Hello Don: If you have cured your RF problems I'm not sure why you are asking your questions. In general adding a choke or capacitors to your power lead shouldn't hurt anything so give it a try. I will add detail to your questions below. BTW you should indicate how much power you are running and where your antenna is located relative to your K3. FT
-----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of gold...@charter.net Sent: Saturday, February 04, 2012 7:03 AM To: elecraft@mailman.qth.net Subject: [Elecraft] RF on power to K3 question Dear Group, I have determined that the majority of my RF shack problems were related to RF on the power lead to the K3. Winding 7 turns thru a 1" clamp on #31 ferrite has cured the symptoms. With this choke in place everything is even happy on 160m. So let me explain how I power the equipment and then ask about putting a CAP across the power. The radio and SGC power cube amp are powered by 5 batteries connected in parallel. I use a very small battery tender connected at all times to keep the batteries at a full charge. When using the amp I also float a battery charger set to its mid range position with a max of 15 amps of charge to help maintain the system. From this perspective it works real well for powering the system. But I wanted to be sure that everyone understands how I power the system as I get to my questions below. Plus there is the normal AC stuff like the PC and so on. All equipment is grounded to a single point ground on one of the negative posts of a battery. Do you have an earth ground? That is a ground rod. Depending on your setup that may or may not help. FT So now to the RF problem. If you have followed earlier posts I have been chasing RF in my shack for quite awhile and finally started playing around with a clamp on meter and that is what tipped me off to the power feed of the K3. With the power feed determined as a problem (there still could be more). One of the tests I did was to remove all of the chargers and disconnect all the AC equipment and connect the amp output directly to the dummy load. RF was still present even after I attempted to remove all influences to verify if something was putting this on the power leads. So now I believe it is there natively when in TX and is not from a charger or PC or other antenna. That suggests you may have other, as yet, undetected problems. FT Based on my reading about chokes, I put 7 wraps in the 1" big snap on ferrite. This killed the RF and like I stated in the opening paragraph with everything reconnected again the system is now happy at 160m. It now actually works real well. This is good. FT In discussing what I found with others, I have learned that batteries are not filters and all the HF energy goes right thru them. Recommendations have been made to put a ceramic capacitor across the batteries to filter the HF out. I also have been cautioned that there may be a problem with a choke on the power feed to the K3 that could put a power spike on the feed line that could do damage when turning the radio on and off. So here are the questions. Can the choke cause a problem with power spikes that could damage the K3. No. FT Should a CAP be placed across the batteries to filter out the HF. If yes how do I determine what size. Adding a cap won't hurt but it probably won't help much either. It might make your battery tender happier. It should be pointed out your K3 already has bypass caps across the input power leads. Take a look at the schematic. As for value it is not critical as long as it is a ceramic cap, 50V or greater. Since you are working 160M I would start with an 0.1uF. It is useful to have a combination of values. If I were working 40M I would add a 0.01uF and for 15M and above a 0.001uF. Put them all in parallel. FT Also if yes for the CAP will this improve battery life. No. FT Also if yes could the CAP have influence that could negatively effect my use of chargers for floating power. Again, no. FT Again as always, that in advance for your help from this great group. Cheers Don ~73 Don KD8NNU ______________________________________________________________ ______________________________________________________________ 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
