Are you saying that current takes the path of least resistance? What a great concept! That sure explains why insulation on a conductor works. 73, Gerald K5GW In a message dated 10/4/2010 3:51:01 P.M.
Hi Dan, there are a couple of data points on this: hole size in the section dealing with rfi and shielding considerations. ventilation; not screen. Any rf leakage is apparently very small or we would
The problem with switchers or using any regulated supply is the cold resistance of the heater/filament is typically 10% of the hot resistance. That issue is automatically handled by the current limit
Jim, please bring me up to speed on why the switcher will not work with a directly heated tube. I am not challenging the information; just asking for enlightenment! 73, Gerald K5GW In a message dated
So, the answer is bid the maximum you are willing to pay and let the system protect you. Let the fools/snipers pay $100 more than it is worth. I have on a couple of occasions been outbid only to have
Hi Roger, 50 ohm to 50 ohm matching can be done with two components by using them as a parallel tuned circuit. I have had good results on 6m using a parallel tuned circuit and taping the inductor for
Hi Paul, there is no reason the tuner "has" to be inside the amplifier is there? If so, maybe a tuner can be scavenged for the application. When you pick a tuner, it needs to be a unit that retains t
Ebay usually has several listed for reasonable prices. 73, Gerald K5GW In a message dated 10/11/2010 8:34:18 A.M. Central Daylight Time, mtnest@hartcom.net writes: To the group.......... When conside
Tom, your isp doesn't like me! 73, Gerald K5GW ____________________________________ From: MAILER-DAEMON@aol.com To: TexasRF@aol.com Sent: 10/11/2010 8:56:52 A.M. Central Daylight Time Subj: Returned
Kevin, when you say no plate current, do you mean there is no idling plate current when the amplifier is keyed on? Gerald K5GW In a message dated 10/18/2010 2:21:06 P.M. Central Daylight Time, knormo
Carl is 100% right. Additionally, zeners fail in the shorted mode typically. I personally have never seen a zener fail in open circuit condition. As far as the bias voltage dropping from 5.8 down to
Carl and all, if the plate choke opened, there would be no plate voltage or current alright. But, with drive, the grid current would be there in abundance. 73, Gerald K5GW In a message dated 10/19/20
Fortunately that tube has a fairly robust grid so short periods of drive without plate voltage probably will not damage the tube. Prolonged operation most certainly would damage the tube. We are talk
With say 1.3A cathode current (plate + grid) and 5.8v, that will be 7.54W dissipation. So, the 10W rating seems ok but not a lot of headroom. Considering the diode is using the chassis as a heatsink,
Shoot! I thought it might mean Electron Induced Destruction. Now trying to figure out what IED is. 73, Gerald K5GW In a message dated 10/19/2010 3:30:40 P.M. Central Daylight Time, km1h@jeremy.mv.com
Hi Kevin, Bob, W6PO, spent many years in the development lab at Eimac/Varian and we enjoy the benefits of his work even today. No doubt he learned early on about zener bias and failures; hence the us
Bill and others, The comment about passive grid and neutralization brings up a question: At VHF and UHF, running grounded grid, the need for neutralization is indicated when the plate current dip and
Before I run off to invent a new square wheel, here is a question for the group: I want to tune up a new cathode input circuit for a 222 MHz amplifier using a GS23B tetrode (I have some already). I a
Jim, in using the string of diodes for bias, do you notice any drift in the idle current as they warm up? Purchased in quantity these big diodes are way less expensive than a big zener diode and woul
Bill, I was thinking the nominal 50 ohm value was derived from the time varying elements of the cathode voltage and current over the drive cycle. It occurred to me that I can easily test this idea on