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Ameritron ALS-1300 HF Solid State Amplifier Review Revisited

Ready for Prime Time??

Having followed this thread, the earlier review thread and the discussions at e-ham I am now wondering if the als-1300 has now been modified to the point it is a dependable product. I have been looking at the als-1300 since it was introduced because it would seem to fill my needs. I have been scared away because of the multiple horror stories seen online.

I would like to hear some opinions in light of the apparent modifications. Also how would one tell that you have newly modified model?


where you had 1500w before on 12m now you only have 850w? huh?

That is correct. I measured this a few times and the power output is down considerable on 12m with this amp. I suspect that whatever changes were made to the design are causing this OR there might be a slight variance in the values of one of the components in the output filtering. It's impossible for me to know. Since it's basically a 1 KW amp, I'm not going to sweat about an 850 watts output on one band.

I would like to hear some opinions in light of the apparent modifications. Also how would one tell that you have newly modified model?

Mine seems to be reliable now. I am still giving it a work out and have some interesting observations that I'll relay in an upcoming post. But so far, so good. I don't know how to tell which "version" of the amp you have. My various emails with Ameritron over the last year about this amp leads me to believe that they don't maintain a large inventory of these. So, it is very likely that if you order one from them it will have been built very recently.
Suitability for MARS Usage

As many are aware, I'm a dedicated Navy-Marine Corp. MARS operator. As a result, I always test out equipment for usage on those frequencies. The manual of this amplifier indicates that usage on MARS frequencies is suitable, but there are limitations. The following is a table from the manual that indicates the frequency ranges that this amplifier is safe to transmit on.

Band | Freq. Range (MHz)
160|1.8 - 2.1
80|3.2 - 4.2
40|6.0 - 7.5
30|7.5 - 14.0
20|13.5 - 15.5
17|14.5 - 19.0
15|19.0 - 22.0
12|22.0 - 25.0
10|28.0 - 30.0

The upper limit frequencies in bold indicate the highest frequency on each band that you can use the amplifier on without the potential for PA damage. The manual also has a cautionary note that says that you can damage the amplifier by trying to operate it in the 25-28 Mhz range.

Unfortunately, between the upper limits imposed on each band, the lack of 60 meter frequency coverage, and the limitations on 27Mhz, this amplifier is only marginally useful to a MARS operator. I realize that this issue is probably only applicable to maybe 1% of the target market, but for those operators that provide MARS services, this is useful information.
Suitability for MARS usage, part 2

I made an inquiry with Ameritron on some specific frequency ranges and the possible damage that the manual indicates may occur. I received some good feedback that may help others that may be considering this amplifier for MARS usage.

First, it's important to understand that the filters in the ALS-1300 are low pass filters. On the 80 meters position, the amplifier should work fine well up into at least the 5Mhz range, perhaps higher (I will do some testing). For 60 meters operations, you should use the 40 meters band switch position.

To use the amplifier at frequency rages outside of the specs indicated, perform the following tuning procedure: First, put your transceiver into a carrier mode (FM, CW, RTTY, etc.). Turn the power output way down on the transceiver and key the amplifier. You may increase the drive to the amplifier until the point at which the current meters on the amp indicate 25 amps. You should never exceed 25 amps of current draw. The meters are too slow to respond quickly enough using modes with voice peaks (SSB, AM) which is why you need to use a constant carrier mode.

The important thing to consider is that some frequencies ranges may cause excessive current drain which will lead to failure. According to Ameritron, by staying below 25 amps, you will be safe.
Suitability for MARS usage, part 3

I did some follow up testing tonight on frequencies in the high 4 Mhz and low 5 Mhz range. I also did some testing the the 60 meter band. The tests were performed into a dummy load.

By following the procedure indicated by Ameritron, I found that I had no problem achieving 1.1 KW output until I went over about 5 Mhz. After 5 Mhz, the low pass filters started to take effect and the power output started to drop. By 5.2 Mhz, the power output was down to 800 watts, which is still very respectable. On these frequencies, I never exceeded the maximum current draw of 25 amps from the amplifier's power supply.

