RE: [Elecraft] Rigblaster Pro RF issue
I am running a RIGblaster Pro with my K2. Under QRP conditions, I have no problems. However, on 40m 80m QRO with an external amp, I am finding that I am getting serious RF getting back into the rigblaster. I have isolated it to the rigblaster's microphone cable that connects the K2 to the rigblaster. I am certain this is the path of the RF because I can replace the rigblaster mic cable with the K2s regular microphone and use its PTT and couple the sound from my headphones into the mic and get transmit without the RF crap on output. My question is this. What is the best way to eliminate the RF on the rigblaster's mic cable? Would several ferrite beads do the job? Anyone else ever have this problem or have suggestions? I had similar very bad problems with RF in the audio of my two K2/100's. They were ok with just a mic on a short cable, but trying to use the soundcard audio during a contest using N1MM software produced terrible results running any more than qrp. And no, I don't have unbalanced antennas, all are dipoles or yagis far from the shack with good baluns and buried feedlines. The interface circuit used isolation transformers and had not given any problems with other radios. Here is what I did: 1) modify the K2 audio input circuit (on SSB module) by adding a RFC and bypass caps. Search the email list for notes on this, I forget exactly who posted it. This helped a LOT. 2) set the K2 mic gain to low (1 setting) and boost external level to compensate. I also had to build a 1-transistor mic preamp (with plenty of RF bypassing) to boost the mic level going into the computer sound card somewhat. (one mic was a Heil HC-4, the other a home-made headset with an elec. mic element). It's now bulletproof at 100W. I haven't tested it with the amp on, but I think it will be ok. It helps a lot to have a second radio to listen to your signal while you are adjusting things. Tor N4OGW ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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] Rigblaster Pro RF issue
Sorry that is not a directly K2 related question, but this list has more ham brains located in one place than any other place I know. I have always appreciated the help I have found here from the members. I am running a RIGblaster Pro with my K2. Under QRP conditions, I have no problems. However, on 40m 80m QRO with an external amp, I am finding that I am getting serious RF getting back into the rigblaster. I have isolated it to the rigblaster's microphone cable that connects the K2 to the rigblaster. I am certain this is the path of the RF because I can replace the rigblaster mic cable with the K2s regular microphone and use its PTT and couple the sound from my headphones into the mic and get transmit without the RF crap on output. My question is this. What is the best way to eliminate the RF on the rigblaster's mic cable? Would several ferrite beads do the job? Anyone else ever have this problem or have suggestions? 73, Bill Allen WA5PB ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
RE: [Elecraft] Rigblaster Pro RF issue
Bill, The very best way to combat RF Feedback is to eliminate it at its source - the antenna. Balanced resonant antennas with a balun at the feedpoint usually are no problem. Balanced fed non-resonant antennas with careful consideration to the run of the parallel feedline away from the antenna are not usually a problem either. Offcenter fed antennas and end fed wires are difficult to tame, as are balanced antennas having a high impedance feedpoint at the shack end of the feedline. Vertiacal with an adequate ground system are usually tame, but verticals with an inadequate ground or resonant ground plane suffer from the same RF-in-the-shack problems as end fed wires. All that being said, one can experiment with counterpoise wires at the shack end to determine if the RF is really the problem. Cut a quarterwavelength wire for the band to be tested and attach one end to the tuner or amplifier ground - the far end is open circuit, just like the end of an antenna - it will contain high RF Voltages, so be certain it is in the clear and out of contact range of humans and pets. If the counterpoise wire solves the problem, it can be used permanently, or one can vow to solve the real problem in the antenna system. In addition to considerations at the antenna system, be certain the mic jack is grounded, and be certain a shielded cable is used between the RigBlaster and the transceiver - that may or may not help. Often grounding only one end of the cable shield will help - experiment to determine which end is more effective, but usually the end connected to the transceiver is the one to ground. Be certain you have not negated the ground isolation between the computer and the transceiver with your connections to the RigBlaster - there are many 'sneak' ground paths that can exist, do not ignore any of them. If you extend the transceiver ground area to other cables and the computer that is just more area for stray RF to impinge upon and cause trouble. Suspect everything until it can be eliminated from th esuspect list. 73, Don W3FPR -Original Message- Sorry that is not a directly K2 related question, but this list has more ham brains located in one place than any other place I know. I have always appreciated the help I have found here from the members. I am running a RIGblaster Pro with my K2. Under QRP conditions, I have no problems. However, on 40m 80m QRO with an external amp, I am finding that I am getting serious RF getting back into the rigblaster. I have isolated it to the rigblaster's microphone cable that connects the K2 to the rigblaster. I am certain this is the path of the RF because I can replace the rigblaster mic cable with the K2s regular microphone and use its PTT and couple the sound from my headphones into the mic and get transmit without the RF crap on output. My question is this. What is the best way to eliminate the RF on the rigblaster's mic cable? Would several ferrite beads do the job? Anyone else ever have this problem or have suggestions? 73, Bill Allen WA5PB ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
