[MAMS] [Midwest-Microwave] SPACING OF ROVER DISH ANTENNAS DURING 10up CONTEST

[KENT BRITAIN]

 Far more likely your interaction was Sidelobes.
As the 3 cm waves bound off the feed support, refract off the edge of the dish, bounce back an forth between the feed and the center of the dish, lots of lobes going out in different directions.     If A has a tiny bit of LO leakage, and B is using a high gain preamp, B quickly has two LO signals at the mixer.
If you both using LOs very close in frequency, the LO is usually coming out the feed as well.   Now you can set some really fun interactions.    Moving farther apart, or even moving forward/back can help.
    On Monday, September 19, 2022 at 01:06:21 PM CDT, Bill Koch via groups.io <ddikoch=yahoo.com at groups.io> wrote:  
 
 


All:
K1RZ, K3WHC and I were roving together for the 10UP contest this past weekend.  We noticed that our dishes, on tripods, interacted with each other causing signals to attenuate or disappear..
We thought about yagi and quagi antennas with their 'rules of thumb' for spacing as well as some WA5VJB comments on spacing.We are wondering whether there are some 'rules' on spacing of parabolic dishesa) between two bands, say 10 and 24?b) between rovers on 10ghz?   
Is there a capture area for a parabolic dish that is markedly different than it's diameter?
We observed some 'not understood' reductions of received signal strength as follows.At Reddish Knob, FM08jl, we were lined up such that all three of us could aim NE and SW relatively straight on.  All all three of us had a 'White Box' 2 foot dish that has a WG feed.K1RZ and I have a WG switch with Kuhne EME LNA.  K3WHC had a high quality coax feed to a relay and LNA..Due to the real estate layout, the centers of our dishes were about 6 feet apart.  K1RZ was on left end, K3WHC was center and I was on right end.K1RZ and K3WHC worked WA4PGI right away; I could not hear WA4PGI and was frustrated.  I generally hear quite well.K3WHC moved his dish to point somewhere else and all of a sudden WA4PGI jumped up to a very strong signal...easily 5x7.
Yesterday, at Blue Knob, FN00rg, we experienced the same impact, albeit that K3WHC and K1RZ did have some interaction as I experienced the day before.We were lined up about 8 feet apart.  We turned our dishes 90 degrees or so from the operating dish and generally made the Q, although the band was up and down.
K1RZ and I have been at FN00rg before although not nearly as closely positioned.  When we worked N1DPM and co. for a 10up contest's long Q, we were a good 50' apart. On the other hand, AF1T, K1RZ and K3WHC work from a tightly sized balcony on Block Island (that W1GHZ uses as well on a different weekend) and they did not have the issue.  I've worked all three of them from FN00rg or FM08us.
Can anyone help us understand what was or may have been happening?  Are there some rules on spacing between dishes to protect against signal reduction?  What are we missing?  
TNX/ 73
Bill  W2RMA

 _._,_._,_  Groups.io Links:
 You receive all messages sent to this group. 

 View/Reply Online (#5150) | Reply To Group | Reply To Sender | Mute This Topic | New Topic
 Your Subscription | Contact Group Owner | Unsubscribe [WA5VJB at FLASH.NET]
 
_._,_._,_