear the S-1/S-2 signal - just like QSB, but it is QSB induced in the receiver, not due to propagation effects. VA7W: Ek! time to kill the agc and back down on the RF gain and up the audio gain? To some degree but you cannot actually kill AGC in a rig like Orion (or perhaps K3 which apparently uses similar analog plus digital AGC). The reason is that the analog AGC (actually more of a peak limiter) ahead of the DSP must *always* be active to protect the DSP from being over-driven. Your Ek! sound is a good description of the sound of a DSP that is over-driven. In Orion digital AGC in the DSP is also never fully turned off. Off is simulated by setting AGC Decay to a high rate (1000 dB/s) but it is never actually off even when Off is selected on the front panel. I've discovered I can make it a little more Off by setting Decay to 2000 dB/s in the Programmable AGC mode, but that is also not truly Off (which has an infinitely fast decay rate). We can basically throw away some of our ideas about AGC based on analog rigs like the K2. DSP rigs simply don't work the same way. I'll repeat again...I've never heard classical AGC pumping in Orion. If you are using a 500 Hz filter (+/- 250 Hz BW) and a S9+30 station is 500 Hz away (then attenuated ~6 dB by the filter skirt), you will hear keyclicks, phase noise, etc long before you hear AGC problems. Also pumping is not a good description of a signal overdriving a DSP. To me It sounds more like a machine gun suddenly going off next to your head. It's more of a digital (i.e. on/off) staccato effect...not the classical analog gain pumping effect. 73, Bill W4ZV ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Price Comparison and Comment
Bill, You are right. After thinking on this for more than 10 minutesI came to the same conclusion. A K3 can be had for 1800 dollars in modular kit form...with just 100 watts and no bells and whistles. The 2.7 roofing filter comes with the unit, so you would have a workable unit after building it. So, the price comparison I put out last weekend was...well...wrong! Wrong on so many levels. I did not understand roofing filters at time and considered them IF Filters. I was informed by very nice people that not all five filters would be needed. So, that was a bogus assumption on my part. Also, I looked at the price from a full blown perspective. What I like about Elecraft is that you can put in the pieces when you can afford them. Not like other companies who do not offer that kind of flexibility. So...sorry about the poor email Lee Buller Making a mistake is not a problem...not learning from mistakes is a big problem. This is assuming the problem is not life or death In our day and age it seems that Common Sense is in short supply. If you don't have any Common Sense - get some Common Sense and use it. If you can't find any Common Sense, ask for help from somebody who has some Common Sense. Is Common Sense devine? ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Price Comparison and Comment
Good chart, Bill. I especially agree with some of your footnote statements. Being a casual DXer and contest dabbler, I ordered a K3/100 with just the KXV3. I ordered the modular kit because I wanted to experience the new kit methodology, and become familiar with the boards and architecture in case I need to do future maintenance. I think a couple evenings of time spent with the manual will be well worth it. I purposely did not make a deposit, so that my unit would fall in the second run. I did this in case there are any hardware revisions after the first run. I should be early in run 2, and I thought that if I waited for feedback from the 1st run guys before ordering, I wouldn't get it until 2008 ;-) I also purposely didn't order any extra filters, as I suspect that the variable roofing filters will be out before my order is ready, and I may want to consider them for added flexibility (at least for CW). I totally agree about internal ATUs... don't like them for a number of reasons. I have one I home-brewed that I like anyway. I also don't need a second receiver at the moment. K3 allows me to have world class performance at a bargain basement price (relatively speaking), with only the features I need, but gives me expandability in case I need more options down the road. Oh, and since I already own a Z90 panadapter, I'm covered on that front. 