RF feedback
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I'm running the K3 with an Ameritron AL800 and a Steppir 3 element
with 40m dipole add-on. I have a severe though intermittent feedback problem on 40m that I did not have with an Icom 751a. The feedback only occurs when I'm using the amp (even with very low drive). I've common core choked virtually every lead with ultimately no luck. I'm using the Elecraft hand mike. Is there a known problem here? Otherwise, I'll just keep searching. Dick Dick Lindzen, KA1SA 301 Lake Avenue Newton, MA 02461 USA 1-617-332-4342 _______________________________________________ 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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Richard S. Lindzen wrote:
> I'm running the K3 with an Ameritron AL800 and a Steppir 3 element with > 40m dipole add-on. I have a severe though intermittent feedback problem > on 40m that I did not have with an Icom 751a. The feedback only occurs > when I'm using the amp (even with very low drive). I've common core > choked virtually every lead with ultimately no luck. I'm using the > Elecraft hand mike. Is there a known problem here? Otherwise, I'll > just keep searching. There is a so-called "pin 1 problem" in the K3's mic input circuitry. The fix is to jumper L4 on the front panel board and L7 on the KIO3. These are RF chokes in the mic return lines. I have not done this yet myself, since I am a CW guy! But I'm sure Elecraft support can provide you with detailed instructions for doing this if needed. The mod has solved RF feedback problems for several K3 owners. -- 73, Vic, K2VCO Fresno CA http://www.qsl.net/k2vco _______________________________________________ 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 rlindzen
In a message dated 12/5/2008 9:05:02 A.M. Pacific Standard Time,
[hidden email] writes: I'm running the K3 with an Ameritron AL800 and a Steppir 3 element with 40m dipole add-on. I have a severe though intermittent feedback problem on 40m that I did not have with an Icom 751a. The feedback only occurs when I'm using the amp (even with very low drive). I've common core choked virtually every lead with ultimately no luck. I'm using the Elecraft hand mike. Is there a known problem here? Otherwise, I'll just keep searching. Dick Dick Lindzen, KA1SA 301 Lake Avenue Newton, MA 02461 USA 1-617-332-4342 _______________________________________________ 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_ (http://www.elecraft.com) ++++++++++++++++++++++++++++++++++++++++++++++++++ Have you tried other bands? What Version Firmware are you using? I have a problem that may also be RF feedback related. I occurs only on 40M and only when I exceed 80 W to my Dipole antenna. No problem full power up to 120 watts into Vertical or any other band. Problem started immediately after upgrading FW to V 2.46. I have a couple upgrades to do on the rig including the AGC upgrade, which I have held off making until my Sub Receiver upgrade. Since that arrived a few days ago I will be doing all upgrades and the subreceiver install this weekend. I don't plan on any changes in FW other than activating the KRX3. I will then test the 40M issue. I do not have a good earth ground on the K3 nor am I running any form of Amp. But, the rig has worked perfectly since it was installed a year ago and the ATUs have always provided a good match in the 1.X:1 range on both Vert and Dipole including 160M, 30M, 12M, 17M in addition to the usual 5 bands the Ants are designed for. Al WA6VNN **************Make your life easier with all your friends, email, and favorite sites in one place. Try it now. (http://www.aol.com/?optin=new-dp&icid=aolcom40vanity&ncid=emlcntaolcom00000010) _______________________________________________ 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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Dick,
I have an 811-H connected to my K3 running 500 to 600 watts cw. I have "problems" that might be similar to yours. I get loud, fuzzy, cw tones on both my noise canceling head phones my external speakers. Both these items are powered devices. One by a wall wart and one by an AAA battery. When I turn off the headphones I get interference free audio in the headset. When I turn off the external speakers they shutdown so I have to unplug these from the PHONES jack and use the internal speaker. The internal speaker never gets the interference. My neighbors were getting the same "cw" interference on "powered" audio equipment. I put low pass filters on both of my antenna feed lines at the output of