+++++++++++++++++++ See Also KAF2_Notes +++++++++++++++++++ Date: Thu, 6 Sep 2001 17:02:26 EDT From: JohnK1JD at aol.com Subject: [Elecraft] 'Real World' KAF2 experience Got a chance to try the KAF2 (part of the FT effort) in earnest this afternoon while working TA1A on 14025. QRM made copy extremely difficult even in the 100Hz XFIL position. Switching in AFIL (AF2) made a DRAMATIC difference in my ability to pull him out of the mess, and I was able to succcessfully complete the QSO. I'm impressed! 73, John K1JD Jamestown, RI IOTA NA31 K2's #139 & #583 ++++++++++++++++++++++ Date: Sun, 9 Sep 2001 17:43:12 -0400 From: Gilbert J Cross Subject: [Elecraft] KAF2 And New Firmware Wayne , Eric , Just a line to say that I have installed my KAF2 and new firmware and think its just great. Calibration is on the nose. Do you fellows ever get to the Orlando Hamfest? Perhaps the coming one this spring. Thanks for all the fun!!!!!!!! Gil K8EAG +++++++++++++++++++++++++ Date: Sun, 9 Sep 2001 21:33:16 -0500 From: "Jack Scheinuk" Subject: [Elecraft] KAF2 a Winner I installed my KAF2 in #2197, and the option is a terrific addition to the rig. In terms of yesteryear one can tune other signals as if they were "clear channel" stations. 73 - Jack W5WSF Jack Scheinuk, P.E. 7927 Maple St., New Orleans LA 70118 Tel: 504-866-1221 - Fax: 504-866-1258 ++++++++++++++++++++++ Date: Mon, 17 Sep 2001 08:32:39 -0400 From: "Mark J. Dulcey" Subject: Re: [Elecraft] KAF2 w/ XFIL? Bill Allen wrote: > Hey gang, > > For those who are couple steps ahead of me and have actually finished and > installed their KAF2, what has been your experiences in using the KAF2 in > conjuction with XFIL? Any caveats or procedural suggestiions? With CW? > With SSB? My experience has been that using AFIL1 with any narrow CW filter setting (700Hz or less) is a worthwhile improvement - it tightens up the skirts and takes out some broadband noise. AFIL2 rings some, so I reserve it for really severe conditions. (The same is true of the 100Hz setting of the crystal filter.) AFIL1 + 700Hz is a nice combo for scanning the band under contest conditions. (I use OP1 for band scanning when there is no contest going on.) AFIL1 also seems to be occasionally useful for SSB reception, used along with the OP1 SSB filter. Unnatural-sounding, due to the rather severe high frequency rolloff, but actually usable. AFIL2 completely mangles SSB. My KAF2 is set up for a center frequency of 500Hz, which is my preferred sidetone frequency setting. The SSB results, in particular, may vary if yours is set up for a different frequency. +++++++++++++++++ Date: Mon, 24 Sep 2001 20:45:08 -0500 From: "Bill Allen" Subject: [Elecraft] KAF2 - a real winner! Hey Gang, The KAF2 is a real winner! I am really amazed at the job it does in cleaning up and emphasizing a well spotted CW signal. So much of the atmospherics are completely gone, the hiss is GONE, and to top it off the audio gain is improved. I love it! I have only played with it a little bit with SSB, but will relate what I found on that front as well. On SSB, AF1 seems useful, testing it on 80m now, but AF2 makes the signal too muddy - the band pass is just too tight there I guess. However on AF1, SSB is clearly brought out from the strong atmospheric static and such and will be useful. In fact, AF1 with a FL at 1.80 sounds really nice on SSB! Yes, the audio is down this way compared to using OPT1, but the static is many magnitudes down from the audio itself so the overall audio does not have to be nearly as loud to understand the SSB signal. However, on CW the KAF2 really shines! I am finding that I am not having to use the preamp nearly as much. I would recommend to any new K2 builder that they get this one of their first add-ons after the initial kit is built, especially if they are going to be working CW. It REALLY helps! :-)) Now, I need to try this thing on PSK31... ;-)) 72 es OO Bill Allen, KC5ADF ++++++++++++++++ Date: Wed, 26 Sep 2001 