OTA Cabling: RG-6, RG-59, RG-11, P3 Hardline, Twin-Lead, Crimping - Page 47 - Canadian TV, Computing and Home Theatre Forums

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post #691 of 694 (permalink) Old 2016-03-05, 11:33 PM
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Quote:
Originally Posted by rabbit73
Commscope makes 75 ohm hardline in 1/2, 5/8, and 3/4 inch used by CATV systems.
Hardline
3/4 inch (.750) example
5204003 | P3® 750 JCA
I've changed the title of the thread to include that great info - thanks for that, rabbit73!
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post #692 of 694 (permalink) Old 2016-03-06, 05:25 PM
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I calculated INCREASE in System Noise Figure (NF) for various Low-Loss Cable Types (plus RG-6 for Comparison), presuming a very long 500-ft Cable Length after a 20 dB Preamp with NF=3. Note that COST of LMS-400-75 is about the same as the SKED40 PVC Pipe I would recommend you PUT it in for protection from the elements...and stepping on:
Signal Amplifiers (Amps, Preamps, Distro Amps)
First Link below was used for the Cascade NF Calculations....which can be adapted for any particular situation.

COAX CABLE LOSS AND INCREASE IN SYSTEM NF FOR 500-FT AT 700 MHz:
Cascaded Noise Figure Calculator [Second Stage is Coax with Gain=0, NF=Loss]
Coax Calculator
Welcome to Times Microwave | Coaxial Cable - Attenuation & Power Handling Calculator

RG-6: About 40 dB, depending on Mfr.
17.1 dB NF Increase with 20 dB, 3 dB NF Preamp [NOT SUITABLE]

RG-11: About 20 dB, depending on Mfr.
1.7 dB NF Increase with 20 dB, 3 dB NF Preamp

Times Microwave LMS-400-75: 16.2 dB + Connectors [75-ohm, 0.405-in O.D., 6.8-lbs/100-ft]
0.8 dB NF Increase with 20 dB, 3 dB NF Preamp
https://www.timesmicrowave.com/docum...LMR-400-75.pdf
Times Microwave LMR 400 75 Ohm Low Loss Coaxial Cable - Per FT | TriangleCables.com [$1.27/ft up to 499-ft + S/H]

Times Microwave LMS-600-75: 10.2 dB + Connectors [75-ohm, 0.59-in O.D., 13-lbs/100-ft
0.2 dB NF Increase with 20 dB, 3 dB NF Preamp
https://www.timesmicrowave.com/docum...LMR-600-75.pdf

Andrews LDF4RN-75A Heliax: 8.7 dB + Connectors [75-ohm, 1/2-in O.D., 16-lbs/100-ft]
0.1 db NF Increase with 20 dB, 3 dB NF Preamp
LDF4RN-75ALDF4RN-75A - Obsolete

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands
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post #693 of 694 (permalink) Old 2017-01-24, 02:08 PM
 
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Velocity Factor

Is there any issue with connecting together 2 40 foot sections of RG6 coax that have different velocity factors?

FTA, Openbox S9, 33” dish, Avenger PLL LNBF. Stab 90HH.
OTA, CM4221HD, 3410 amp, 4 way split, HW-150 PVR[SIZE="1"
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post #694 of 694 (permalink) Old 2017-01-25, 04:34 PM
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NO....although the SPEED of Electrical Signals is different, there are no significant IMPEDANCE differences and hence no VSWR problems.
Same thing occurs when connecting 300-ohm Twinlead or Open-Ladder-Line to 75-ohm Coax through Balun Transformer....
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