[CQ-Contest] Multi-Multi

[Jon Suehiro]

Dear contesting OM, personally I am always SO and never even tried SO2R.  In ‘80’s and ‘90’s, I had operated from MM / Multi-2 and I thought I understand the setup rules.

 

In last few years in Club FD and WFD operation, we are expanding from 2 ~ 3 ~ 4 radios.  Now the high band opening cannot be expected, so the operation stays in 80, 40 and 20 most of the time.

 

Typically the radios are Flex 6600, TS-590, FT-950, TS-440 (and IC7300), all in 100W and old analog to SDR combination.  No key click or audio distortion issue.  IC7300 is indicating ‘OVF’ without P.AMP so obviously over loaded.

 

Antennas are in the wide range of 40~10 multiband Yagi at 110’, 75/40 inverted vee (2 antennas placed in N/S and E/W probably 20’ apart), 2 separate 40 and 20 ¼ wave full size ground mounted verticals, 80-10 base loaded ground mounted vertical …  Antennas have balun, current choke, LMR400 or RG213 cables, Array Solutions band-pass filters …

 

Type of the interference is not the single signal 2nd harmonic.  Typically when 80 is on TX, the RX on 40 is interfered with S5-9 noise in almost entire band up and down – desense by fundamental or 2nd harmonics ?  Some in the backward by ½ harmonics ? is also happening.  RX does not use NB.  ATT reduce the amount of interference but the wide band interference does not disappear – cut more real signals than the interference.  Rule allows 2 TX’s in the same band as long as in the different mode but we are not even close to 2 different bands simultaneously.

 

Radios are at least 10 ~ 30’ apart, not grounded.  What could be the next step should I take ?  Running 6 full regal power TX’s in 160 – 10 in the MM environment is beyond the imagination.  Ground Cu plate under each radio ?  More current choke ?  Antenna separation in 100’s of feet ?  (How do you do if you have different band antennas on the same tower ?)

Your expert advice will be very much appreciated.  73 de Jon NN5T