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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Originally Posted by rabbit73
Commscope makes 75 ohm hardline in 1/2, 5/8, and 3/4 inch used by CATV systems.
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.

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
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

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
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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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