I'd definitely terminate the shield at one end. You don't want it floating. And
terminating at both ends might be a way to get an inadvertent loop. Jim will
probably weigh in - shielded twisted pair is his jam.
On Wed, 12 Feb 2025 07:30:42 +0000 (UTC), Vojtech Ritzko via TowerTalk
<towertalk@contesting.com> wrote:
HI Rick
TNX for all inputs.
The balanced lines are terminated by common noise baluns and
isolation transformers too.
I tested commercial SMD balun.
The performance with 50dB common noise isolation at 1MHz is well over
my expectation.
https://productfinder.pulseeng.com/product/HX2326NL
The other version of smd product will be murata 50475C and 50474C in
balun /transformer setup.
The only drawback of small SMD devices are the power handling
capacity.
So far several active high impedance vertical phased arrays are
running in close TX antenna
(60m proximity) without any problems.
What is still not tested how to handle the FTP cable shielding .
Connect the shielding to common system ground or leave floating?
VY 73 DX
Bela OM8AW
Forwarded Message ----- From: Richard (Rick) Karlquist To:
"towertalk@contesting.com" Sent: Sunday, February 9, 2025 at 07:07:09 PM
GMT+1Subject: Re: [TowerTalk] CAT5E based RX SWITCH for remote RX ANT
distribution
The critical thing you need is baluns at both ends of each pair.
There are baluns for purchase that are intended for data on
CAT5, but I suspect they aren't very effective on 160m, but
you could buy one and test it. Otherwise, you can make your
own with the usual binocular ferrites. The RS485 is already
differential, so it may be OK as is, although it might help
to put common mode chokes at the ends. The four pairs each
have a different number of twists per unit length. This
well known technique goes back 100 years to telephone trunk
cables. It keeps them from coupling to each other. I think
you will have a high probability of success if you play your
cards right.
73
Rick N6RK
On 2/9/2025 7:42 AM, Gary NA6O via TowerTalk wrote:
> Very nice work Bela. One question for you. I have never measured crosstalk in
> CAT5E cable so I was wondering if the RS485 couples into the receive signals
> at all. From the data that I have seen, isolation should be very good in the
> HF bands, at least 60 dB. Good thing you have a LNA for each signal.
>
> 73,
> Gary NA6O
>
>>
>> From: Vojtech Ritzko >
>> Subject: [TowerTalk] CAT5E based RX SWITCH for remote RX ANT
>> distribution
>>
>> HI ALL
>>
>> Our QTH at OM0M ?islimited in space and there is not room for extended
>> phased beverage systems.
>> I am trying my best to build system with RDF well over 14dBon limited space
>> QTH.
>>
>> (Kill the side lobs and your RX will love you too.)
>>
>> W1FV-9 circle for 4 directions as well as linear 4el inlinesystem for USA
>> were built in field day styleprior the CQ 160.
>>
>> Well done, but how to connect the hamshack with RX HUB?
>>
>> Single RG6 and CAT5E FTP ?cable were directly ?buried ?undersurrounding
>> road? in past.
>>
>> Initial design - RG6 for RF and CAT5E for relay control isnot sufficient
>> nova day.
>>
>> No cable duct = no way to extend anything.
>>
>> The only chance is to use the unoccupied 100 Ohms pairs inCAT5E to carry RF
>> too.
>>
>> CQ WW 160 was the best chance to test RX systems in toughcontest conditions.
>>
>> Technicaldetails on enclosed google disk file:
>>
>> PDF :
>> https://drive.google.com/file/d/1gTtywxB_sgZYRfgy42YB9wCTE9RqV3Cr/view?usp=sharing
>>
>> Eznec for 9CC:
>> https://drive.google.com/file/d/1idf6JsQ32UrEQNs_7yc3hrrMWKT77DQH/view?usp=sharing
>>
>> Eznec for 4el:
>> https://drive.google.com/file/d/19E_VXwYVG1HiDWNU9yybygsKPt0yjeKY/view?usp=sharing
>>
>> VY73 DX
>> BelaOM8AW
>
> _______________________________________________
>
>
>
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