Getting Ready For The 2nd RX
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Hi All,
I got a chance to briefly see the 2nd RX for the K3 at Dayton. Sure looks like a winner! Hopefully they will start going out the door at Aptos soon. In the meantime, those of us who are waiting for one need to do some serious thinking about just how we set up RX #1 and RX #2 as to filters. Unless you are loading both of them up, you want to be sure you get the ones you want in the right RX from the get-go. As someone recently posted, it takes a couple of hours plus to install the 2nd RX. So it isn't going to be easy to get it in and out if you want to change filters in RX #1. RX #2 sits on top of RX #1, if I understand it correctly, so changing filters in RX #1 will be something of a chore. Hope I get mine right the first time, but bet I don't!!!! Dave W7AQK _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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David Yarnes wrote:
> RX #2 sits on top of RX #1, if I understand it > correctly, so changing filters in RX #1 will be something of a chore. Actually, changing filters in the second rx is harder. To change the filter in rx 1, you can just lift rx 2 out of the way. But to change the filter in rx 2, you must remove it and take the board out of the shield box to get at the screw that holds the filter! -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
SV: Getting Ready For The 2nd RX
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Actually, changing filters in the second rx is harder. To change the filter in rx 1, you can just lift rx 2 out of the way. But to change the filter in rx 2, you must remove it and take the board out of the shield box to get at the screw that holds the filter! -- 73, Vic, K2VCO Fresno CA ... and what filters do the test pilots recommend? Presently I have 6, 2.8, 0.4 and 0.25 kHz - all being 8 pole. Would a 2.8 and a 0.4 be enough to keep cost down for a non FM/AM man? Len/SM7BIC _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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That should be fine Len. There are also a couple of other issues people should be aware of, especially if you plan to use diversity: 1. I would not mix filters of different types that are near the same bandwidth (i.e. a 2.7k 5-pole with a 2.8k 8-pole). Use both 5-poles or both 8-poles, not one of each. The reason is that you want the passband shape and filter offset to match as closely as possible. 2. If you have 5-pole filters, it may be necessary to get matched sets from Elecraft. The reason is that there will be a frequency difference in diversity if the filters don't have the same offset. If you have two 500 Hz 5-pole filters with slightly different offsets (e.g. -0.89 and -0.85), it may be possible to set them both to -0.87. Elecraft needs to do some more testing and will provide more information about this issue. 3. Because of 1 and 2 above, 8-pole filters may be preferable to 5-pole filters if you plan to use diversity. Now that there is only $25 difference between the 5-pole and 8-pole filters, this may be a good reason to consider 8-pole filters when placing your order. 73, Bill |
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In reply to this post by Lennart Michaëlsson
One more issue Len. In your example above, you should only use diversity in the WIDTH range where identical filters will be in use. You would want to avoid using diversity with bandwidths where you would have filters of two different bandwidths in use (e.g. above 2800 and below 400). BTW, on another issue, I assume you know the 250 Hz is actually ~370 Hz and the 400 is actually ~435 Hz according to measurements provided by Elecraft: http://www.zerobeat.net/mediawiki/index.php/K3_Roofing_Filters If it were me, I might consider removing the 250 while you have the radio open to do the KRX3 installation. You could sell it and use the proceeds to help pay for the second 400 to use in the KRX3. There is so little difference in actual BW between the "400" and "250" that I believe having both may be redundant. 73, Bill |
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I keep seeing talk of the 400(435) or 500 combined with the 250(370). I see
very little talk about the 200. My thought was to use the 400 and the 200. Maybe the decision should include the 500/200 combination. Is the 200 just "too narrow" or why don't I see more apparent use of it? I know, what is my use? I want to be able to operate most all modes except AM and FM where I have very little interest at this time. Will the 400 cut out RTTY? The other configuration I was considering was the 500 and the 250 but hadn't added the filters to my order yet as I was trying to make up my mind but comments here aren't really helping with my decision. Thanks es 73, de Jim KG0KP ----- Original Message ----- From: "Bill W4ZV" <[hidden email]> To: <[hidden email]> Sent: Wednesday, May 28, 2008 6:23 AM Subject: Re: [Elecraft] SV: Getting Ready For The 2nd RX Lennart Michaëlsson wrote: > > > ... and what filters do the test pilots recommend? > Presently I have 6, 2.8, 0.4 and 0.25 kHz - all being 8 pole. > > One more issue Len. In your example above, you should only use diversity in the WIDTH range where identical filters will be in use. You would want to avoid using diversity with bandwidths where you would have filters of two different bandwidths in use (e.g. above 2800 and below 400). BTW, on another issue, I assume you know the 250 Hz is actually ~370 Hz and the 400 is actually ~435 Hz according to measurements provided by Elecraft: http://www.zerobeat.net/mediawiki/index.php/K3_Roofing_Filters If it were me, I might consider removing the 250 while you have the radio open to do the KRX3 installation. You could sell it and use the proceeds to help pay for the second 400 to use in the KRX3. There is so little difference in actual BW between the "400" and "250" that I believe having both may be redundant. 73, Bill -- View this message in context: http://www.nabble.com/Getting-Ready-For-The-2nd-RX-tp17504714p17510519.html Sent from the Elecraft mailing list archive at Nabble.com. _______________________________________________ Elecraft mailing list Post to: [hidden email] 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: [hidden email] 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 |
