[Skimmertalk] Another Skimmer Antenna Idea

[dd5xx at web.de]

I forgot to sent following message to our reflector, only Dave received it :) As Wes already said, I am also favouring PA0RDT miniWhip.

 
Thanks for sharing Dave. It's really not the brave art to copy things and re-publish them under own name. You just need to enter the search keywords "mini whip" into eBay and you'll see how many clones there are available. I want to emphasize that the original one is by PA0RDT (Roelof Bakker). Roelof is a really nice guy and very helpful whatever you need related to the miniWhip. You can even tell him to use SO239 or N jacks or whatever you like. He builds you the antenna to suit your needs. Just enter his callsign PA0RDT into eBay and you'll find the original mini-whip antenna.

Additionally I want to add that PA3FWM (=author and owner of www.websdr.org[http://www.websdr.org]) has written a very nice article with explanation about PA0RDT mini Whip antenna. There's also a nice HowTo which explains the necessity of correct grounding for every active antenna receiving the E-field.

http://www.pa3fwm.nl/technotes/tn07.html[http://www.pa3fwm.nl/technotes/tn07.html]
http://www.pa3fwm.nl/technotes/tn09d.html

Related to this topic and the mentioned Ukranian clone, I'd like to add following spech data, so you see the difference:

PA0RDT Mini Whip:
=================
Frequency range: 10 kHz – 30 MHz
Power: 9 – 15 V , 65 mA
Intercept Point 2nd order, IP2: > +75 dBm
Intercept Point 3rd order: IP3: > +40 dBm
Jack: SO-239 or N or BNC or whatever you like
Dimension: 100 mm x Ø 40 mm

The highlight of his latest models built is, that he uses a small ferrit core (HF decouple) which allows to disconnecting DC of the outer shield of theconnected coaxial cable. There is a jumper inside and you can choose if you want a DC connection or not. Your mileage may vary according to your setup. The instructions and illustrations that come with his antenna are self-explained.


For comparison, here's what the technical specs are for the Ukranian clone:

Frequency range: 10 kHz - 30 MHz
Power: 12 - 15 volts at 150 mA
Second order output intercept point: > + 70 dBm
Third order output intercept point: > + 30 dBm
Maximum output power: in excess of - 15 dBm
PCB Size: Length (mm): 155 x 27
Connector: BNC  

I want to add that I am nor a relative with PA0RDT neither I get some benefits for pointing this out. I just want to express how satisfied I am with the PA0RDT mini Whip antennas (I own 4 of them) and that it's fair to support the real producer of the real mini Whip.

Just my 2 cents.

73
Saki, DD5XX

Gesendet: Mittwoch, 17. Januar 2018 um 08:19 Uhr
Von: "David Gilbert" <xdavid at cis-broadband.com>
An: skimmertalk at contesting.com
Betreff: Re: [Skimmertalk] Another Skimmer Antenna Idea
Pretty much any linear conductor is an e-field probe.   That's what most
antennas are. This one is simply very short, and it even looks like it
has a large plate at the end to provide some capacitive loading.

By the way, here's the web site of the PA0 who did the original design. 
He doesn't sound very happy about the Ukrainian offering and seems to
question whether the Ukrainian version has the same dynamic range of his
design.

http://www.pa0nhc.nl/Miniwhip/indexE.htm[http://www.pa0nhc.nl/Miniwhip/indexE.htm]

Dave   AB7E


On 1/16/2018 8:46 PM, N4ZR wrote:
> Recently, I stumbled across an inexpensive active antenna kit offered
> by a Ukrainian ham
> <https://www.ebay.com/itm/MiniWhip-Active-Antenna-Assembled-in-Box-HF-LF-VLF-mini-whip-sdr-RX-portable-/222469570201[https://www.ebay.com/itm/MiniWhip-Active-Antenna-Assembled-in-Box-HF-LF-VLF-mini-whip-sdr-RX-portable-/222469570201][https://www.ebay.com/itm/MiniWhip-Active-Antenna-Assembled-in-Box-HF-LF-VLF-mini-whip-sdr-RX-portable-/222469570201[https://www.ebay.com/itm/MiniWhip-Active-Antenna-Assembled-in-Box-HF-LF-VLF-mini-whip-sdr-RX-portable-/222469570201]]>
> He acknowledges that it is based on a design by a PA0, but that's
> between them.  Anyhow, it is a cute little package (photo at the
> link), with the antenna proper housed in a 6-inch plastic housing
> about 2 inches in diameter.
>
> My thought was to use this for the RBN's gap-filling program, since
> shipping an 8-foot whip is a royal pain, and I assumed you would
> attach a wire antenna to the top.  Imagine my surprise to discover
> that the antenna is completely inside the small plastic package.  I
> don't pretend to understand the  theory of the thing - something
> called an E-field probe, I gather - but the only antenna in it is a
> roughly 1.5 x 2.5 inch section of the PC board at the top end.
>
> Humph, I thought - how can this work?  Well, it does, and very well -
> as I write this my QS1R is happily copying stations on 160, 80 and 40
> meters with signal-to-noise ratios at least as good as my Clifton Labs
> whip, my standard of comparison for years. Earlier today, I compared
> sensitivity and noise on 40-10 meters, and was pleasantly surprised.
> My methodology was pretty crude - SDRMAXV and a Mark 1 eyeball - but
> the two antennas appear to be within 5 dB at most, with the advantage
> on 20M and above going to the "MiniWhip".
>
> I think this first copy of the antenna is going to find its way to
> EL-land, soon.  Stay tuned.
>

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