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References: [ +subject:/^(?:^\s*(re|sv|fwd|fw)[\[\]\d]*[:>-]+\s*)*LF\:\s+PA\s+problem\s*$/: 11 ]

Total 11 documents matching your query.

1. LF: PA problem (score: 1)
Author: N1BUG <>
Date: Tue, 7 Nov 2017 17:33:07 -0500
I wonder if anyone can help me with this. I built one of these: http://qrp-labs.com/ultimate3/u3mods/lfamp.html It's not what I want but it's what I can afford. In all cases, I was driving it with 25
/rsgb_lf_group-archives/html/rsgb_lf_group/2017-11/msg00063.html (9,882 bytes)

2. Re: LF: PA problem (score: 1)
Author: misan <>
Date: Wed, 08 Nov 2017 03:27:09 +0100
Hello OM N1BUG, For class E @85%eff you would need some more components. - An inductor in the DC between 1u capacitor and the drain / transformer low impedance input, typical >0.5mH at LF! - A 'tunin
/rsgb_lf_group-archives/html/rsgb_lf_group/2017-11/msg00065.html (11,690 bytes)

3. Re: LF: PA problem (score: 1)
Author: N1BUG <>
Date: Wed, 8 Nov 2017 08:00:28 -0500
There were many replies to my plea for help. I won't reply to all individually but every reply is much appreciated! Thank you all! To respond to a few things: I do not need a linear amp. I spent much
/rsgb_lf_group-archives/html/rsgb_lf_group/2017-11/msg00066.html (10,163 bytes)

4. Re: LF: PA problem (score: 1)
Author: DK7FC <>
Date: Wed, 08 Nov 2017 14:37:31 +0100
Hi Paul, My answer may be a bit late. It sounds to me like a EMC issue. A RF choke is needed in the supply line. 1 mH may be a good choice. And i would add a 1000 uF electrolytic capacitor with a low
/rsgb_lf_group-archives/html/rsgb_lf_group/2017-11/msg00067.html (10,710 bytes)

5. Re: LF: PA problem (score: 1)
Author: DK7FC <>
Date: Wed, 08 Nov 2017 14:52:34 +0100
Am 08.11.2017 14:37, schrieb DK7FC: And i would add a 1000 uF electrolytic capacitor with a low internal resistance (the good ones :-) ) near the Drain, in parallel to the 1 uF capacitor. Sorry that
/rsgb_lf_group-archives/html/rsgb_lf_group/2017-11/msg00068.html (9,273 bytes)

6. Re: LF: PA problem (score: 1)
Author: N1BUG <>
Date: Fri, 10 Nov 2017 13:44:24 -0500
Hi Stefan, Your answer is not late at all. After working very hard on antennas the past days I am just now getting back to the little PA. About RF choke in the supply line: This is something I don't
/rsgb_lf_group-archives/html/rsgb_lf_group/2017-11/msg00084.html (11,725 bytes)

7. Re: LF: PA problem (score: 1)
Author: DK7FC <>
Date: Fri, 10 Nov 2017 20:35:44 +0100
Am 10.11.2017 19:44, schrieb N1BUG: I see a nice clean sine wave at the other side of the LPF. With a good LPF, the output often looks quite good on a scope, even with massively distorted input signa
/rsgb_lf_group-archives/html/rsgb_lf_group/2017-11/msg00085.html (10,315 bytes)

8. Re: LF: PA problem (score: 1)
Author: Rik Strobbe <>
Date: Fri, 10 Nov 2017 20:30:24 +0000
Hello Paul, I just had a look at the circuit (http://qrp-labs.com/ultimate3/u3mods/lfamp.html). One end of the output transformer connected is to the +13.8V should be "cold" (no RF). As already menti
/rsgb_lf_group-archives/html/rsgb_lf_group/2017-11/msg00086.html (13,339 bytes)

9. Re: LF: PA problem (score: 1)
Author: N1BUG <>
Date: Fri, 10 Nov 2017 16:53:53 -0500
OK. I understand the problems with having RF reach the meter and power supply. To be honest I don't fully understand what you are suggesting with a very small coil (few uH at best) and capacitor... O
/rsgb_lf_group-archives/html/rsgb_lf_group/2017-11/msg00088.html (12,874 bytes)

10. Re: LF: PA problem (score: 1)
Author: N1BUG <>
Date: Fri, 10 Nov 2017 16:58:07 -0500
Hello Rik, Thanks for the good suggestion. I tried it on a battery removed from my lawn mower. I won't be needing the lawn mower for some months! Running it from the battery does not significantly re
/rsgb_lf_group-archives/html/rsgb_lf_group/2017-11/msg00089.html (11,180 bytes)

11. Re: LF: PA problem (score: 1)
Author: N1BUG <>
Date: Fri, 10 Nov 2017 17:37:32 -0500
So as a final test today I put a 50 uH choke and then a bypass capacitor on the power supply side of it. With 100 uF I (oddly) found 2V pk-pk RF on the power supply. So it is worse with the choke plu
/rsgb_lf_group-archives/html/rsgb_lf_group/2017-11/msg00090.html (12,412 bytes)


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