[TenTec] No 6M on the Orion (WTB: Ten-Tec 526 6N2)

[WA3FIY]

On 13 Aug 2002 at 15:46, George, W5YR wrote:

> 
> I don't doubt that the final devices can dissipate 100 watts - with
> that optional fan only?? - but if Joe Ham decides to operate with a
> 10:1 SWR on 40 SSB (using his 10-meter dipole) what will he sound
> like? After all, the specs say that he can operate into any SWR . . .
> 
> I agree, Lee, that unless TT has done an exceptional design, unlike
> other 12-volt finals, the overall performance must be similar.
> However, there must be limits to the load mismatch for the distortion
> products to remain within limits.
> 
Perhaps the IM will not be too bad into mismatched loads.  On 
the low Z side, the drive to the final in later Ten Tec rigs is 
limited by the current delivered to the PA.   So, once the PA 
hits around 20 amps or so, the drive will back down and keep 
the power transistors in their linear region.   Note, this is  
different than the more common SWR shutdown philosophy.   
In this case, the final will still be delivering somewhere around 
100 watts, maybe a little more, depending on the reactive 
component of the load.  

In the case of a high Z load, the ALC detector will sense the 
higher than normal RF voltage and back the power down 
accordingly, again keeping the transistors in the linear region.  
In this case however, the final will not be delivering 100 watts.  
It will be somewhat less depending on load Z.   

Solid state amplifiers seldom match output impedance to load 
impedance as in the case of tube amplifers.   As a rule, solid 
state amplifiers have much lower output impedance than the 
load to which they are attached.  That is why for instance in 
solid state sound equipment, you will  see the highest output 
power being delivered into the lowest load impedance.   Ten 
Tec goes into this in detail in their older manuals.  Makes 
interesting reading and helps one understand the PA stages a 
little better.

The point of all this is, that low transmit IM does not depend 
heavily on the PA stage and load being impedance matched, 
hence, we may well see good IM numbers over a wide load 
impedance range.    But, it would still be an interesting 
measurement to make.      :-)

-73-

-Lee-