[AMPS] Amp. Bypass SWR

[measures]

>
>Hello Amp. Fans
>
>Should the amp. bypass circuit introduce a SWR reading of around 1.3 to 1
>at 14 MHz. when a 50 Ohm dummy load is connected to the output of the amp.
>and a SWR analyzer connected to the amp's input?
>
If enough stuff is messed up, surely. 

>The homemade amp. has a RB2A Jennings DPDT vacuum relay for switching the
>input and output.  A 4 inch run of 1/2 inch wide copper flashing is run
>from the ouput pole of the RB2 to the center pin of the output coax
>connector (SO 239).  A couple inch length of 3/8 inch braid is used between
>the normally closed terminals,  A 10 inch length of RG 58 is run from the
>other RB2 pole to a BNC chassis connector (the shield is connected to the
>chassis at one end).  
>
>A Heathkit Cantenna and a MFJ SWR Analyzer are used.  The RG 58 cables have
>a 1 to 1 reading when used to connect the MFJ directly to the Cantenna.  
>
>As you go higher in freq. looking at the Cantenna through the amp. bypass
>arrangement, the SWR increases and vice versa when decreasing freq. from 14
>MHz.  
>
>Are these type of readings normal, 

 Most turkeys overload the Cantenna - and overheat the resistor. This 
causes the  resistance to increase. 

> should they be lower - closer to 1 to 1,
>is this an indication of a bad component in the bypass circuit? 

No.  You need to cancel the series L in the relays with a shunt C.  I 
would start with a 50pF variable and a 50 ohm termination that measures 
within +/- 5%.  .  
>
good luck, Mike

-  Rich..., 805.386.3734, www.vcnet.com/measures.  


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