my external MFJ-989D tuner. Perhaps I should put them between the amp and the tuner! Anyway this seemed to help but in fact it only shifted the problem frequencies from 20 to 40 meters. The low pass filters did cleanup TV interference but not the audio level problems! My next step will be to properly ground all the gear! Yes, I am guilty! In a rush to get on the air for ARRL-SS and CQ-WW I did not properly ground the new amp and tuner! I'll let you know if this fixes the problem. I had investigated chokes myself but did not want to get them until I properly grounded all my gear! BTW, the amp, tuner and K3 did well in the contests! I easily got the last 5 states I needed for WAS. All have been confirmed either by card or LoTW. I also got 8 new countries, 3 of which are already confirmed! Power helps! A lot! I let you know the grounding works out. -----Original Message----- In a message dated 12/5/2008 9:05:02 A.M. Pacific Standard Time, [hidden email] writes: I'm running the K3 with an Ameritron AL800 and a Steppir 3 element with 40m dipole add-on. I have a severe though intermittent feedback problem on 40m that I did not have with an Icom 751a. The feedback only occurs when I'm using the amp (even with very low drive). I've common core choked virtually every lead with ultimately no luck. I'm using the Elecraft hand mike. Is there a known problem here? Otherwise, I'll just keep searching. Dick ++++++++++++++++++++++++++++++++++++++++++++++++++ Have you tried other bands? What Version Firmware are you using? I have a problem that may also be RF feedback related. I occurs only on 40M and only when I exceed 80 W to my Dipole antenna. No problem full power up to 120 watts into Vertical or any other band. Problem started immediately after upgrading FW to V 2.46. I have a couple upgrades to do on the rig including the AGC upgrade, which I have held off making until my Sub Receiver upgrade. Since that arrived a few days ago I will be doing all upgrades and the subreceiver install this weekend. I don't plan on any changes in FW other than activating the KRX3. I will then test the 40M issue. I do not have a good earth ground on the K3 nor am I running any form of Amp. But, the rig has worked perfectly since it was installed a year ago and the ATUs have always provided a good match in the 1.X:1 range on both Vert and Dipole including 160M, 30M, 12M, 17M in addition to the usual 5 bands the Ants are designed for. Al WA6VNN _______________________________________________ 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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Gentlemen - No amount of adding low-pass filters, inserting antenna tuners, grounding your set, etc. will clear up these problems. Don't let anyone tell you different. Facts is facts, and that's that. While all these steps are good things to do, and follow what is commonly known as "good amateur practice", the problem is outside the radio-amplifier-antenna "package". This sort of problem is caused by the strong signal from your transmitter overloading the audio amplifier circuitry in the powered devices. There is nothing you can do at your own station, other than running much lower power, to reduce the problem. Consider this: The speakers and headphones, wired telephones,, intercom systems, etc. are by definition, not designed to receive radio signals directly. Ergo, they are malfunctioning in the presence of strong RF fields. The problem is created inside the device by the strong RF field that your antenna (hopefully) is radiating. Manufacturers of consumer devices, in their attempt to be competitive (and to maximize profits) tend to leave out the parts that would prevent this type of problem. They take the chance that their product will not end up in near proximity to a ham transmitter (or other strong RF source) . This gamble works often enough that they get away with sub-standard construction, plus they count on the scenario that the general public won't understand the real problem, and blame it on the poor ham. In other words, they prefer to skate on their responsibilities by shifting the blame to someone else, anyone else, rather than doing their job. The fix, both for your own equipment and the neighbor's stereo, telephones, etc. is to install filtering or suppression devices on each device that is experiencing problems. Installing ferrite RFI suppressors in series with speaker or headphone leads, wrapping the cables around ferrite rods or cores, capacitors across speaker leads (also from each side of the speaker connection to ground), and similar