If there wasnt such a big market for cheap amps then Ameritron would have
been out of buisness ages ago.
The POJ AL-811 series is a huge seller and the AL-80B isnt far behind. The
various SS models are also selling.
All their others combined are just a small fraction.
Get out into the real world and see what others actually buy.
Carl
KM1H
----- Original Message -----
From: "Jim Thomson" <jim.thom@telus.net>
To: <amps@contesting.com>
Sent: Thursday, May 03, 2012 8:03 AM
Subject: [Amps] Tubes vs. Solid State
> Date: Thu, 03 May 2012 02:34:46 +0000
> From: Manfred Mornhinweg <manfred@ludens.cl>
> Subject: Re: [Amps] Tubes vs. Solid State
>
>
> - Hams are obviously willing to pay 5000 bucks for an amp, so why
> destroy the market by making amps that sell for 700 bucks? The
> intermediate option, making amps that are cheap to make, and then sell
> them at 4000 bucks, probably won't live long with hams. They want to see
> where the cost is.
>
> ## I can hb a pretty big tube amp for $5000.00 I can do a really
> big one for $7000.00
>
>
> And another technical problem is that my amplifier probably won't end up
> particularly rugged. If you set your mind on it, you can probably blow
> it up just by slowly tuning an antenna tuner through its whole range,
> until you find a setting with sky-high SWR that just happens to create
> high enough drain voltage peaks to fry the FETs. Protection circuits can
> keep FETs alive, as long as the high SWR comes up slowly (milliseconds),
> but if you have a loose connection in the antenna system, that provides
> 1:1 SWR most of the time, but suddenly goes up to a condition that
> causes those high voltage peaks, this amplifier can be blown up more
> easily than one that uses just a few, rugged FETs. The reason is that
> I'm using many small FETs, directly in parallel. That's simple to do,
> and inexpensive, but any overvoltage will make a single FET enter
> breakdown, and that single FET cannot survive the big discharge. When
> using just a few large FETs, which is much more expensive, the big FET
> that breaks down has a much larger chance to survive.
>
> ### Aside from all the typ problems of SS amps, there is even more
> problems. None of em will run full bore rtty, etc into a 3:1 swr !
> So now you require the mating automatic 2 kw CCS rated tuner.You
> don’t need the auto tuner with the tube amp, not mine anyway.
> 5 kw CCS rtty into a 3:1 swr....no sweat. Lets do lunch.
>
> ## With these SS amps, you also require a monoband 2kw CCS
> rated LP filter for each band ! At least a min of 5-6 required
> to cover 160-10m + warc. Plus you have to be able to switch
> them in and out.
>
>
>
>
>> As to home brew, there are very few of us who actually do that be it SS
>> or tubes.
>
> I can't help it, I worry that this is spelling the end of ham radio. To
> me, ham radio is about being interested in radio technology. I can
> perfectly well accept the fact that not all hams are professionals in
> electronics, but I would expect that all hams, without exception, should
> at least be interested in electronics, and try to learn, at their own
> rate. I just can't understand those people who say they love ham radio,
> but whose love for radio ends precisely at the front panels of their
> rigs! To me, they DON'T really love radio. Instead, they are after the
> utilitarian side of ham radio, such as keeping in touch with friends and
> family, or having emergency communications. In my surroundings, at least
> 90% of hams, and probably much more than that, belong to this group that
> doesn't have any interest whatsoever in electronics. Hear them talk on
> the bands: The weather, the brand and model of their rig and antenna,
> and that's about it. I call them "empty QSOs".
>
> ### ham radio is in its dying years. They hand out ham tickets
> like popcorn, and they still cant give then away. Empty QSO’s,
> that’s at least one step better than 10,000 brain dead contesters
> on every 2nd weekend.
>
>
>
> Of course, anything like that is too complex for the "typical ham", the
> one at whom the ARRL is addressing QST. But even the simplest tube type
> amp is neither for the typical ham, because that typical ham would never
> dare to build anything having 3000 volt in it. Or rather, he would never
> attempt to build anything at all, period!
>
> ### You may be right. No such thing as a slight electrical shock
> with HV. Take all precautions, and its not an issue. My hb RF decks
> are separate from the HV supplies. Each box that has HV or B+ inside
> it, gets it’s own dedicated HV meter...wired directly between B+
> and B-. If the B+ HV fuse blows open in the rf deck, the HV meter
> in the rf deck reads zero. Mean while the hv meter in the HV supply
> still reads full B+. The whole issue when dealing with hv is rather
> simple.
> You have a better chance of getting mashed in your car by a soccer mom,
> trying to do some texting while driving vs HV accidents.
>
>
>
>
>> I still maintain SS is not ready for prime time, but for those with the
>> knowledge and desire to experiment it's a great field.
>
> Well, I think differently: I think solid state is the way to go,
> definitely, at the power levels hams are allowed to use.
>
> #### How am I supposed to get 750 watts AM CXR, and 3750 watts
> pep out.... and measured at the feed-point of the antenna..with
> SS. Almost forgot.... that’s into a high swr. Repeat for all bands
> 160-10m, including warc.
