The AM Forum

need some input from the hive mind.

I've decided to build a single band amp for 160 over the summer as opposed to a whole tx. Easier construction, no huge mod iron,  a lot lighter, etc.

Don't care about the low efficiency. ::) I care about AFFORDABILITY. As in, buy a bunch of them for cheap. sockets and tubes. Something audiophools dont care about.

I'm going to use the ft 101's to drive it. So let's talk affordable tube and socket choices. I'm assuming G-G layout because I have lotsa drive power
and , well, it's easy. I'm real big into easy these days. I have to be. I have a 240 vac outlet available so a 220 1 phase plate transformer is a must.

What tube(s) would you use assuming 3 voltage choices?

1500 to 2000 jolts

2000 to 2500 jolts

>2500 jolts

Most depends on what kinda plate iron I nab during hamfest season. It will be a choke input suckply with a swinger and a smoother and oil caps full of pcb's. I dont give a shit about teh pcb's - what is it gonna do, give me cancer? FU, TOO LATE, BITCHES!  ;D

 

Go Classic Derb.

Pair of GG 3-500Zs. 1000 watts of plate dissapation and rugged proven pubes.
Plate supply and a zener for biass. Can't go wrong.

I've forgotten some of the specs on a 3-500. What's the max joltage on them? Around 2700 practically speaking?

P.S. Yeasu #1 is working again, mostly. I went in it and sprayed everything with CRC contact cleaner worked every control and switch and blew it out with the air kompressor. Only failed once in like 100 keydowns, where before it would fail on every other one. Gotta turn the bias pot all the way over to the stop to get to 50 ma, cant reach 60.

Gonna start pulling boards out and looking at what Frank did re the mods so I can do it to #2 once I get the tx working.

I digress. 3-500's, check.

In leanyar service it's 4 kV, Derb. They'll take more than that though.

well, like everything else, it's gonna be what I can find at the festers this year. Antenna is gonna be a vertical 65 ft with a kewl looking top hat and a base insulator. i'll throw down 500 ft  of ground radials in the spring.

Here's hoping for a good fester year with lots of old junk thats heavy they dont want to take home. I'm glad I got a heavy duty wifey.  ;D

P.S. Lookit the rig kart pix with the grounding bar installed over in station links and photos.  Do you want yours done up like that?

Its dem Cu standoffs that make it cool beanz............  klc

eh it goes into 1/2 " thick particle board.  :P I thought about using real insulators for mounting it in the rare case that I actually got a ground return strike -   but it was like 12 bucks for a new beehive vs. $1.29 at the depot. Cost aside, as long as you provide the lowest impedance path to ground you can, it doesn't matter how it's mounted.

In my case, there's a CU bulkhead 1/4" thick at the PVC pipe entrance to the shack, an everything is bonded to that and goes in and out using 4 stands of #6 about 3 ft long splitnutted and soldered together until it hits the first ground rod where it branches into 2 others 3 ft apart. Then 2 more going back to the service entrance using #6 and I got one more rod to drive before it gets too cold.

4 X 813s would work well on 160 gg at 2500 to 3000 v. fc

It's hard to beat a 572B as far as price goes. 225 watts of plate dissipation for $39.95 with a warranty from MFJ and the sockets are only $3.00 each.

4 of those and a good power supply should get you to the legal AM limit.

73

Marty WB2RJR

you may want to consider the russian gs-35b availible on epay.. i have 5 of them awaiting some plate iron.  about 100 bucks each shipped 2.5 kw plate diss..  sockets are easy to home brew or there is a guy in 4 land machining them with tephlon chimneys for about 150.. check out stews web page ab2ez..

I bought extra and would be willing to part with one for what i paid

yeh, that's what Jenny and Johnny Gonset are gonna be having hot gonset sex with.  ;D 572B is the damn near unbeatable tube. Also, I'm more a low voltage/hi current leaner - voltages above 2200 or so tend to get me nervous. It's like damn, is this feedthru gonna arc over? WHAT ABOUT THIS ONE?  ???

Would be kewl to see some hot glowing anode action through the tube porno peek a boo window though. If you see a carbon plate tube doing that, better shut off the rig.

Ya know, Marty's got a point. Those 572Bs are hard to beat.

Hey Bud, got yer care package today.  8)  Also got some parts from JN :D so we will be a busy bee over the next week or so.

Gotta transport da box to the da shack for opening. Not feeling so good today so taking it easy. We'll take a look at her tomorrow. maybe I'll feel a bit froggier later tonite. Spent most of day in bed. Wife says I am doing too much and not getting enough sleep.

