Topband: Skimmer calibration

[Yuri Blanarovich]

Depends what are you expecting from Skimmer-RX-ANT setup.

If you want skimmer to find DX before the pack and looking for low angle 
signals, then setup better use antenna with proper low angle vertical 
pattern. Also getting true report when evaluating beach antennas with 
low vertical angle, skimmer should be using similar antenna to even 
detect the signals. High angle skimmer antenna would make TX beach 
vertical vs. horizontal or other antennas inland look about the same and 
erasing the "impossible" 10 -20 dB advantage. 
Just like say if one is driving mobile on the land, you don't hear low 
angle signals. Get close to the water, or better, bridge over salty 
water, band comes to life, 10 - 20 dB enhancement becomes reality.

Skimmers and testing over longer distances is fine to get ball park idea 
how, or if the antenna works, but the true indicator of performance is 
the field strength measurement in the vicinity of antenna, eliminating 
finicky propagation and other undesirable variables. 

For unbelievers in salty beach phenomena, I recommend reading K2KW and 
Team Vertical exploits, tests, measurements 
 http://www.k2kw.com/verticals/verticalinfo.htm  and take to the beach 
with radio and "see" it, before posting "authoritative" denials.

I did, I knew salt water is good, but wanted to "see" it with my own 
ears. I packed 10m setup ( 3el. vertical Omni with Stackmatch) and went 
to Cape Hatteras, NC. Just driving around the banks, bridges and sandy 
islands it was an eye and ear opener. Second time I brought 4 square and 
vertically polarized 2 el. Quad on a boat deck. I saw that 10 - 20 dB 
difference and the ability to work juicy stuff before packs got to it. 
(Still US 10m LP record as N2EE/4) I figured 10m would be least 
advantageous band to take advantage of the effect (low bands would be 
more enhanced), but I was sitting there "unbelieving".

Good enough for me, I understand the phenomena, I figured how to take 
advantage of it and when I get the chance to play I will pack my 
"fishing rods" and play on the beach. I don't need skimmer to tell me 
that.

Yuri, K3BU.us
www.MVmanor.com for your DXContestvention or ham radio weddings


 
 
 On Tue, Aug 19, 2014 at 05:01 PM, Guy Olinger K2AV wrote:
 
 > Do we really care that skimmers aren't hooked up to antennas with
> pattern and gain?  One of the things in using VOACAP is knowing the
> pattern of the RX antenna as well as TX. Omni pattern at RX removes RX
> antenna bias.  Why shouldn't we specifically use omni on RX, so that
> any enhancement is from the sender or the propagation/environment?
>
> The thing about sensitivity is that it rarely matters if the
> out-there-on-the-band noise is controlling. Band-noise controlling is
> far more common on 160 than 80 and above.
>
> Running stuff from here to W4KAZ 7+ miles away always shows an initial
> 3-4 dB drop in S/N when the band just starts to open.  Why I generally
> run stuff to him in the middle of the day when I want to know the
> numbers.
>
> 73, Guy
>
> On Tue, Aug 19, 2014 at 12:06 PM, Tim Shoppa  wrote:
>> I quickly noticed that some skimmers seem to have more effective 
>> antenna
>> systems than others.
>>
>> More than S/N, I look at kinda the breadth and depth of where I'm 
>> spotted.
>> On 160M, GW8IZR and DL1A are where I'm first spotted. If I'm getting
>> spotted more broadly or deeply than that, then I know conditions are 
>> really
>> good.
>>
>> Tim N3QE
>>
>>
>> On Tue, Aug 19, 2014 at 5:33 AM, Mike Waters  wrote:
>>
>>> When I last investigated, all the skimmers and Web SDRs that were 
>>> outside
>>> of North America all had terrible receive antennas for copying DX 
>>> signals
>>> on 160. (And who knows how many of them are in quiet locations?)
>>>
>>> When I say "terrible", I mean small "magnetic" loops, very short 
>>> whips, low
>>> dipoles, a random end-fed wire, etc. No phased arrays or Beverages, 
>>> and not
>>> even a Flag, K9AY, EWE, etc.
>>>
>>> Does anyone know if that is still the case?
>>>
>>> 73, Mike
>>> www.w0btu.com
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>>> Topband Reflector Archives - http://www.contesting.com/_topband
>>>
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