On 60 meters, I was able to safely drive the amp with about 80 watts, achieving around 800 watts of power output. At this drive level, I was drawing about 22 amps from the supply. Increasing the drive beyond 80 watts tripped the PA protection circuit on the amp.

The conclusion from these tests is that the band limits indicated in the manual are conservative. If you need to use the amplifier for MARS use, make sure to keep the amplifier's current draw below 25 amps and you should be fine.
How about doing a day of RTTY and put that thing thru it's paces? Voice is a walk in the park for an amp, digital=work load

I've used it to do some MT63 and PSK31, although it hasn't been for hours at a time. I'll do that next.
Following up on the digital mode request...

I spent some time using the amplifier on PSK31. I ran the amp at 800 watts, which is obviously less than it's rated output. Honestly, I don't understand the point of using this much power with a digital mode like this, but I did it to test the amp.

When you use a digital modes like this, you spend several minutes transmitting, followed by several minutes of receiving, which gives the amp a break. It had no problems throughout the duration of using it like this.

I also spent some time testing it using 10 meter FM. The constant carrier that FM provides is a pretty harsh use case scenario. At times I was able to push the amp harder than it liked and was able to trip the PA protection. In general, the amp seemed pretty happy running FM around 800 watts, although it could be pushed up to 1KW most of the time. It became quickly apparent that the more power you use with a constant carrier mode, the more sensitive that the amp's SWR protection became. When I was able to adjust the tuner closer to 1.1:1 SWR, the amp would output more power without tripping the PA protection.

The more I use this amplifier, the more I like it's ease of operation, no waiting for warm-up, and instant band change.
The noise level was covering you up when you were using 100 watts. Then you switched to the amp and you were armchair copy. The S meter on the 897D was showing S+ for what that is worth.

In the past I could usually tell when someone was running an amp because they were very "raspy" on my receive. Your audio was crystal clear.

Then it did not matter if you were running 100. 1000 or 10000 watts, the dx gods shut off conditions and the entire West Coast disappeared from the Midwest.
Review Summary

Now that I've used the amplifier quite a bit, I have to say that I'm really pretty happy with it. After the initial design issue was resolved, the amp has been reliable and without fault. It is reasonably quiet, much less noisy than my tube amp. It stays cool, and I like the fact that the power supply is separated from the power amplifier. It consistently delivers 1KW or more of power, which is more than sufficient for most operations. The optional remote head is useful and also works with the other Ameritron solid state amplifiers. The auto band switch (ARI-500) is an interesting idea, but unfortunately it doesn't provide a method for resetting the amplifier with modifying the device. I've had several operators who use panadapters look at my signal and they've all commented that it both sounded and looked quite clean.

Here are a few things I would to see in the next revision of this amp:

  • 6 meters - easy enough to understand why
  • Incorporate amplifier reset and power on/off via the ARI-500
  • A higher power version - a 2KW version for those in other countries or MARS operators that have higher power limits
In summary, I feel that ALS-1300 is definitely worth consideration of you are looking for a Kilowatt solid state amplifier. The price point is very attractive when evaluated against the competitors. While there were some initial design issues that needed to be worked out, this latest version has shown that Ameritron is dedicated to delivering a reliable product.
Not So Happy With ALS-1300

Although you may be happy with the amplifier now that Ameritron did a major re-design on your particular unit, there are those of us who are about ready to heave it out the window and see how many pieces it can be break into. Mine has failed four times since I bought it almost a year ago, 3 of those 4 failures has to do with the +12V module in the power supply. Ameritron is sending me a newly designed power supply this week in the hope it will correct the problem. It's apparent that there was a design flaw with the 12V section as it's also failing on the ALS-600 supplies if you read some of the comments in this thread:


Anyway, I'll let you know how it goes once I receive the new power supply and give it time for some thorough testing.
Have you received a fix for your amplifier yet? I've continued to use this one and it continues to work well. It's so convenient that I'm not sure I even want to switch back to the Ameritron AL-800H.

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