73, Larry N8LP Bill Tippett wrote: K0WA wrote: I am sure many of you have done this alreadybut it is interesting to meand I thought I would share 1. FTDX9000 Contest $5699 (no extras) 2. Orion II $4395 3. K3 $3436 (Includes 5 filters) 4. FT2000D$3399 5 Omni VII $3050 (with two filters) 6 IC756PROIII$2999 No coupons were added or any reduction of price for this small study of price. As I see if, you just save $330 from putting it together. HM. That kind of makes he happy and sad. I had the fun of building the K2...but that doesn't seem worth it to build a K3. Of course, I could be (and usually am) wrong in my thinking here. Be careful with comparisons like this! It depends very much on your K3 configuration, and it also depends on how you value issues like the quality of the Sub Receiver, etc. The beauty of the K3 is that it can be configured very economically depending on what your needs are. Elecraft has cleverly configured the K3 to allow it to appeal to many different users: 1. Budget minded DXers who need an exceptional RX. Include the basic K3, no ATU, KXV3 (for RX antenna input) plus 500 Hz filter equals $2149. CW filter depends on IMD/BDR measurements but most likely the 500 Hz 5-pole will be entirely sufficient based on my experience with Orion. Build one yourself for $1907. 2. Budget minded contesters who need 2 for SO2R. Twice the above for $4298 assembled or $3814 kitted. 3. Those who need truly high performance Sub RX for diversity or for use in very crowded conditions. K3 + Sub RX + KXV3 + two 500 Hz filters for $2825 assembled or $2525 kitted. IMHO this combination cannot be duplicated by any of the above rigs due to the quality of both K3 receivers (pending actual IMD/BDR measurements of course). 4. Those who want a truly high performance panadapter/bandscope using the K3's IF output to an outboard SDR (e.g. Softrock 40, Clifton Laboratories Z90/91 Panadapter, etc.) This gets tricky to price but it's nowhere near the $10k range of a full blown IC-7800 or FTDX9000. I'm not a fan of ATUs but you can add it to the above if necessary. Thank you Elecraft and Ten-Tec for not forcing me to pay for an ATU if I don't feel I need it (ditto for the 20 and 6 kHz filters I never use in my Orion). I simply wanted to offer a counterpoint view to the pricing listed above. I'm sure many others would do things differently but I believe Elecraft has been very clever in allowing us to configure exactly what we need...and nothing more. 73, Bill W4ZV ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] Price Comparison and Comment
I ordered just the 10 watt kit and a 6Khz filter, which will allow me to play a lot before I get the 100 watt amp and the atu. I don't contest or DX, so its nice to not have to get a lot of filters, and a 2nd receiver. I do want the band scope though! The soft entry makes it a bit better than having to plunk down a truck load of cash Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Lee Buller Sent: Friday, May 04, 2007 11:07 AM To: Bill Tippett; Elecraft Reflector Subject: Re: [Elecraft] Price Comparison and Comment Bill, You are right. After thinking on this for more than 10 minutesI came to the same conclusion. A K3 can be had for 1800 dollars in modular kit form...with just 100 watts and no bells and whistles. The 2.7 roofing filter comes with the unit, so you would have a workable unit after building it. So, the price comparison I put out last weekend was...well...wrong! Wrong on so many levels. I did not understand roofing filters at time and considered them IF Filters. I was informed by very nice people that not all five filters would be needed. So, that was a bogus assumption on my part. Also, I looked at the price from a full blown perspective. What I like about Elecraft is that you can put in the pieces when you can afford them. Not like other companies who do not offer that kind of flexibility. So...sorry about the poor email Lee Buller Making a mistake is not a problem...not learning from mistakes is a big problem. This is assuming the problem is not life or death ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Price Comparison and Comment
Well then, I have finally got to know the skinny on this ceiling filter (er roofing) issue and I am totally confused (still). I thought I had a handle on it (order them all), but now someone says that we DON'T need them all. How do you know which ones you do need? And I have seen someone say that one (or all) of them will be tuneable. Can some (again please) lay this out in laymens terms for the ignorant, non savy (ME) of us. Stan Rife W5EWA Houston, TX K2 S/N 4216 Lee Buller [EMAIL PROTECTED] wrote: Bill, You are right. After thinking on this for more than 10 minutesI came to the same conclusion. A K3 can be had for 1800 dollars in modular kit form...with just 100 watts and no bells and whistles. The 2.7 roofing filter comes with the unit, so you would have a workable unit after building it. So, the price comparison I put out last weekend was...well...wrong! Wrong on so many