am for the k2
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just wondered if am would be possible with the k2 eventually .and if it was how would one go about doing this. have heard a couple am'ers on 80 a couple of times and it seemed awfully hard to copy a qso ,not everyone was on perfect frequency . just a thought
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Sean,
While AM transmit with the K2 would be a MAJOR change, it may be possible to achieve AM receive - I haven't tried it, but D1 on the control board in the AGC section looks a lot like a diode detector that might just be used for AM demodulation. You may want to try connecting an Audio Amplifier to the cathode of D1 and see what happens - the value of C2 may be a bit on the large size for proper operation, so a bit of experimentation may be in order. I think I can assure you that AM transmission is not in the Elecraft product plan - that is for the boat-anchor folks. You were likely hearing some old-time transmitters and some do have a difficult time getting on frequency (by today's standards) and many will drift more than is considered 'state of the art' today. These WERE state of the art transmitters back in the days they were in common use, but what was acceptable then is no longer OK on the ham bands (except in specialized areas). 73, Don W3FPR > -----Original Message----- > > just wondered if am would be possible with the k2 eventually .and > if it was how would one go about doing this. have heard a couple > am'ers on 80 a couple of times and it seemed awfully hard to copy > a qso ,not everyone was on perfect frequency . just a thought > _______________________________________________ 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 know of at least one AM'er I saw online that ised his K2 as a (n expensive)
VFO for this tube transmitter. You won't find AM'ers always "on frequency", as most old vfo's are only accurate to 5kHz (1kHz with Collins). I have thought of playing with AM (tx and rx) with a K1 or K2 when I get one. But I would doubt Elecraft themselves would bother with such endeavors, especially on a rig that is designed to be such a fine CW rig. The issues I think I would encounter are: rx: 1) detection: cut the BFO and perhaps insert a diode detector 2) bandwidth: would have to open up to at least 4kHz tx: 1) modulation: you could just drop a book on the key in CW mode and then you need to modulate with voice, one way might be via series PDM modulation David, K3TUE . --- Don Wilhelm <[hidden email]> wrote: > Sean, > > While AM transmit with the K2 would be a MAJOR change, it may be possible to > achieve AM receive - I haven't tried it, but D1 on the control board in the > AGC section looks a lot like a diode detector that might just be used for AM > demodulation. You may want to try connecting an Audio Amplifier to the > cathode of D1 and see what happens - the value of C2 may be a bit on the > large size for proper operation, so a bit of experimentation may be in > order. > > I think I can assure you that AM transmission is not in the Elecraft product > plan - that is for the boat-anchor folks. You were likely hearing some > old-time transmitters and some do have a difficult time getting on frequency > (by today's standards) and many will drift more than is considered 'state of > the art' today. These WERE state of the art transmitters back in the days > they were in common use, but what was acceptable then is no longer OK on the > ham bands (except in specialized areas). > > 73, > Don W3FPR > > > > -----Original Message----- > > > > just wondered if am would be possible with the k2 eventually .and > > if it was how would one go about doing this. have heard a couple > > am'ers on 80 a couple of times and it seemed awfully hard to copy > > a qso ,not everyone was on perfect frequency . just a thought > > > > _______________________________________________ > 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 Sean Duncan
Sean wrote:
just wondered if am would be possible with the k2 eventually .and if it was how would one go about doing this. have heard a couple am'ers on 80 a couple of times and it seemed awfully hard to copy a qso ,not everyone was on perfect frequency . just a thought ------------------------------------------------ An AM receiver (with a traditional 'envelope detector' such as used before SSB) is fairly broad tuning, just like your AM broadcast band radio. Since the carrier is arriving with the sidebands, there is no critical frequency adjustment at the receiving end. So it's very common for AM stations in a round table to be several hundred cycles apart. Most AM stations would "zero beat" each other upon arriving on the frequency, but it wasn't at all critical to