Hi Mike,
What you are seeing is to be expected. The wiring adds a bit of
inductive reactance to the line. I would not bother with it, but if you
want to get rid of it, connect a small value cap with a voltage rating
good enough to handle the full output of the amp to the junction of the
1/2" copper strap and the output connector and ground. Pick the value
for lowest SWR on all bands.
73, Bob, W5AH
Mike wrote:
>
> 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?
>
> 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, should they be lower - closer to 1 to 1,
> is this an indication of a bad component in the bypass circuit?
>
> Hope this is sufficient explaination of what is in the amp and how it is
> connected? Any information will be appreciated as have to do a bit of
> rework in the amp. Now is a good time to do the investigation and repair
> to the bypass if needed.
>
> 73,
> Mike, K4GMH
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