levels. I did not understand roofing filters at time and considered them IF Filters. I was informed by very nice people that not all five filters would be needed. So, that was a bogus assumption on my part. Also, I looked at the price from a full blown perspective. What I like about Elecraft is that you can put in the pieces when you can afford them. Not like other companies who do not offer that kind of flexibility. So...sorry about the poor email Lee Buller Making a mistake is not a problem...not learning from mistakes is a big problem. This is assuming the problem is not life or death In our day and age it seems that Common Sense is in short supply. If you don't have any Common Sense - get some Common Sense and use it. If you can't find any Common Sense, ask for help from somebody who has some Common Sense. Is Common Sense devine? ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Price Comparison and Comment
Bill, All of what you say is true *EXCEPT* for one item - and that is the AGC. The hardware AGC is developed before any DSP processing, so when there are strong signals inside the roofing filter passband, they will activate the AGC and reduce the receiver sensitivity. If you have the DSP cranked down to a narrow bandwidth, you may not even hear the offending strong signal because it is outside the DSP bandwidth but still inside the roofing filter bandwidth. BTW, this can happen on the K2 (and many other receivers) if a wide bandwidth is selected and the DSP is used to reduce the signal to only the desired one. That is not really tough to deal with if you are already listening to an S-9 signal even though an S-9 +30 signal comes on - the S-9 signal will be reduced to the equivalent of an S-4 or S-5 signal and that can easily be solid copy (because other signals in the DSP passband are similarly reduced). Now, if the signal you are trying to copy is an S-1 or S-2 level and an S-9 signal comes into the roofing filter passband (again it may be out of the DSP passband and will not be heard), the receiver gain will be reduced and you will no longer hear the S-1/S-2 signal - just like QSB, but it is QSB induced in the receiver, not due to propagation effects. I will have at least one narrow filter available in my K3. Bill, you were correct that a filter is needed for each major mode, but the filters that any one person needs will be determined by their operating habits, and not based on the 'average'. For ragchewing and casual contacts, even the wide 2.7 kHz filter may be all that is needed, but for serious CW, QRP, contesting or DX chasing, an array of filters will be needed - just how many will depend on the operator's desires to reduce QRM and the amount available in the ham radio budget. 73, Don W3FPR Bill Tippett wrote: W5EWA: but now someone says that we DON'T need them all. Definitely not...unless we have more money than sense. You need only ONE per major mode, which will cover the widest bandwidth you ever expect to use in that mode. For example: CW - 500 or 400. 250 and 200 are definite overkill IMHO and not necessary in addition to narrow DSP BWs. The reason is that IMD/BDR spurious issues at 500 Hz will be far overridden by other issues such as phase noise, key clicks, etc that come from the transmitted signals. There is no point in making a receiver many dB better than the environment in which it must live! No matter how good a receiver is it cannot eliminate transmitter defects (maybe Flex's SDR-X can but that remains to be proven). SSB - 2.7 kHz unless you want ESSB (not sure how high that goes these days but IMHO we should be trying to minimize communications bandwidths rather than playing broadcast disc jockey (my personal opinion!). Those folks should go to 29 MHz FM if they want to do that. AM - 6 kHz FM - 15 kHz In fact you may not need ANY filters beyond the 2.7 kHz stock filter unless you expect to have lots of very close spaced S9+30 dB signals on CW (e.g. huge low-band pileups or in contests). The 2.7k should be perfectly adequate for nearly any situation on SSB, although it wouldn't surprise me to see someone offer 1.8 kHz, mainly for contesters. A roofing filter's purpose is simply to minimize spurious artifacts from being created *inside* the RX by external signals. It does NOT create the ultimate selectivity (which is determined by the DSP filter at the 2nd IF). Please read the last sentence again! Here's a simple summary: Antenna roofing filter DSP filter ear. ...roofing filter prevents very strong signals from creating spurious (i.e. *NOT REAL*) signals which will then appear inside the DSP. ...DSP filters provide the ultimate selectivity (i.e. separating the *REAL* signals from each other). The number of poles (i.e. shape factor of the filter) can affect IMD/BDR issues inside the RX. For this reason hopefully Elecraft will provide actual IMD/BDR measurements with each option to help answer the following questions: 1. Is the optional 8-pole 2.8 kHz better than the stock 5-pole 2.7 kHz (by better I mean resulting in better IMD/BDR performance which is the primary purpose of a roofing filter). 