Don: Thanks for your comments (and since we haven't corresponded in a while....for your ongoing amazing help to all Elecraft owners through the email reflector).
Actually, the issues I have had with the TX IF port have all been while receiving (with another nearby rig transmitting on VHF...or other signal source), so they do not have anything to do with the transmit power itself. The K2 seems to interpret a bit of power showing on the VRFDET line when in receive mode as a dangerous overload condition (as it would be if it appeared on the much less sensitive detector at the 10W antenna jack....and switches the rig (mostly) into transmit. I suppose a high field strength leakage from a nearby transmitter could indeed affect the transmit power as well....I haven't knowingly observed that. I have been working on a 10 GHz transverter (modifying a commercial radio) which will have a 21 MHz IF....which got me thinking about having a broadband solution to the RFI problems, so I wouldn't have to use two different filters to avoid the K2 being upset by nearby talkback link transmissions on 2m. I suppose a low pass filter is another option, but it is more difficult to get a sharp cutoff between 28 and 50 MHz than with a bandpass filter. An even better solution would probably be to apply a bias to the detector circuitry in the K60XV, while in receive mode, which prevents it from operating....but I haven't looked into the feasibility of this. 73, Steve VE3SMA --- On Tue, 11/8/11, Don Wilhelm <w3...@embarqmail.com> wrote: > From: Don Wilhelm <w3...@embarqmail.com> > Subject: Re: [Elecraft] [K2] Solutions for K2 Transverter Quirks > To: "Steve Kavanagh" <skavanag...@yahoo.ca> > Cc: elecraft@mailman.qth.net > Received: Tuesday, November 8, 2011, 9:14 AM > Steve, > > The answer to your question involves a discussion about how > the K2 handles control of the power output level - in all > cases, it tries to measure the actual power output and the > microprocessor controls the drive level early in the > transmit chain to achieve the power output requested by the > power knob. > > Just as information about what is happening with that "RF > Sensitivity" problem is that *if* some of the VHF/UHF energy > appears on the K60XV TX output. That condition causes > the RF detector on the K60XV to produce an output on the > VRFDET line in the K2 (the detector is not frequency > selective - it is just a diode, similar to an RF probe) - > the result of all that is the K2 microprocessor ends up > receiving a signal telling it that there is too much power > at the TX output, and the microprocessor dutifully reduces > the power. > > The simple low pass filter is just as effective at curing > that condition as a unity gain buffer stage would be. > > The ideal solution would be to modify the transverter so > that none of its output frequency energy appears on the > input cable, but that is not realistic in some situations - > it all depends on the transverter. > > 73, > Don W3FPR > > On 11/8/2011 8:15 AM, Steve Kavanagh wrote: > > My apologies regarding the link...as W1RT correctly > figured out there should be an L at the end of it: > > > > www.qsl.net/ve3sma/downloads.html > > > > I had seen Don's circuit and decided to go a different > route...not having to dig into the K2 was a plus for me (and > I had a good supply of the Omron G5Y PC-board-mount RF > relays). > > > > I had wondered how W1RT dealt with the RF sensitivity > of the transverter out line....now I know ! I have > been thinking lately a better solution than the filter might > be a high isolation buffer amp with 0dB gain (or an > attenuator and then a buffer with gain) built into the K2, > but I haven't started looking to see where there might be > room. > > > > 73, > > Steve VE3SMA > > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
