[UK-CONTEST] 2 Station setup ideas please for CQWW

[Don Beattie]

Jim,

As you know, there are really four ways of fixing the inter-station problem:

a) Bandpass filters on each rx (switchable, or need to change with each band 
change)
b) Co-ax stubs (need changing for each band change)
c) LOTS of spacing between antennas
d) Magnificent dynamic range/blocking performance in the receivers (although 
this does not cure all elements of inter-station problems) In reality no 
amateur equipment comes very near the range required here.

There are two reasons to use these:

a) Inter-station breakthrough
b) Blowing the front-end of the one or both receivers with excess RF voltage 
down then feeder

At 100m spacing (provided that really is true for all parts of all antennas) 
I think personally you will be safe on (b). But (a) remains a problem. I 
suspect you will still get overload and "whiskers" from the other station - 
particularly so if you are trying to receive on a harmonically related 
band - e.g. listen on 14 whilst working on 7Mhz.

You can reduce the effects by cross-polarising your antennas - vertical 
polarisation for one and horizontal for the other - although this really 
only works for the HF bands. You can also gain a few extra dBs of protection 
by considering the relative positions of your antennas so that the HF beams' 
most commonly used directions put a partial null towards the other stations 
antennas.

 At 100m (which is about the spacing I have here between the two towers) I 
don't think you will get away without some problems. In the end, you need 
filters of some sort - co-ax or Dunestar/ICE etc. I use a pair of switched 
200W Dunestars here, and that kills the problem except for second harmonic. 
If I were really worried about that, I would add the odd stub to take it 
out, but it's not a big issue. If I disable the Dunestars, I get phase 
noise, and also some overload (but I don't seem to fizz the front end)

It may be that others will have additional comments (or even disagree with 
mine !) but I'm sending them for what they're worth.

I guess in the end you try it out, and if you judge that it's all to hard, 
you do a single station entry

Good luck !

73

Don, G3BJ




---- Original Message ----- 
From: "Jim Balls" <jim at j1mbo.f9.co.uk>
To: "Uk-Contest at Contesting.Com" <uk-contest at contesting.com>
Sent: Thursday, September 07, 2006 7:52 PM
Subject: [UK-CONTEST] 2 Station setup ideas please for CQWW


> Hi all,
>
> We are thinking about running a 2 station setup for CQWW SSB.
>
> We currently have no experience of this and was looking for pointer on a
> cheap and easy filtering option (I their is such a thing!).
>
> We are looking to run lets say 20m - 10m on one setup (HFstation) and
> 40m - 160m on the other setup (LF Station).
>
> Antenna's will have a separation of about 100m, we are going to run a
> vertical and dipole setup for 40m - 160m on the second station tower and
> a 10 - 20m beam (Spider) and a 2 element Moxon for 40m on the main tower
> (I guess the 40m beam will be used on the 10 - 20 m station and not the
> LF station)
>
> Both will run 400w.
>
> Radios will be
>
> HF station 756PROII -  TL922 In Caravan
> LF Station with be Either FT990 or TS870 - 811H (with 572B tubes) In 
> Awning
>
> We cannot afford luxuries like the Dunestar filter setup at this point.
>
> Any ideas guy's, Would we suffer much breakthrough etc, is it even worth
> attempting?
>
> Thanks
>
> Jim M0CKE
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