Ok, gang, while the pot has been stired again, let me ask a related question of the group of experts. Without access to a spectrum analyzer, how does one determine what frequency your new amp has any
Mike asks: To some extent, does it matter? In the 'good old days', the recommendation was to reduce the bias and the HV so the tube was dissipating about 2/3rds of rated plate dissipation. Using a du
Here is what I did: First of all, if the amp is unstable you can easily make it oscillate. You can do this by a couple of ways. Keeping an eye on a TV is NOT the way as you have no idea of what freq
On Wed, 07 Apr 1999 01:51:09 -0700 "Michael J. Baker" <K0qz@primenet.com> writes: A GDO in diode mode will work with reasonable accuracy if you have it set for minimum coupling. Follow Peter's sugges
It seems to me that this business of the resistors opening/going high etc is a potential problem, since a perfectly stable amp can after a few years develop parasitics just because the resistors get
Typical globar resistors have 3 to 7 times more intrinsic L than is optimal for vhf suppressor service.. Cesiwid Co. told me they could manufacture a resistor with under 10nH of intrinsic L. The pri
-- To: <amps@contesting.com> Then how can the neon glow orange as you stated if no drive is applied? Surely this must be a test with drive applied. And if it is with no drive applied and the neon glo
To: <amps@contesting.com> ? amen. In parasite-arced bandswitches, damage occurs primarily on the 10m and 15m taps. . ? However, in uhf amplifiers the anode-resonance is the tank. In hf amplifiers th
Agreed. Still you can design an HF amp to be unconditionally stable and test for that condition as well. Well, then those amps have design problems. Did those oscillations that you mention from your
ALL SNIPPED Completely subjective and unproven Rich. Another option which I subscribe to is Peters/Ians version when it comes to parasitics. In a real amp that is 100% stable to start with, the switc
? Tuning the HF tank circuit and disconnecting the hf load have virtually nothing to do with what is happening in the anode-resonant circuit where the parasitic oscillations take place. ? Both. Resi
? the photographs lie? ? The TL-922 and SB-220 bandswitches have a withstanding potential of a bit under 6000v at sea level. The peak RF potential in both amplifiers is around 2900v. (see arced band
Ah contrair! You yourself have said that the anode-resonant circuit is composed of Ctune. Is not Ctune in the tank circuit??? Sooooooo.......tuning the tank circuit DOES make a difference. Also, it
I say: So the bandswitch arced. OK, I'll give you that it could be an oscillation. But how can you say that Rsupp increased 100% AFTER the bandswitch arcing? Did you measure Rsupp BEFORE the bandswit
? Adjusting C-tune makes little difference in the anode resonance since C-tune is effectively in series with C-anode, which is much smaller. ? 'Tis hardly a good idea to tempt fate this close to the
Not necessarily, Rich. In many, many tubes (such as the 4-1K), the Canode of the tube can be large. In the YC-156 (I think) Canode is on the order of 35 pF. The 4-1K has a Cout of 7.6 pF. However, o
I've always been told (and I believe it) that a stage drawing grid current with no drive is either a stage that is oscillating or has a very gassy tube. I have seen a 4-250A drawing 50mA of grid curr
? What is the anode-resonance when your amplifier is tuned to 10m? . . to 80m? thanks. ? one end of C-anode connects to C-tune through chassis gnd. When viewed from the ungrounded ends, these two ca
Anthing taken long after the fact is open to question. Simple I believe. The voltage is not an issue in the SB-220 but the current is. I have examined almost 200 bandswitches and amps that have been
? So it is the loss of contact tension that indirectly causes the resistance of the suppressor resistors to substantially increase without showing an outward sign of resistor overheating? ? only ope