2. Is the 5-pole 500 Hz better than the 8-pole 400 Hz? 3. Is the 8-pole 250 Hz better than the 5-pole 200 Hz? (academic to me since I don't feel either is necessary ...see comment above re TX key clicks, phase noise, etc). The variable BW filters are interesting but I would not consider them until we have some actual results for IMD/BDR. They are NOT providing ultimate selectivity as they do in the case of the K2, which seems to be confusing many folks. 73, Bill W4ZV ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change,
Re: [Elecraft] Price Comparison and Comment
At 07:34 PM 5/4/07, Don Wilhelm wrote: All of what you say is true *EXCEPT* for one item - and that is the AGC. Don you are absolutely correct. The reason I never considered it is that I have never experienced it with my Orion. I seldom operate with strong signals spaced much closer than 500 Hz. The most severe case of this may be in the CQ 160 CW Contest where it's not uncommon for S9+20 to 30 signals to be spaced every 500 Hz. With typical key click bandwidths, very few people will try to get closer than 500 Hz. Given 500 Hz signal spacing and given a 500 Hz BW filter, the filter easily knocks them down to a reasonable level, since the filter BW is +/- 250 Hz and the signals are +/- 500 Hz. Orion uses a two-stage AGC system, one is analog and ahead of the DSP. It has has the main function of preventing over-driving the DSP stage. ADC overload can never be allowed to occur because when that happens, signals are irrevocably corrupted. Signals that are larger than the full-scale range of the ADC must force reduction of gain in the analog section of the receiver. So both analog and digital AGCs are used in the Orion. Resort to analog AGC only need be made when signals inside the roofing bandwidth exceed about S-9 plus 30 dB. At that point, sensitivity is reduced but what we are discovering is that phase-noise performance-- as determined by reciprocal-mixing measurements-- already limits what you can hear. So performance is phase-noise limited and not DSP limited. Even so, the Orion gives you the option of kicking in a crystal filter, preventing movement of the analog AGC and the sensitivity reduction described above. http://www.doug-smith.net/orion.htm As stated, this analog AGC does not activate until signals reach the S9+35 range. The second AGC is digital and internal to the DSP (which works very well). As the resolution and speed of ADC hardware improve, digital radio receivers become less dependent on analog AGC to meet dynamic-range requirements. State-of-the-art 24-bit IF-DSP converters, such as those used in the Ten-Tec Orion, produce about 100 dB of dynamic range. That means a receiver can handle signals from the noise floor to almost 40 dB over S9 without analog AGC. Above that level, analog AGC is still necessary to maintain the linearity of analog circuits and to prevent overload in the ADC hardware. http://www.doug-smith.net/dspdynamics.htm I haven't seen much about the K3 AGC but I hope it uses a similar same technique as Orion. I have NEVER heard any AGC pumping in Orion, even under severe situations like the CQ 160 CW Contest which I consider the ultimate test for any receiver. I guess that's why it did not occur to me to mention it. Maybe one of the Elecraft folk will tell us more abour the K3 AGC. 73, Bill W4ZV ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Price Comparison and Comment
Bill, I did ask Wayne about the AGC (with respect to the roofing filter selection) and he indicated that the AGC was developed in hardware before the A/D conversion and there is additional AGC action created in the DSP. As I understand it, it is similar to that which you describe in the Orion. Yes, from a receiver performance standpoint, only the A/D overload problem counts (and it is critical), but from an operating (AGC pumping) standpoint, there can be undesired performance in the presence of strong signals that pass through the roofing filter even though they are filtered out by the DSP because they will reduce the overall gain of the receiver. Quite apart from the receiver specs, it does show up during operation and the AGC pumping can be a real problem for weak signal reception regardless of the total dynamic range of the receiver. We both await the real details on the K3 AGC (and other things too). 