K2 RTTY
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How well does the K2 work in RTTY mode? I presume it is AFSK only? I
seem to recall that some do not recommend the K2 for serious RTTY operating but I don't remember the reasoning behind this. I vaguely recall reading this about 2 years ago from somewhere. I'm a RTTY operator first then SSB. I've never been good with CW and probably never will so I focus on these two modes. I know it's a poor attitude but let's just not go there, at least I am honest about it. Most of my RTTY operation is centered around contest weekends simply because I can only operate portable due to antenna limitations at the home QTH. However, I am not a hardcore contester. I merely operate during the contests to maximize QSO numbers although getting a good score never hurts. Around August, I'm finally going to be able to upgrade to something in the K2 price range. Will the K2 be acceptable for the way I operate RTTY or should I hold out for a K3? I know the K3 will be a much better data rig. I can't really afford a K3 but I could probably make it happen. Thanks guys. - JT _______________________________________________ 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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JT,
There is nothing wrong with AFSK - in fact, if the carrier balance on the KSB2 board is adjusted correctly, AFSK is indistinguishable from FSK. The only 'problem' with the K2 is that the BFO range is limited, with the result that narrow filters cannot be set with a center frequency equal to the 'true RTTY' tones. MTTY and other soundcard RTTY programs offer a selection of tone frequencies - so if you align your narrow RTTY filters to at 800 or 1000 Hz, MTTY can accommodate that center frequency. When I set up RTTY filters on a K2, I set the FL1 filter the same as the SSB filter and then set FL2 at 1.00 kHz, FL3 at 0.70 and FL4 at 0.400. The narrow filters are centered at either 1000 Hz (or 800 Hz if the BFO range will not accommodate 1000 Hz for the 0.40 filter on both sidebands). In operation, the RTTY signal is tuned to center on 1000 Hz (or 800 Hz) and the program will decode the signal - transmission will occur at the same offset and noone on the receiving end will know whether you are using real FSK or AFSK. So the short answer is: the K2 will operate just fine on RTTY, and yes, you can use narrow RTTY filters to minimize the QRM. 73, Don W3FPR John Tobias Croteau wrote: > How well does the K2 work in RTTY mode? I presume it is AFSK only? I > seem to recall that some do not recommend the K2 for serious RTTY > operating but I don't remember the reasoning behind this. I vaguely > recall reading this about 2 years ago from somewhere. > > I'm a RTTY operator first then SSB. I've never been good with CW and > probably never will so I focus on these two modes. I know it's a poor > attitude but let's just not go there, at least I am honest about it. > Most of my RTTY operation is centered around contest weekends simply > because I can only operate portable due to antenna limitations at the > home QTH. However, I am not a hardcore contester. I merely operate > during the contests to maximize QSO numbers although getting a good > score never hurts. > > Around August, I'm finally going to be able to upgrade to something in > the K2 price range. Will the K2 be acceptable for the way I operate > RTTY or should I hold out for a K3? I know the K3 will be a much > better data rig. I can't really afford a K3 but I could probably make > it happen. > 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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I've decided to take the plunge into digital modes and 'found' the RTTY mode (and extra set of filters) in the SEC menu. There is still much about my 1 year old K2 that I'm still finding out. What a radio!
When I went in to set the filters in RTTY mode and decided to check the SSB filters as well. Using Spectogram, I cannot ajust anything to make the 300 cycle point at -60 db down. I CAN adjust it such that it is -60 db down at 2500 hz. There appears to be no low frequency roll-off at all. Adusting the BFO moves the high frequency point; it does not move the low frequency point. My setup: K2# 6110. AF option is OFF and switched out of the circuit. I'm using the External Speaker Output to drive the sound card. I don't see this porblem with the CW filters. Is this normal? Received SSB signals sound fine. 73, Clark KE4RQ
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I hope the group will pardon me while I engage in a bit of RTTY heresy.....
When you use a PC sound card for decoding RTTY, the center frequency is no longer important, just the tone spacings. With MTTY, I can pick any center frequency I want to use (typically 1000 Hz so I stay away from the roll-off) and tune until I see it in the MTTY spectrum window. I make any fine adjustments with the cursor to pick the signal I want if there are multiple signals shown. If I want a bandpass filter, I use the bandpass function in MTTY. MTTY uses the same audio frequency for encode as it used for decode so the signal is inherently locked to the received signal. It even has an AFC function to track any drift. Using just the SSB filter for receive and transmit avoids the problem of center frequency tracking between the SSB filter that is always used on transmit and whatever receive filter has been selected. It also has the advantage of allowing you to hear what is happening across the audio bandwidth so you know whether to go higher or lower for the next signal. Very useful in a contest. I use Writelog with the MTTY decoder for contests and the whole setup works very well. Using the mouse wheel for tuning and macros for the exchange, I rarely touch the K2 at all. Hope this helps. 73 Logan, KZ6O -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Clark Macaulay KE4RQ Sent: Thursday, September 04, 2008 7:39 PM To: [hidden email] Subject: Re: [Elecraft] K2 RTTY I've decided to take the plunge into digital modes and 'found' the RTTY mode (and extra set of filters) in the SEC menu. There is still much about my 1 year old K2 that I'm still finding out. What a radio! When I went in to set the filters in RTTY mode and decided to check the SSB filters as well. Using Spectogram, I cannot ajust anything to make the 300 cycle point at -60 db down. I CAN adjust it such that it is -60 db down at 2500 hz. There appears to be no low frequency roll-off at all. Adusting the BFO moves the high frequency point; it does not move the low frequency point. My setup: K2# 6110. AF option is OFF and switched out of the circuit. I'm using the External Speaker Output to drive the sound card. I don't see this porblem with the CW filters. Is this normal? Received SSB signals sound fine. 73, Clark KE4RQ <snip> _______________________________________________ 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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Logan,
