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I am thinking of adding a tuned input to one of my amps.? Does anyone make a board?? I searched around and there seems to be nothing available. Does anyone have a board laying around?? Maybe from

What negative voltage ranges should a find in this amplifier’s ALC circuitry? I know it depends on the setting of the pot. Just curious about what variation I should see. Richard WB5NEN

Just check the FU-81(GU-81M) amplifier, the screen grid current is 260mA for two tubes.so I guess 130mA per tube.Don't believe the rumors that the GU-81M won't work at 21MHz and above. This is

Hsu, Thanks for the details on the gu81m tubes. They look great too. Too pretty to be hidden. I have settled now on two gu43b tubes. Should be happy at 2kw and push to 3kw if needed.

Hal, When I got the transformer I did some experimenting, as you do :) . I found that if I run the outer two phases in parallel ( with one reverse polarity from memory, tbc) I could also parallel the

Jeff, I have parked the idea of the triode and have ordered the tetrode boards from Dom, f1frv who has been very helpful. I am also finalising an order with Alex Ur4LL, for some gu43b tubes,

Negatory. Being HFers, we can be forgiven, perhaps, for forgetting that at V/UHF, things are different... and there are such things as "transmission lines". This is a traditional stripline plate tank,

Watch out.? You will introduce a ton of stray C on that hb teflon? plate block cap assy.....to the chassis below it. That amounts to a bunch more anode to chassis C. Knowing the spacing, and the

Insert a teflon sheet or other suitable insulator between 2 copper slabs, one of which is directly on the anode. Here is mine to give an idea. It's based on plans published by YU1AW. (Ignore the

Yes, similar to a K2RIW amp.

An even better option, if your tank is well insulated (as mine is) is to remove the blocking cap entirely How can this be done?

Tim and anyone interested : Here’s looking inside the RF box. You can see the original blocking cap - just like yours ! This is a YU1AW “Lazy Builder” design. Suited my construction capabilities

Tim - here’s what happened to my 2200pF blocking cap. Cracked and a little burnt. This caused ALL of the “thermal” power output drift in my 2m amp. She’s rock solid now, for complete JT65B

No probs. An even better option, if your tank is well insulated (as mine is) is to remove the blocking cap entirely and connect the anode directly to the tank. I used large Teflon standoff posts and

The G2 volt is 850V， yes， very large G2 current, hundreds milliampre Hsu Steve <k0xp@...> 于2023年12月28日周四 04:08写道：

Hsu, what g2 did you use? It seems as though the GU-81M consumes a LOT of g2 current, too... 73 & HNY, Steve K0XP

It seems that the GU-81M is what you want. I just built an amplifier using a pair of FU-81/FM-8 (GU-81M/GI-8) with output power: 1.8-14MHz, 2900W, 21-28Mhz, 2500W.grid driven, if you only want 1KW,

Des, Ian's callsign is GM3SEK. When I was involved in Underground Coal Mining many of the Vehicles ran on 3 phase a.c., with stout umbilical cords connecting To 4160, 3-Ph distribution xfmrs dragged

I would have to disagree with the 2500V in the case of the GS35 specifically.? To get 1.5KW out, I think the Ig will be too high at that low of a voltage. I ran 4300V on mine and that was very nice

Thanks! I'm down with COVID right now, the junkbox has some other Ceramic button caps, I switch it out in a few days and let you know how I got on. vy73 Tim