Luck doesn't matter so much here. Tubes like 8877 are inherently good under this perspective and do not require VHF suppressors, other tubes aren't stable and suppprssors must be installed, that's al
** Not quite, Mauri. The 8877 has about 2/3 as much feedback-C as the 3-500Z, but it has about 2x as much gain at 100 - 150MHz. 3-500Zs have a history of vhf parasite problems, so the 8877 should no
Author: Ian White, G3SEK" <g3sek@ifwtech.co.uk (Ian White, G3SEK)
Date: Wed, 6 Nov 2002 14:32:28 +0000
The 8877 is well known as a *stable* tube for amplifiers at 50MHz and 144MHz. With the input and output both tuned to the same frequency, and typically 15-18dB of on-frequency gain, it's stable. If y
** Agreed, Ian. However, VHF amplifiers do not have two resonances to deal with in the anode circuit - wherein the tube exhibits substantial gain. HF/MF amplifiers uniquely do -- one at the operatin
Author: Ian White, G3SEK" <g3sek@ifwtech.co.uk (Ian White, G3SEK)
Date: Wed, 6 Nov 2002 16:26:24 +0000
On the contrary, every VHF/UHF amp I can think of has at least one parasitic resonance. For example... 50MHz pi- or pi-l: parasitic resonance above the operating frequency, for exactly the same reaso
YES, YES, YES, this agrees with what I have seen in my amplifier projects. Reverse feedback must be kept below forward gain at any frequency. The grids (including g2) must be grounded effectiviely a