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81. [Amps] 4CX800/GU74B Socket (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Fri, 14 Jun 2002 08:28:42 -0700; Good point, Dick. However, the screen needs to be grounded with a low-L spring-finger collet as directly as possible to the chassis. [see Figure 5 on my Web site for an overview of grounded-screen o; /archives//html/Amps/2002-06/msg00093.html (7,607 bytes)
82. [Amps] Solid state relay question (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Sat, 15 Jun 2002 21:48:53 -0700; Solid-state relays around high power RF tend to be problematic. - R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, www.vcnet.com/measures. end; /archives//html/Amps/2002-06/msg00105.html (8,168 bytes)
83. [Amps] Solid state relay question (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Sun, 16 Jun 2002 06:48:09 -0700; The near-field from the antenna might be the culprit. I would go with conventional 24vdc mechanical relays and, since speed is not important in this app., use c. 18v on the coils. - R. L. Measures,; /archives//html/Amps/2002-06/msg00111.html (8,037 bytes)
84. [Amps] Re: Big HV Transformer for Sale (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Sun, 16 Jun 2002 10:01:28 -0700; 2800v with a FWD is c. 7kVdc -- virtually ideal for an 8166/4-1000A on SSB. for CW and RTTY, a FWB is good. See Figure 3 on my Web site for a dual-V SPST-switchable FWD/FWB circuit. - R. L. Measures; /archives//html/Amps/2002-06/msg00114.html (9,036 bytes)
85. [Amps] gla1000 (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Sun, 16 Jun 2002 17:59:37 -0700; Sounds like an open bandswitch contact. - R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, www.vcnet.com/measures. end; /archives//html/Amps/2002-06/msg00117.html (7,278 bytes)
86. [Amps] 8877 Max Grid Current (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Mon, 17 Jun 2002 18:57:36 -0700; There were two, published ratings for 8877 max grid dissipation, 20w and 25w. Since the typical grid-cathode driving V is c. 65Vrms, the corresponding grid current can be calculated from ohm's law.; /archives//html/Amps/2002-06/msg00131.html (7,917 bytes)
87. [Amps] 8877 Max Grid Current (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Tue, 18 Jun 2002 06:07:01 -0700; The 8877 grid is widely viewed as extremely delicate. My guess is that this is due to the tendency of gold to evaporate from the grid and cause sometimes-fatal grid/cathode arcing. Roughly half of t; /archives//html/Amps/2002-06/msg00136.html (11,172 bytes)
88. [Amps] 3-400Z Tube problem (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Tue, 18 Jun 2002 10:51:22 -0700; Measure the grid-fil V when the amp is in standby and the fil is lit. If the result is 0v, you probably have a tube that shorts when the fil is hot/expanded. [See *QST*, September, 1990] I have been; /archives//html/Amps/2002-06/msg00142.html (6,868 bytes)
89. [Amps] 8877 Max Grid Current (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Tue, 18 Jun 2002 10:51:23 -0700; Few VHF users of 8877s aparently do. The sticky wicket is that MF/HF amplifiers have a somewhat less than obvious tuned circuit between the anode and the Tune-C that is resonant at several VHF and U; /archives//html/Amps/2002-06/msg00143.html (9,835 bytes)
90. [Amps] RE: [Amps] 8877 Max Grid Current (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Tue, 18 Jun 2002 10:51:25 -0700; Indeed. Less anode-V means that more electrons flow through the grid. - R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, www.vcnet.com/measures. end; /archives//html/Amps/2002-06/msg00144.html (7,431 bytes)
91. [Amps] 3PDT Relay for Dentron Clipperton L (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Tue, 18 Jun 2002 21:27:34 -0700; the high-spped switching mod. See figure 7 on my Web site. However, with older radios there would be no advantage other than quietness. - R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, www.vcnet; /archives//html/Amps/2002-06/msg00147.html (6,708 bytes)
92. [Amps] 8877 Max Grid Current (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Thu, 20 Jun 2002 05:41:28 -0700; Trivia questions' solutions: The minimum anode-to-grid potential for an 8877 is c. 250V. Thus, with a 4000Vdc anode supply, the anode voltage swing is c. 3750V-peak, or 2650Vrms. At 250 MHz the react; /archives//html/Amps/2002-06/msg00150.html (11,906 bytes)
93. [Amps] Re: Big HV Transformer for Sale (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Thu, 20 Jun 2002 08:13:24 -0700; I thought phase modulation was akin to FM. - R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, www.vcnet.com/measures. end; /archives//html/Amps/2002-06/msg00152.html (8,408 bytes)
94. [Amps] Re: Big HV Transformer for Sale (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Thu, 20 Jun 2002 09:23:44 -0700; tnx, Gary. AM linear sounds a lot easier to do. - R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, www.vcnet.com/measures. end; /archives//html/Amps/2002-06/msg00156.html (8,982 bytes)
95. [Amps] Re: Big HV Transformer for Sale (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Thu, 20 Jun 2002 10:15:58 -0700; For multi-frequency/multiband operation, trick modulation is a Pandora's Box. Modern transceivers that use an AN-612 modulator IC can produce inaudible IMD when amplified by a linear amplifier. - R.; /archives//html/Amps/2002-06/msg00158.html (8,722 bytes)
96. [Amps] Re: Big HV Transformer for Sale (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Thu, 20 Jun 2002 18:07:57 -0700; I heard the same thing. A Class AB1grid-driven, or AB2 g-g linear amplifier is typically 60% efficient. Class C may be 78% efficient but the difference would be virtually not noticeable at the Rx en; /archives//html/Amps/2002-06/msg00166.html (8,933 bytes)
97. [Amps] 8877 Max Grid Current (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Fri, 21 Jun 2002 04:40:16 -0700; The I^2 x R heating of the grid at 144MHz is probably minimal because gold is a fairly good electrical conductor, and there are over 100 grid-bars to share the current burden of 24Arms. An interestin; /archives//html/Amps/2002-06/msg00173.html (9,610 bytes)
98. [Amps] Need hints.... (wordy) (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Fri, 21 Jun 2002 04:40:21 -0700; The grid V requirement is such that the grid-terminating R can be 50-ohms -- with the grid driven directly. What is the design Q of your tank? 5cx1500s are fairly rugged because the thoriated-tungst; /archives//html/Amps/2002-06/msg00174.html (7,943 bytes)
99. [Amps] Re: Big HV Transformer for Sale (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Fri, 21 Jun 2002 04:40:22 -0700; usual True. When I run AM, I use VOX so there is minimal carrier time. Whilst talking, the efficiency is better. For better efficiency I run DSB and SSB. The trouble with most AMers is that they lik; /archives//html/Amps/2002-06/msg00175.html (9,577 bytes)
100. [Amps] 8877 Max Grid Current (score: 1): Author: 2@mail.vcnet.com (Richard); Date: Fri, 21 Jun 2002 06:11:04 -0700; is The gold plating is pretty thick judging by the quantity of meltballs I find. RE: Figure 24 on my Web site. . My guess on the frequency that causes gold evaporation is above 700MHz. Looks like ma; /archives//html/Amps/2002-06/msg00177.html (9,284 bytes)

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