[MAMS] April 2011 Microwave Activity Day

Mon Apr 4 16:29:38 EDT 2011

Wind is often a significant hinderance to VHF and microwave propagation. 
Without wind and clouds, night radiant cooling of the earth's surface 
cools air near the surface causing a temperature inversion that enhances 
refraction. Evaporative cooling over water bodies gives much the same 
effect. In the prairie typically that morning inversion is about 1000 
feet above the ground. Often visible when flying up in a small airplane 
or observing a smoke or steam plume from a fire or power plant. Wind 
stirs the boundary layer and destroys the inversion by mixing. Gusts are 
better at mixing. Cloud cover over land holds in heat and so tends to 
prevent the little inversion forming.

A high pressure dome has no wind under it and that inversion can build 
and isn't destroyed and can build up over days to cover a large area 
with propagation out to 1500 miles or better.

We work beyond line of sight with normal conditions because of the 
atmosphere is less dense with altitude and that gradient of density 
causes some refraction, the 4/3 earth radius rule.

73, Jerry, K0CQ

On 4/4/2011 10:31 AM, Zack Widup wrote:
> Conditions on Saturday were evidently very poor. I cannot verify that
> I was NOT putting out power on 902 MHz, so I am going to assume I
> actually was when I tried to work Wally W9OBG. When I got everything
> home and checked it out, it appeared the only damage to the IF rig
> from a fall onto the ground was a damaged squelch control knob/shaft,
> and everything else was working normally. I was getting 10 watts out
> of the 902 MHz transverter as expected. Since Wally was running 200
> watts or more and I was only getting him S9, and he couldn't hear my
> 10 watts at all, I am now assuming conditions were that bad. Lloyd
> NE8I has said that condx were really poor up in Michigan where he was.
>
> I can get to the hilltop in EN50rl just about any morning of the week
> between maybe 6:30 and 8 AM CDT. as well as some hours during most
> weekends. If the Hepburn forecast looks good and if anyone wants to
> try to work me, let me know. I just hope it isn't a windy day!
>
> I haven't attempted an SDR radio for a microwave IF. It might be a
> good idea as you could see a good chunk of the spectrum all at once,
> and when you've identified a signal all you have to do is peak your
> dish on it. But there is so little time and I'm spending a lot of time
> trying to get my 24 GHz transverter going. I just made a few boards
> that are basically the W1GHZ Miniverter-F but the helical filters for
> 432 that I have are smaller than the ones he is using (hence I made my
> own boards with my filter size specs rather than order some from him).
> I want to use this as a 432 MHz IF for the 24 GHz SDH transceiver I
> have. I'm also working on putting together the LO chain to give me 6
> or 7 dBm at 11.800 GHz. I might get that done this week.
>
> Then I'll start thinking about 47 GHz.
> :-]
>
> 73, Zack W9SZ
>
>
> On Mon, Apr 4, 2011 at 9:56 AM, M Ragouzis<n0obi at yahoo.com>  wrote:
>> Hi Dave
>>
>> Thanks for the note of the 11th.
>>
>> My brother  Bruce ,  may have a 6 foot fiberglass dish to give away , he spoke
>> about it yesterday and he lives near you.
>> I have a phone call in to his message center now just so he doesn't cut it up
>> before some one has a chance at it.
>>
>> I hope things are going well for you , we should have a breakfast meeting some
>> time , what do you think ? , I do not know anyone in the club by face ( how many
>> are here in the st louis area ) .
>>
>> Is anyone working on SDR using the Apple i-phone or i-Pod products for  a 10
>> ghzreceiver ?
>>
>> I'm still working on getting the SDR radio up and running , I found a 741 OP amp
>> in the junk drawer last night , the RF front end will work through the computer
>> sound card but not through Jim's i-phone or i-pod , so it looks like the i stuff
>> needs more gain , Jim discovered ad added the 10M ohm resistor across the mic
>> input to let the i-phone/pod know that it has and external mic.
>>
>> Plugging in the mic/sdrrffront end caused a spike to form on the display but
>> nothing more than this , were getting closer.
>> I don't know that the 741 will be quiet enough , but as things are right now
>> something would be better than nothing.
>>
>> If we go through the 1/8 inch jack we only get one channel so it I or Q and we
>> have just a one channel direct conversion radio ( ? ).
>> But we will have the ability to use the software to narrow down the band width ,
>> so this should be real good for 10 ghz.
>>
>> I have the 2 meter N-channel amp built , I just need to tune it up .as you know
>> we were talking about dynamic range problem's , I hope this and sdr will make a
>> running receiver.
>>
>> OH , I picked up a "Gunn Oscillator " that I tuned to 10.368 ghz , so it might
>> be good for CW even though its a little wide  ( I have a filter ) .
>>
>> So much stuff to do so little time.
>> Mike
>> N0obi
>> 73
>>
>>
>>
>>
>>
>>
>>
>> ________________________________
>> From: Dave Calvert<kb0pe at yahoo.com>
>> To: Mid-America Microwave Society<mams at mailman.qth.net>
>> Sent: Sat, April 2, 2011 9:28:53 PM
>> Subject: [MAMS]  April 2011 Microwave Activity Day
>>
>> I went to EM49au ( AT&T microwave tower site ) and setup at 6am and was ready to
>>
>>
>> go on 902, 3456 and 5760....  It was windy and the bands were dead!  I looked
>> around
>> for the beacon on 902 (K3SIW's) and nothing.  I did have some long q's on
>> 144.200
>> at around 11am with South St. Louis and that was it....
>> 73,
>> Dave -KB0PE
>>
>> Starting Monday April 11th, 7-11PM local. 2M Sprint.
>> Tuesday April 19th - 222 Sprint.
>> Wednesday April 27th - 432 Sprint.
>>
>>
>> ______________________________________________________________
>>
>>
>>
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