>Not only is it a good idea to use a BC filter to protect the your preamp but
>also use it when making antenna measurements.
>
> I recently put up a two element array on 160. While checking the SWR
>matching adjustment using an MFJ-249 the results were wildly off from
>predictions. A quick check with an RF millivoltmeter showed 60 mV+ of local
>broadcast station signal. The local station is neither very powerful or
>very close. Putting in a BC filter in line with the MFJ calmed it right
>down. I saw the same problem with more advanced instruments like the HP
>4815A and the HP 3577A.
>
> Almost any antenna on 160 will pick up the local stations and so I make
>it standard practice now to use the BC filter.
>
I solved the BCI problem by using a high-pass L-network (series-C,
shunt-L) to match the high-Z Hertz antenna to 50-ohms. The second
harmonic was still down 59db.
cheers, Rudy
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
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