[Lowfer] thoughts on PA0RDT "mini whip"

n8tl n8tl at woh.rr.com
Thu Dec 22 10:03:50 EST 2016 

Doug:

The 5 foot ground rod protrudes above the ground by 5 inches. Atop of 
the rod is a rat shack mini box containing the power transformer 
supplying the 12 volts to the whip box at top of pole. The co-ax from 
top of pole ties into that transformer and the shield is directly tied 
to the ground rod at this point. The secondary of this power transformer 
couples the co-ax to the shack.  Sorry, forgot to mention the power 
coupler transformer in last message. The mini box for the probe and 
power coupler are sealed using liquid tape obtained from Lowes.


Tom N8TL



On 2016-12-22 09:46 AM, Douglas Williams wrote:
> Tom, that sounds like a great setup. How did you weatherproof the coax
> connection at the antenna base where you attached the grounding point?
>
> On Thu, Dec 22, 2016 at 9:44 AM, Douglas Williams <
> williamsdoug1966 at gmail.com> wrote:
>
>> Same here, Jack. I have a 90% completed AMRAD whip that I just need to
>> seal in PVC pipe and attach the connectors.....
>>
>> On Thu, Dec 22, 2016 at 9:41 AM, Zack Widup <w9sz.zack at gmail.com> wrote:
>>
>>> Any idea how it does compared with the AMRAD e-probe antenna? I built an
>>> AMRAD whip but have yet to put it up. Since I have the next week off from
>>> work and it might be unseasonably warm, this is probably a good time to do
>>> it.
>>>
>>> 73, Zack W9SZ
>>>
>>>
>>> On Wed, Dec 21, 2016 at 4:50 PM, Howell, Laurence J <
>>> L.Howell at conocophillips.com> wrote:
>>>
>>>> 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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