http://elecraft.85.s1.nabble.com/RF-on-power-to-K3-question-tp7254202p7255907.html
choke by another ham. He was not fully sure and suggested that I post
Power is an SGC power cube good for 500w. Antennas are a 2 WL loop for
total ignorance. Hey but I do learn slowly at times :-). Example I now
> 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:
[hidden email]
> [mailto:
[hidden email]] On Behalf Of
>
[hidden email]
> Sent: Saturday, February 04, 2012 7:03 AM
> To:
[hidden email]
> 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
>
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