What you say is true and quite workable *except* for the times when there is a strong undesired signal inside the IF passband. That strong signal takes over the AGC and reduces the receive gain causing all signals (including your desired signal) to become weaker. The solution is to set up the RTTY set of filters so one can narrow the receive IF bandwidth when a strong undesired signal is present. I set the RTTY filter widths as follows: FL1 = OP1; FL2 = 1.00; FL3 = 0.70; and FL4 = 0.40. I use Spectrogram to center the narrow filters at 1000 Hz (you can simply copy the SSB FL1 BFO frequencies to the RTTY FL1 settings. In use, tune the desired signal using the K2 VFO to the vicinity of 1000 Hz (your narrow filter center) and enjoy the QSO. Should an undesired signal enter the passband, you may switch to a narrow filter to reduce the AGC pumping effect. A great advantage for using the RTTY filter set instead of the SSB filters for data modes is that there is a compression setting independent of the SSB compression setting - you can use any compression for SSB and set the RTTY compression to 1:1 for best transmit IMD. The only problem with this approach is that there may be a slight shift in the audio frequency of the received signal when you change to a narrow filter (up to 20 Hz). One can easily counter that shift by clicking on the "Lock Transmit Frequency" in the software before switching filters - that will keep the QSO from 'walking the band'. 73, Don W3FPR Logan Zintsmaster wrote: > I hope the group will pardon me while I engage in a bit of RTTY heresy..... > > When you use a PC sound card for decoding RTTY, the center frequency is no > longer important, just the tone spacings. With MTTY, I can pick any center > frequency I want to use (typically 1000 Hz so I stay away from the roll-off) > and tune until I see it in the MTTY spectrum window. I make any fine > adjustments with the cursor to pick the signal I want if there are multiple > signals shown. If I want a bandpass filter, I use the bandpass function in > MTTY. MTTY uses the same audio frequency for encode as it used for decode > so the signal is inherently locked to the received signal. It even has an > AFC function to track any drift. > > Using just the SSB filter for receive and transmit avoids the problem of > center frequency tracking between the SSB filter that is always used on > transmit and whatever receive filter has been selected. > > It also has the advantage of allowing you to hear what is happening across > the audio bandwidth so you know whether to go higher or lower for the next > signal. Very useful in a contest. > > I use Writelog with the MTTY decoder for contests and the whole setup works > very well. Using the mouse wheel for tuning and macros for the exchange, I > rarely touch the K2 at all. > > Hope this helps. > 73 > Logan, KZ6O > > 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 Logan Zintsmaster
On Sep 5, 2008, at 1:30 AM, Logan Zintsmaster wrote: > I hope the group will pardon me while I engage in a bit of RTTY > heresy..... > > When you use a PC sound card for decoding RTTY, the center frequency > is no > longer important, just the tone spacings. With MTTY, I can pick any > center > frequency I want to use (typically 1000 Hz so I stay away from the > roll-off) > and tune until I see it in the MTTY spectrum window. I make any fine > adjustments with the cursor to pick the signal I want if there are > multiple > signals shown. If I want a bandpass filter, I use the bandpass > function in > MTTY. MTTY uses the same audio frequency for encode as it used for > decode > so the signal is inherently locked to the received signal. It even > has an > AFC function to track any drift. All this is true for receiving. You can pick just about any center frequency you want. One problem with using the waterfall display and selecting from a wide bandpass is you don't get the level of unwanted signal rejection that is possible when using narrow crystal or DSP filtering. If there is a strong signal adjacent to your desired signal, you may not be able to decode properly. The K2 is equipped with a variable-bandpass filter that works very well on RTTY as it does on CW. In order to use this effectively, you've got to select a particular center frequency and adjust the filters around that frequency. This does require one to "tune in" a RTTY signal, but that is a pretty easy process using the crossed ellipse display. > Using just the SSB filter for receive and transmit avoids the > problem of > center frequency tracking between the SSB filter that is always used > on > transmit and whatever receive filter has been selected. Except that you often don't want to use the SSB filter for receive. I generally use the variable-bandwidth filter set for 1.0 kHz. I also have settings for 0.5 and 0.3 khz. I only use the SSB filter to receive RTTY on a very quiet band. One other consideration -- when you are transmitting, you want only the AFSK signal to fit in the passband. This is the reason traditional RTTY was so high in the audio bandwidth. If you send tones of about 1000 Hz or so, then their second and possibly third harmonics may be transmitted as well. To avoid this, pick frequencies higher in the passband. With the limited BFO ranges on some K2s, it may be hard to center the variable-bandpass filter. I chose 1500 Hz as the center frequency for my RTTY tones for these reasons -- it places the second harmonic outside the passband of the SSB filter. I also chose a whole number as the center frequency so I can bring the DSP passband filters into play. > It also has the advantage of allowing you to hear what is happening > across > the audio bandwidth so you know whether to go higher or lower for > the next > signal. Very useful in a contest. In a contest, I don't want the radio's AGC pumping against nearby signals -- I want those signals rejected -- another reason to use a narrow filter. Bill Coleman, AA4LR, PP-ASEL Mail: [hidden email] Quote: "Not within a thousand years will man ever fly!" -- Wilbur Wright, 1901 _______________________________________________ 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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