Adjusting the Ameritron ALS-1300 Power Supply voltage

[Captain Kilowatt]

Your right, I was in the discusion with toll free about the device itself and then about the amplifier as a whole. Without knowing the Q of the filters, I have no clue how hard you could push the amp before killing the overall IMD. Im guessing no matter what, its better than an sb220. They were never required to meet IMD specs since they were a kit. I think I heard best IMD product was -35db. FCC requires 43db.

A kit or not or even homebrew amps must meet FCC spec. The SB220 was made back when the FCC spec was, IIRC, 30 dB. It did meet spec in it's day and like most gear of that time is in effect grandfathered .43dB is the newer spec standard.

 

[dxhound]

I had to stop reading at that point, as your output filters (no filtering, actually) can reduce in band IMD, which is what people get pissy about.

Apples and Oanges.

Who CARES that the device can do 190 watts output cleanly. It's not DESIGNED for that. I can get 4000 watts out of a single 8877, too. BUT IT ISN'T DESIGNED FOR THAT!

Please, do a bit more research.

--Toll_Free

I think you need to do research on in band IMD. Band pass filters pass whatever is within their passband. Doesnt matter if its IMD or the fundamental freq.
They are not selective on IMD alone and if the artifact being created is a few hundred hertz away from the fundamental, and within the pass band, It will be passed to the output of the filter.

And I see now that you are just looking for a pointless arguement since i already stated a few times " I WOULD NOT RUN THE AMP IN THIS FASION, THIS IS A SIMPLE GEE WIZZ TEST OF CAPABILITIES!"

Maybe you should have kept reading.

TOLL FREE, Ive read alot of your posts here and they are mostly insightful, but I think your missing the point of my question to Mole. I simply asked about a quick test of say 110 watts pep input to see if the amplifier stays linear or if the extra is turned into heat. I just want to know the headroom the amp has and find out if Ameritron has left any room for error, or if the amp is already under strain at 1200 watts Po. Hence my question about Voltage Sag and possibly setting the idle voltage a few volts higher to keep the PA's from starving under load. The bias wouldnt suffer from this small change in voltage nor would the transistors.

Hey captain. I knew they passed the std of yesteryear (I couldnt find the spec though, where did you locate the info?)
I was just making that comparison since SOOOO many of those sb 220/1 are still in use and people rarely complain about interferance from them. So if the IMD suffered a bit in this test of the ALS-1300 It wouldnt hurt too much on the bands

 

[Toll_Free]

Your right, I was in the discusion with toll free about the device itself and then about the amplifier as a whole. Without knowing the Q of the filters, I have no clue how hard you could push the amp before killing the overall IMD. Im guessing no matter what, its better than an sb220. They were never required to meet IMD specs since they were a kit. I think I heard best IMD product was -35db. FCC requires 43db.

They met IMD requirements as of the date of MFG.

ALSO, they do better than -35. Thats Eimacs number, the nfb on the grids //supposedly\\ increases that number: The caveat, you get worse imd out of the exciter.

Incidentally, VE7RF has compared the SB220's output to an Alpha. They where the same at the same Pout.

ALL Motorola RF devices are rated at 30 to 1 SWR "at all phase angles", except nobody has blown an MRF477 in a 2510 / Lincoln / 2600, have they? Any MRF devices blown in the 80s or 90s due to swr, antenna issues, etc? Oh yeah...... The Toshiba devices where actually WAY MORE RUGGED, and they won't go into a 30 to 1 swr.......

Tubes have guidelines, transistors have RATINGS. That was my tagline for years, and it still holds true today.

You go ahead and push YOUR MRF150s, volt them, run them into a 30 to 1 swr (I mean, Ameritron is USED to wasting money on things like VSWR overprotection, right), say what you want.

BUT, the fact remains... At 55 watts PER device, they ARE blowing up with a 2.5 to 1 swr, in Yahoo and other xceivers.. I'M NOT GOING TO PUSH MINE, just so I can make my Dosy swing farther to the right.


--Toll_Free

 

[Toll_Free]

I think you need to do research on in band IMD. Band pass filters pass whatever is within their passband. Doesnt matter if its IMD or the fundamental freq.
They are not selective on IMD alone and if the artifact being created is a few hundred hertz away from the fundamental, and within the pass band, It will be passed to the output of the filter.

That's exactly what I stated. YOU stated IMD would be reduced by the filtering of the amplifier, but couldn't tell us by how much, since you didn't know the Q of the xformers.

Please don't confuse my posts with yours.

I'm not looking for any kind of argument. I'm simply pointing out that your request is CBer-ish. Volting an amateur amplifier, overdriving it, etc. shouldn't even be tested, as it's an ABUSIVE test.

Unless the transistors are SHUNT FED (read, NO DC GOING THROUGH THE OUTPUT XFORMERS), then increasing input increases loss in the transformers. This was proven by Granberg in the 80s. ERBTech also confirmed it, and they do NOT run DC through their xformers. The increased heating of the cores increases IMD because of being closer to saturation (as well as other issues that are semi or totally unrelated...... The entire binocular xformers idea isn't the best in the world). I found this out building battle boxes in the late 80s and early 90s. Pulling the DC feed OFF the output transformers will INCREASE Pout, especially as the xformers heat up.

You HONESTLY meant to say that transformers have no loss, combiners have no loss, etc? Please, I'd like to know...... My MATH says different. It's not an argument when someone presents factual evidence and mathematics to back their statements up....


--Toll_Free

 

[dxhound]

I had to stop reading at that point, as your output filters (no filtering, actually) can reduce in band IMD, which is what people get pissy about.

THIS IS YOUR QUOTE!!!

Seems to me that your stating even NO filtering can reduce IMD??? Either you just have no concept of this or, you butcher the english language to the point that no one can understand it.

The output band pass filters do nothing for IMD, and only attenuate out of band IMD
END OF STORY!!!

You say my request for a "stress test" is cber-ish yet you build "battle boxes" .......huh

The point of this "Abusive Test" is to discover weather or not Ameritron has engineered this thing like a tight rubber band ready to snap or if there is room for error.

Show me where I said combiners and transformers have no loss. The only reference I made to no loss was to Iron loss. Otherwise I said the loss was negligible, .5db or so. Everything in the circuit has some loss. Hell even a piece of wire is lossy to a point. The cores should not heatup unless they are excessively taxed. The .8db more that I am interested in should not cause this unless the amplifier is already under too much stress at 1200Po. I figured I could speak in generalities but I see I need to talk as I would to a child.

Id like to see where VE7RF did this test with an unmodifierd sb-220 with similar IMD to a alpha. If so, then I will stand corrected.

If MRF150s are poping at 55watts, then there are other issue than SWR. Bias, Thermal/junction breakdown, there could be a number of things to cause this premature failure. I find it funny that you think these reputable manufacturers have overrated their device by that much.

Say what you Want the facts are on the data sheet as MINIMUM ratings

 

[Moleculo]

This whole discussion turned into a thread jack on the actual review of the 1300, so I moved the posts to a new thread based on the original question.