23:12:06 -0700 From: Phil Wheeler Subject: Re: [Elecraft] KAF2 - a real winner! Yes, the KAF2 is a great addition. I found I had to redo my CAL FIL fr best results. I used Spectrogram .. and found "graphically" that you cannot do CAL FIL with 'Gram with the KAF2 in the narrow filter mode. Duh :-; 73, Phil +++++++++++++++++ Date: Tue, 09 Oct 2001 20:49:34 -0600 From: Larry East Subject: [Elecraft] Praise for the KAF2 I assembled the KAF2 AF Filter / Real Time Clock board last week. It went together quickly and worked on the first try! The narrow audio filter is really great! Here are some measurements that I made using my trusty old HP 403B AF Voltmeter on the K2 audio output: IF filter setting: 150 Hz With preamp ON, switching in AF2 reduced the background noise by 2 dB and boosted the desired CW signal by 2 dB for an apparent 4dB improvement in the S/N. With the preamp OFF, switching in AF2 reduced the background noise by 6 dB (!) and also boosted the desired signal by 2dB. Does this really mean an increase of 8dB in the S/N? I'm not sure -- I'll have to borrow my friend's calibrated signal generator and measure the MDS with and without AF2. - - - - - - - - - I don't see any real need to select one or two stage of narrow filtering, so I opted to install the jumper so that my AF filter settings are AF2 and OFF. The LP filter also produces a significant reduction in HF background noise when using wide SSB filters. But since I can't hear much of anything above 5 kHz, the HF noise never bothered me very much anyway... -- snip -- 72/73, Larry W1HUE/7 +++++++++++++++++++ Date: Wed, 31 Oct 2001 19:51:07 -0800 From: "N7SG K7FD" Subject: [Elecraft] KAF2/AF1 on SSB Although not designed for SSB reception, you can push the envelope and use AF1 while on phone. Tonight was a good example. I was trying to listen to a net on 3.768MHz only to be blown off the band by a 25db over nine signal on 3.770MHz. Amazingly, with the AF1 pushed in, I was back in business & all but eliminating the splatter from '70'. Of course the fidelity was compromised but the intelligence was not...in a pinch, when the going gets tough, try AF1 on SSB! Happy Halloween! But take it easy on the boo's... 73 John K7FD Overheard: "Hams do it until their gigahertz!" +++++++++++++++++++++++++++ Date: Thu, 01 Nov 2001 20:15:55 +0100 From: Heyder.Family at t-online.de (Norbert Heyder) Subject: [Elecraft] Impressive KAF2 performance! After a long waiting period (over 2 years) the audio filter option finally arrived this week. Till now I used an external analog filter which works well for my purposes except the fact that it is an additional external unit which requires its own power supply, cable wiring etc. And I always felt the K2 to be somewhat incomplete without a built in AF with a similar performance like my external one. May be I'm not with the majority but for me, a QRP-TRX providing a built in audio filter is more important than a serial interface or a PA. I know, there are different views. The KAF2 came with the latest Rev. 2 firmware and was kitted within a few hours. No problem to build, everything works fine at the first try. Must say that my focal point is CW (using headphones of course). The performance of this filter is really impressive! It is best demonstrated by switching the filter in and out with the provided switch on the filter's board, BTW a nice demonstrating procedure step in the manual ;-) I trimmed both bandpass stages well to maximum at 600Hz with the help of a stable carrier and a (real) scope. If you ever need a moderate stable carrier, instead of the weak one on 7.0Mc, you can take benefit from the 4.0 Mc signal of the K2's CPU clock which produces a clear S9 signal. With the KAF2 I can forget the preamplifier on most bands, perhaps except on 12/10M. The difference is most noticable when digging out really weak CW signals with noise and QSB - which would not be readable without the AF! In most such worstcase circumstances