[TowerTalk] Need balun advice

[Jim Brown]

On Wed,11/11/2015 5:48 AM, Herbert Schoenbohm wrote:
>
>
> On 11/11/2015 8:11 AM, john at kk9a.com wrote:
>> Repeat after me --
>>
>> SWR is NOT an indicator of antenna performance.
>
> But it determines whether or not my very sensitive  Alpha 87A will 
> trip off or a solid state amp will fold back.

Right. And the match of the antenna to the coax determines loss in the 
line. But the matches that the original poster described were not 
sufficient to generate much additional loss.

And several things that K6XX taught me -- First, the output devices 
(tube or transistor) in ANY power amp must work into a matched load to 
achieve minimum distortion. Tube amps can accomplish that match with 
careful tuning, but solid state amps that lack an adjustable matching 
network require an antenna tuner to achieve that match.  In teaching me 
this, Bob was not entirely altruistic -- we're close-in neighbors, so he 
has a vested interest in my amp being clean. :)

Second, it's important to know whether your amplifier is "auto tune" or 
"auto-recall" of previous settings on the same band. BIG difference. 
I've never owned an Alpha, but I think that some models are auto-recall. 
That means if you're using a different antenna, you've got to re-tune 
the amp. My guess is that in addition to minimizing distortion, it will 
also prevent the amp from tripping off or folding back.

73, Jim K9YC