Author: "Dr. David Kirkby" <david.kirkby@onetel.net>
Date: Mon, 13 Sep 2010 16:33:47 +0100
There's also some "air spaced" cables that have very high RF power handling. There not a lot of support of the inner conductor to the outer conductor. I forget what they call the stuff, but PTFE insu
Author: "Dr. David Kirkby" <david.kirkby@onetel.net>
Date: Wed, 15 Sep 2010 22:56:23 +0100
I would not let that worry you too much. I've found it often cheaper to buy things from the USA and get them shipped over to the UK than it is to buy the same item in the UK. I bought a Sun Blade 200
Author: "Dr. David Kirkby" <david.kirkby@onetel.net>
Date: Wed, 15 Sep 2010 23:54:51 +0100
If you go down with cash, you can often get offcuts from them too - at least that was the case. I've not been for over a decade Dave _______________________________________________ Amps mailing list
Author: "Dr. David Kirkby" <david.kirkby@onetel.net>
Date: Mon, 04 Oct 2010 13:08:48 +0100
I don't know the depth, but I know I had a 2 m anode line silver plated for a dual 4CX250B amplifier. Careful measurements before and after plating showed no statistically significant difference. The
Author: "Dr. David Kirkby" <david.kirkby@onetel.net>
Date: Tue, 05 Oct 2010 17:29:53 +0100
I can see some logic in that, though I agree with you it's not as simple as current just taking the lowest resistance path. The only analytical equation I've seen for skin depth assumes just two mate
Author: "Dr. David Kirkby" <david.kirkby@onetel.net>
Date: Thu, 07 Oct 2010 13:20:32 +0100
I think that assumption is probably invalid. If you covered the coil in heat shrink, which is a poor conductor, but much thicker than the skin depth, the current would not stay in the heat shrink, bu
Author: "Dr. David Kirkby" <david.kirkby@onetel.net>
Date: Sun, 02 Jan 2011 12:40:45 +0000
I don't have any of that exact spec, but have some Sprague devices which will probably do what you want. For feedthough applications, the value is generally not critical. They look identical to this:
Years ago when I was a school I part time (Saturday and some evenings) job working in Tandy (Radio Shack). Tandy used to see fuses in packs of 3. This guy came in and bought a pack of fuses. Then a f
Author: "Dr. David Kirkby" <david.kirkby@onetel.net>
Date: Tue, 01 Feb 2011 23:32:06 +0000
If you can get a free trial of some finite element software for thermal analysis, this sort of thing would be relatively easy to model. You could then see the effects of changing the thickness and le
There was a question here a few days ago about the dimensions for a heat spreader for an amp. I noted that in my opinion finite element software was the best way to solve this. Today, I decided to lo
Author: "Dr. David Kirkby" <david.kirkby@onetel.net>
Date: Thu, 10 Feb 2011 18:53:01 +0000
As I remarked before, I think the way to do this is to use finite element software. I found this, which is free for a limit of 1300 nodes, but is modestly priced ($50) to unlock the software, removin
Author: "Dr. David Kirkby" <david.kirkby@onetel.net>
Date: Tue, 15 Feb 2011 16:33:13 +0000
"Typical pulsed performance at frequency of 225 MHz, a supply voltage of 50 V and an IDq of 40 mA, a tp of 100 s with of 20 %:" Then it shows 1200 W. Everything on the data sheet refers to "pulses".
Author: "Dr. David Kirkby" <david.kirkby@onetel.net>
Date: Fri, 15 Apr 2011 09:23:51 +0100
I would not think it be very significant myself. My ex-boss (Prof. D. T. Delpy) used a technique for measuring air *velocity*, which I don't think is particularly relevant here, but I'll describe it
Wirewound resistors are not perfect, but at least they will be stable with temperature and power applied. The same can not be said for light bulbs. At 2.0 MHz, wire-would resistors might well be OK.
Author: "Dr. David Kirkby" <david.kirkby@onetel.net>
Date: Wed, 18 May 2011 05:36:40 +0100
1) Calculate the input power = V * I where V is anode/collector/drain voltage (depending on whether its tube or semiconductor I is the anode/collector/drain current (depending on whether it's tube or
Author: "Dr. David Kirkby" <david.kirkby@onetel.net>
Date: Fri, 20 May 2011 12:06:12 +0100
I don't know what one of those are, but the biggest problem is measuring RF power accurately. Let's be honest, it makes very little practical difference if you are running 90 W or 110 W, so a power m
<snip> I must admit, I tend to agree with your reasoning. Dave, G8WRB _______________________________________________ Amps mailing list Amps@contesting.com http://lists.contesting.com/mailman/listinf
My understanding was the constant voltage transformers basically saturated the core, which limits the output voltage. If so, then they would indeed produce a rather distorted waveform, as the core wo
Author: "Dr. David Kirkby" <david.kirkby@onetel.net>
Date: Mon, 06 Jun 2011 21:24:58 +0100
Are there any published designed for 2m linears using the 4CX1000A tube? I tried to build an amp with a pair of them in push-pull grounded screen, but it never worked well. Now thinking about somethi