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 <[email protected]> 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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