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Re: [IRCA] DKAZ questions
Thanks Nick. Careful measurements this summer suggested there was no noise
difference between an FLG/transformer/Coax and FLG/straight coax. (Yes
there's a 1:2 transformer added to the mix when the FLG feeds coax.) But
I'm in a very quiet area, QRM-wise, so that test might have been irrelevant.
Yes I've gone to Amazon and purchased weatherproof boxes, feed-throughs and
weather-proof wire-to-wire connectors. Using that approach I'd sleep better
leaving an FLG100 out in the rain and cold.
As you know I'm planning to anchor and terminate the Cat-5 inside these
enclosures, to eliminate potential wire breakage. The banana plugs will
stay on the PORTABLE antennas but that Cat-5 will have stranded pigtails.
Live and learn. <g>
And I sure can't argue with you guys that the FLG-at-the-antenna is a solid,
simple solution. What got me started on "amp in shack" in the first place
was a wish to be able to easily reverse the antenna. But I couldn't find a
noise-based reason not to continue with that approach.
Cheers!
MD
-----Original Message-----
From: Nick Hall-Patch
Sent: Friday, October 07, 2016 9:52 AM
To: Mailing list for the International Radio Club of America
Subject: Re: [IRCA] DKAZ questions
Thanks Mark. I do think that your points about twisted pair are
correct, and it would be intriguing to see if using twisted pair with
the FLG100 would make any further difference to the noise
pickup. My suspicion is not, but it's only a suspicion. One of
the things one seems to be paying for with the FLG100, as with the
ALA100, is eliminating the concerns about noise being conveyed on the
coax shield, which is what a balanced pair will do for you as well,
at lower cost.
The difference for me has been the "out of the box" nature of the
FLG100 solution. There are costs and costs, and time has been a big
one of them in my years as a DXer. And once the FLG100 is up,
there's been no tinkering with connections.
One thing that has made twisted pair not "out of the box" for me has
been the lack of remotely weatherproof connectors at a price that is
not at least a down payment on a FLG100 (and yes, the BNC on the coax
is not totally weatherproof, but a few inches of rubber tape is
pretty close). If you have something that works well with CAT5
(banana plugs don't count; I've been troubleshooting with you,
remember), then I am all ears. I think we discussed feed-through
glands at one time. Is that what you have in mind?
best wishes,
Nick
At 11:58 07-10-16, you wrote:
I do love the way the varied interests in this hobby are propagated through
this club from member to member and I'm grateful for the knowledge and
experience that's so freely shared.
One baby elephant in the room is Mark's antenna "ambience." If his QTH
there in the Land O' Goshen is in a field of electrical interference (and
perhaps significant local RF?), the noise gathered by the lead-in may be an
issue best resolved not by common-mode choking but by "balancing" the
feed-lines.
I've bored folks to death by espousing the balanced twisted-pair approach,
in the form of Category cable (Cat 5, Cat5e etc) with an impedance around
110 ohms. IMHO such a BALANCED transmission line pretty much eliminates
stray pickup without the need for common-mode choking. Cat-5 sells for
around $45/1000 feet...although if the budget allows, I'd go for STRANDED
Cat-5.
As I type this I'm watching the Perseus on a D-Kaz facing mostly west and
watching Seattle rolling in, here in North-Central Minnesota. Using a 9:1
transformer and Cat-5 with a DXE RPA-1 in the shack and watching a noise
floor of -111 dbm in 5 kHz, after the amplifier's 15 db gain.
An absolute YES to the Vactrol approach for the null component. The design
for that circuit somewhat obviates the potential for stray common-mode
pickup, so coax may work FB, but again...twisted-pair is so easy to
implement.
As to mounting the RF amplifier at the antenna: I've tried the FLG and the
DXE, planting them both at the antenna and in the shack. Like Don Moman, I
can't really find any significant improvement...though in theory
antenna-mounting of the amplifier is the better approach; weathering issues
notwithstanding. (You would however, need a balancing transformer after
the amplifier if you fed twisted-pair.)
A winterized installation at my site would include twisted-pair lead-ins, a
9:1 transformer and a Vactrol control, mounted in weatherproof boxes and
the amplifier in the nice warm shack. Amazon fans have found all sizes of
weatherproof boxes and wire feed-throughs:
At Amazon's greedy query, type in: "Cable Connect Waterproof Plastic Case
Junction Box" and "Plastic Waterproof Cable Connectors"
Decent transformers (if you don't have strong RF nearby)
http://www.minicircuits.com/pdfs/T9-1.pdf
Now for the famous YMMV <g> Have fun Mark; continue to share your
experiences!
Mark Durenberger, CPBE
-----Original Message----- From: Mark Pettifor
Thanks for the advice guys - much appreciated!
I should also publicly thank Tim Tromp for getting me interested in the
DKAZ to begin with.
Mark
On 2016-10-06 10:02 pm, Nick Hall-Patch wrote:
Agreed. They do cost a fair amount (mind you the exchange rate with the
pound isn't bad right now), but are solidly built and work very well.
Money well spent.
Nick
At 22:17 06-10-16, you wrote:
I very strongly recommend the Wellbrook FLG100LN, They go right at the
antenna and replace your xfmr. Now what is picked up by the antenna is
amped 22 dB whereas what is picked up by the coax is not amped at all.
I have two of these and they've survived IL weather for over 3 years. 73
KAZ Barrington IL
On Thu, Oct 6, 2016 at 4:29 PM, Mark Pettifor <mark@xxxxxxxxxxxxxx>
wrote:
> For those of you who have DKAZ antennas, which preamp do you
use? Do > you
> find it makes much difference whether you put it at the antenna
or in > the
> shack?
>
> I need to "finish" construction on mine. Right now, I have two 470-ohm
> resistors alligator-clipped together for the null end, and a
> hand-wound
> transformer (my first ever) on a core made of unknown material,
to go > from
> 940 to 50 into a 50-ohm feedline.... RG-8X, 150 feet. That is also
> alligator-clipped together. It was for testing, ya know? :^)
>
> It's been pretty good as is, but I want to get it ready to survive the
> winter.
>
> BTW, it's amazing the amount of noise just a short length of RG-8X
> 100%
> shielded coax will pick up. I have it mostly on the ground, but have a
> small part of the run overhead for now (30 feet?) so I don't
mow over > it.
> Thanks!
>
> Mark Pettifor
> Near Goshen, INdx.com
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Nick Hall-Patch
Victoria, BC
Canada
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