QRO indirectly heated or rugged tubes for mobile leenyar

[Opcom]

I'm thinkin about how to equip the new "M8109" communications/camping truck. I may have mentioned that I sold the M35 commo truck and am building a new vehicle.

What is missing is an amplifier that will stand up to constant AM use at the legal limit as well as survive bouncing and jarring inherent in a 5-ton military truck. For this reason I won't use an amp like the NCL-2000.

All of the inexpensive 'large' tubes I see discussed around here are directly heated. I am concerned that tubes like the 3-500Z and the more costly 3-1000 or  3CX3000 will suffer filament damage if subjected to the mechanical shock of being driven around in the truck.

What I am looking into is a tube solution with 1500-2000 watts dissipation and a rugged design.

There is an RF deck here with six 4CX250B's in it, an old IFI broadband amplifier. It could be a candidate but I have never run that many in parallel and it could cause instability. I'd prefer 1 or 2 tubes at most. There's that big Russian tube, question is how available are they really, and is there an actual socket.

I want to be clear the amplifier will only be used while stationary.

I' be grateful for suggestions including any experience of using directly heated tubes in a mobile environment. I will build the amplifier from parts or modify something.

[WQ9E]

Patrick,

Most of the big Soviet era power tubes on ebay were designed for mobile and/or airborne application so take a look at some of those possibilities.  I use GU74B/4CX800 tubes in my home built amp and they work well but they are a lot more expensive now than when I designed the unit 10 years ago.  There are a lot of low cost choices out there now.

[KM1H]

A couple of GU-81M's?

[K5IIA]

i'm a rookie but man coudnt you do something similiar to the class e rigs?

[KD6VXI]

OpCom,

Haven't had a problem with the 3CX3000 mobile yet.  I've put a few in service, mostly in diesel trucks.  The constant RPM keeps the alternator happy, a single 300A leece neville will power it, but barely.  Some people run them 'goin down the highway', some people swear it will kill the tube.  Haven't had a problem yet.

The 4CX5000R (THE ARE VERSION!!!) is a ruggedized tube, I've run it in the Suburban as well as the toter.  It's NEVER had a problem.  The R nomenclature is the "ruggedized" version, and with rated airflow, you won't have a problem stuffing 20 thousand watts + input into it.

4CX15,000s have been OK in the toter as well.  They run off a genset on the trailer.  I haven't run them mobile, but I have run the 4X5R mobile, and haven't had ANY problems with it.  The RF deck was originally a 4-1000....  Specifically built for mobile and base use:  The fils xformer (it's GG) is built into the RF deck, heavy, but you disconnect input, output, HV and unplug the amplifier from the inverter.  Plug it in to the base power supply, good to go.

Those are the tubes I'VE USED MOBILE!  Of course, your mileage may vary, but I'd suspect as long as you don't drive with the fils on, you'd be fine with any of them.....  I've DRIVEN with all the above mentioned tubes, keyed mobile, and haven't lost a fils yet......  And these are in either 3/4 ton suburbans (keep in mind, usually these have a LOT of weight in the back, xformers, caps and batteries for solid state drivers, so they DON'T bounce as much as stock ) or a big toter or other LARGISH vehicles.  The toter has a 33K GVWR, so it has HEAVY suspension and bounces around quite a bit on the California roads

--Shane
KD6VXI

[N6WDR]

Shane,
Sounds like you have been around the Superbowl Channel with that laundry list of tubes  .  I'll just be happy to get this plate modulated 4-1000 done  .

Richard

[Opcom]

i'm a rookie but man coudnt you do something similiar to the class e rigs?

I must confess I do not really understand how Class E works as an amplifier without a lot of distortion.
A minimum of 1500W CCS over the HF band (roughly 1.5 to 30 MHz coverage) might call for some expensive transistors and I am liable to have mismatches I can't do anything about.

I mentioned the 'big' directly heated tubes only as an example. It's interesting that they have taken the mechanical abuse in some cases, but it will be considerably worse in a military truck as anyone who has ridden in the back of an M35 or 5-ton would attest. It isn't trivial to build a large amplifier and I would hate to do it and then crack a 3CX3000.

[W7TFO]

The Collins HF-80 10kW amplifier used in the TSC-60 shelter that rode in several tactical vehicles (such as your 5-ton) used a pair of 4CX350's driving a 4CX15000.

They used regular Eimac sockets, and the whole transmitter was suspended by coiled steel cable shockmounts bolted to the shelter floor.  I decomissioned several of these and all the tubes were fine, even after years in mobile service.

73DG

[KD6VXI]

Oh boy, the 208U-10 brings back some serious memories!!!


--Shane
KD6VXI

[KD6VXI]

Again, check the R versions of the tubes...  They where made for moe-beels.

--Shane
Kay Dee 6 Vee Eckz Eye

[Opcom]

I remember seeing those kind of mounts. The first time I saw them, huge ones with several 1/2" cables, I didn't understand they were mounts. then realized the huge motor was not otherwise suspended.

Now you guys have me lusting with megalomania. I must resist the temptations of the dark side!  Remember my generator set is only rated 6KW. In TeXas, there is a little question of air conditioning power needs as well, even if only to keep the air intake for the tube cool. With some single phase trickery almost anything could be run at "QRP" levels.

