[Amps] AL-1500 pi-network capabilities

[Vic Rosenthal]

R.Measures wrote:

> 
> On Aug 30, 2004, at 3:16 AM, Pete Smith wrote:
> 
>> One of the things I really like about the SB-220 is 
>> that its pi network has sufficient matching range on the low bands so 
>> that, for example, I can run my 40M yagi, which is cut for the CW end, 
>> up well into the phone band, or run my 80m K3LR array, which is cut 
>> for 80CW, up to at least 3900 kHz.
>>
>> Does the AL-1500 have similar matching range, or will I find myself 
>> more restricted?

I would be careful about using the pi-network of an AL-1500 as an 
antenna tuner.  It is designed to operate at a particular Q when 
transforming the plate impedance of the tube to 50 ohms.  Although it 
may have sufficient range to match other impedances and cancel out a 
certain amount of reactance, under these conditions the operating Q will 
be higher or lower than the design value.

If the Q is too low, harmonic suppression will be reduced.  If too high, 
the circulating current in the tank circuit will be increased.  The 
coils and bandswitch in the AL-1500 are, er, not over-engineered (!) and 
might be damaged under these conditions.

-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco