Filters
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I am thinking about a K3 for RTTY. What do you think the best filter
configuration should be.
Thanks,
Bruce
W4LWW
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We had good success this week end in the ARRL RTTY RU with the 500 hz
roofing filter and a DSP setting of 300 hz most of the time. At times we went to 250 hz. and used the 250 hz roofing filter when the going really got tough. We are talking about a serious effort to win # 1 which we have done in the past but most years we are second or third multi-op. You really did not say if it is for RTTY general contacts, chasing DX or contesting? That is the key question! If it is the first two then a 500 hz roofing filter and and use the DSP to narrow down more when wanted would be all you need. The 500 hz with DSP would be fine for CW as well. If you want to contest on CW and RTTY then adding the 250 hz roofing filter is worth having. For CW if you want the ultimate then also adding the 200 khz roofing is great for contest CW and will work in a huge pileup on RTTY even though it rolls off the edges. We did use it a fair amount this week end. If you are not seriously into CW contesting but want to do some serious RTTY contesting the most you need it the 250 hz roofing filter. It is far two early to say but we did not seem to be able to see an advantage to the Dual PB but like I say we tried it some and could see no improvement and a couple of times we thought we seen it was worse so we quit using it. Howeverthis was a quick gut feeling decision made in the midst of the competition so we may ultimately find it is OK. Future firmware updates may make it more effective. Using two K3's in some serious contest efforts this season starting with the IARU with a number of top 10 finishes according to unofficial results I have to back up what has been said on the users group many times and that is "IF" you are not in some very serious and I mean serious contest efforts with extreme crowding and big signals there is ABSOLUTELY no need to spend a lot of money on filters!!! One for SSB, the one that comes with the radio is excellent and a 500 hz roofing filter for CW and RTTY is absolutely all you need and use the DSP! I can guarantee this to be true! I am of course assuming you don't want to do FM and AM. Ed W0SD _______________________________________________ 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 Bruce Kryder
On Mon, 5 Jan 2009 20:12:46 -0600, Bruce Kryder wrote:
>I am thinking about a K3 for RTTY. What do you think the best >filter configuration should be. I'm quite pleased with the 400 Hz filter. A very good choice for both CW and RTTY contesting. If you're REALLY serious, pay attention to what W0YK has to say on this. He's a top RTTY contester, uses K3s, and reads this list. He will likely comment. 73, Jim K9YC _______________________________________________ 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 Ed Gray W0SD
very Serious Ed ? ;o)
The 500 Hz filter is very nice and worth the investment to take the edge off a crowded band like 160, 40 or 20 during any of the "major" CW contests. I do agree that the DSP filtering is amazingly effective, but having the 500Hz filter kicking in during ARRL 160 noticeably cut some of the overpowering adjacent signals down to a more manageable rumble. It will be interesting to see how many folks were using K3s and made the top 10 in the 2008 contests. I wouldn't be surprised if it was close to half in many categories. Thanks for keeping one of the tough states active! CU in NAQP this weekend. 73, Julius n2wn
Julius Fazekas
N2WN Tennessee Contest Group http://www.k4ro.net/tcg/index.html Tennessee QSO Party http://www.tnqp.org/ Elecraft K2 #4455 Elecraft K3/100 #366 Elecraft K3/100 |
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In reply to this post by Bruce Kryder
> I am thinking about a K3 for RTTY. What do you think the best filter
> configuration should be. Here is the post I made to the RTTY reflector yesterday in response to the same question ... > I'm considering purchasing a K3. Which filter do I want for RTTY > (both DX & contesting)? 200 Hz 5-pole or 250 Hz 8-pole? Or is there > some other configuration I should consider? Between those two, the so-called 250 Hz 8-pole filter. Some things to consider: 1. The primary IF filtering the K3 is done via the continuously adjustable DSP. The crystal filters in the K3 are designed to be wider than the DSP filter bandwidth to protect the DSP from very strong signals nearby that would otherwise keep the DSP from doing its job. Don't think of the K3 crystal filters like IF filters in older radios. They are more like "roofing filters" which used to be on the order of 15 kHz and in modern radios are going down into CW bandwidth. Still, their purpose is to protect the DSP, not be the radio's only filter. 2. The 200 Hz 5-pole filter is about 224 Hz wide. The 250 Hz 8-pole filter is nominally 370 Hz wide. The 400 Hz 8-pole filter is 435 Hz wide. The 500 Hz 5-pole is about 530 Hz. Any of the three widest filters are great for RTTY. They are essentially the same for the purpose they are intended. 3. Generally, 300 Hz is a good bandwidth for completely passing a 170 Hz shift RTTY signal, assuming you are centered in it. Operationally, I've found that a 200 Hz bandwidth works great in huge pile-ups because it passes the fewest signals that are still good enough for the decoders. Yes, the outer skirts of the two frequencies are rolled off, but the trade-off is less signals presented to the decoders, assuming they are not all perfectly zero-beat. Turns out to be a net win in heavy pile-up conditions. 4. The DSP filter is used to vary between 300 and 200 Hz as conditions warrant. If you use the Dual-Tone Filter, also a DSP constructed filter, it effectively narrows the bandwidth to about 200 Hz anyway, regardless of where you set the main DSP filter. I operated the entire Round-Up with a 370 Hz crystal filter (marketed as "250 Hz 8-pole"), 300 Hz DSP and the DTF. So my effective bandwidth in both K3s was about 200 Hz and it was protected by a 370 Hz roofer. If the pileups had been smaller (no thanks!) or if I had the opportunity to tune around more (running both radios is good when you can do it), then I would have possibly turned off the DTF and used a 300 Hz bandwidth. But, even the limited tuning around I did do, was not hampered by the 200 Hz filtering. Ed - P49X (W0YK) _______________________________________________ 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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