[Lowfer] thoughts on PA0RDT "mini whip"

Douglas Williams williamsdoug1966 at gmail.com
Thu Dec 22 08:53:47 EST 2016


Thanks guys, I ordered a kit version of this off eBay because, why not,
right? More antennas are always better than fewer antennas (unless you have
a homeowners association to deal with, which I thankfully do not). ;-)

D. KB4OER

On Wed, Dec 21, 2016 at 5:50 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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