[Skimmertalk] Antennas for Skimmer radios?

Sat Dec 24 09:02:12 PST 2011

Besides, you're talking apples and oranges.  A receive antenna works 
well when it maximizes the signal/noise ratio at this end of the path.  
A transmit antenna works well when it maximizes the signal/noise ratio 
on the far end of the path.   Those are not at all the same things.

Although there are skewed paths, and all send-receive paths aren't symmetrical, 
actually, as a practical matter, they are generally the same-- apples for 
apples. If you look at VOACAP charts when doing antenna and terrain analysis, 
the take off (and receive) angles and the gain lobes generally benefit both 
incoming and outgoing signal strength.

My point here is-- just like in contesting-- a mediocre omnidirectional antenna 
is never a good idea, whether it's convenient to use or not. An active, 
omnidirectional antenna is convenient and easily matched across a broad band of 
frequencies-- less work for mother. But for contesting, if you know where your 
bread and butter target areas are (producing most QSOs and MULTs) you want 
specialized directive gain antennas to amplify incoming and outgoing sigs to 
those target areas.

Out here in San Diego I use my skimmer as a second op in assisted class 
contesting. I want my skimmer to hear the most Europeans (or JAs, or South 
Americans) it can, so I can bang down the N1MM bandmap and work them quickly for 
points before the thundering herd from the clusters arrives. So I will add a 
2-el yagi with wide beam width aimed 045 to cover NA and EU, and the Pacific 
islands off the back. Ideally, I would have stacked yagis in those directions to 
choose upper, lower or both depending upon arrival angle, but there is not room 
here for that. Even though a 2-el yagi is not optimal, from experimentation out 
here I know adding one aimed in the bread and butter directions makes a big 
difference in what my skimmer hears.

I suppose as a mere propagation tool, an omnidirectional antenna produces 
omnidirectional information. But even for propagation study purposes, rotating 
gain antennas (a rotating yagi, or switched four square or phased verticals) 
would make more sense because it would hear more.

73, Larry N6NC

________________________________
From: David Gilbert <xdavid at cis-broadband.com>
To: skimmertalk at contesting.com
Sent: Sat, December 24, 2011 6:23:58 AM
Subject: Re: [Skimmertalk] Antennas for Skimmer radios?

Yes ... that is exactly what we want from CW Skimmers.   We want to know 
who's on the air and whether they can be heard at a particular 
location.  It's up to everyone else to try to work them.

Besides, you're talking apples and oranges.  A receive antenna works 
well when it maximizes the signal/noise ratio at this end of the path.  
A transmit antenna works well when it maximizes the signal/noise ratio 
on the far end of the path.   Those are not at all the same things.

Dave   AB7E

On 12/23/2011 7:27 PM, Andrew O'Brien wrote:
>   I guess this brings up the question about the purpose of the skimmer
> antenna.  It seems to me that an active antenna such as the ones
> mentioned in this thread , receive better than the antenna to be used
>   when transmitting.  I always assumed that a station's receiving
>   skimmer antenna should be generally reciprocal to the performance of
>   the transmitting antenna.  This based on the the theory ...if you hear
>   'em, you can work 'em.  Super skimmer antennas churning out "spots"
>   for the world maybe useful , but is that what we want from skims ?
>
>   Andy K3UK
>
>> On Tue, Dec 20, 2011 at 3:31 PM, John Reilly<reillyjf at comcast.net>  wrote:
>>> I'm using a Pixel Magnetic Loop (RF Pro-1B) mounted at 10 ft; however,
>>> it is surrounded by 25 ft houses!  I'm planning to move my loop up to 25
>>> ft plus next Spring to see if getting it at or above the houses will
>>> improve performance.  I also have a Clifton Labs vertical, but it
>>> doesn't seem to perform as well as the mag loop.
>>>
>>> I also studied the N6TV stats and asked K3LR what they were using --
>>> vertical(s) (I assume they are active). I use a QS1R.
>>>    - 73, John, N0TA
>>>
>>>
>>> On 12/20/2011 12:09 PM, H Lawrence Serra wrote:
>>>> Pete N4ZR suggested I put this out to the group:
>>>>
>>>> I would like to hear from skimmer ops on what ANT systems they are using 
for
>>>> their skimmers.
>>>>
>>>> I am in the SW corner of the US, on the wrong (west) side of close-by Mt.
>>>> Soledad and have roof space-limited ANTs. I use a PA0RDT active mini-whip 
>ANT
>>>> about 5 ft above my roof for my SDR-IQ radio which feeds the skimmer. I was
>>>> surprised to see from N6TV's RBN stats that I have the lowest SNR average 
>for
>>>> signals of reported RBN skimmers, and post only 1/5 the spots N6TV had and 
>>>1/10
>>>> the spots WA7LNW had from my part of the country.
>>>>
>>>> I have tried putting my 2-el Steppir yagi pointed 045T on the skimmer when I 
>>>am
>>>> not contesting, and even that little extra gain results in more skimmer 
>spots
>>>> from NA and EU. My plan now is to find a used A3 tri-bander that I can cut 
>>>down
>>>> to a 2-el due to space limitations and because I want a broad beam width. I 
>>>>plan
>>>> to use a coupler to feed both the active mini-whip and the 2-el yagi to the
>>>> skimmer's feedline, so I don't have to mechanically switch ANTs when 
>SkimScan
>>>> switches to the low bands at night.
>>>>
>>>> Anyway, I would be interested in what SDR or other radio you use, and what
>>>> ANT(s) you use for your skimmers.
>>>>
>>>> 73, Larry N6NC
>>>> _______________________________________________
>>>> Skimmertalk mailing list
>>>> Skimmertalk at contesting.com
>>>> http://dayton.contesting.com/mailman/listinfo/skimmertalk
>>>>
>>>>
>>> _______________________________________________
>>> Skimmertalk mailing list
>>> Skimmertalk at contesting.com
>>> http://dayton.contesting.com/mailman/listinfo/skimmertalk
> _______________________________________________
> Skimmertalk mailing list
> Skimmertalk at contesting.com
> http://dayton.contesting.com/mailman/listinfo/skimmertalk
>
_______________________________________________
Skimmertalk mailing list
Skimmertalk at contesting.com
http://dayton.contesting.com/mailman/listinfo/skimmertalk