[TowerTalk] SO2R or Multiop Contesting without interference

Jeff Blaine KeepWalking188 at ac0c.com
Tue May 29 01:52:38 EDT 2018

Kostats touched on one important factor.  No two stations are the same.  
And while the problems are all in the same sets of families, the 
specific cause and specific fix varies.  It can take a lot of time to 
determine what the source of a problem is and get it mitigated somehow.  
There are lots of variables and the mixer-type of noise sources really 
can make you crazy tracking them down because they can come from almost 
anything electrical, electronic or metal in the environment up to quite 
some distance from the antennas.


On 28-May-18 11:46 PM, kostas sv1dpi wrote:
> I know it can be done without interference. In EP6T were I was a 
> member, we were working the 1st day with a hexbeam on 10, 15 and 20m! 
> Interference in k3 was less than an 1S unit! We used 4O3A triplexer 
> and high power band pass filters and w3nqn low power band pass.
> In SZ1A (my club) we use dunestar low power band pass filters, stubs 
> after the amplifier and monobanders. Also the interference is accepted 
> except between 20 and 10m (not very usual situation and not bad but 
> more than we would like).
> My experience from SZ1A says that your problem is a switching power 
> supply. Some years ago we had an ethernet switch. We tested the 
> switch's power supply and it was quiet during rx. But the interference 
> from 20 to 15 was S9! Same between 40 and 20m. Searching I found the 
> problem to be the switching power supply. It re-transmits the noise! 
> An easy search to find such a problem is to increase the power and 
> watch the problem. For example 5w - no problem, 50w - no problem, 100w 
> - no problem, 200w -S9 noise. This is not normal. If the problem was 
> because of bad filtering, the interference noise would be more linear. 
> For example 5w - no problem, 50w - S1, 100W S3, 200W S5 and goes on.
> 73 Kostas SV1DPI
> Στις 29/5/2018 05:32, ο Timothy Coker via TowerTalk έγραψε:
>> Is anyone out there operating high power SO2R or Multi-Op without 
>> interstation interference (besides being on or very near a harmonic)?
>> I read reviews of various antennas, new filters, etc of having 
>> non-existant issues. However, in my limited experience it seems that 
>> tribanders will have these issues even with the latest high power 
>> triplexors and band pass filters. Even problems will arise at 
>> multi-tower stations with monoband yagi stacks and/or different 
>> direction facing yagi's.
>> Has anyone got the ability to say that they are trouble free on their 
>> various band combinations?
>> For instance, at home I have lots of interference when receiving on 
>> 15m and while transmitting on 20m. Same goes when receiving on 20m 
>> and transmitting on 40m. For me, it can be both direction and/or 
>> antenna limited depending on what band combination and which 
>> tribander that I take out of the stack.
>> I'm curious about the true confessions that other operators have 
>> about what they are dealing with when transmitting on multiple bands 
>> at once? Have some of the stations got this under control? If so is 
>> it mainly the big property owning stations with many towers or have 
>> guys on 1-2 tower setups quelled this also?
>> 73,
>> Tim / N6WIN.
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