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Total 246 documents matching your query.

121. Re: [Amps] Alpha 76A - 120hz hum on 160m only (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Fri, 18 Oct 2013 11:01:13 +0200
I'm guessing a bit here.....but the numbers should be 'ballpark'. The 'cold' end of the plate choke is bypassed with maybe a total of around 5000pF to ground. That's about -j17 ohms. The plate choke
/archives//html/Amps/2013-10/msg00318.html (9,248 bytes)

122. Re: [Amps] 200-ohm tank and "un-un" in HF amp design? (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Sun, 20 Oct 2013 19:36:50 +0200
probably best done with a transmission line transformer, using a 100 ohm line - maybe 91 ohm coax? But I read somewhere that it is not as forgiving on SWR as the classical way, plus of course, the lo
/archives//html/Amps/2013-10/msg00357.html (8,079 bytes)

123. Re: [Amps]  200-ohm tank and "un-un" in HF amp design? (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Mon, 21 Oct 2013 10:32:27 +0200
As a Class AB stage has a second harmonic component of plate current only 6dB down on the fundamental, what sort of Q do you run in the pi network to get the extra 37dB of suppression needed to meet
/archives//html/Amps/2013-10/msg00374.html (7,195 bytes)

124. Re: [Amps]  200-ohm tank and "un-un" in HF amp design (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Tue, 22 Oct 2013 19:26:50 +0200
Jim, The regulations state in level in the feedline. However, I could ask one of my friends at Industry Canada what they think..... 73 Peter G3RZP == Message Received: Oct 22 2013, 03:06 PM From: "Ji
/archives//html/Amps/2013-10/msg00401.html (9,423 bytes)

125. Re: [Amps] Screen regulation (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Wed, 23 Oct 2013 02:01:38 +0200
Vic, Seriously, I'd be surprised if anybody actually would know except by experience! As the old saying goes (admittedly capable of mis-interpretation in the USA!) 'Suck it and see!' 73 Peter G3RZP =
/archives//html/Amps/2013-10/msg00408.html (8,298 bytes)

126. Re: [Amps]  200-ohm tank and "un-un" in HF amp design (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Thu, 24 Oct 2013 14:36:33 +0200
Jim, ITU-R Rec. SM.329-12. Although this is a recommendation, through a somewhat complex route, it is called for in the International Radio Regulations, which are considered to be a treaty in interna
/archives//html/Amps/2013-10/msg00421.html (10,715 bytes)

127. Re: [Amps] Small mystery (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Tue, 29 Oct 2013 19:17:11 +0100
Vic, The negative screen current is normal in a 4CX1000. See the Eimac data sheet. In 'ENABLED', you need more negative bias to cut off the tube, and it's a good idea to get into cut off (but only ju
/archives//html/Amps/2013-10/msg00447.html (9,098 bytes)

128. Re: [Amps] Large Variac controlling HV power supply (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Thu, 31 Oct 2013 14:12:17 +0100
I have seen it said that it isn't a good idea because the variac regulation isn't that good. Having said that, in my youth, I worked on a tx where we had a fairly large 3 phase variac feeding a 25kV
/archives//html/Amps/2013-10/msg00463.html (10,084 bytes)

129. Re: [Amps] GS23B Plate load resistance for HF (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Thu, 31 Oct 2013 18:54:18 +0100
Assuming 3kV on the plate, 500 volts on the screen and AB1 operation in grounded cathode, I calculate a PEP output of 1540 watts, a dissipation of 1240 watts, efficiency 55% and a load resistance of
/archives//html/Amps/2013-10/msg00476.html (8,680 bytes)

130. Re: [Amps] GS23B Plate load resistance for HF / audio analogy (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Thu, 31 Oct 2013 23:45:39 +0100
Leigh Personally, I prefer the load line approach, which is basically what RCA advise. But, as the old French saying goes, 'each dog to his own vomit'. 73 Peter G3RZP == Message Received: Oct 31 2013
/archives//html/Amps/2013-10/msg00480.html (8,973 bytes)