572B/T160L isn't it. I thought they were 160 watts still not a lot of emission. Big bucks tubes. Quad 813s cheap and glow nice.

yeah quad 813's would be nice. I thought of that - thinkin on 160 the P-P Parallel setup would not be vis a vis gP issue. You'd need a hell of the fil xformer though. How much current would you need to light up 4 813's????? I have no reference material of any kind here anymore. wouldnt you need 20 amps + to light those things off @ 10 volts? hard to find .   :-X

GFZ,

I thought the same thing too. I have old stuff so it lists the 572 not the 572B. At that time I thought the 813 was the best buy for your money (it's price has gone up recently). A 572B is 225 watts plate dissipation, NOT 160. An 813 is 125 watts.

Can you buy an 813 for $39.95? Can you get a socket for it for $3.00? What's the cost, today for a 10v filament transformer vs one for 6.3v, to feed the tube/s and to run the same plate dissipation?

Derb has brought up an interesting question. Most of the stuff we work with is designed around cost. Always has been. He's thinking along these lines, as he mentioned sockets, and PS considerations. I'm sure he was thinking about it, but didn't say so, it's a lot easier to find a variable cap today good to 2 or 2.5 kv than one for 5 kv.

That could make a big cost difference. Not a big deal if you have old stuff around like me, but could be if the design calls for stuff you can't find in a modern linear, and thus is unavailable.

At any rate I was just thinking about this from a cost perspective, as that's what Derb mentioned.

73

Marty WB2RJR

572 is a very good tube but a 25 watt heater vs a 50 watt heater in the 813. $80 a pair would make a heck of a modulator.

Has anyone ever worn out an 813 under normal operating conditions?

Here is a good quick reference to compare different tubes.  It has the 572B listed.

http://www.rfparts.com/tubespecs.html

Least expensive has to be the 813's.

If I had to choose between 572b and 813, I'd likely go 813.

But yer all gone daft! The choice has to be 4-400s? Ya??

Big, glowing and cheep!  ;D

Nice sexy plates too!

Of course if you run them as triodes you can use the same amp as a 3-500 or 4-400 lineyarrrr.


But actually the choice is simple... it reduces to this: the first decent set of tubes that fall into your lap! That's the *best* choice!!!   :o :o ;D ;D :D


                  _-_-bear

yeah bear has it down. It's pretty much always been what I find at the festers over the summer that tells me what I'm gonna build.
Kinda like a cat adopting you. Courtesy of teh Jonny Novice I already have a good supply of 572's for the Gonset Amp (s) Jenny and Johnny Gonset.

This actually makes me wanna build a Quad 813 amp more. The 572's are for the Gonsets, if'n I use them on the amp I wont have any spares anymore. But finding a fil xfmr for 4 813's will be a problem.

Idea: buy another GSB 201, carefully take out tank circuit, install new tank circuit for 160. need a lot more C on the plate and
what not but thats not a problem. lotsa space. That might be the way to go. Instead of 80 A B C it would be 160 A B C adding or taking out fixed capacitance as needed to load the munky.

Reading about what tubes to use in an amp, and the problem finding a big transformer for the filaments got me to wondering. I wonder if you could get 10v at 20 amps out of a slightly reworked/adjusted switching power supply? 12 volt switchers seem pretty easy to come by, I think I bought some surplus ones for about $5 each that do 10-15 vdc at 12 amps. Not sure how hard they would be to decouple RF wise, RF chokes and caps I guess, but they might be an unconventional solution to finding big iron for filaments. Anyone got any thoughts on that?

how about a variac on a 12 volt transformer?

Finding a switcher at 5 volts is a piece of cake - use two for 10 volts!
They made them and still make them for a ton of current.

Otoh, big arse 5vdc regulated supplies used to be everywhere, and cheap.
I think you can probably still find them in a variety of sizes and shapes.
The transformers in them are still good.

As is the variac idea.

No reason to not regulate your fils, I expect. That means you can use a much higher voltage xfrmr and regulate it down... but that is a bit more work than a couple of xfmrs in parallel for extra current, or two in series for extra voltage...

And yes, you'd have to keep the RF out of a switching supply, probably more than you'd have to do with a standard regulated supply, but maybe not that much.

At least that's my take on it.

Ymmv.

           :D

                      _-_-WBear2GCR

PS. there may a reason to not use DC on a Directly Heated tube - one side of the tube's cathode/filament may not emit enough... that appears to happen with audio DHTs, iirc.

