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Ameritron ALS-1300 HF Solid State Amplifier Review

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928bolo

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Jul 7, 2008
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www.nb3r.com
I'm late to this thread, but my new ALS-600 has been to Ameritron twice with same symptoms as your 1300.

I never had a chance to use it. Ameritron had it for 3 months.

I purchased it at Ham Radio Outlet and called them before I sent it the first time to Ameritron. They said they would take it back for store credit. After the second trip to Ameritron I decided to return it and bought something else.

It may have been fixed after the second trip but I didn't have much faith that it would hold up over time.

Good luck with your 1300.
 

Moleculo

Ham Radio Nerd
Apr 14, 2002
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It's been a few days since my last update so I thought I'd drop a quick note. This new amplifier has not failed me, operating every band (except 160m) that it is capable of. Ameritron says that they improved the efficiency of the amplifier so it doesn't require as much current. Apparently it has made a difference.

More to follow...
 

eagle1911

Active Member
Jan 21, 2011
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One thing that I like is that they are working with you, which in turn I guess is helping them "cure an issue"?

My thoughts are similar to the above mentioned with the filtering. Most amps that have 10 and 12 meter capability unfortunately can operate on 11 meter. This one specifically says DO NOT because damage will occur.

That leads me to think the "tolerance" of that filtering is so "tight", trying to prohibit 11 meter use is causing these headaches for them?

I looked at that unit at Dayton and to me the inside looks like a pair of ALS-600 stacked. I have not heard of the ALS-600 having these problems on ten meter, I believe the ALS-600 will work on 11 meter? I am not saying that is a smart or legal thing to do, just saying that "appears" to me the difference between the 600 and 1300. So maybe "opening" the filtering up like the ALS-600 may be the cure, after all, the person operating the amp has the ultimate responsibility to use it legally for their jurisdiction.

I am not the smartest knife in the chandelier and I may be way out in 4th base on that assumption.

continue on,,,,,,,,, :pop::pop:


I don't think you're too far off at all myself, especially since I just took a crash course in filter design due to a couple projects I've been working on. During a discussion i had with W8JI awhile back he stated his aversion to the use of filters with more than 5 poles, which means that the Ameritron amplifiers are likely using simple filters. In my experience I've found that simple filters display much more variation in input impedance across their intended frequency range than more complex filters, so there could be a spike in the input SWR at certain frequencies, quite possibly 11m. In my experience elliptic filters provide the most level input impedance values across their intended frequency range and then some.

Here are some plots that should help demonstrate what I'm describing (made these for a different thread that some folks may already have read):

here's a fairly basic 5-pole Chebyshev filter for 30MHz:

5-poleschematic.gif


and it's transmission/VSWR curves:

vswrandcutoff5-pole10mLPF.gif


You can see some large variation in the input VSWR indicating variations in input impedance which causes losses, heating, and potentially damage at those operating points where the SWR is high. You can see by the transmission curve (red) that there are slight losses occurring where the SWR is higher. At high power levels, even slight losses add up to a good amount of heating and damaging effects.

Here's the same filter with 2 more poles added, making a 7-pole Chebyshev:

7-poleschematic.gif


Plots for the 7-pole Chebshev:

vswrandcutoff7-pole10mLPF.gif


You can see that the input SWR across 10-12m is much more acceptable, resulting in less losses and heating at those frequencies.

Here's a whole different animal, a 7-pole Elliptic filter for 30MHz:

7-poleellipticRFProjectsschematic.gif


and plots for the 7-pole elliptic:

7-poleellipticRFProjects-1.gif


Here you can see that the input SWR is very low across the whole HF band, which is very nice.

Unfortunately "opening up" a simpler filter to gain similar performance to a more complex filter isn't always easily done, most times you'd have to alter the whole topology of the design.. performance is pretty much always better with more complex filters, within reason of course. Also, more complex filters provide sharper cutoff and in the case of elliptic filters they can even be tuned to supress specific harmonic frequencies. The transmission curve for the elliptic filter above shows these distinct and sharp suppression spikes after cutoff.
 
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Moleculo

Ham Radio Nerd
Apr 14, 2002
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Wow, cool graphs. You should post a thread in one of the other sections so that those will get more notice!
 

eagle1911

Active Member
Jan 21, 2011
327
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Tnx Moleculo.. I've been planning on starting a thread about filters and other methods of keeping an amplifier's output clean with low distortion, since all the data I've posted on the topic is in threads that aren't dedicated to that subject. As I'm sure is obvious from some of my posts, I've become somewhat obsessed with the idea of clean power.. to the point that I'd rather have no power than dirty, unfiltered overdriven power. Hopefully I'll have a chance to work on a thread later today or tomorrow.
 

Happy_Hamer

Administrator
Staff member
Mar 22, 2001
5,061
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I don't think you're too far off at all myself, especially since I just took a crash course in filter design due to a couple projects I've been working on. During a discussion i had with W8JI awhile back he stated his aversion to the use of filters with more than 5 poles, which means that the Ameritron amplifiers are likely using simple filters.

I believe W8JI is the one who fixed the last ALS-1300 for Ameritron that Moleculo tested?????
 

eagle1911

Active Member
Jan 21, 2011
327
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I believe W8JI is the one who fixed the last ALS-1300 for Ameritron that Moleculo tested?????

I think that's probably right.. he designed or had a hand in designing a bunch of their stuff. The conversation I was referring to happened awhile back when I was having issues with a different filter.. he's a smart dude, it's not that he's overlooking anything really, he likely knows more than I could hope to about electronics, so I would assume he's using some very sound designs. I was only speculating about the conditions on 11m, as most amateur radio design engineers are not overly concerned with 11m. The filters Ameritron used will likely have SWR spikes somewhere, I haven't seen a filter that doesn't, but as long as they don't fall in a used portion of the spectrum it's not too big of a deal. A good engineer would tune things so that they are optimized for transmitting in the amateur bands.
 

Moleculo

Ham Radio Nerd
Apr 14, 2002
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Actually I don't think he did fix it. My last communication with Ameritron and W8JI gave me the impression that he was a little busy. It's entirely possible that he did look at the unit and make some design changes, though.
 

Moleculo

Ham Radio Nerd
Apr 14, 2002
9,034
1,335
283
The amplifier is now working great and I believe that the design issue has been fixed. To be both fair to Ameritron and also help get the review back on track, I'm going to duplicate this thread, removing the off-topic discussion and the lengthy delays while we were waiting for the problem to be identified. I'll reference initial failures to this thread but am not going to dwell on them in the new thread because we're essentially dealing with a new product.

This thread will be closed to avoid confusion.
 
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