I've decided to use a 4-wire circuit, including a neutral for the 120v loads. The connectors are expensive and most of the local hardware stores didn't have the 4-conductor cable for the line cord, b
It's become an oscillator! The high swr is an indication that it is oscillating on a frequency removed from the resonant frequency of the antenna. How to fix it could be complicated. You need to dete
I believe that the major portion of the heat dissipated by the plate is radiated rather than conducted to the plate cap. The job of the cap is primarily to keep the seal area cool. -- Vic, K2VCO Fres
According to the G3SEK Pi/L design spreadsheet, the values are as follows: Class A: 1.3 Class AB: 1.5-1.7 Class B: 1.57-1.8 Class C: 2.0 -- Vic, K2VCO Fresno CA http://www.qsl.net/k2vco/ ____________
Most of the "parasitic tank circuits" consist of 'accidental' capacitance and inductance and vary greatly depending on construction practice. For example, one "tank coil" consists of the inductance i
Does anyone know what the actual plate voltage under load (at 500 ma or so) of the SB-200 is? -- Vic, K2VCO Fresno CA http://www.qsl.net/k2vco/ _______________________________________________ Amps ma
Thanks. That agrees with the PSU Designer program. I'm using an SB-200 transformer and just a bit more capacity in the supply for my 813 amplifier. I wanted to get a sanity check before cutting the p
Concerning the metal film resistors, I just tried to measure the inductance of several different types of 3 watt 100 ohm resistors that I had, including some that I had successfully used in parasitic
My guess is that this is the company: <http://www.temex-ceramics.com/site/en/home-1.html> I didn't see an HPA series, though. -- Vic, K2VCO Fresno CA http://www.qsl.net/k2vco/ _______________________
I have a recurring problem with this with a homemade switchbox (luckily in my shack, not on a tower). Deoxit does help, but the problem recurs. It's been suggested that I run a bit of DC through the
The capacitors don't replace batteries, but they can save a lot in power supply and cable size. I used to have a ss amp which required around 90A at 12v, and I used a pair of 75 amp Astrons and some
The schematic shows a swamped grid-driven circuit. I think you will need to develop about 225 volts across that 50 ohm resistor in order to drive the tube in class B, which means that you'll need to
Since it's a single-band amplfier, it would be simple to use a balanced grid tank circuit and connect the 'bottom' to a neutralizing capacitor to the plate. I'm using a grid-driven circuit in my 813
My guess is that the area of the grid is very small. So even though it is closer to the plate than the filament is, there's less capacitance. In a higher-mu tube there is much more grid area. -- Vic,
I don't have an 833A to measure, but why is this impossible? The filament is big and has a lot of area and so is the plate. Although the grid is lightly closer to the plate than the filament is, the
I did some testing of my 2 x 813, class-c grid-driven amplifier under HV for the first time today. After adjusting the neutralization (with HV off), I applied HV and set the bias for 50 ma ZSAC (ther
Yes, there are VHF suppressors. I am thinking that the neutralization was upset because I adjusted it before I installed the plate transformer, which is not that far from the neutralizing capacitor.
That's what I observe. As several others said, there are plenty of feedback paths, especially without the shielding. When I adjusted the neutralization I got a significant dip in RF feedthrough, but
My t/r circuit applies bias beyond cutoff when the ptt is open. When it's closed, the bias drops to a point which allows 50 ma of zero-signal plate current (about -50V). When drive is applied, rectif