the signal really becomes readable with the KAF2 in its narrow bandpass stage. When hunting for CW signals by tuning witin a CW bandsegment I use a moderate IF-Bandwidth (say 1.7kc) combined with AF2 (the narrow stage). This combination really "emphasizes" even gentle CW sigs while turning the VFO knob slowly. Now it means even more joy to listen/search to weak CW sigs! Also for SSB audio sigs the difference by the lowpass stage is amazing. I always thought the K2 already has a quiet receiver but the KAF2 makes the remained background noise even quieter with a wide IF setting. If you like fishing for weak, almost unreadable, sigs with QSB, noise etc. this audio filter is a must have! No need to say that the KAF2 has replaced the external analog filter. Thank you Elecraft team for this really useful, already enough promised been, option! The usual disclaimer: I'm not an Elecraft shareholder, I'm just a happy, satisfied K2 owner/operator. Now back to the headphones ... 72 de Bert DL8BDF K2 #433 +++++++++++++++++++ Date: Fri, 2 Nov 2001 17:22:41 +0100 From: "M. van Wijk" Subject: [Elecraft] KAF2 compared to internal DSP/outboard DSP Hi, This KAF2 Low Noise Audio Filter works superb!!!! Enabling the circuitry (internal switch on pcb) results in a small s/n ratio enhancement as the low pass filter cuts off the small left amount of high freq. hiss from the lf amplifier. Switching the filter on AF1 or even smaller AF2 truly works very effectively for CW. Comparing this with the internal DSP from my FT1000MP or the external MFJ 748B shows the following: - - Both the DSP's and the KAF2 effectively cut out nearby interfering signals. - - When setting to the smallest bandwidth 80Hz on the K2 and both 60Hz on the MP and MFJ, the DSP's suffer from some minor signal loss which is significant on weak signals. The MFJ has a switchable AGC here which again pumps up the incoming signal, but the input signal level has to be tracked continuously to avoid distortion. On very weak stuff the MP's internal DSP looses a bit on readability. - - The KAF2 audio filter, as a typical LF high order filter not only narrows bandwidth but the Q factor also swings up the signal. The enhancement works like the 'audio peaking filter' from vintage transceivers but without any ringing effects. - - The K2 simply pulls out weak CW signals from the noise which is a must for those using the K2 as an IF transceiver in conjunction with a transvertor on VHF/UHF. Thanks for superb engineering. '73 Mark, PA5MW #2036 ++++++++++++++++++++ From: "David Gropper" To: "Peter Schuyffel" , Subject: Re: [Elecraft] KAF2 audio filter/clock module Date: Tue, 15 Apr 2003 17:28:51 -0700 Peter, IMHO - the KAF2 works fantastically on CW!! Almost to single signal level.... Dave KK7SS K2 #3003 From: "Peter Schuyffel" > I have a K2 transceiver and operate mainly CW, would > it be an advantage to install the KAF2 audio filter/ > clock module. ++++++++++++++++++++++ From: WJuergens at t-online.de (Wolf-Ruediger Juergens) Organization: privat To: elecraft at mailman.qth.net Subject: Re: [Elecraft] K2Z - Anybody know reason for K2 RTC Update Delay?? Date: Thu, 17 Apr 2003 15:30:36 +0200 Am Donnerstag, 17. April 2003 14:45 schrieb Tony Wells: > I'm not concerned about delays in updating the RTC display. I'm talking > about delays in the RTC display appearing after the DISPLAY button is > pressed. I think this is normal, my K2 shows the same behavior. To display the time at first the main micro send the command to the slave that the slave should read from the realtime clock. After that the slave sends the clock and date informations to the main micro. After converting to a human readable format the main micro displays the date and time. This takes about 1 second because the refresh rate is 1 second. I assume this is correct as I dont have programmed the Pics, at least I would had programmed it, like I have described. :-) 72 de Wolf, DL2WRJ K1 #1136, K2 #2857 ++++++++++++++++++++