Ameritron ALS-500M

[n3lrx]

Anyone ever used one of these amps for AM? Ameritron/MFJ tell me it's not suited for AM and may damage the finals. How is this possible since the carrier would be much lower than the sideband pep input? I figured it would be at least a few hundred watts pep with around 25w carrier. and 50w pep. Just curious. 

[flintstone mop]

The amp is a 500 PEP amplifier.
On AM you could drive it to produce a 100 W carrier and that will take it very close to it's limitations (400 PEP). And being it is solid state there may be other issues using this amp in AM mode.
Fred

[n3lrx]

Yeah, that's right about what I figured. I just thought it funny that AM "could cause damage"  I didn't know if that was just the canned reply of if there was actually some science behind it. I remember a friend having one, probably before MFJ bought Ameritron. Or have they always owned it? Dunno.. Anyway, we used it on AM a lot and never had problems. I'm not going to risk it though.

[N2DTS]

ssb is very light duty, cw is a little harder, and AM, with its steady carrier output PLUS the pep rating is hard on amps.

You have the heat issue, and the power supply issue.
For ssb, a very light duty power supply will do, not so for AM.

A 500 watt amp in AM service would be good for 500 watt pep AM, say 125 watts of carrier IF the amp could deal with the heat and current load.
Not much point in it unless you have a 5 watt radio you want to run at 100 watts...

I find it really odd that to go from 25 watts to 100 watts carrier out only gives about an S unit at the far end.
And going from 100 to 300 watts is likely another S unit...

[Steve - K4HX]

Most likely you could get a SB-220 for what you would pay for the ALS500. That's another reason not to get it.

[n3lrx]

Well, it is forced air cooled. Part of its 'features' is a quiet temp controlled fan and thermal overload shutdown.

This would be going in the car. So an SB-220 just wouldn't be feasible. I'm considering buying a mobile HF rig. (A Yeasu FT-857D) And thought the extra few hundred watts will keep me out of the 'piss weak little mobile' scenario. I've still got a full power rig for the house. Unless some 100w BA comes along I can't see any reason to buy an SB-220.

[WQ9E]

Mobile full carrier AM is going to definitely give your vehicle electrical system a workout if running this or a similar amp.  Although standard vehicle alternator sizes are much larger today it is because they have to be for the normal vehicle load and not to make things easier for the high power mobile op. 

Quite a few current vehicles exercise power management when total system current draw is excessive and if you don't have an aftermarket upgraded electrical system you may find your vehicle starts to shut down some of its electrical accessories when you are transmitting at high power.

From the product description it sounds like the cooling system for the 500M is designed only for light duty cycle modes and is biased towards quiet operation.  The MFJ concern is probably that it cannot keep up with high duty cycle mode operation-especially if the ambient temperature is anything other than quite cool.  You might be able to address this issue with a higher volume fan that speeds up at a lower set point and maintains this speed to a lower set point.  Of course then you lose the quiet factor.

[n3lrx]

Yeah, I'm going to scratch this off my list of gotta haves. I seriously doubt the alternator in my 1997 Escort has the ass to provide 80+ amps. Besides it looks like most of the affordable antenna designs (Ones that will fit on my car) are all rated at either 200 or 250 watts. I've got plenty of 75m whips in my collection I could just buy more hamsticks for 10,20,40m and have all the antennas I need then run piss weak mobile and hope for the best.

I worked the world on my HR2510 back in the day when I first got my license, I could probably do pretty well when conditions are right with 50w pep on AM. I'm not chasing DX so around the corner, across the street, or a hop to another state I really don't care. Just somebody to talk to will suit me fine.

[Steve - K4HX]

Ok, it's for mobile use. Yes, the SB-220 would be out.   

Didn't Heathkit make a mobile amp with two 572Bs? HA14?

[flintstone mop]

Well, it is forced air cooled. Part of its 'features' is a quiet temp controlled fan and thermal overload shutdown.

This would be going in the car. So an SB-220 just wouldn't be feasible. I'm considering buying a mobile HF rig. (A Yeasu FT-857D) And thought the extra few hundred watts will keep me out of the 'piss weak little mobile' scenario. I've still got a full power rig for the house. Unless some 100w BA comes along I can't see any reason to buy an SB-220.

AM mode in a mobile on 160 and 80 will be piss weak any way. SSB will be a little better on 80 and even better on 40 cuz you can run higher power, ALS500, and be heard than using AM. It will always be a struggle to make any useful contacts on AM mobile. Maybe some others here have another view..........dunno
Fred

[WQ9E]

Ok, it's for mobile use. Yes, the SB-220 would be out.   