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Here are the options you are considering: 400 and 250: A waste of money IMHO. Since the 400 is actually 435 and the 250 is actually 370, there is only 65 Hz difference in this combination and you'll probably never notice the difference between them (370/435 = only 15% narrower). Total cost $250. 500 and 250: The 500 (actually 565) is a nice BW for contests since you can hear callers who are off-frequency. The 250 (actually 370) is 35% narrower so you'll notice a little more difference than above. Total cost $225. 500 and 200 (mine is ~210 Hz): This is my choice. I like the 500 since it is "wide enough" for off-frequency callers and yet the 200 is great for severe contest QRM situations like the bottom end of 40m was during CW WPX or 160m during one of the 160 contests. Having used the 200 in several 160 contests, I wouldn't consider being without it. Total cost $200. RTTY/PSK considerations: I'll let someone else address since I don't use either. Diversity considerations: If you choose 5-pole filters the offsets need to be matched but I believe Elecraft will provide some alternatives for this. For CW filters, it should be possible to split the difference in minor offset differences and any passband shape differences are not as critical as on SSB (i.e. probably not an important consideration for CW filters). IMD differences: Negligible as Inrad, Sherwood and Ten-Tec have previously stated, and as shown in Elecraft's own IMD measurements on the roofing filter page previously cited. You'll probably get N different opinions from N different users so you'll have to decide for yourself! 73, Bill |
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In reply to this post by Lennart Michaëlsson
Lennart Michaëlsson wrote:
> ... and what filters do the test pilots recommend? > Presently I have 6, 2.8, 0.4 and 0.25 kHz - all being 8 pole. > Would a 2.8 and a 0.4 be enough to keep cost down for a non FM/AM man? It depends on what you want to use the 2nd receiver for. I am primarily interested in using it for finding the correct spot in a CW pileup to call a DX station, so I will mostly be using a relatively wide bandwidth. Therefore I chose to use a single 2.8 kHz filter in the sub (I have 400 Hz, 1 kHz and 2.8 kHz in the main rx). I am also interested in experimenting with diversity reception. If I were to do this seriously I might want another 400 Hz to match the one in the main. Also, for diversity reception it's best for the filters to have the same offsets (which is why I swapped the 2.7 in sub receiver for a 2.8 to match the one in my main rx). -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco _______________________________________________ Elecraft mailing list Post to: [hidden email] 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: SV: Getting Ready For The 2nd RX
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In reply to this post by Bill W4ZV
> >Lennart Michaëlsson wrote: > > > > > > ... and what filters do the test pilots recommend? > > Presently I have 6, 2.8, 0.4 and 0.25 kHz - all being 8 pole. > > > > I am getting only the standard 2.7 for my second receiver. You can use the DSP to narrow the response to whatever you need even though you only have the 2.7 "roofing" filter installed. The DSP works so well in this way on the K3 I have at present that I see no reason to spend money on a narrower filter to be used in an _auxiliary_ receiver. Jerry W4UK _______________________________________________ Elecraft mailing list Post to: [hidden email] 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: K3 Filter selection
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In reply to this post by hf4me
I have the 400/200 and have been happy with it for CW and digital modes,
though I added the 1KHz for CW tuning and wide digital modes (not RTTY). Leigh/WA5ZNU Jim Miller wrote: > I keep seeing talk of the 400(435) or 500 combined with the 250(370). I see > very little talk about the 200. My thought was to use the 400 and the 200. > Maybe the decision should include the 500/200 combination. _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by Bill W4ZV
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Re: SV: Getting Ready For The 2nd RX
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In reply to this post by Lennart Michaëlsson
On Wed, May 28, 2008 at 11:49 AM, Bill Tippett <btippett at alum.mit.edu> wrote:
Elecraft will eventually publish some instructions regarding 5-pole filters for diversity, but my understanding is that the peak variation between 500 Hz filters is a maximum of 50 Hz. My guess is that they'll simply tell us to split the difference on the 500s and not worry about it. If the 200 Hz has total variation of 50 Hz, then it might require more careful matching (since 50/210 is a significant percentage of total BW), but I've not seen any variation numbers on the 200 yet. Bill, The variation in filter offsets must be larger than you think. My KFL3A-500 has an offset of -0.75 kHz, which is 90-100 Hz higher than the values cited by Orin. The offset of my KFL3A-200 is -0.95 kHz, which oddly enough matches the offset of my KFL3A-2.7K, not that it matters. Thanks for the heads up on filter matching for diversity receiving. 73, Gary, N7IR _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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The 50 Hz total variation I quoted for 500 Hz filters came directly from Wayne N6KR so I'm sure Elecraft will look at this more carefully before giving us some guidance. In some cases it may be necessary to return or exchange filters, but in others (like Orin's) that will probably be unnecessary. Note that it's not as critical that both RX filters be matched between bandwidths (e.g. a 2.7k and 500) as within bandwidths (e.g. one 500 to the other 500). Also remember if you aren't planning to use diversity, it makes no difference at all as long as you don't assign both RXs to the same VFO frequency. 73, Bill |
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In reply to this post by Gary Hembree
Now I'm curious.
