Author Topic: KA3005P power supply -- RF interference  (Read 746 times)

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Offline jimdeane

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KA3005P power supply -- RF interference
« on: August 13, 2017, 06:21:45 pm »
Whoo, I found a limit on the KA3005P power supply. I tried using it to power a 2m 30w amplifier driving an antenna about four feet from the power supply. Key-down produces a Poltergeist-level series of malfunctions in the power supply.

I must be sending a lot of RF interference back through the power cables. I guess I'll use a linear supply for that one.
 

Offline bd139

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Re: KA3005P power supply -- RF interference
« Reply #1 on: August 13, 2017, 06:35:16 pm »
While the power supply is clearly poo, that PA shouldn't be dumping that amount of noise on the supply. Needs some filtering on the DC in.

Edit: it is also a linear supply apparently, just a naff one.
 

Offline Wirehead

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Re: KA3005P power supply -- RF interference
« Reply #2 on: August 13, 2017, 07:02:08 pm »
RF in the shack is hardly "normal" to be honest and should always be avoided. Not really the KA3005P's fault to be honest. Choke the transmission line  :-+
"to remain static is to lose ground"
 

Offline daqq

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Re: KA3005P power supply -- RF interference
« Reply #3 on: August 13, 2017, 08:24:13 pm »
RF nastyness can affect lots of lab power supplies. I remember being mystified by an efficiency going well over 100% when developing a switching power supply that threw interference left and right... apparently the built in meters did not like it and the ammeter in particular was prone do displaying bullshit when interfered with.
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Offline jimdeane

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Re: KA3005P power supply -- RF interference
« Reply #4 on: August 14, 2017, 04:43:00 am »
I mean linear like regulated but dumb linear. The RF clearly was getting into the control panel and making things very unhappy.

I was propping up a Tiny-2 antenna to try and hit a distant repeater. No luck with my HT so I thought I'd put the amp into service. I was already looking askance at the long power cable and thinking they were too antenna-like. Not the supply's fault, it does a perfectly fine job as a bench supply.
 

Offline T3sl4co1l

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Re: KA3005P power supply -- RF interference
« Reply #5 on: August 14, 2017, 07:32:15 am »
Yeah, you might want to look into antenna balance...

......This one?
http://www.rollanet.org/~rrars/tech_files/tiny2.pdf
It doesn't happen to say precisely what the feedpoint is.  It does seem to suggest using unbalanced (50 ohm) coax to connect to a balanced, symmetrical antenna.

Who comes up with these fucking antennas?  Ugh.

Yeah, put a balun on that retarded thing.  And shoot an angry email to the above host noting the same.

Tim
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Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

Offline jimdeane

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Re: KA3005P power supply -- RF interference
« Reply #6 on: September 23, 2019, 09:59:49 pm »
Fun update -- when I next went to use my HTX-202, the audio is dead. Hopefully I just fried the 386-type audio amp chip.

I'll get into it and see.
 


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