Didn't Heathkit make a mobile amp with two 572Bs? HA14?

I have a HA-14, AKA the "compact KW" but with no cooling fan I bet those 572B tubes wouldn't be very happy running full carrier AM.  Mine came with the AC supply (and an external fan) and I have heard the DC supply wasn't very reliable.

Mine is set up with a HX-20/HR-20 station but NOT mobile

[KB2WIG]

HLR ran 80m mobile, probably still does. He did have a 'large' antenna under a wagon/cadaverlack. The 'dog log' antenna if I remember correctly.

I ran AM ricebox on 40, got out some watt. Its a grounding thing.


klc

[WB2EMS]

It will always be a struggle to make any useful contacts on AM mobile. Maybe some others here have another view..........dunno

I ran 80 and 40m AM mobile for years using an Alinco DX70 in a minivan with a BB3 screwdriver antenna on a home made shelf on the back door with very satisfying results. Even though I only had a 20 watt carrier, I was able to work folks all over the northeast on a regular basis, often managing qso's that spanned hours and a good portion of NY state in the process.

That vehicle and antenna are long gone, but for the last couple of years I've been doing some work with a Hi-Sierra screwdriver with a 60 or 102 inch whip, with less wonderful results. Which has been a disappointment because the current vehicle is a Golf TDI diesel, which is wonderfully quiet compared to any other vehicle I've ever had. This recently led to the acquisition of a bigger and better antenna, a Hi-Q Piranha -5R.

I was curious how much better the new antenna might be compared to the old, so before I swapped it on the mount, I ran some tests on my 'poor mans antenna range'. I set up the mobile to run 10 watts carrier on 75 meters and using my HF vertical on the Flex I took some measurements of the carrier level. The range was about 150'. The received level with the 60 inch whip was -36dbm, with the 102 inch whip, was -24dbm. Then I swapped on the Piranha and ran the same test again. +2dbm! A 26 db improvement! Wow. 

I had hoped for maybe a 10 db improvement. I can see a big difference already on mobile contacts on sideband around 40 and 80 meters and hope to be not as PW mobile soon on AM. Also made my very first 160 AM mobile contact last week. Still some tweaks to do on a base matching coil to get the best performance with the Turbo Tuner, but overall I'm very pleased.

Anyway, my take on it is that you can make decent contacts on 75 and 40 at least with a regular mobile rig and a good antenna.


 

[N2DTS]

I had a TS 440 in the car a long time ago.
My problem was with noise and static when moving, ssb worked real well, but AM was a hash of all sorts of noises, even without all the electronics on modern cars.

Parked, it worked well, moving ssb worked, but these days, I do not want to mess with radios in the car, got to dodge the people texting (and operating radio)....
 

[Steve - K4HX]

Mobiles can be quite competitive with home/base stations on 40 meters. I've worked quite a few mobiles in Europe on sideband. I would not have known they were mobile if they hadn't told me. Others were PW. Depends on conditions, location and the antenna/power used.

It's tougher on 80/75 meters but it can be done, especially if you pick your times appropriately. One long time AMer operated mobile quite a bit years ago because he didn't have a home station. He had a location or locations where he could put a wire up in the trees. He was often just slightly lower in signal strength than many home stations.

[KD6VXI]

When I drove truck as an owner / operator,  I ran 40 through 70 cm all modes.   Even Am.

Yes,  I was PW,  but I had fun,  and made contacts.   That was with 100 watts.  Peak.

It can be done.   You are about as competitive as a qrp station into a trap antenna.

--Shane
KD6VXI

[w1vtp]

Ok, it's for mobile use. Yes, the SB-220 would be out.   

Didn't Heathkit make a mobile amp with two 572Bs? HA14?

I have a HA-14, AKA the "compact KW" but with no cooling fan I bet those 572B tubes wouldn't be very happy running full carrier AM.  Mine came with the AC supply (and an external fan) and I have heard the DC supply wasn't very reliable.

Mine is set up with a HX-20/HR-20 station but NOT mobile

My experience with the HA-14 is identical.  Without minimal cooling, it got so hot you could smell it.  I still have that amp but am missing the detent for the band switch.  The AC power supply is homebrewed and is really beefy.  A slow running fan is all it needed to de-stinkify it.

Having said that and getting on topic, the ALS 600 is  rated for AM - I think Ameritron is too generous with an AM rating of 150 watts but Rich, K1ETP has one and runs it at 100 watts and loves it.

I gotta give Ameritron points for even considering rating their some of their amps for AM.  I still run my AL82 at 300 watts carrier and it just keeps running with no problems.  If Ameritron advises against using the ALS 500, I'm guessing that's based on problems associated with that mode.

Al