73, Don W3FPR Bill Tippett wrote: At 07:34 PM 5/4/07, Don Wilhelm wrote: All of what you say is true *EXCEPT* for one item - and that is the AGC. Don you are absolutely correct. The reason I never considered it is that I have never experienced it with my Orion. I seldom operate with strong signals spaced much closer than 500 Hz. The most severe case of this may be in the CQ 160 CW Contest where it's not uncommon for S9+20 to 30 signals to be spaced every 500 Hz. With typical key click bandwidths, very few people will try to get closer than 500 Hz. Given 500 Hz signal spacing and given a 500 Hz BW filter, the filter easily knocks them down to a reasonable level, since the filter BW is +/- 250 Hz and the signals are +/- 500 Hz. Orion uses a two-stage AGC system, one is analog and ahead of the DSP. It has has the main function of preventing over-driving the DSP stage. ADC overload can never be allowed to occur because when that happens, signals are irrevocably corrupted. Signals that are larger than the full-scale range of the ADC must force reduction of gain in the analog section of the receiver. So both analog and digital AGCs are used in the Orion. Resort to analog AGC only need be made when signals inside the roofing bandwidth exceed about S-9 plus 30 dB. At that point, sensitivity is reduced but what we are discovering is that phase-noise performance-- as determined by reciprocal-mixing measurements-- already limits what you can hear. So performance is phase-noise limited and not DSP limited. Even so, the Orion gives you the option of kicking in a crystal filter, preventing movement of the analog AGC and the sensitivity reduction described above. http://www.doug-smith.net/orion.htm As stated, this analog AGC does not activate until signals reach the S9+35 range. The second AGC is digital and internal to the DSP (which works very well). As the resolution and speed of ADC hardware improve, digital radio receivers become less dependent on analog AGC to meet dynamic-range requirements. State-of-the-art 24-bit IF-DSP converters, such as those used in the Ten-Tec Orion, produce about 100 dB of dynamic range. That means a receiver can handle signals from the noise floor to almost 40 dB over S9 without analog AGC. Above that level, analog AGC is still necessary to maintain the linearity of analog circuits and to prevent overload in the ADC hardware. http://www.doug-smith.net/dspdynamics.htm I haven't seen much about the K3 AGC but I hope it uses a similar same technique as Orion. I have NEVER heard any AGC pumping in Orion, even under severe situations like the CQ 160 CW Contest which I consider the ultimate test for any receiver. I guess that's why it did not occur to me to mention it. Maybe one of the Elecraft folk will tell us more abour the K3 AGC. 73, Bill W4ZV ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Price Comparison and Comment
Bill, I've had my eye on the Orion since it came out. I almost got to the point of clearing getting one with my xyl, but about that time the QST review came out and it wasn't all that kind to the Orion. So I've held on to my K2. I've been happy with it, but it's human nature to always look for a bit more. The reason I'm writing you is I'd like to know if you think the (2) QST reviews were unfair and what you think of the Orion... (Your reply, below, is quite complimentary; but are you coping with other deficiencies to get the raw performace the Orion is giving you?) Tnx in advance 73, Lenny W2BVH -- Original message -- From: Bill Tippett [EMAIL PROTECTED] At 07:34 PM 5/4/07, Don Wilhelm wrote: All of what you say is true *EXCEPT* for one item - and that is the AGC. Don you are absolutely correct. The reason I never considered it is that I have never experienced it with my Orion. I seldom operate with strong signals spaced much closer than 500 Hz. The most severe case of this may be in the CQ 160 CW Contest where it's not uncommon for S9+20 to 30 signals to be spaced every 500 Hz. With typical key click bandwidths, very few people will try to get closer than 500 Hz. Given 500 Hz signal spacing and given a 500 Hz BW filter, the filter easily knocks them down to a reasonable level, since the filter BW is +/- 250 Hz and the signals are +/- 500 Hz. Orion uses a two-stage AGC system, one is analog and ahead of the DSP. It has has the main function of preventing over-driving the DSP stage. ADC overload can never be allowed to occur because when that happens, signals are irrevocably corrupted. Signals that are larger than the full-scale range of the ADC must force reduction of gain in the analog section of the receiver. So both analog and