Fw: Topband: Inverted L for TX

Dave Heil k8mn at earthlink.net
Sat Mar 29 16:41:46 EST 2003

Jerry T Dowell wrote:
>  Your trouble may be that the MFJ259 usually will give erroneous readings on
>  160M because of BC station pickup on the antenna. That meter is not useable
>  at my QTH on any 160M antenna. I have heard that there is a high-pass
> filter
>  available from MFJ that can solve the problem.

Just to echo what Jerry writes, I had a terrible time getting a borrowed
'259 to give good 160m readings in Helsinki.  Using my own meter in
Tanzania, I still observed 160m readings which were off by 30-40 KHz.

Here in rural West Virginia, the nearest MW broadcasters are 25 miles
away.  The nearest high power broadcasters is closer to 40 miles away.
I still note errors in the readings off by 30 KHz on 160m and by 75 KHz
on 80m.  Once I calculated by how much the readings were in error, it
was a simple matter to adjust the 160m coaxial inverted "L" and to tweak
the vacuum variable cap used in the 80m inverted "L".  

MFJ's high pass filter is a good idea but it may not be the cure.  A
high pass filter could easily be homebrewed and mounted in a minibox as
an alternative to purchasing the MFJ unit.

Dave Heil K8MN

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