When I installed my 400 Hz filter, it had no offset info on it. Is this normal? 73, Bob N6WG K3 #811 ----- Original Message ----- From: "Gary Hembree" <[hidden email]> To: "elecraft" <[hidden email]> Sent: Wednesday, May 28, 2008 10:52 AM Subject: Re: [Elecraft] SV: Getting Ready For The 2nd RX On Wed, May 28, 2008 at 11:49 AM, Bill Tippett <btippett at alum.mit.edu> wrote: Elecraft will eventually publish some instructions regarding 5-pole filters for diversity, but my understanding is that the peak variation between 500 Hz filters is a maximum of 50 Hz. My guess is that they'll simply tell us to split the difference on the 500s and not worry about it. If the 200 Hz has total variation of 50 Hz, then it might require more careful matching (since 50/210 is a significant percentage of total BW), but I've not seen any variation numbers on the 200 yet. Bill, The variation in filter offsets must be larger than you think. My KFL3A-500 has an offset of -0.75 kHz, which is 90-100 Hz higher than the values cited by Orin. The offset of my KFL3A-200 is -0.95 kHz, which oddly enough matches the offset of my KFL3A-2.7K, not that it matters. Thanks for the heads up on filter matching for diversity receiving. 73, Gary, N7IR _______________________________________________ Elecraft mailing list Post to: [hidden email] 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: [hidden email] 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: SV: Getting Ready For The 2nd RX
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Yes. All of the 8 pole filters have a zero offset.
Its the 5 pole filters that have varying offsets. 73, Eric WA6HHQ ----- Bob Tellefsen wrote: > Now I'm curious. > When I installed my 400 Hz filter, it had no > offset info on it. Is this normal? > 73, Bob N6WG > K3 #811 > > _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by hf4me
My choice:
Main RX: 2.7 / 2.1 / 500 / 200 Sub RX : 2.7 / 400 73 Arie PA3A _______________________________________________ Elecraft mailing list Post to: [hidden email] 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: SV: Getting Ready For The 2nd RX
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In reply to this post by Jerry Flanders
I have a somewhat similar philosophy. I ordered the second receiver
without additional filters. When/if Elecraft introduces their variable-bandwidth CW filter I will order one to replace the 500 Hz filter I now have in the main receiver, and put the 500 Hz filter in the second receiver. Al N1AL On Wed, 2008-05-28 at 08:34, Jerry Flanders wrote: > > > >Lennart Michaëlsson wrote: > > > > > > > > > ... and what filters do the test pilots recommend? > > > Presently I have 6, 2.8, 0.4 and 0.25 kHz - all being 8 pole. > > > > > > > > I am getting only the standard 2.7 for my second > receiver. You can use the DSP to narrow the > response to whatever you need even though you > only have the 2.7 "roofing" filter installed. The > DSP works so well in this way on the K3 I have at > present that I see no reason to spend money on a > narrower filter to be used in an _auxiliary_ receiver. > > Jerry W4UK > _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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In reply to this post by Bill W4ZV
Bill W4ZV wrote:
> > 400 and 250: A waste of money IMHO. Since the 400 is actually 435 and the > 250 is actually 370, there is only 65 Hz difference in this combination and > you'll probably never notice the difference between them (370/435 = only 15% > narrower). Total cost $250. I think you are generalising from a single sample. It may well be the case that to guarantee a bandwidth of at least 250 Hz, without doing expensive select on test procedures for the capacitors, one will have some samples at 370 Hz. What you may be getting is 250Hz with a given shape factor, but individual units may achieve that shape factor by going flat to a higher frequency and then cutting off much more sharply. -- David Woolley "The Elecraft list is a forum for the discussion of topics related to Elecraft products and more general topics related ham radio" List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm> _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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David and All,
