[TowerTalk] Metal Roof

Jim Brown jim at audiosystemsgroup.com
Thu Jan 11 23:30:57 EST 2018

On 1/11/2018 5:31 PM, Grant Saviers wrote:
> How well the seam capacitance suppresses diode rectification RFI is a 
> good question as is what is the likely power output of such a diode.  
> Unsoldered copper seams sound like the devil's playground. 

The pros who have chimed in certainly know this, but I'm emphasizing 
this point for Gilbert. BECAUSE this is a repeater, suppression of any 
intermod must be REALLY REALLY good to keep it below the level of the 
very weak mobiles you want the system to hear. AND, because we're 
talking VHF or UHF, the spacing between bonds must be pretty close.

Another point. IM follows the square of the signal strength that excites 
it, so reducing TX power by 3 dB reduces the IM by 6 dB. I'd keep the TX 
power up while diagnosing and evaluating your fixes, but I'd reduce 
power for general operation until you've declared victory on the fix.

Also, consider moving the RX antenna, even making it a split site system.

73, Jim K9YC

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