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Author Topic: Pa0rdt Mini-Whip Active Antenna  (Read 43872 times)
AUSSIE
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Posts: 39




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« on: January 04, 2014, 03:33:19 PM »

Hi everyone this is a Youtube Video of my new mini active whip have to say when i received it few weeks ago i thought its going stright in the bin to my surprise its only 10 centimetres in length started at 1.5 metres high picked up a few ndb stations & ameturs talking on 20/40 metres at the moment its 4 metres high picked up lots of aero traffic & volmet stations with in the next few weeks will be around 8 metres high and its giving my 3 wellbrook active loops a good run..

http://www.youtube.com/watch?feature=player_detailpage&v=v7msfFVQCKU

Regards Lino..

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W4OP
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« Reply #1 on: January 05, 2014, 07:13:06 AM »

Until just recently, VK1OD had an in depth analysis of the PA0RDT antenna on his site showing that  the outside of the feed coax is the main antenna. If you write Owen, he would  probably send you a copy if interested.


Dale W4OP
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AUSSIE
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« Reply #2 on: January 05, 2014, 08:21:53 AM »

Hi Dale thanks for that im not an expert when it comes to specs and the technically of antennas been in the hobby for 36 years and have been surprised what works and what doesnt when it comes to antennas over the years as one said in another review it was picking same as his wellbrook loop and better some times and im finding that out at a qurter of the price..

Regards Lino..
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JAHAM2BE
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« Reply #3 on: January 06, 2014, 06:00:24 PM »

You can still see some of VK1OD's comments on the PA0RDT antenna here:

http://groups.yahoo.com/neo/groups/600m/conversations/topics/8070
http://www.youtube.com/watch?v=EWqJHTOijdE

I've built one of these from scratch. I used it in a second-floor apartment situation where it was impossible to ground the antenna properly. My experience, using it for HF listening, was that the antenna had a lot of noise caused by common mode currents. I understand that these common mode currents are all but impossible to stop if you don't ground the antenna; in particular, choking the feedline without proper grounding is insufficient because the choke impedance will always be less than the extremely high input impedance of the amplifier (which is necessary because the small whip is a high impedance antenna). See these links for some more details:

http://active-antenna.eu/tech-docs/comm-filter-ftp-10.pdf
http://www.qth.net/pipermail/lowfer/2003-September/010196.html

I gave up on the active whip antenna and instead used an active loop antenna (which, unlike the whip antenna, has a very low input impedance, making it easier to choke off common mode currents), the M0AYF active loop design based on 2 BJTs in a differential amplifier arrangement. It works surprisingly well, even inside of a concrete building.
« Last Edit: January 06, 2014, 06:22:10 PM by JAHAM2BE » Logged

W4OP
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« Reply #4 on: January 07, 2014, 09:03:50 AM »

I have gone  the same route. 7' active shielded loop similar to the Pixel or Wellbrook.
Excellent, balanced deep nulls indicate that the antenna is performing as it should with little common mode issues.

Dale W4OP
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KD7RDZI2
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Posts: 79




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« Reply #5 on: February 05, 2014, 04:13:44 PM »

Dale, have you ever thought to an Active HF Omniangle with a well matched high IP3 amplifier?
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ZENKI
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« Reply #6 on: April 11, 2014, 07:27:05 PM »

You might also read  further information here, especially if you do want to build a better antenna.

http://g8jnj.webs.com/activeantennas.htm

There is a few options there that you could explore.

I would rather build the LZ1AQ antenna.
http://active-antenna.eu/order-and-pricing.php
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K5TED
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« Reply #7 on: May 22, 2014, 06:17:14 PM »

So, Aussie, the consensus here is apparently that your antenna can't possibly be working as well as as you claim, despite your favorable comparison, in your particular location, in your particular implementation.

Sheesh... Roll Eyes
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AUSSIE
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« Reply #8 on: May 23, 2014, 04:40:54 AM »

Hi The antenna is working excellent and bought another oner few weeks ago..

Regards Lino..
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PBPP
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« Reply #9 on: May 24, 2014, 01:34:14 PM »

Hi The antenna is working excellent and bought another oner few weeks ago..

Regards Lino..
Yeah right............  I'd bet a 10 foot piece of wire would work much better.
How much are you selling these whiz-bang POS antennas for??

~ Mitch ~
« Last Edit: May 24, 2014, 01:42:07 PM by PBPP » Logged
KD8IIC
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Posts: 171




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« Reply #10 on: May 27, 2014, 12:01:32 AM »

   Why be so Rude P? I have a couple these and they work FB...best to get them above 20 feet I have found....excellent antennas.
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KD7RDZI2
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« Reply #11 on: May 27, 2014, 10:24:16 AM »

There' something I cannot get. The input impedance of the amplifier is extremely high and that's fine as many active antenna are made in this way and the amplifier matches the high impedance of the antenna and the cable. But just close to the antenna you could make a good choke as the impedance on the cable is low if this is desired. The internal unit should just supply the dc voltage so, am I wrong?
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PBPP
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« Reply #12 on: May 27, 2014, 12:29:49 PM »

KD8IIC,

Not being rude... just expressing my opinion.  I highly doubt these are anything close to an 'excellent' antenna.   Roll Eyes
Strange that you and 'Aussie' both have two of these.  Enough to make a reasonable person suspicious.
So, would you care to qualify your statement with some empirical data??  Preferably something we can all verify??   

Thanks,
~ Mitch ~
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K0OD
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« Reply #13 on: May 27, 2014, 01:45:11 PM »

Quote
Yeah right............  I'd bet a 10 foot piece of wire would work much better

Smiley Quite possibly, PBPP. I use essentially the equivalent to DX longwave... my ham 43' vertical... a VERY short "piece of wire" at 100 kHz.  Works fine and cost me nothing for that VLF capability. I can't believe the garbage SWLs waste money on, and then rave about on EHam.

Did anyone read the article in May's QST (p.93) about Gotham antennas, where-- 50 years later-- the ARRL tells how those products were junk. Gee thanks, League!

Gotham's ads were short on technical details (the average buyer was probably age 14) and long on examples of DX supposedly worked.  That no radial "all band" vertical consisted of an aluminum tube, a coil and an alligator clip.
 
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KD8IIC
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Posts: 171




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« Reply #14 on: May 28, 2014, 03:46:49 AM »

 Considering the fact that some of us do not have the room for a 43ft vertical or any wire antennas then a logical solution is found in obtaining the best working small antenna for the frequencies interested in. If you are looking to get stellar results above 75m, then the PA0RDT is not for you, neither are my two Pixel loops. The frequencies these active antennas seem work best are lower than 7mhz from my experience. LW and BCB reception is vastly improved using a well designed active antenna, for me at least. If you do not want to listen for NDB's or Broadcast stations quietly then these antennas are likely to be a foolish investment of your money...
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