The AL-80B? does not use real deal plate block caps, but a pair of disc caps.? ?The disc caps are not RF rated either.? ? Any plate block cap needs to have enough pf? so it's reactance (XC)? is 5% ( or less) at 1.8 mhz.? There is barely any RF current flowing through a plate blocker on 160m...... but the current through em progressively increases as freq increases.? ? On 10m, there is loads of RF current through a plate blocker.? ?Reason is.... on 160m, the tube C (anode to grid) is directly in parallel with the C1 tune cap.? ?They are in parallel...via the plate block cap? between em.? ?On 160m, the tube C makes up a fraction of the total required C1 value.? On 10m, the tube C makes up most of the C1 tune C.? ?Think of the C1? tune cap as being a tiny variable padder, in parallel? with the tube C.?
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Correct component would be a pair of HEC? 500 pf HT-50/58,? 7.5 kv? ceramic doorknob caps in parallel .? You can buy those cheap, directly from mfj / Ameritron.? That's what's used in the Ameritron AL-1500 / AL-1200 / AL-82.?
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What else that will work is higher V rated disc caps.? Typ the higher V rated disc caps? will also handle more RF current.? I just finished testing a mess of new? .01uf ( 10,000 pf)? @ 30 kv? disc caps.? These are HUGE things at 1.125" diam x? 7/16" thick.? ?These are the blue chinese disc caps that I bought from their ebay store.? ?They tested between 9200-9700 pf..... and all 30 of em test to 15 kv? ( which is the limit of my hi-pot tester that I bought last year from CTR engineering).? ?These things handle stupid amounts of RF current.? ?They come in 10/20/30 kv rated.? They are so cheap, and shipping was cheap, so bought 30 of em.? ?So far, so good.? I can't blow em up.?
