[CQ-Contest] I've heard it all now!

Bill Tippett btippett at alum.mit.edu
Wed Dec 10 08:31:44 EST 2008



         I was one of the stations on W4ZT's 3655 Wall of Shame 
list.  The only problem I have with his list is that it appears you 
remain on it forever...even after you fix your harmonic.  Here's how 
I fixed mine with a shorted stub made of ~89' of polyethylene RG-8 (Vf = 0.66).

                                 73,  Bill  W4ZV

"Raoul Coetzee" <raoulc at smmcape.co.za> wrote:

 > I am having a bit pf a problem with a second harmonic when 
operating on 160m.
 > This is of course falling in the 80m band segment and causing mild 
to severe
 > qrm to my local 80m friends on phone.

         I had a similar problem when we gained SSB access to 3600 and
above.  My solution was a shorted 1/4 wave stub for 160 at the output
of my amplifier.  Use (246/1.83)*Vf to determine the length in feet
and cut it a little longer if you aren't certain of the velocity
factor of your coax.  I used an MFJ-259B analyzer and pruned the stub
for minimum impedance at 3.650.  Just remember to switch out the stub
for other bands!

         I had reports that my harmonic was S7 before I did this.
Afterwards I had W0FLS check it using his 4-Squares on both 80 and
160.  On 160 I was S9+30 and on 80 I was inaudible, and I've not
received further complaints from anyone.

                                        73,  Bill  W4ZV
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