We know that negative feedback in audio amplifiers improves linearity and reduces distortion. What would it take to improve RF linears with feedback? In thinking about it for a bit (not enough time,
Grounded grid amplifiers already have a very high level of almost perfect negative feedback as long as the grid is properly grounded. Some tubes have long grid leads that add some amount of uncontro
True enough. However, with a grid-driven tetrode, cathode R subtracts from the cathode/screen potential on voice peaks, so R must be kept fairly low. Eimac recommends 11-ohms of Rc for the 4CX600JA.
Collins has used negative rf feedback over the tube final and driver stages for years. More of this in W6SAIs RADIO HANDBOOKs. The SB 220 har rf feed: the grid capacitors and grid to anode capacitanc
It's actually 1964. There's an awful amount in there about applying NFB in tube linears, over one, two and three stages too. Not an easily available book, but a super one. I wouldn't be without mine.
Author: Ian White, G3SEK" <g3sek@ifwtech.com (Ian White, G3SEK)
Date: Tue, 26 Sep 2000 11:16:42 +0100
I found one about a year ago at bookfinders.com, a network of mostly small second-hand book dealers. You enter some search data - in this case, "pappenfus" (one "s") will find what you want - and it
The "Orr system" is useless. It adds uncontrolled RF feedback with undesired phase shift to the PA. Feedback level varies with drive power, and from band to band. It adds instability, and if you use
Capacitive feedback in grounded cathode circuits can work well - BUT:- In the 'standard' Bruene neutralising circuit, where a grid tuned circuit has one end to the grid and the cold end via a capacit
Hi Peter. Let's look at that. The grid to ground reactance is 70 ohms per tube on 3.5 MHz. That reactance is fed from the cathode's ~100 volts or so peak through a series resistance of about 100 ohms
I obviously didn't make myself clear. I was musing along the lines of 'it was done in the 30L1 for another reason that is not immediately apparent', rather than 'this is an approach designed to give
Another possible reason for the 220pF grid to ground in the 30L1 comes to mind. 220pF and 125 nH resonate about 30MHz. The grid structure inductance plus socket plus capacitor lead length could just
________________________________________________________________ Is a resistor in the cathode true negative feedback? Sounds more like a gain reduction/stability method to me. Putting a resistor in t
yea, verily What tuning cap? The Bruene circuit uses no tuning capacitor. The tuning is done with a roller coil to cancel grid reactance. Add a tune cap. to the grid and you get a master oscillator.
On 40m, I couldn't hear the difference. end - Rich..., 805.386.3734, www.vcnet.com/measures. end -- FAQ on WWW: http://www.contesting.com/FAQ/amps Submissions: amps@contesting.com Administrative req
If you look at the series of "production changes" and field mods to the 30L1, plus their suggestion of using a long cable to the exciter, it appears they were somewhat unsuccessful at making the amp
Of course it is! 100% of the output current flows through the cathode. That places the output and input in series. Adding a series resistor there adds negative feedback that is always very near or i
As Rich would say, verily. I suspect part of the problem is that the 811 isn't really an RF tube - at least not above 15MHz or so. 73 Peter G3RZP -- FAQ on WWW: http://www.contesting.com/FAQ/amps Sub
least Not so, a push-pull pair will make a good amp on six meters. es 73 de Pete WA5JCI EM21 6 meter VUCC # 361/658-WAS # 490-WAC CW 2 meter VUCC # 346/190 -- FAQ on WWW: http://www.contesting.com/F
you surprise me. Surely wouldn't be my first choice - or second.....even though they're rated to 60MHz at full input. So, for that matter, are 807s. Are they stable enough in linear service not to ha
though they Check out 73 magazine, July 1970. K1CLL built an amp using 811As in push-pull. I actually duplicated the amp and it worked as stated. He claimed 400 watts out on CW. I didn't have a watt