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

Tue Sep 20 07:21:39 EDT 2022

I'll chime in as well ... 

Maybe not relevant, but I think it might be ... the original poster I don't think mentioned that they were at the top of a sky hill with metal buildings and chairlifts etc in front of them ... that's what they told me as they some of this was being figured out while they worked me ... so, many reflections WOULD have been bouncing back to the multiple dishes.

KH

-----Original Message-----
From: Microwave <microwave-bounces at mailmanlists.us> On Behalf Of Brian Justin, WA1ZMS via Microwave
Sent: September 19, 2022 10:51 PM
To: Tom Williams <tomw at wa1mba.org>
Cc: Zack Widup <w9sz.zack at gmail.com>; Midwest Microwave <Midwest-Microwave at groups.io>; Microwave List <microwave at mailmanlists.us>; Mid-America Microwave Society <mams at mailman.qth.net>
Subject: Re: [Mw] [Midwest-Microwave] SPACING OF ROVER DISH ANTENNAS DURING 10up CONTEST

That is “an odd one” for sure.

My thoughts lead me away from antennas and head towards: strong broadband noise from Station A leaking-out and getting into Station B’s RX at an RX image frequency.

Without knowing all the LO and IF frequencies of the stations, I cannot do the math to prove it’s possible……

However w/o real true image-reject mixers or double conversion receivers with say a 2GHz first IF, ultra narrow filters, etc.  in our ham-grade 10GHz gear, an IF of 144 or 432MHz *may* may odd things possible.

Like Tom said…..run a few well-documented tests but consider out-of-the-box potentials too.

I like to know the root cause. 

-Brian, WA1ZMS
iPhone

> On Sep 19, 2022, at 21:55, Tom Williams via Microwave <microwave at mailmanlists.us> wrote:
> 
> I personally do not know of this kind of interaction, and it seems unlikely because the capture area of a dish is effectively its size. But as Einstein said "Save the evidence, through away the theory." So, I strongly suggest doing some experiments if you can, and writing a paper to give at a conference. We might all learn something.
> 
> Tom WA1MBA
> 
>> On 9/19/2022 2:23 PM, Zack Widup via Microwave wrote:
>> I traveled with a group of 4 to 7 vehicles in the 10 GHz contest this 
>> past weekend roving the Wisconsin side of Lake Michigan. We often 
>> parked right next to each other down a row of parking spaces in a 
>> parking lot. It was an organized effort - there were 6 or 7 other 
>> stations across Lake Michigan we were trying to work. Each station at 
>> our end took a turn calling all the stations on the other end and we 
>> generally worked them in the same order each time. We never had any 
>> problems with that, but if you are doing some kind of disorganized 
>> operation where different people are trying to work different people 
>> at random, I see how it could cause a problem. It works out really 
>> well when only one station is transmitting at a time and everyone is 
>> listening for the same other stations. They get their turn to work them.
>> 
>> 73, Zack W9SZ
>> 
>> On Mon, Sep 19, 2022 at 1:06 PM 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 dishes
>>> a) 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
>>> 
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