Tubes versus Solid State.
In those days gone by and when I first started in ham radio the only method for final amplifiers of a medium power class were vacuum tubes. Often, many operators would give a description of the transmitter as a pair of 807’s or three 6146’s or for higher powers 813’s could generate the legal limit.
Other tubes often used were 250th, 4-125 and the list went on for a long one indeed. Like today hams of yesterday would try and squeeze the last watt out of the finals. In some cases tubes would die because of misuse, you really had to punish those finals in order to blow them. A most common problem was the loss of grid drive by a failed driver tube, this would cause the plate current to rise in excess and if the operator did not notice it right away, well you had a melt down. The more expensive transmitters had a clamper tube, this detected the loss of grid current, lowered the screen grid voltage on the final and in many cases saved the tube from destruction.
In time tube finals of transmitters and some of the early transceivers were slowly vanishing, the newer more modern rigs, now called transceivers boasted of solid state finals. Rigs were on the market with 100 and 200 watt finals running solid state. In time the big three Icom, Kenwood, Yaesu were touting their rigs with 200, 250 and even one transceiver with a 400 watt solid state final
However, we as hams and the makers of linear amps still clung to tube technology, you could find a good linear amp from Heathkit, SB200 using 572B tubes, or a legal limit SB220 using 3-500Z tubes. In later years the ceramic tube was introduced for higher power, ceramic tubes began to appear on the market. Ameritron hit the market with their line of amps, one model using a single 3CX1500 ceramic tube. The ceramic tubes offered longer life, but you needed to be easy on them, namely a three minute warm up time was required and limit the abuse.
During the last decade a Japanese company, namely Tokyo High Power emerged with a number of amplifiers all solid state. They offered a 500 watt, a 1000, and a 1500 watt amplifier. These units were a revolution in ham radio, the size of the Tokyo amps, plus the weight were about 2/3rds less then the monster tube amps on the market.
For about a year I admired the THP HL 2.5 unit convincing myself it would look great on the desk of my shack and of course I could claim to be the first all solid state station in Henderson County. Since i have some farm land I lease in the adjoining county and get paid every year I decided to wait until I received payment and then place my order.
I bought mine from HRO and got a spring sale item with about 10% off the regular price so off went my check. In about three days a box arrived from UPS, it was not that heavy. I opened the box pulled out the amp and asked if that was all there was to it? How small it was in comparison to one of the Ameritron Amps I had. I eagerly hooked up my radio to it, installed a 220 plug and the moment of truth I turned it on and started to bring up the drive.
Easily, it made 1500 watts, plus before it red lined I could push it to 1800 watts, but why?
So, what is all the myths about regarding solid state and tube amps?
1. You cannot make as much power with solid state.
That is just bunk, those making this statement relying upon their wattmeter to tell them about power. Is the watt meter an average or PEP instrument? In my Tokyo HP the wattmeter shows average on SSB. But on CW the same meter shows 1500 watts, or 1200 what ever I choose to run it. Make no mistake I am as competitive on SSB as anyone with a tube amp.
2. Tube type linear sound better.
Really? Your audio quality is based upon your microphone and what ever rig you are using to drive the amp. Good audio in, good audio out, terrible audio in, terrible audio out.
3. I cannot tune a solid state amp like my tube amp.
You have no problem not being able to tune your transceiver you pick a frequency and there you are, why do you need to tune a solid state no tune amp?
4. I can tune my tube amp till it is perfect.
Most hams tune an tube amp one way, maximum power output, most do not own, or have access to a monitor scope, a two tone generator, or understand a trapezoid pattern.
With solid state your trapezoid pattern is perfect, you do not have to do a thing to it, there is nothing to adjust. Keep in mind that a tube amp will react on the trapezoid pattern by adjustment of the loading capacitor. Plus you will find that maximum power and perfect linearity on the trapezoid do not occur at the same time. You will find that by reducing the power about 100 watts you will have much better linearity. Less coupling and loading are the keys to this process.
For those that squeeze out the last watt, they may think their amp is perfect, but looking again with a monitor scope might reveal a different story.
5. Tubes can take more abuse.
This reply I love, why would you abuse your tubes, or amp in the first place? Many hams when changing bands hit their untuned amp with a full amount of drive power and then start to tune it. Wrong! Reduce your drive to near nothing and find the new resonant point, doing it the other way shortens tube life and may produce currents that destroy internal components, tubes included. You do not have this problem with solid state.
6. If you make a mistake with solid state amps it is over and you will have a big expense.
Ok, blow the tubes in your tube linear and you will spend a considerable sum of money for replacement, Plus you may have damaged the tank coil, the plate RF choke and power supply components. Ka Ching!
These are just a few of the more common comments I have heard in the last few years, now granted THP did go out of business. However, there is a new kid on the block, namely Expert and they offer three models of amps. I kw, 1.3 that will make 1500 watts, or the 2k. Ours will be delivered the first week of June and we are looking forward to using it on six meters and 40, that is our second station. The first station stays on 20/15/10 using the THP.
So, in a summation, I have run the THP in contests, long hours, off and on chasing dx and not once has it given me any problems. The average time to contact a dx expedition is dependent on conditions, the amount of the pile up and your location, if you are closer, or further away from the DX.
I do not have splatter problems, or overdrive, my amp is protected with high SWR trip out and should the temperature get too high, it also will shut down. I have never had this happen. I cannot overdrive, it will shut down if I try.
In the last six years I have amassed several thousand DX contacts, check out my pages on QRZ, instant on, ready to go, no waiting, or huge expense for tubes. Do I ever plan to look back? No, the tube era is history, we are moving on to new technology. If you are in the market for an amplifier, give Expert a good look. You will spend as much money for it as you do a tube amp, maybe more. You will have the piece of mind to know that with care you will never have to replace a tube again.
Avoid doing something stupid trying to shove 1500 watts down a wet string thrown out your apartment window, make sure antenna connections are secure and tight. Most solid state amps at least my THP warn you about antenna tuners and exercising caution.
Consider this, you change bands and I am talking about a manual tuner, the tuner is off resonance on the new band. You fire up and attempt to tune up the tuner. In doing so, you place the output of the solid state amp in to a non resonant condition. Guess what, the finals may pop unless the SWR protect kicks in and shuts things down. Solid state amps normally recommend an automatic tuner if you must have one. Expert offers one, I declined, since my antennas are less then 1.5 on 20.15.10 meters and the same with the six meter antenna. My gain would be near nothing in terms of signal strength on the receiving end of the signal Just watch what you are doing, exercise caution and that solid state amp will run for a long time.
