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Author Topic: Using 75 ohm coax with a 52 ohm low pass filter.  (Read 2751 times)
K9EEH
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Posts: 34




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« on: March 23, 2013, 12:00:40 PM »

Using 75 ohm coax with a 52 ohm low pass filter...
Will using the 75 ohm with the 52 ohm filter cause problems with receive or transmitt??  I am using RG8 from the
transmitter to the filter from there is goes to vertical that uses RG8.
Tnx for your coments.

73 Dick K9EEH
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KK5J
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Posts: 82




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« Reply #1 on: March 23, 2013, 12:32:04 PM »

RG8 is 50 coax. Were you going to replace it with 75 or did you mean to say RG6?
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K9EEH
Member

Posts: 34




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« Reply #2 on: March 23, 2013, 12:51:46 PM »

I am using 50 ohm for the vertical, and 75 rg59 for a dipole going into a coax switch going to the low pass filter.
So was woundering if that 75 ohm would be ok when I switched to the dipole
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WB6BYU
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Posts: 13574




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« Reply #3 on: March 23, 2013, 08:00:03 PM »

It probably won't make much difference.  The SWR might be slightly off, but there
likely will be a bit of mismatch anyway.  It's the same thing as using the filter in 50
ohm coax when the SWR is 1.5 : 1:  the impedance will be 75 ohms at some point
along the coax.
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KK5J
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Posts: 82




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« Reply #4 on: March 24, 2013, 02:49:09 AM »

I agree with WB6BYU. I doubt if you will see much of a difference.
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K5RT
Member

Posts: 169




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« Reply #5 on: March 24, 2013, 06:43:28 AM »

Why are you using a Lowpass filter? Do you have TVI problems or something? This day and time there's generally fewer reasons to have a Lowpass filter in the line.

Vy 73
Paul
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K9EEH
Member

Posts: 34




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« Reply #6 on: March 24, 2013, 09:42:24 AM »

Thanks to all for the replies...

Paul K5RT...Probably could do with out the filter...I use antennas for my tv and they are very close to them, so just left
the filter in.

Dick
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W4OP
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Posts: 452


WWW

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« Reply #7 on: March 24, 2013, 10:05:20 AM »

Virtually all of today's TVI is not caused by harmonic radiation from your station (where a low pass filter would help), but rather front end overload of the television- that requires a high pass filter on the TV.
If your station is not radiating harmonics, I'd toss the LPF and its attendant loss- whatever that might be..

Dale W4OP
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NV2A
Member

Posts: 151




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« Reply #8 on: April 01, 2013, 01:08:03 PM »

Why are you using a Lowpass filter? Do you have TVI problems or something? This day and time there's generally fewer reasons to have a Lowpass filter in the line.

Vy 73
Paul

Lowpass filters sure make it a bear to operate 6 meters which many new rigs have!  I never gave it a thought and was just working on reflexes and then it hit me like a ton of bricks.  Grin
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W8JX
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Posts: 6671




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« Reply #9 on: April 01, 2013, 01:25:50 PM »

Thanks to all for the replies...

Paul K5RT...Probably could do with out the filter...I use antennas for my tv and they are very close to them, so just left
the filter in.

Dick

HD TV is in UHF range and digital too. Only interference might see is brute force overload and low pass will not help that but a high pass with a cut off of 60mhz on tv would help 
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