techniques are what is required. A PR problem exists here. It is difficult to get a consumer to understand why his brand new (whatever) is malfunctioning. The problem happens only when you transmit, so it must be a defect in your station. The PR problem lies in convincing the poor neighbor that while you are the cause of the problem, it is not your fault. A fine definition to be sure, and one where you r local club's RFI committee can help no end. No club or RFI committee? Start one, and become the local expert. Once your have solved a couple of cases, you become the "guru", and your word will be taken as gospel. As an aside, also remember that SWR or other mismatch issues will not in itself increase interference problems, other than in extreme cases high SWR might have the effect of reducing interference because it causes the applicable transmitter to back off it's power output so much that little signal is reaching the antenna - but then nothing is left to make contacts either! - Jim, KL7CC Jack Regan wrote: > Dick, > > I have an 811-H connected to my K3 running 500 to 600 watts cw. I have > "problems" that might be similar to yours. I get loud, fuzzy, cw tones on > both my noise canceling head phones my external speakers. _______________________________________________ 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 Vic K2VCO
----- Original Message ----- From: "Vic K2VCO" <[hidden email]> To: "Richard S. Lindzen" <[hidden email]> Cc: <[hidden email]> Sent: Friday, December 05, 2008 6:10 PM Subject: Re: [Elecraft] RF feedback > There is a so-called "pin 1 problem" in the K3's mic input > circuitry. The fix is to jumper L4 on the front panel > board and L7 on the KIO3. These are RF chokes in the mic > return lines. ------------------------------ I just did these mods today, along with the audio upgrade mods. I was too lazy to pull off the front panel to get to L4, so I just jumpered pin 8 on the mic plug (not the jack on the K3) to the metal shell of the plug. Dave Hachadorian, K6LL Yuma, AZ . _______________________________________________ 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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Dave,
Many thanks. With all the suggestions, I hesitated to pull off the front panel, but I did quickly try your approach, and it appears to solve the problem. Apparently the "pin 1 problem" struck again. Dick, KA1SA At 08:57 PM 12/5/2008, Dave Hachadorian wrote: >----- Original Message ----- From: "Vic K2VCO" <[hidden email]> >To: "Richard S. Lindzen" <[hidden email]> >Cc: <[hidden email]> >Sent: Friday, December 05, 2008 6:10 PM >Subject: Re: [Elecraft] RF feedback > > >>There is a so-called "pin 1 problem" in the K3's mic input >>circuitry. The fix is to jumper L4 on the front panel board and L7 >>on the KIO3. These are RF chokes in the mic return lines. >------------------------------ > >I just did these mods today, along with the audio upgrade mods. I >was too lazy to pull off the front panel to get to L4, so I just >jumpered pin 8 on the mic plug (not the jack on the K3) to the metal >shell of the plug. > >Dave Hachadorian, K6LL >Yuma, AZ > > > > > > > > > > > > > > > > > > > > > > > >. > > >_______________________________________________ >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 Dick Lindzen, KA1SA 301 Lake Avenue Newton, MA 02461 USA 1-617-332-4342 _______________________________________________ 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 Jim Wiley-2
The way I explain it is to say
"If your roof leaks only when it rains, do you blame the rain or the roof? " David G3UNA > > > A PR problem exists here. It is difficult to get a consumer to understand > why his brand new (whatever) is malfunctioning. The problem happens only > when you transmit, so it must be a defect in your station. The PR problem > lies in convincing the poor neighbor that while you are the cause of the > problem, it is not your fault. _______________________________________________ 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 Jack
On Fri, 5 Dec 2008 13:31:57 -0800, Jack Regan wrote:
>I let you know the grounding works out. It's NOT about grounding. But matters a LOT about how you connect cable shields. Yes, the K3 has a Pin 1 problem. Read about it in the tutorials below. Free, no cookies, no advertising. http://audiosystemsgroup.com/RFI-Ham.pdf http://audiosystemsgroup.com/HamInterfacing.pdf 73, Jim Brown K9YC _______________________________________________ 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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