>
>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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