Not necessarily! I think Bill is pretty much on point since that is the posted spec for the 250 hz filter (not just some random test). I am led to believe these filters do not vary widely in manufacturing. So it would appear that a 400 hz/250 hz combinations is not a particularly good combination. The 200 hz may well be a better choice if you want to go that narrow. I have the 400 hz/200 hz combination, but I find I don't use the 200 hz filter nearly as much as I thought I would. I think that is primarily due to the fact I just don't seem to need to go that narrow, which speaks well for the K3 generally. I have used narrow filters a lot in other radios, but those were audio filters, not roofing filters. The DSP in the K3 seems to provide just about any additional filtering I need while using the 400 hz filter. Digital ops may actually find the 200 hz filter more useful. But I haven't really given my K3 a good baptism under contest fire. I missed the CQ WPX contest last week, and that would have been a great test for the narrow filter I think. I can also tell you from my experience that you need to set the 200 hz filter (and presumably the 250 hz filter) up with more gain added than they recommend in the manual. There seems to be a very noticeable reduction in signal level when the 200 hz filter is engaged. I believe this is on the "to do" list that Wayne has--to improve this signal level issue. I think Bill has analyzed the filter combination issue more than just about anyone. You may want to go back through the archives and read some of his prior posts to get some good insight about selecting various filter combinations. He may not be "the last word" on the subject, but I think it will give you added perspective. Dave W7AQK ----- Original Message ----- From: "David Woolley (E.L)" <[hidden email]> To: <[hidden email]> Sent: Thursday, May 29, 2008 3:03 AM Subject: Re: [Elecraft] K3 Filter selection > Bill W4ZV wrote: > >> >> 400 and 250: A waste of money IMHO. Since the 400 is actually 435 and >> the >> 250 is actually 370, there is only 65 Hz difference in this combination >> and >> you'll probably never notice the difference between them (370/435 = only >> 15% >> narrower). Total cost $250. > > I think you are generalising from a single sample. > > It may well be the case that to guarantee a bandwidth of at least 250 Hz, > without doing expensive select on test procedures for the capacitors, one > will have some samples at 370 Hz. > > What you may be getting is 250Hz with a given shape factor, but individual > units may achieve that shape factor by going flat to a higher frequency > and then cutting off much more sharply. > > -- > David Woolley > "The Elecraft list is a forum for the discussion of topics related to > Elecraft products and more general topics related ham radio" > List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm> > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > 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: [hidden email] 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 |
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In reply to this post by David Woolley (E.L)
> I think you are generalising from a single sample. No, that is INRAD's own specification and is found in the filter curves on both their web site and in the 8 pole curves on the Elecraft site. The same was true with the Fox Tango filers before the filter line was acquired by W2VJN many years ago. All of the filers are slightly wider than "nominal" so that the effective bandwidth of two cascaded filters (e.g., 8 MHz and 455 KHz) is approximately nominal. Unfortunately, the 8 and 9 MHz filters in particular are significantly wider than the notational value in the narrow values - more than necessary to maintain the desired bandwidth in cascade. 73, ... Joe, W4TV > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of David > Woolley (E.L) > Sent: Thursday, May 29, 2008 6:04 AM > To: [hidden email] > Subject: Re: [Elecraft] K3 Filter selection > > > Bill W4ZV wrote: > > > > > 400 and 250: A waste of money IMHO. Since the 400 is actually 435 > > and the 250 is actually 370, there is only 65 Hz difference in this > > combination and you'll probably never notice the difference between > > them (370/435 = only 15% narrower). Total cost $250. > > I think you are generalising from a single sample. > > It may well be the case that to guarantee a bandwidth of at > least 250 > Hz, without doing expensive select on test procedures for the > capacitors, one will have some samples at 370 Hz. > > What you may be getting is 250Hz with a given shape factor, but > individual units may achieve that shape factor by going flat > to a higher > frequency and then cutting off much more sharply. > > -- > David Woolley > "The Elecraft list is a forum for the discussion of topics related to > Elecraft products and more general topics related ham radio" > List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm> _______________________________________________ Elecraft mailing list Post to: [hidden email] 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 |
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