131. Re: [Amps]  GS23B Plate load resistance for HF (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Fri, 01 Nov 2013 09:16:42 +0100
Jim, GS23B tetrode, not a GS35B triode. What was the IMD on the 2 times GS35B amp? 73 Peter G3RZP == Message Received: Nov 01 2013, 05:31 AM From: "Jim Thomson" <jim.thom@telus.net> To: amps@contesti
/archives//html/Amps/2013-11/msg00002.html (9,935 bytes)

132. Re: [Amps] Measuring IMD (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Sun, 03 Nov 2013 11:28:05 +0100
A very simple method which is adequate for most amateur use is to couple diode detectors to the input and output of the amplifier. The input detector goes to the X input of an oscilloscope and the ou
/archives//html/Amps/2013-11/msg00025.html (8,747 bytes)

133. Re: [Amps] Measuring IMD (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Sun, 03 Nov 2013 18:03:58 +0100
The ARRL handbook amp used the detectors to fix the load line - you have to tune for maximum plate RF Volts first and then get the ratio of grid to plate volts correct to get the load line right. Aut
/archives//html/Amps/2013-11/msg00034.html (11,604 bytes)

134. Re: [Amps] Measuring IMD (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Sun, 03 Nov 2013 19:04:50 +0100
Manfred, For SS amps, the detector approach has the problem that it doesn't readily bring out the generally poor high order IMD of SS amps. For tube amps, it's adequate. 73 Peter G3RZP ______________
/archives//html/Amps/2013-11/msg00036.html (8,266 bytes)

135. Re: [Amps] Measuring IMD (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Sun, 03 Nov 2013 22:25:53 +0100
The reference given to Pappenfus gives the equations for determining the level of 3rd and 5th order products from the curvature of the line. Noise testing is good, provided you are sure about the pea
/archives//html/Amps/2013-11/msg00039.html (8,542 bytes)

136. Re: [Amps] Chinese 15KV 2A rectifier modules? (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Thu, 07 Nov 2013 09:21:50 +0100
Give a thought to the peak current if you are using a capacitor input filter - I don't think ovens have much reservoir capacity. 73 Peter G3RZP == Message Received: Nov 07 2013, 12:37 AM From: "Jim B
/archives//html/Amps/2013-11/msg00097.html (8,582 bytes)

137. Re: [Amps] Question for the tetrode experts (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Fri, 08 Nov 2013 10:51:15 +0100
Vic, Gerald may well have a point about loading. What inductance is the plate choke, what capacitors are there at the 'cold' end of it and what type and is there another smaller RF choke going off fr
/archives//html/Amps/2013-11/msg00142.html (11,403 bytes)

138. Re: [Amps] Question for the tetrode experts (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Fri, 08 Nov 2013 23:21:53 +0100
Vic, OK, on 40 you have 375mA or so of RF current in the choke. My suspicion was that maybe the capacitors didn't like it or were small enough that they were heating up with RF, but it doesn't appear
/archives//html/Amps/2013-11/msg00160.html (8,517 bytes)

139. Re: [Amps] Autek WM-1 Schematic or Help (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Sat, 09 Nov 2013 10:41:56 +0100
I refuse to buy any new equipment where there isn't a schematic as a minimum. The few bits I got very cheaply in fleamarkets with no manuals, I've traced out the schematic if I haven't been able to g
/archives//html/Amps/2013-11/msg00172.html (7,407 bytes)

140. Re: [Amps] Plate Choke question (score: 1)
Author: peter chadwick <g8on@fsmail.net>
Date: Sat, 09 Nov 2013 22:14:36 +0100
BUT at 3.5 MHz, that 50 microhenries has an inductive reactance of 1100 ohms, and needs an extra 50pF of plate tuning capacity. Now let's assume a plate voltage of say 2500 volt and a minimum plate v
/archives//html/Amps/2013-11/msg00179.html (8,009 bytes)

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