Preamp Input Voltage Tolerance Help

MDScanFan

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Jan 23, 2010
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I just completed a temporary outdoor antenna installation that includes a Mini-Circuits ZX60-P103LN LNA. It will be powered a power inserter from the shack through ~150’ of RG6. The preamp shows a 5V input is required (no tolerance listed). I made the mistake of not measuring the voltage drop along the coax before weatherproofing and installing the antenna. I would probably take a couple hours of work to take everything down, measure the drop, and then put into back up. Two questions:

- What is the typical tolerance range on this type of LNA? +/-0.5 V, 1V, etc?
- What is the impact of running it outside the tolerance range? Performance hit or damage?

I am debating taking a roughly equivalent length of the rg6 and measuring the drop of it and using that value. Thanks.
 

pro92b

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Jun 27, 2002
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The ZX60-P103LN+ datasheet lists maximum supply voltage is 5.5V. Above that you might get damage. That implies a max operating voltage around 5.25V so use 5V +/-0.25V for power.

From the Belden catalog, RG-6/U, their type 7710A has a DC resistance for the shield of 2.8 Ohms per 1000 feet. The center conductor is 6.4 Ohms per 1000 feet. So 150 feet of both for the round trip is 1.4 Ohm. The supply current for the P103 is about 100 mA so the drop is 0.14 volt.

Some variants of RG-6/U are not as low resistance as 7710. Use the specs for your cable to calculate the resistance.
 
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MDScanFan

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Joined
Jan 23, 2010
Messages
227
Location
USA
Thank you very much for the suggested way to approach it. My mistake on the amp, the one I installed today was the ZX60-P105LN+. It lists a supply voltage of 5+/-0.2V and a max input of 5.5V. Current draw is 63mA. That does not give me much margin for error on the voltage.

I looked up my cable and the loop resistance is 40.9 Ohm/kft. That leads to a 0.38 V drop at 150 ft. I can recheck the cable length easily tomorrow - just for a tolerance check, at 200 feet the drop is 0.51V. It seems like a 5.5V input supply would be about right.

The ZX60-P103LN+ datasheet lists maximum supply voltage is 5.5V. Above that you might get damage. That implies a max operating voltage around 5.25V so use 5V +/-0.25V for power.

From the Belden catalog, RG-6/U, their type 7710A has a DC resistance for the shield of 2.8 Ohms per 1000 feet. The center conductor is 6.4 Ohms per 1000 feet. So 150 feet of both for the round trip is 1.4 Ohm. The supply current for the P103 is about 100 mA so the drop is 0.14 volt.

Some variants of RG-6/U are not as low resistance as 7710. Use the specs for your cable to calculate the resistance.
 
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