ALINCO/HF AM AMPLIFIER

[K8LEN]

Anyone have a suggestion , I am running an ALINCO DX70T on am, at 40 watts. I would like to increase to 150 to 200 watts max on am.
Anyone suggest or know where to purchase  an amplifier.
I was thinking of a KL-Italian amp, but I think they are class c, not sure.

Obvious not spending a fortune on an amp either.

Look forward to any answers.
73
POB/K8LEN

[W1ITT]

The KL and RM Italy and similar Chinese amps sold on Ebay are nasty, with most of them barely making minus 20 db third order IMD numbers.  Regardless of mode, they are a good way to make a bad name for yourself on the airwaves. 
Probably a used SB200 or maybe an Ameritron would make more sense financially and RF-ically. They should approach minus 30 db third order IMD if you don't drive them too hard, and tune them properly.  And if something fails, you can fix them more readily.

[Opcom]

I like my DX-70 (plain model), The receive audio quality is better than the IC-706.

[WQ9E]

Full carrier AM is tough on amplifiers.  The maximum carrier power you can run is 1/4 of its capable peak output but the power supply and/or cooling system of many linear amplifiers won't hold up long under these conditions so for many amps you are down to a safe carrier output of around 15-20% of rated peak, especially if you like to make long transmissions.   To put it into perspective going from 40 to 160 watts output is 6 dB which is equivalent to one S unit with typical receiver S meter calibration so to get this on S unit gain you will need an amplifier which can safely produce 160 watts carrier/640 on modulation peaks.  A SB-200 can provide this as long as you keep transmission length fairly short with some cooling in between. I would stay away from the low end solid state amps.

I feel fairly confident that my Heathkit KL-1 Chippewa and homebrew 4CX800 (three) based amps stand up well to AM but both have plenty of cooling air and solidly built power supplies.  I have used my Drake L-7 on AM a few times driven by a TR-7A but the cooling system is clearly undersized for this type of service.  The older Drake 4 line gear that runs controlled carrier AM coupled with the L-4/L-4B amps that use a proper blower an chimney cooling system work well for AM without stress or strain.

[w1vtp]

The ALINCO DX70T is rated at 100 watts PEP.  Given that spec, 40 watts is too much carrier level (even though the mfg specs it that way).  Dial the carrier back to 18 watts and your DX70T and whatever amplifier you get will thank you.  So will your HF neighbors on the HF band.

Given a 40 watt carrier, going to 100 watts is only a ~4 dB increase: barely 1/2 s unit.  If one accepts the 18 watt drive level and goes for ~200 watt carrier level that would yield a ~ 10.5 dB increase - a noticeable improvement in signal level at the other end and no flattopping (assuming proper tuning up of the amplifier). Again, your HF neighbors will thank you.

Al

PS: I've included a delta power calculator Excel spread sheet

PPS: I just looked at what I think is your reference to the Italian KL amplifier and they are stated to be "Linear" - if so, they are NOT class C

[N2DTS]

I think it would be a lot better of an idea to build a plate modulated rig  or buy one like a 32v.
About the same price as a huge amp that will make the alnico sound like a strong ssb rig run in the AM mode.
100 watts carrier with plenty of audio and a good antenna works.
Got 220 in the shack?
You need it for a good AM amp.
You also get a loud blower noise to go with the high electric bill.

Small amps are more reasonable, say to go from 5 or 10 watts to 50 or 75.

[kb3rdt]

I use an Kenwood TL-922 and DX-60.

DX-60 carrier set at 7 watts