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41. Re: [Amps] Skin Effect and Wire Current Capacity at HF (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Fri, 15 Apr 2005 07:58:04 +0200; The theory behind this is quite involved, but is well described in Terman's "Radio Engineer's Handbook" (pp 28 - 37 in my 1943 edition). Basically you can find the RF resistance per unit length at a; /archives//html/Amps/2005-04/msg00292.html (10,640 bytes)
42. [Amps] Follow up: Skin Effect and Wire Current Capacity at HF (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Fri, 15 Apr 2005 17:34:24 +0200; A reasonably general expression for the RF current capacity of wire or tubing at a given frequency can be derived as follows: First, it will be assumed that the current limitation is due to temperatu; /archives//html/Amps/2005-04/msg00295.html (12,226 bytes)
43. Re: [Amps] Co-ax adaptor (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Sat, 23 Apr 2005 08:33:47 +0200; The adapter between N(f) and LC (m) is the UG-999/U. It can be obtained (at a price) from Surplus Sales of Nebraska. 73/ Karl-Arne SM0AOM _______________________________________________ Amps mailing; /archives//html/Amps/2005-04/msg00460.html (7,858 bytes)
44. Re: [Amps] RE : Led display problem (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Sat, 23 Apr 2005 10:05:42 +0200; I would recommend "attacking" this problem in two ways. The first is to arrange all current metering so it takes place at the lowest potential point possible referenced to DC and RF ground. In a DC g; /archives//html/Amps/2005-04/msg00463.html (12,293 bytes)
45. Re: [Amps] Bleeder Resistor Inquiry (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Sun, 24 Apr 2005 16:04:21 +0200; Expect a 225W resistor dissipating 160W to become quite hot... On a more serious turn, good engineering practice has been to overrate any bleeder with a safety factor of 4. The current 100 k bleeder; /archives//html/Amps/2005-04/msg00473.html (10,197 bytes)
46. [Amps] Bleeder thermal ratings... (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Mon, 25 Apr 2005 08:33:44 +0200; Just found a graph on the Danish power resistor manufacturer Danotherm A/S website that plots the temperature rise for tubular vitreous resistors as a function of power. Their resistors are rated for; /archives//html/Amps/2005-04/msg00516.html (8,375 bytes)
47. Re: [Amps] Resistors (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Tue, 26 Apr 2005 18:26:28 +0200; I certainly can vouch myself for the longevity of the "Oilite" bearings. In the blower motors of our ex-Air Force 208U-10's these sleeve bearings are used, and to date only one single bearing failure; /archives//html/Amps/2005-04/msg00556.html (11,316 bytes)
48. Re: [Amps] DC Blocking Capacitor (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Wed, 27 Apr 2005 07:50:33 +0200; I wonder if you may have gotten the numbers "backwards"... In my understanding of AC circuits, the requirement for the reactance of the blocking capacitor is to decrease with decreasing plate load im; /archives//html/Amps/2005-04/msg00570.html (12,243 bytes)
49. Re: [Amps] Plate transformer current unknown (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Fri, 29 Apr 2005 18:31:22 +0200; As a rough estimate and starting point you can use the weight of the transformer. A 1 kVA CCS rated transformer weighs about 45 lbs or 20 kg, and it will most certainly hold up for 2 kVA ICAS. In you; /archives//html/Amps/2005-04/msg00619.html (9,590 bytes)
50. Re: [Amps] Input Impedance of RF MOS amp (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Thu, 5 May 2005 16:58:30 +0200; It is most likely that the KL300 is optimized for the 27 MHz range, as being a CB amplifier. This usually means that the magnetic core area and number of turns in the input transformer may be insuffi; /archives//html/Amps/2005-05/msg00084.html (10,148 bytes)
51. Re: [Amps] Type 813 BP Pentode (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Sun, 8 May 2005 15:38:31 +0200; For some ideas, take a look at: http://stevepage.netfirms.com/813_amplifier_2.htm or http://w7iuv.com/813.htm I sometimes run myself 4 x 813 in parallel (Va 2,8 kV, Ia 900 mA on the peaks), usually d; /archives//html/Amps/2005-05/msg00134.html (8,807 bytes)
52. Re: [Amps] ARF1505 (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Sat, 21 May 2005 10:36:25 +0200; A comment on the 13.56 MHz ISM frequency tolerances. There are allocations in all 3 ITU regions between 13200 and 13360 kHz for air-ground HF/SSB. It is quite common in Europe to have to listen at VE; /archives//html/Amps/2005-05/msg00236.html (13,725 bytes)
53. Re: [Amps] RE : copper or silver in tank circuit? (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Fri, 17 Jun 2005 21:02:39 +0200; "While it is straight forward mathematics to calculate the depth of penetration of RF current, at any given frequency, it suffices to say that at HF, there is no penetration, and hence the currents f; /archives//html/Amps/2005-06/msg00136.html (8,377 bytes)
54. Re: [Amps] Cheap network analyser on eBay (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Sat, 25 Jun 2005 10:36:07 +0200; This early 1970's "network analyser" is only a small part of a measuring system. The unit offered is the transmission test part, and was intended for measuring the transmission properties of componen; /archives//html/Amps/2005-06/msg00224.html (11,470 bytes)
55. Re: [Amps] Signal Generators (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Sat, 2 Jul 2005 11:01:22 +0200; In my opinion the HP8640 is a superior signal generator. Its phase noise performance is hard to match even by today's signal generators, and it is still in the same class as the best HF receivers aro; /archives//html/Amps/2005-07/msg00003.html (9,398 bytes)
56. Re: [Amps] Trans question (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Sat, 9 Jul 2005 09:31:39 +0200; Usually this means that you have first choices of either 208 V or 240 V by connecting between 0 and 208 or 0 and 240. If you need to use non-standard line voltages, you can connect to -10 and 240 V t; /archives//html/Amps/2005-07/msg00073.html (8,420 bytes)
57. Re: [Amps] HP noise figure meters (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Sat, 9 Jul 2005 16:25:36 +0200; The main differences between the 8970A and B are the frequency range of the B, that goes to 1800 MHz (option 020, 2047 MHz), and the somewhat tighter accuracy specification. A "bargain" would also be; /archives//html/Amps/2005-07/msg00077.html (8,584 bytes)
58. Re: [Amps] Transformer core shorted to secondary winding?? (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Sun, 24 Jul 2005 14:18:50 +0200; Have you measured the no-load DC voltage (the 811A's pulled out or biased off) with the HV probe? There are not so many components that can fail in such a circuit, and usually they tend to give out s; /archives//html/Amps/2005-07/msg00294.html (14,811 bytes)
59. Re: [Amps] Transformer core shorted to secondary winding?? (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Sun, 24 Jul 2005 15:14:42 +0200; A bleeder resistor should not be so hot that it smells or discolors. 1500V over 50000 ohms generates about 35 W, so an 100 W resistor has a reasonable safety margin. A way to check if the full-wave c; /archives//html/Amps/2005-07/msg00297.html (20,545 bytes)
60. Re: [Amps] Amp question (score: 1): Author: Karl-Arne Markström <sm0aom@telia.com>; Date: Tue, 26 Jul 2005 10:25:07 +0200; The reason why this works is that the output combining network in most solid-state PA's are "zero-degree hybrids", which means that they expect the voltages (or currents) driving them to be in-phase; /archives//html/Amps/2005-07/msg00314.html (10,792 bytes)

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