[AMRadio] PA set up using ant analyzer


Mike Dorworth, K4XM k4xm at arczip.com
Thu Jun 8 18:09:43 EDT 2006


----- Original Message ----- 
From: "Edward B Richards" <zuu6k at juno.com>
To: <amradio at mailman.qth.net>
Sent: Thursday, June 08, 2006 5:48 PM
Subject: Re: [AMRadio] PA set up using ant analyzer


> Hi Dennis;
>
> I am having trouble resonating the plate tank on the linear amplifier I
> just built. When checking for resonance with a grid dip meter using a
> 5,000 ohm resistor from plate to ground, should the tubes (4-400 X 2) be
> in the circuit?




This is not Dennis but the answer is the tubes must be there or a capacitor
equal to the total output capacity of the tubes in their place. i.e.28 pf
( 14 each) for a pair of 813's check tube table for output cap. The analyzer
should show a 1 to 1 swr from the antenna looking in when it is resonated.
The grid dipper technique is differnet. You take the resonate plate load z ,
plate volts divided by 2 time plate current and divide by disired operating
Q, 10 or so for the input capacitor, with the tank cold disconnected. use a
capacity meter to set the C1 and then leave it alone, the output cap C2 is
the load z ( 50) divided by q, about 2. These give the x sub c value which
must be converted to capacity.  Then you tap ( short coil till the analyzer
shows one to one from the output jack). Hope this helps..For pi-network.
check ARRL handbook for pi-l. Mike





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