[Amps] How about a Solid State MARS amp

[kg7hf at comcast.net]

Hi Chaz,
Yea, you can buy a lot of inverter for $250, but you won't get far with it.  I have a 3000 watt inverter in my boat, works great, runs the electric range top, micrawave, and my wifes' hairdryer.  Problem is, it produces so much RF that you can't run a radio receive.  A pure sine wave inverter might be cleaner, especially on transmit, but pure sine wave inverters are going to be a lot more expensive.  

Well, your not going to get to legal limit very easily in solid state by using a 12v device.  I would suggest using a ~100 volt MOSFET such as the MRF1500 These run on 120 volt DC, and require about 15 amps each to produce legal limit. Take a look at this article, it should be good reading for you:  http://www.arrl.org/qex/2006/09/qx9ohsawa.pdf  

I still think that you won't get to the 1.5 kw level at $1/watt in a commercial venture in tube or solid state with a power supply included.  In all reality, the RF deck is the easy part, it's the stuff around it, PS, tuning, filtering, protective circuits that add the complexity and the cost.  

Consider this, assueme that I am right, and the Ameritrons can be used outside the ham bands with no modifictions.  Can you buy a legal limit from them (tube or solid state) for a $1/w?  Nope, the AL-82, that they advertise as legal limit (1.5kw) is MSRP of over $2600, and that's the cheapest one!    Now examine the Tokyo hipower HL-2.5K, one of the solid state legal limit amps.  MSRP is $8000, and like I said before, I know mine can be used on non amateur bands, but it is well outside the budget, and you haven't gotten an inverter yet to run them mobile with.  At least the thp, you could put 4 24v batteries in series to get the ~100v  DC to run it ;)

> How would you be able to go tube without a selector coil much like that 
> on a Dentron Tuner??? and then the band circuitry about every 20 meters 
> or less??? iow, probably about 8 taps and slug tuned coils, etc ??? 
I'm not sure what your asking, tube or solid state?  With a tube amp, your just using the output tank circuit.  As you mention, with a few taps on the coil, you will match across the entire range.  The second portion is the input matching, wich only has to match the exciter to the amp input, and isn't that big of a deal either.   I have already tried a few Mars frequencies on my LK500, works fine.    If your talking about the output filtering of a solid state amp such as one based on the MRF1500's, it is just a matter of dealing with the 3rd order harmics since the IMD should be acceptable for the pair of devices.

I'm not trying to be negative, but I just don't see it as a viable commercial venture.  What your looking for is a militarized amp, for a low price, but your not getting volume purchasing power.



-------------- Original message -------------- 
From: schuetzen <chasm at texas.net> 

> >One thing that I don't understand is the requirement for solid state. 
> If the request is to run from 110v and produce legal limit from 1.5 - 
> 30 mhz, why not go tube and a switching power supply? That could be 
> done and be rugged and light weight (probably not for $1/watt though). 
> The real weight is in the power supply anyway with either solid state or 
> tube. Paul 
> 
> 
> Not sure but I think, the real cost of the whole thing is going to be 
> the PS also.. for 140A or so, it would be in the neighborhood of $600. 
> But, make it a 110-220VAC amp and it would likely be down to close to 
> the cost of $1/W. point is, you can run it off mains at base and thru 
> an inverter from an Optima battery pack of 900AH+ blue or yellow 
> batteries. You can buy a lot of inverter for just 250$ vs a PS. 
> 
> I have an offer of 1100$ for a kw but I would have to add a PS. I have 
> done a lot of looking for PS but as we all know, there are PS and there 
> are PS. Some or most of them are totally worthless as RF purpose 
> equipment power supplies. 
> 
> How would you be able to go tube without a selector coil much like that 
> on a Dentron Tuner??? and then the band circuitry about every 20 meters 
> or less??? iow, probably about 8 taps and slug tuned coils, etc ??? 
> Obviously I do not know what I am talking about here and I freely admit 
> that but... even with continuous tuning, there is the problem of 
> ruggedness, etc. Ability to stand marginal electric supplies in the 
> field, bouncing in the back of an Excursion while operating into a nice, 
> wide banded screwdriver antenna, etc. 
> 
> A lot of things to consider Paul, but I really think that the SS is the 
> way to go EXCEPT for the huge power supply to feed those pills or 
> Mosfets or whatever. 
> 
> thanks 
> chas/k5dam