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Author Topic: Pa0rdt Mini-Whip Active Antenna  (Read 106200 times)
K0OD
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Posts: 2991




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« Reply #30 on: November 20, 2017, 06:57:49 AM »

That may only tell you that KB8SPI has a good quiet location for receiving NDBs or that he has lots of beacons nearby  (and he does... Detroit). Or that propagation was good when you listened. Jeesh!  Why do so many of these endorsements for active antennas read like ads? If you've done valid A/B comparisons between two antennas then post those results.

For longwave how about using WSPR on the new 630 or 2200 bands for testing? I can regularly print Hawaii on 474 KHz  with my DXE ham vertical for an antenna. And it didn't cost a cent extra for its longwave capability.

Quote
"Rather than contribute to the "noise" from uninformed commenters..."
 
Glad your first EHam post cleared up everything.

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PA0DGL
Member

Posts: 5




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« Reply #31 on: November 20, 2017, 08:34:33 AM »

I visited the suggested page and checked a few transmissions that should have comparable results with my location in Panama. These are 4583, 7646, 10100.8 (German meteo, RTTY), 6358.5, 8439 (Dutch navy, RTTY), 8473 (US CG Miami, 45 RTTY and FEC). Only the last one can be received in daytime here, the others after sunset. SDR here G31DDC, mode FSK (frequences will differ when using SSB mode). The KB8SP setup indeed could receive 8437 but not the others. However the waterfall display suggests a lot of interference from the usual culprits (switch mode power supplies etc.) and the other RTTY signals were below the noise floor. From my perspective that is a bad location for an omnidirectional whip (mini or otherwise). So I visited a few other SDR setups which confirmed that for a whip, location and altitude are everything but increasingly rare. I lost interest in whips a while ago and am doing some design work on low noise loop amps, including the issue of active load resistors (for mini dual flag) that produce less noise than passive resistors.
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G4AON
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Posts: 1029




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« Reply #32 on: November 21, 2017, 04:03:45 AM »

I don’t understand the hostility towards active antennas expressed by some on this thread, nobody is under any obligation to use one, buy one, or give up radio because they haven’t got one.

The PA0RDT antenna is one of the simplest to build and install, I’ve added a page to my web site that may help others, on a “take it or leave it” basis.

FWIW, mine is used with a QS1R SDR receiver and CW Skimmer Server to provide my own local “spots” on my logging program. It’s an invaluable tool to me. My version of the DC injection (bias T) drops the active antenna supply when transmitting to avoid overload or damage to my SDR.

73 Dave
http://www.qsl.net/g4aon/
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VA3VF
Member

Posts: 944




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« Reply #33 on: November 21, 2017, 05:16:26 PM »

I don’t understand the hostility towards active antennas expressed by some on this thread, nobody is under any obligation to use one, buy one, or give up radio because they haven’t got one.

For the cost involved, it simply does not make any sense not to try. It does not compare to a log periodic, but it does work, specially below 16MHz.
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ZENKI
Member

Posts: 1439




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« Reply #34 on: November 24, 2017, 08:48:36 PM »

Its just ignorance. It is a well established fact in EMC and  Professional HF circles that active antennas always will have the  feedline as  part of the antenna. 

There are many active antenna designs that hams have not tried, if they did try them they would not be so negative about  what is possible with active antenna designs. We  as hams tend to use the worst performing of designs like small 1 meter loops and noisy voltage probe antennas with poorly decoupled feedlines..

Hams should try some of the larger active loop antennas ,, something  like the Bonito  MegaActiv loop and see how well these antennas perform.

http://bonito.net/ml052/en/index.html


I don’t understand the hostility towards active antennas expressed by some on this thread, nobody is under any obligation to use one, buy one, or give up radio because they haven’t got one.

The PA0RDT antenna is one of the simplest to build and install, I’ve added a page to my web site that may help others, on a “take it or leave it” basis.

FWIW, mine is used with a QS1R SDR receiver and CW Skimmer Server to provide my own local “spots” on my logging program. It’s an invaluable tool to me. My version of the DC injection (bias T) drops the active antenna supply when transmitting to avoid overload or damage to my SDR.

73 Dave
http://www.qsl.net/g4aon/

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K4FMH
Member

Posts: 431




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« Reply #35 on: November 25, 2017, 12:15:05 PM »

Mitch PBPP,

Since you like objective facts, your statements regarding active loop antennas, such as Andy Ikin’s Wellbrook line, are as FOS as a Christmas Turkey. There are MANY technical comparisons and evaluations of them. You could’ve googled them. Much lower noise and nulls that are directional with a rotator than your “tuned” length of wire. The Quantum Loop (and the older Kiwi Loop) achieve very good results on MW and KW where your LW would llikely be a good noise antenna for a phaser.

Now, the pard0t antenna is something I’ve just purchased but have not installed. I’ll put it up about 12’ on a PVC pipe behind an evergreen tree next to my house with the ground being attached to the house electrical ground nearby. I’ll likely do some comparisons against my Wellbrook 1530 and MFJ Rx Loop...and perhaps a “tuned” long wire. I’ll see how it works. But I WON’T dismiss it out of hand without these direct comparisons!

KD8IIC,

I'm sure you've got room for a 10 foot antenna and probably longer, right? 

Just so you know, a random wire antenna with a LC tuner will vastly outperform
the four overpriced active antennas, the virtues of which you are extolling. 
Since you haven't provided us with any verifiable data, one can only conclude
your claims are without merit. 

Sorry, but buying any of these active antennas is foolish waste of money,
no matter what type of abode you live in.

~ Mitch ~ 
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PA0DGL
Member

Posts: 5




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« Reply #36 on: November 25, 2017, 06:53:28 PM »

Quote
Its just ignorance. It is a well established fact in EMC and  Professional HF circles that active antennas always will have the  feedline as  part of the antenna. 

The probably too obvious prevention of feed line issues is to abandon the use of an active monopole (by whatever (commercial) name) and to use an active dipole instead. That does away with the demand for a good (or any) earth as it also will work in free space. Common mode rejection can be made high by the use of a differential first stage and a second stage coupled to an RF transformer. 
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KX4OM
Member

Posts: 210




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« Reply #37 on: December 07, 2017, 09:28:30 AM »

Try out a voltage probe antenna, it is free; it uses the internet.

You can check out the activity on 20 meters SSB right now, IV3CVN calling CQ DX on 14.245, heard from the WebSDR at he University of Twente, The Netherlands. That is a voltage probe antenna based on the PA0RDT. The SDR was built(hardware and software) by Pieter, PA3FWM at UTwente over a period of about 8 years, continually improving it. The antenna is mounted on some air conditioning on the roof of the building. I often listen to 40 meters in the early evening to east and midwest US hams working Europe.

http://websdr.ewi.utwente.nl:8901/

Ted, KX4OM  
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W4OP
Member

Posts: 783


WWW

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« Reply #38 on: December 08, 2017, 04:16:47 PM »

If one does not believe that the outside of the coxial shield (or a conducting mast) does not play an important part in the short active whip, please see Owen's article. It is only relatively recently that active whip designers have had to admit that the active whip itself does not tell the entire story. Argue  with Owen if you will- I see nothing incorrect in his analysis:
http://owenduffy.net/antenna/PA0RDT-MiniWhip/

With that said, I do use an active whip on a grounded tower- way out in the woods for some LF work, but my Shared Apex Loop Array being electrically steerable outperforms it.

Regards,

Dale W4OP
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