do and a lot of stations are pretty careless. Many of the old glowbug rigs will drift several hundred cycles over a half hour or hour's operating period as well, especially if the rig hadn't warmed up completely when it was put 'on frequency'. Of course, "AM" is simply SSB with the carrier reinserted. Well, it's really both sidebands with a carrier, but it's virtually impossible to tell when one sideband is missing, even on a traditional AM receiver. So one could "unbalance" the balanced modulator to insert carrier, except the carrier is normally outside of the filter bandpass. I don't recommend trying it. Also, AM is much, much less efficient requiring a lot more power dissipation for a given "talk power" than SSB or CW. Even if you could get around the problem of the filter, you'd have to seriously de-rate the K2 for AM. Probably limit yourself to 20 or 25 watts output from a K2/100 or less than 5 watts from a QRP K2. Notice the derating that the few SSB rigs who do offer "AM" indicate. Typically a 100 watt SSB rig will be limited to 25 watts AM or less. That said, the K2 does make a very effective AM receiver. The filters in the K2 eliminate many of the problems associated with AM reception, especially on the short waves. Some of the things AM reception is plagued by include selective fading, in which the small frequency difference between the sidebands and carrier causes their phase to shift dramatically at the receiver after those waves are refracted by the ionosphere. The signal stays strong but the audio becomes hopelessly garbled. Another common difficulty with AM are the heterodynes caused by two or more carriers within the audio bandpass. When AM was the mode of choice for Amateur "phone" it wasn't uncommon to hear two or three strong beat notes on top of a station's audio on a crowded band. By tuning in an AM signal as a SSB signal, many of these issues goes away, especially the one about selective fading. Your SSB receiver is no longer using the other station's carrier or one sideband. The 'carrier' is being generated locally by the BFO, just as in normal SSB reception. My K2 has the SSB filter bandwidth opened up to 2.5 kHz, and with it tuned into a standard broadcast AM station it's hard to tell its sound from a conventional AM receiver. Probably the best way to get on AM is to get a transmitter designed for it, but expect it to be heavy and large. The great reduction in size for transmitters was only in part due to the use of solid state devices. Much of the size reduction came from no longer having to have high-powered audio amplifiers to modulate the carrier or having the large RF amplifiers needed to generate the carrier. Ron AC7AC _______________________________________________ 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 Toepfer
I've been using my K2 as a VFO for my Drake 2-NT for the last several weeks,
including SKN this year. Got quite a few "HUH??" reactions. Hi. You can see what's involved at: http://www.ke6us.com/boatanchors.htm I'm retiring it tomorrow, though. I just finished putting a KD1JV DDS controller, DDS-60 and Keyall in a little sloping case that sits by my straight key. Heresy for try boatanchor fans, but it works. Not sure why anyone would want to put a K2 on AM. There are so many great old boatanchors available for AM. Not only do you get a rig MADE for AM, you get a rig that reminds you of the K2's place in history. Spend a week or so with some 60's gear, even very good receivers like my 2-B, and you will be reminded how very far engineers like Wayne Burdick and his contemporaries have brought the state of receiver art. Eric KE6US www.ke6us.com -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of David Toepfer Sent: Monday, January 09, 2006 6:17 PM To: [hidden email]; Sean Duncan; [hidden email] Subject: RE: [Elecraft] am for the k2 I know of at least one AM'er I saw online that ised his K2 as a (n expensive) VFO for this tube transmitter. You won't find AM'ers always "on frequency", as most old vfo's are only accurate to 5kHz (1kHz with Collins). I have thought of playing with AM (tx and rx) with a K1 or K2 when I get one. But I would doubt Elecraft themselves would bother with such endeavors, especially on a rig that is designed to be such a fine CW rig. The issues I think I would encounter are: rx: 1) detection: cut the BFO and perhaps insert a diode detector 2) bandwidth: would have to open up to at least 4kHz tx: 1) modulation: you could just drop a book on the key in CW mode and then you need to modulate with voice, one way might be via series PDM modulation David, K3TUE _______________________________________________ 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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