>
>
> Only at much
> higher power levels do tubes make real sense. Simply because tubes are
> available for several tens of kilowatts in a single device, while
> transistors are not, and would need to be stacked up in too large
> quantities. But at 1.5kW, and even 10kW and some more, solid state is
> more practical than dealing with tubes and their inevitable
> narrow-banded tuned circuits, their lifetime of a few thousand hours,
> and sockets costing a thousand dollars!
>
> ### say what. A typ 3CX-3000A7 will last 4 years at full CCS
> output. That’s 35,000 hrs...not a few thousand hrs. I use a regulated
> AC Sola constant V xfmr.. that feeds the input of a variac... that then
> feeds the input of the fil xfmr. The new Tube is run at rated fil
> V,measured
> at the socket for the 1st 200 hrs. After 200 hrs, fil v is reduced to the
> pint
> where the Po just barely drops off a few watts, then the fil v is
> increased
> by .1 or .2 volt. As the emmision wears down, the fil v is raised up by
> .1 v. When I end up with the fil V at +5%..then send it in to be
> rebuilt,
> for half the price of a new tube. The socket for a 3CX-3000A7 is
> cheap.
> The YC-243 has no socket. GG triodes dont need sockets anyway, nor
> does the YC-156. Just bolt the grid flange to the chassis..done. The
> F7 version of the 3CX-3000A7 also does not require a socket. Heck,
> they even make a water cooled version of a 3CX-3000A7.
>
>
>
> One could argue that a lifespan of a few thousand hours for a tube will
> last a ham's lifetime of normal operation. But practical experience
> shows that tubes are less reliable: Among the local hams I know and who
> own power amps, the spread is about 2/3 tube amps, and 1/3 solid state,
> changing fast to increase the proportion of SS. Most of these hams turn
> to me when something fails. Over the last several years I had to replace
> several 3-500Z, and a few other tubes, but not a single high power
> transistor.
>
> ## I know folks with SB-221’s who are still getting full PO
> from the original tubes. I have replaced one pair of tubes
> in my drake L4B linear since I bought it new, back in 1977.
>
>
>
>
> The only time I got a solid state amp for repair, a Quadra
> that had seen extensive contest and DXpedition use, the problem was a
> broken solder joint that took five minutes to find, and one second to
> repair.
> In several tube amps I had to replace electrolytic caps, and I had to
> rewind two power transformers. In SS amps, so far I have seen no power
> supply trouble. Of course, the number of amps that could possibly fall
> in my hands when broken is small, but I believe that it's enough to do
> at least a broad statistic about their reliability.
>
> ### What is the TX IMD on these SS amps you have built.
> That Elecraft K3 xcvr is crap at -29db IMD-3. I don’t think
> their KPA-500 is much better.
>
>
>
>
>
> Years ago I looked into the possibility of making broadband tube
> amplifiers, because I just hate having to retune an amp after changing
> bands or even changing frequency a lot within a band. But I quickly
> found that the tubes' combination of high internal capacitance and
> required high operating voltage makes this totally impossible. Tubes
> force the use of tuned circuits, while transistors give the designer the
> choice between tuned and broadband impedance matching.
>
> ### Using 3-4 x drake L4B amps, all wired nose to tail in series,
> (since they will handle 2 kw on bypass mode), I just tune each
> one up on a different band ! One rotary switch ensures only
> one key line is active at any one time. Simple.
>
> ## the hb 3CX-3000A7 amp and also the YC-243 amp uses
> vac tune and load caps.. + a pair of broadcast variables for the
> tuned input. Separate bandswitch for the tuned input and high
> power Pi net. Each vac cap gets its own turns counter..which reads down
> to .01 of a turn. The pair of broadcast variables get a 4 inch diam,
> jackson bros
> ball drive, which is calibrated 0-100 over a 180 deg arc = 6 inchs.
>
> ## it takes exactly 45 secs to qsy from 15m to 160m. Just dial up
> using pre-sets. 1 pre-set for cw and 1 for ssb on 20-10m. On the
> lower bands its 1 pre-set for cw..and 2 x pre-sets for ssb. The secret
> is
> to lower the loaded Q a tiny bit. Even with the drake amps, I tune it
> at 14.200 and its good from 14.100 to 14.325 with a flat ant swr.
> I cant squeeze any more out of it by retuning at 14.100 or 14.325
> so just tune it once at 14.200.
>
>
>
>
>
> Tube dissipation ratings instead are true, real, directly usable, as
> long as you assure enough airflow. This difference comes from the simple
> fact that tubes usually have their heatsinks built-in, while transistors
> do not, so transistor ratings have to be given in a way that allows
> equipment designers to calculate the true allowable dissipation, after
> fitting a certain heatsink.
>
> ## large metal tubes are easy to cool. Plus they are usually
> specified with an IN-take air temp of 40-50 deg C. Now
> I put mine in the un heated workshop next door to the shack.
> If Im working in the shop, then the shop gets heated. In take
> air temp is more like 15-20 deg C. Anode diss goes way up.
> Crank up the air pressure, combined with colder air..and it goes
> WAY up. I can easily get another 50% CCS anode diss with that
> technique. For cw-ssb use, the pressure can be turned way down
> of course.