I missed a huge oppty on a 208U-3A when I was a youngster I orget how young but I was still riding a 10-speed. A surplus scrapper who was hard on his luck offered it to me for $125 and it seemed complete. My "elmer" and my father both were against it but for different reasons. By the time 1 week later I had begged my way into my father agreeing to use the station wagon to help me get it as well as allowing me to spend most of my saved cash on it (educational purposes), the man had stripped it for parts. Now I look at Fair Radio and only wish. Phil said he has enough parts to put one together.

I'll offer this: the first real QRO amp showing up at the Bunker will be ceremoniously installed.

I'll think about it. The 3CX3000 Henry amp I already have would provide everything except the PI network, or PI-L.  There are also three 3-1000 amplifiers here, or rather RF generators. They don't work but it is not the power sections that burned up. Would a 3-1000 be durable enough assuming it would stay in the socket? I am concerned about the plate staying concentric with the other elements.

Another thing to think about is the HV. Fair Radio has the friont panel of the GRC-106 amplifiers available. These are 2500V 500mA power supplies operating from 27.5VDC. The power transformer is integral to the panel, which is why they don't sell well.

[KD6VXI]

I know of 8877s that are run mobile, but I wouldn't.  1200A7s are another story....  According to the story I was given, they where the 'solid state' 3 and 4-1000s (grounded grid).  I've run them mobile.

Look at the mobile amplifier xformers in the dahl catalog and roll your own.  A single 300A Leece Neville will power the xformer for a 3x3000, especially on SSB!  It's 3 phase, to boot, so you don't need LOTS of capacitors.  The CBers will sell them when they step up to Electrodynes...  Those have a pair of 600A stators on them....  BIG money there, the only 'legit' use I know of is railroad, but again, you can find CBers selling them off sometimes when down on their luck.

PERSONALLY, I wouldn't trust glass seals to hold up......  ESPECIALLY if they where hot.  But, 4 or 5 of the big 11 meter builders where using 3-500s up until recently... 

Those 3-1000s are nice...  I'd like to get my hands on one someday to throw back in my Harris... LOW drive, 65 in vs 120 for the 4-1000 in GG.  I can't up the voltage on the plate.....  Due to the rarity, I'd advise against throwing them mobile....  Bigger bottles = more forces on the pins of the tubes as they sway back and forth.

I'm guestimating this is a "duece and a half" like we had in the volunteer firefighting departments in Nevada...  Yeah, they do have fairly stiff suspensions.  How about using air bags to suspend the thing on?  They have chinese built ones for like 125 a pair capable of 1500+ pounds of lift for a pair...  A quad should do you nicely

--Shane

[Opcom]

I know of 8877s that are run mobile, but I wouldn't.  1200A7s are another story....  According to the story I was given, they where the 'solid state' 3 and 4-1000s (grounded grid).  I've run them mobile.

Look at the mobile amplifier xformers in the dahl catalog and roll your own.  A single 300A Leece Neville will power the xformer for a 3x3000, especially on SSB!  It's 3 phase, to boot, so you don't need LOTS of capacitors.  The CBers will sell them when they step up to Electrodynes...  Those have a pair of 600A stators on them....  BIG money there, the only 'legit' use I know of is railroad, but again, you can find CBers selling them off sometimes when down on their luck.

PERSONALLY, I wouldn't trust glass seals to hold up......  ESPECIALLY if they where hot.  But, 4 or 5 of the big 11 meter builders where using 3-500s up until recently...  

Those 3-1000s are nice...  I'd like to get my hands on one someday to throw back in my Harris... LOW drive, 65 in vs 120 for the 4-1000 in GG.  I can't up the voltage on the plate.....  Due to the rarity, I'd advise against throwing them mobile....  Bigger bottles = more forces on the pins of the tubes as they sway back and forth.

I'm guestimating this is a "duece and a half" like we had in the volunteer firefighting departments in Nevada...  Yeah, they do have fairly stiff suspensions.  How about using air bags to suspend the thing on?  They have chinese built ones for like 125 a pair capable of 1500+ pounds of lift for a pair...  A quad should do you nicely

--Shane

Yeah I better go with ceramic. I am not going to use it while in motion, only when parked and an antenna is set up. The truck is a real handful to drive and the only 2-way I am considering for cab use is a stock CB and a 2M rig on the calling freq. For safety reasons I don't want to distract myself while operating the vehicle.

I have an onboard APU, a 6KW 240V diesel generator to use for power. The truck engine alternator needs to stay unchanged. There is room for a Leece-Neville under the hood, but I think an air conditioning compressor would go better there.

The bags might be good on a regular size bobtail or 2-3 ton box truck but this is completely different. It's the next size up from the deuce and a half and a lot heavier. The truck's true nameplate cargo rating on-road is 10 tons therefore the per axle static weight on a bag could be 7000+. The 5 Ton rating is the "worst case" off-road rating. It's too big for me to start messing about like that because I am not qualified. The suspension is really super anyway, a lot of articulation all around. Just hard on the seat. A pic is attached to help clarify why it is not something I am confident assuming liability for.

[KD6VXI]

Agree 100 percent on all.... 

BUT, let me clarify...  On the airbags, I meant mount a plate to mount the leen-yar to...  NOT to actually bag the trucks suspension



80 meters is boomin right now...  Listenin to 80 meters AMI, everywhere seems to be over S9


--Shane
KD6VXI

[Opcom]

haha I see, an air bag for the windbag! I must not have been paying attention.