QTH.COM Swap Chat

I currently run an HF amplifier which puts out about 600 watts. I have been considering upgrading to a larger amp with 1200 watts output. Everyone says the first 600 watts makes the biggest difference and an additional 600 is bearly noticable. Yes, I understand the formula...doubling of power equals a 3 db gain and half an "s" unit. However, in the real world these formula's seem to sometimes work differently than expected. So the question is...from your personal experience, is it really worth upgrading?

I had a high power amp that when driven to max would easily do 15000. But do to the fact i seldom used it i made a deal with another ham and we worked out a trade for his 600 watt amp. To be perfectly honest i have noticed little to no difference. Being as i'm no contester or no big time DX chaser the smaller amp works perfect for me.

My main amp loafs at the legal limit with 35 watts of drive. I keep the radio at that level. I make about 70% or more of the contacts "barefoot" but when I need to hit the switch, it comes alive. Regardless of the math, you will see a bigger difference between 600 and legal limit than you will between 100 and 600 as far as results in my opinion.

From my experience and of course the amount of money involved the first 400 to 600 watts gives the biggest bang for the buck.

I can afford a legal limit amp but I certainly do not intend to pay that kind of money for one. I'm not interested in being the loudest guy in the pileup every single time I power up, others would enjoy that and therefore justify the expense and enjoy the extra power.

Tweaking the antenna, good operating practices and not having to spend a huge amount of money makes this a perfect hobby for me!

73, Dave AE5PM
PS, the wife would argue about the money part probably

If you are going to be a contester and run RTTY at full 1500 watts, you'll need a BIG AMP to handle the duty cycle. If you are going to be a Big Gun DX'r, again you'll need a 1500 watt amp to get those very weak stations.
If you are just an average ham and like to get on the air with a better than average signal, save you money and get an amp that is good for 600 to 800 watts output power.
The best advise anybody can give you is, "Put your money in the antenna !" You will get gain both ways, transmit and receive.

I have two home brew amps that will run 1500 watts out 24/7 and hardly use them. I have an SB-1000 amp in my shop and find that running that amp at 700 watts out I can break most any pileup in non contest conditions.

When I run the BIG AMPS I only run them at 1200 watts, but they can easily put out 2 KW plus into a dummy load.

You do not mention what antennas your are using nor what bands you are interested in "upgrading." So there is no single answer to your question. Having said this, here are some thoughts on the subject.

Higher power amps are not really worth the resources needed, unless you really need a "quick fix" for more QSO's.

A practical reality is if you are using your 600 watt amp on an antenna with no gain and you switch to using an antenna with a modest 3 db gain, your signal at the receiver end is similar to what it would be if you changed from a 600 watt amp to a 1,200 watt amp.

In most cases, the change from a no-gain antenna to a 3db gain antenna costs less than a higher power amp. Quite a bit less.

But wait. The same applies it still want a better signal. Increase your 3db gain antenna to a 6db gain antenna and your signal at the receiver end will be the same signal as if you were running a 2,400 watt amp.

Better yet, antennas, in general are less costly than amps and require very little maintenance, when compared to a high powered amp.

That's not all. When you improve your antenna's transmitting gain you also improve the antenna to your receiver. It too, benefits from a better antenna -- and you can hear the weak ones better! This is not true when you just increase the power of your amp, no receiver gain there at all.

Finally, when practical for the band of interest, install an antenna with front to back gain, a yagi or quad, perhaps. The advantage, of course, is you can poke your signal in the direction of the guy at the other end. This makes both of you happier.

However, in the real world these formula's seem to sometimes work differently than expected.

For some reason the second most important of most ham's antenna system really isn't given a lot of thought -- the feed. Using available manufacturer specs for all parts of the feed, calculate the db LOSS of all the feed components, ALL of them, not just the coax. Include the adapters, the switches, the connectors -- everything. You will be surprised to discover the a chunk of your 600 watts is being "eaten" by the feed line from the amp to the antenna.

Suggestion: start with the feed line (use the best coax you can find) then check out the antenna. This where the on-half of the db value starts to really rear its head. Who knows, you might not even need an amp at all.

When I run an amp, which is seldom, it is a Collins 30L-1, the best overall value in an amp purchase on the planet. It will go on any HFband above 160M and will continue to increase in value if you maintain it properly.

Cheers,73's and good DXing...
AL
K4ICL

I use a pair of 813s at 800W on 75Mtrs ,but when static is bad I step up to my 4-1000A at 1500W and it DOES make a difference wheather I am heard. .

Of course, if you could have switched to an antenna with only 3 db more gain in the right direction it would be the same thing.

Right?

I run a AL811 here at about 500 watts. that seems to be all I need. bigger amp=more electric where i am from. so in short.......I was told by my elmer the first 500 counts and also no matter how much power you have...if the band is no good......its no good. I have talked across the world on 25watts but sometimes i couldn't talk across the state with 1500 watts. Just my input

I run a FT 950 bare foot 95% of time into a Tenedyne log up 65 ft.My amp is an old refurbished Collins 30-L1, on stby. I very seldom need it but wneI do I run it at 500 watts. Like most said put you money into a good antenna first. I am an OLD TIME DX HOUND from the 60's

As another poster mentioned - low loss feed line (like balanced feeders) fed into a good antenna is the first part of the battle. After that you have the receiver and it's noise figure. Can't work what you can't hear. My experience from out on Guam and various places stateside is that only when band conditions get really marginal, then an amp can make the difference between being heard or not. It is comforting to feel that if I have to, I can flip the switch and get that little extra oomph in there but then it also means I'm doing something serious such as passing traffic or working the rare one and don't want to wait for better conditions.
Just my thoughts on the matter
73
Dick KH2G