>
> ## whether it’s a tube amp or a SS amp... and it makes noise,
> just put em into another room. Then zero noise in the radio
> room..and no heat either. In winter, heat from the amps
> stays in the basement shop. In summer, its routed to the outside.
>
> ## My other problem with SS is eff. Your typ SS amp operates at a
> lousy 50% max eff..and that’s when run at max output ! Reduce
> the PO by half....and eff will drop down to 35%. At that point,
> you have to reduce the vdc a bit to get the eff back up. The
> problem with reduced vdc is.... the TX imd drops off !
>
> ## a 1.5 to 2kw output CCS SS amp, that covers all 9 x bands, and
> will handle
> a 3:1 swr and LOW IMD, is no simple task. Hats off to anybody who
> can
> pull it off at any price. BTW,,, these 1-52 kw SS FM broadcast amps
> you see typ
> consist of 1-52 x 1 kw SS modules, with mating switching supplies.
> Then a myriad of combiners. They operate at up to 92 % eff..and are
> NOT linear amplifiers. They operate on a single freq..with a 1:1 swr.
> So don’t use them as some kind of reference or standard as to what could
> or should be done with 9 band ham type SS linear amps.
>
> ## ONE instant on GG triode, no socket, simple un regulated B+ supply
> with a
> tuned pi input and a pi output is about as simple as it gets. You will
> go broke
> trying to get YC-156 power levels from SS. Why not back up one
> notch..and start
> with a LOW imd xcvr that puts out 200 w pep, without going into melt down.
> The K3, with its lousy –29 db IMD-3 and 100w pep out simply does not cut
> it.
>
> later.... Jim VE7RF
>
>
>
>
>
>
> Note that some solid state devices, such as many diodes and also some
> switching MOSFETs, nowadays are rated for dissipation and/or current at
> a more real-world temperature, such as 75 or even 100 degrees Celsius.
>
>> Depending on frequency we set the internal limit at 100C and max
>> internal operating temp at somewhere between 70 and 90C.
>> dopant migration was starting to become noticeable at 100C so when I was
>> in the industry.
>
> That's a bit lower than I had known. Anyway one has to keep in mind that
> these phenomena are time-related. A ham amplifier can probably get away
> with pushing the silicon to 150 degrees when delivering full output,
> because this will only be short-term. If the transistors live for 10,000
> hours at that temperature, that should be enough. A broadcaster instead,
> running 24/7 at full power, will want to get much more than 10,000 hours
> of life from his transistors, and so they need to run cooler.
>
> That said, and having done calculations on the thermal aspects of
> widespread ham equipment, I can't avoid the suspicion that many ham
> transceivers run their finals well in excess of 150 degrees internally!
> The typical max ratings are often 175 degrees or even 200 degrees for
> transistors that are NOT encased in plastic. Particularly brave
> manufacturers even specify 225 degrees. I don't know how much of that is
> due to processing techniques that reduce dopant migration. The rest is
> probably based on decisions to accept shorter lifespans as "typical". In
> any case, silicon by itself survives much higher temperatures. It's the
> migration problem that sets a limit, and the attachment of the chip to
> the case (usually by some solder) sets another limit.
>
>> You can also use *cold* or chilled water. Just draw the water out of an
>> open PVC tank and return to the same tank. 20 gallons will run a KW amp
>> for quite a while. Throw in a few chunks of ice and have at it. We use
>> the water in plastic bags for our picnic coolers , so you just grab a
>> couple and drop in the tank
>
> But one needs to be always careful about avoiding condensation inside
> the amp. At my former job, we had tons of actively cooled electronic
> equipment. There were big coolers to chill the water/glycol mixture just
> enough to keep the outside of the electronic racks precisely at ambient
> temperature, to prevent thermal turbulence. The controllers monitored
> ambient moisture, to keep the water always above the dew point.
> Sometimes something went wrong, and then we got dripping wet
> electronics, with all the obvious consequences.
>
> The coolers were mostly of the plain common compressor heat pump type,
> but in some vibration-sensitive locations we decided to try Peltier
> coolers. They turned out to be a disaster. The place was at 2600 meter
> altitude, the Peltiers overheated due to the low air density, and died
> faster than we could throw them in the trash.
>
>> You can take it down as far as you like as long as you don't get
>> condensation on the circuit board,
>
> Exactly. And with a typical comfortable ambient humidity of 60 to 70%,
> condensation happens at just about 6 degrees below room temperature!
> It's not worth doing, for such little temperature difference.
>
>> or ice up the pump.
>
> At any normal room temperature and humidity, condensation will occur far
> sooner than any ice can form. The dewpoint at comfortable room
> conditions is always above 10 degrees Celsius. You would need an
> extremely dry or very cold environment, to get the dewpoint below
> freezing!
>
>> BTW there is a fungicide used in swimming pools that will do a good job
>> of keeping *stuff* from growing in your cooling system. I'm not
>> referring to Chlorine.
>
> I will have a look in the swimming pool section of the home improvement
> store! Thanks for the hint!
>
> Manfred
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