digital AGCs are used in the Orion. Resort to analog AGC only need be made when signals inside the roofing bandwidth exceed about S-9 plus 30 dB. At that point, sensitivity is reduced but what we are discovering is that phase-noise performance-- as determined by reciprocal-mixing measurements-- already limits what you can hear. So performance is phase-noise limited and not DSP limited. Even so, the Orion gives you the option of kicking in a crystal filter, preventing movement of the analog AGC and the sensitivity reduction described above. http://www.doug-smith.net/orion.htm As stated, this analog AGC does not activate until signals reach the S9+35 range. The second AGC is digital and internal to the DSP (which works very well). As the resolution and speed of ADC hardware improve, digital radio receivers become less dependent on analog AGC to meet dynamic-range requirements. State-of-the-art 24-bit IF-DSP converters, such as those used in the Ten-Tec Orion, produce about 100 dB of dynamic range. That means a receiver can handle signals from the noise floor to almost 40 dB over S9 without analog AGC. Above that level, analog AGC is still necessary to maintain the linearity of analog circuits and to prevent overload in the ADC hardware. http://www.doug-smith.net/dspdynamics.htm I haven't seen much about the K3 AGC but I hope it uses a similar same technique as Orion. I have NEVER heard any AGC pumping in Orion, even under severe situations like the CQ 160 CW Contest which I consider the ultimate test for any receiver. I guess that's why it did not occur to me to mention it. Maybe one of the Elecraft folk will tell us more abour the K3 AGC. 73, Bill W4ZV ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Price Comparison and Comment
Hi Don, At 08:47 PM 5/4/07, Don Wilhelm wrote: I did ask Wayne about the AGC (with respect to the roofing filter selection) and he indicated that the AGC was developed in hardware before the A/D conversion and there is additional AGC action created in the DSP. As I understand it, it is similar to that which you describe in the Orion. If it is like Orion's I'll be happy! Yes, from a receiver performance standpoint, only the A/D overload problem counts (and it is critical), but from an operating (AGC pumping) standpoint, there can be undesired performance in the presence of strong signals that pass through the roofing filter even though they are filtered out by the DSP because they will reduce the overall gain of the receiver. Quite apart from the receiver specs, it does show up during operation and the AGC pumping can be a real problem for weak signal reception regardless of the total dynamic range of the receiver. I'm not sure I agree. If analog AGC is not activated, there is no analog gain change or pumping. According to the note I posted from Doug Smith, the DSP can internally handle AGC within the ballpark of 100 dB (noise floor to S9+40). It first filters signals digitally and then applies AGC only to signals appearing within the selected DSP bandwidth, so there is no pumping by signals outside the DSP bandwidth...unless I misunderstand ...which is completely possible of course! All I can say is I have never experienced the problem in Orion. I've got to get ready for a symphony concert now so hopefully all will be answered in the fullness of time! 73, Bill ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] Price Comparison and Comment
You seem to think the only time someone is going to use wider bandwidths is on a packed band. I personally only get on 80 or 40 on weekends, in the morning, when the band is wide open. You can say ssb is a waste, since its much wider than CW. Brett N2DTS SSB - 2.7 kHz unless you want ESSB (not sure how high that goes these days but IMHO we should be trying to minimize communications bandwidths rather than playing broadcast disc jockey (my personal opinion!). Those folks should go to 29 MHz FM if they want to do that. AM - 6 kHz FM - 15 kHz ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] Price Comparison and Comment
I am sure many of you have done this alreadybut it is interesting to meand I thought I would share 1. FTDX9000 Contest $5699 (no extras) 2. Orion II $4395 3. K3 $3436 (Includes 5 filters) 4. FT2000D$3399 5 Omni VII $3050 (with two filters) 6 IC756PROIII$2999 No coupons were added or any reduction of price for this small study of price. As I see if, you just save $330 from putting it together. HM. That kind of makes he happy and sad. I had the fun of building the K2...but that doesn't seem worth it to build a K3. Of course, I could be (and usually am) wrong in my thinking here. Lee K0WA ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
