[Lowfer] thoughts on PA0RDT "mini whip"

Wed Dec 21 17:50:31 EST 2016

Doug, I have three or four probes up various trees, some just separated by 5m or so, but as ever, the selection of the height and location sweet spot for best s/n is manifestly important here. A few feet either way can make a hooge (hooge) difference  - I ve run various shoot outs on what works best and though we get the odd earlier long haul decode on 475 with the highest probe (50ft or so), the best here is one at around 35ft or so called "Aces high" - slightly higher than RDT states but I do see that curve too in s/n using NDB and W&G test set.

 It took me a season or two to get just the right tree. Out of all the antennae here the probes tend to work best over active or passive large or small loops but that's probably because of the bespoke nature of the E/M interference fields on this acre and related to off site man made electrical noise sources. It will be different elsewhere - what works best here wont elsewhere.  

I figured out that the best type of tree to have one on is the Genus "Acacia" - which is pan-global and typically the worse is the Coconut Palm.

I see a lot of comments on they are just mickey mouse appliance antenna but Ive been using them in military and commercial situations for over 35 years and its horses for courses, and they work best here (and in a lot of other countries around the globe) over anything else. Stat. Used to use them in Antarctic for air-to-ground ops when the main wideband or LPA were snow static bound....

I ground the RG6 where it typically hits ground (boggy ground into a lake typically), large series J common mode choke at that end, another in the shack, keeping the power injector away from noisy mag fields that intrude even metal ali boxes, then Bino isolated transformer which is usable at 1kHz up to 500kHz or more - quite a few turns on 73 material from memory. Power is battery though simple unstab DC from 110VAC is pretty good if you decouple well. Playing with the voltage from 9-18VDC can help with iMod - mine appears happy around 15V but my local blow torch on 1430kHz appears to have a issue with pins stuck in its coax quite often :-) (joking)

Laurence KL7L

-----Original Message-----
From: Lowfer [mailto:lowfer-bounces at mailman.qth.net] On Behalf Of N8OOU
Sent: Wednesday, December 21, 2016 1:32 PM
To: Discussion of the Lowfer (US, European, & UK) and MedFer bands <lowfer at mailman.qth.net>
Subject: [EXTERNAL]Re: [Lowfer] thoughts on PA0RDT "mini whip"

Doug,

The mini whip is mounted and grounded to the top of a galvanized steel 
trellis that I grow hops on. The trellis is about 15 feet tall, and 
grounded at the base. RG-6 quad shield coax is grounded at the mini 
whip/trellis, and runs back to the shack. Nothing in the shack is 
externally grounded. I'm not sure if the DC power supplies ground back 
to the mains.

73   de   N8OOU - Mike Meek

On 12/21/2016 03:55 PM, Douglas Williams wrote:
> Mitch & Mike,
>
> Thanks for the info.
>
> Mike, did you ground the antenna at the base, halfway point, or at the
> house?
>
> Anyone else have any info, feel free to chime in.
>
> D. KB4OER
>
> On Wed, Dec 21, 2016 at 4:48 PM, N8OOU <n8oou at meekfarm.us> wrote:
>
>> Doug,
>>
>> A few observations on the mini whip.  I built one from my junk box parts
>> based on the original design. I had to add a notch filter to block my local
>> 500W AM BCB station. Inserted in the whip between the FET and Buffer amp. I
>> also must use a 500 Khz low pass filter at the receiver for LF. I have it
>> mounted about 15 Ft above ground, away from the house, and grounded
>> according to common information found on the web.
>>
>> It works (all the way up to 10m), better than a long random wire, but not
>> as good as the Low Noise Vertical I just finished.
>>
>> 73   de   N8OOU - Mike Meek
>>
>>
>> On 12/21/2016 03:07 PM, Douglas Williams wrote:
>>
>>> Have any of you used one of these on VLF/LF? What are your experiences?
>>> They seem to be everywhere on eBay, from kits to fully assembled, and
>>> averaging $12 - $40.
>>>
>>> D. KB4OER
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