Bear and Frank,
I would be concerned about keeping the switching power supply crap out of the radio. I have been unsuccessful getting rid of their buzzy sound on 160-40M every 30khz. You need a real transformer for that task. SOMEONE here has to have a fil transformer that they'd let go reeeel cheep

Fred

Derb,

If your serious about quad 813's and start building it this summer, I'll send you or give you at a fester a Raytheon 10v @ 20 amp fil. xfor. , gratis.  Just trade me sumpin'  someday.

One item of note though, it has a 210/220/230 v. primary.

Yeah Fred, it depends much on the specifics of the switcher.
Some can be made extremely quiet.
There's an ICOM, iirc, that uses one as an (optional?) internal supply!
The better ones are running up around 500khz or higher. That may seem like a problem, and it can be, but that's really much much easier to filter out than a lower switching freq. And, yes you need shielding and bypassed feedthroughs, LPF, etc... some of the companies sell a "brick" whose sole purpose is to cancel out "nasties" and they're bosting some very low noise levels for critical applications...

Check the Vicor site for some up to date technology.

They're based up in northern Mass, iirc.

But yes, good old iron is reliable, simple and obtainable.

                 _-_-bear

Hey Derb,

 I waz looking through the Zed.L.R. Den of Partz...I founded a 4 1000 it's was a pull never used it...you want it it's yours...

4-1000A you will want at least 3300 volts to make 1500 watts out.
Really wants over 4 KV

Derb,
        I gotz to hit you back wit yo own wisdom that you hit me with!! Build the biggest maul you possibly can!!

If you think back some years ago you and I were tooling around at the M.D.F.M.A. fester at the howard county fairgrounds. I was talking to you about building a HB rig, something around 150w class with some unusual lashup of tubes. Kind of a "just for the hell of it" thing. You looked back at me and said "what in the hell ya wanna do that fer??"  "You gotta think C.B., build the biggest maul you possibly can" And the next tailgate vender I walked up to had a 4-1000 socket for $20!! The rest is; as they say..............history ;D ;D
                                         
                                                            The Slab Bacon

I ran a 4-1000A GG for years. Even tried it at 5500 volts once.
You need a real lot of air at 5500 because the monkey is really swinging.

How much power you guys think a quad 813 rig would do in am service? I have zero reference material here anymore. Whats the top joltage on a 813, around 2200? That amp will be running offa 220/240 so the fil transformer is good to go.

I went surfin. With 2250 you can get 375 out of a pair in ICAS service. X2 for a set of quads and derate a little bit. That's not a bad munky to swing. If I could find 2 more Gonsets this summer, I could rebuild one to be a 160 monobander or even a 160/75/40 3 bander. Just design and change the tank out for more C.

It occurs to me I may be biting off more than I can chew tryin to build something from scratch again. I've got a window of time now where I dont have any health insurance. Hauling around mauls may not be a good idea for a while. I be on the ala carte medical plan. I pay for everything. I outlived my insurance coverage. ::) and they cut me off. I'll get Medicare coverage later in the year.

We'll see what happens. I am going to get one more Gonset for sure so Jenny can have hot amplified munky sex with Johnny Gonset when I am out of the shack and they are in the dark. :-X That's the next thing after I finish my current workload. Another gsb 201 mark 2 or 3 to match the EE buddly sent my way. Easy fix on that radio unless the transformer is lunched out due to the 20 amp 'no blow' fuse. I'm hoping the resistor was enough of a fuse when it sizzled like a Bob Evans Breakfast. Why do poeple do such dumb things?

Then 160 time. 

 

Frank,

5500 is a joltage number that scares me.  :-X

P.S. I didnt get any work done today. One of my meds (Keppra) that was covered by my former insurance is 250 bucks a bottle now. We just cant do that. So I am under a seizure watch for a few days until I stabilize. I got a lot of parts I could be wiring in too. :'(

In AM leanyar service, a pair of 813s are good for 100-150 watts carrier and something around 100% modulation. Plate dissipation becomes the limiting factor. You may be able to get more, with higher voltage and piss beat operation. So a quad should get you near the 300 watt carrier level.

A mutual friend of our has used 813s in plate modulated service with 2500-3000 volts on them with no problems. In leanyar serive, triode connect them and run them at 2500 volts and you are golden.

Following your "build as big a maul as you can" philosophy, I'd go with a pair of 3-500Z with the 2500 volt supply.

yeah I gotz to admit that would be a good combo. How much do the pyrex chimneys cost for those? a fair amount as I remember.

I think I have some. If you get serious about doing this, let me know.

ok will do. I expect the decision will be made for me by whatever I find at the festers this year.

p.s. my doctor was able to set me up with 2 months worth of free samples of Keppra while I try to get on the manufacturers assistance program for po folks. That crap is $235 a bottle. So I am out of the woods on that for now. Gonna get back in the shack and get back to work today.