One can use coax, with adequate grounds at both ends to mitigate stray
pickup, although I strongly suspect that there's a distance at which point
the other options might be better.
I should also note that good Cat5 cable is also not cheap in and of itself.
For the upcoming LBI DXpedition we'll continue to use coax grounded at both
ends, although we're dealing with feedline distances of LT 100', not
straight line. We have plenty of electrical noise in the area but no RF
closer than 20 miles or so.
Russ Edmunds
15 mi NW Phila
Grid FN20id
<wb2bjh@xxxxxxxxx>
AM: Modified Sony ICF2010's (4) barefoot w/whip
FM: Yamaha T-80 & T-85, each w/ Conrad RDS Decoder;
Onkyo T-450RDS; Tecsun PL-310 ( 4);
modified Sony ICF2010's (3) w/APS9B @ 15';
modified Sony ICF2010 w/whip
On Fri, Oct 7, 2016 at 10:52 AM, Nick Hall-Patch <nhp@xxxxxxxx> wrote:
> 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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