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101. Re: [Amps] RF insulating materials - engineered plastics (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Tue, 28 Aug 2012 07:51:20 -0600; John, This is extremely interesting but something seems incorrect. Assuming your teflon dielectric puck: C(pf) = .2248 * K * A * (N-1) / d = .2248 * 2.1 * PI * (1.5^2) * 1 / .75 = 4.45pF Xc @ 90MHz =; /archives//html/Amps/2012-08/msg00499.html (10,660 bytes)
102. Re: [Amps] RF insulating materials - engineered plastics (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Tue, 28 Aug 2012 09:23:57 -0600; Jeff, Whoops! You are are correct and thanks for finding the error. That makes the current amplitute discrepancy 4 times less but the calculated current is still 32 times the reported current. Will w; /archives//html/Amps/2012-08/msg00504.html (14,086 bytes)
103. Re: [Amps] Amplifier Tuning Device (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Mon, 10 Sep 2012 12:40:57 -0600; LTSpice can create the wave file with any sampling freq, number of bits, and with complete control of ramp up/down times, duty cycle etc. Program is totally free. Larry, W0QE If anyone has access to; /archives//html/Amps/2012-09/msg00153.html (8,981 bytes)
104. [Amps] Using small relays at RF (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Tue, 30 Oct 2012 09:01:47 -0600; To all, I recently ran some fairly extensive tests on common signal relays at RF frequencies. Some of you might find this interesting as these relays are as fast as vacuum relays and can hot switch m; /archives//html/Amps/2012-10/msg00215.html (6,637 bytes)
105. Re: [Amps] hf-2500 (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Sat, 22 Dec 2012 09:25:27 -0700; I used to think that shorted turns on powdered iron toroids was bad until I did some tests. My tests were not exhaustive but winding some the inductance to ~1/2 of the inductance with the turns not s; /archives//html/Amps/2012-12/msg00134.html (10,808 bytes)
106. Re: [Amps] hf-2500 (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Sun, 23 Dec 2012 11:08:29 -0700; Gary, Nothing is black and white! Just because someone says something there is always more to the story. Air (u=1) definitely has considerable flux leakage. Obviously as the permeability goes up so d; /archives//html/Amps/2012-12/msg00164.html (9,310 bytes)
107. Re: [Amps] Ameritron AL-1500 inquiry (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Thu, 24 Jan 2013 19:02:09 -0700; Jim, Look at TE Connectivity (Schrack) RT31C0xx which has the same footprint with bifurcated contacts. This will fix the intermittent RX issues. I have a web page with the datasheet at http://www.w0q; /archives//html/Amps/2013-01/msg00147.html (8,522 bytes)
108. Re: [Amps] Ameritron AL-1500 inquiry (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Fri, 25 Jan 2013 09:50:44 -0700; Jeff, Jim, and a few others who emailed me, Has no one heard of places like FindChips and Octopart? Don't waste your time going to distributors one at a time when places like FindChips will do it for; /archives//html/Amps/2013-01/msg00155.html (10,064 bytes)
109. Re: [Amps] Freescale LDMOS devices (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Fri, 08 Mar 2013 16:02:11 -0700; There are 2 type of power factor calculations. For linear loads PF = true power / apparent power = cos(theta) where theta is the angle between the voltage and current entering the device. Think "moto; /archives//html/Amps/2013-03/msg00099.html (11,750 bytes)
110. Re: [Amps] Power factor correction (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Tue, 12 Mar 2013 20:34:47 -0600; Nothing is missing here at all. I posted the industry accepted formula for power factor here a few days ago. You can find it on Wikipedia. A few minutes with LTSpice will show that the power factor c; /archives//html/Amps/2013-03/msg00193.html (9,976 bytes)
111. Re: [Amps] Advice needed for SS amp (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Thu, 06 Jun 2013 08:24:58 -0600; 2000W of power(heat) into 1 gallon of pure water raises the temperature 7.7deg. C (13.7deg. F) per minute. Anything you do to water such as mixing in alcohol reduces the cooling capacity somewhat. In; /archives//html/Amps/2013-06/msg00104.html (11,864 bytes)
112. Re: [Amps] Advice needed for SS amp (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Thu, 06 Jun 2013 12:52:25 -0600; Jim, I have done this calculation several times so maybe someone else will do it as verification. Using the temperature rise I posted and your example of 1500W & 1/2 gal. water starting at 50deg F wo; /archives//html/Amps/2013-06/msg00129.html (10,079 bytes)
113. [Amps] Cable shielding and grounding paper (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Sat, 08 Jun 2013 08:34:57 -0600; http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090030527_2009031335.pdf The above paper shows noise measurements made from .01 to 400 MHz for several cable configurations including the classi; /archives//html/Amps/2013-06/msg00180.html (6,745 bytes)
114. Re: [Amps] Cable shielding and grounding paper (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Sat, 08 Jun 2013 09:38:31 -0600; Joe, Another very interesting source of EMI information is http://www.compliance-club.com <http://www.compliance-club.com/> which you need to join (free) to view their archives. For example look at h; /archives//html/Amps/2013-06/msg00183.html (9,476 bytes)
115. Re: [Amps] The Pin One Problem (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Sat, 08 Jun 2013 23:03:23 -0600; Let me make a brief comment. I think it is more accurate to say Pin 1 problems are the most common cause of RF Suscepiblity (not RFI). In industry terms, susceptibility is interference from an intent; /archives//html/Amps/2013-06/msg00198.html (11,227 bytes)
116. Re: [Amps] NFB vs IMD question (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Wed, 07 Aug 2013 10:25:08 -0600; Jim, I believe you are measuring the IMD of the K3 or at least seeing results that are influenced by the K3. I have made IMD measurements of the K3 and they are not that great and were the best at th; /archives//html/Amps/2013-08/msg00060.html (11,667 bytes)
117. Re: [Amps] 200-ohm tank and "un-un" in HF amp design? (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Sun, 20 Oct 2013 16:16:02 -0600; The way I see it the 200:50 ohm bifilar xfmr reduces the loading cap value but doubles the voltage requirement and eliminates the need for a choke to ground in case the plate blocking cap(s) fail. It; /archives//html/Amps/2013-10/msg00363.html (10,425 bytes)
118. Re: [Amps] minimum length of 1:1 transmission line balun ? (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Tue, 22 Oct 2013 12:44:25 -0600; Carel, This is a very easy problem to solve with a minimal amount of test equipment. Your 1/10 wavelength (VF = 1 ion outside of coax) is a pretty reasonable number but this length can be reduced con; /archives//html/Amps/2013-10/msg00404.html (10,302 bytes)
119. Re: [Amps] Best source for Gigavac GH-1 ? (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Sat, 09 Nov 2013 23:38:19 -0700; Jim, What is failing on the relays? Is it the coil opening up, the contacts sticking, the receive side contact appearing open, or the pivot getting sloppy and the contacts bouncing too much? I have t; /archives//html/Amps/2013-11/msg00195.html (10,476 bytes)
120. Re: [Amps] Best source for Gigavac GH-1 ? (score: 1): Author: Larry Benko <xxw0qe@comcast.net>; Date: Sun, 10 Nov 2013 08:39:52 -0700; Jim, Relay contacts stick only if hot switching is involved in some way. There is no mechanism for them to stick (unless the internal contact pivot wears down to nothing or the spring fails) that doe; /archives//html/Amps/2013-11/msg00213.html (12,242 bytes)

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