Don KA9QJG wrote: > And Here is a Dumb Tech Question , If You had a PL And had the > receiver SQ All the open would Not the Receive Be hotter then with No Pl > and the SQ Closed enough to keep from keying up /
It's not a dumb question, but it is a common misconception. The answer is, no. Setting a squelch usually involves injecting a very weak signal (below 12dB SINAD) with a service monitor. You can set the squelch with the antenna disconnected, but as soon as you plug in the antenna -- site noise is going to open it. Most folks set their squelches by measuring the real receiver's USABLE sensitivity (with the site noise floor/antenna connected), and set the squelch to close just above that number. At most sites, and in most configurations, that's well below the 12dB SINAD point in the receiver... if it's not, you're at a really noisy site, or you have other interference issues to deal with. Opening it wide open from that set-point won't add any appreciable "hotness", because you're already set below the 12dB SINAD point, and that's weak enough that it's going to get hard to copy, real quick from that point on down. Or put another way, the only way to improve a receiver, is to improve the receiver/receiver system! The squelch knob doesn't fix a weak receiver, and it makes no appreciable changes to a good one, either. (Well, unless it's set too HIGH, which is a common mistake. You do have to measure it, and know where your squelch closes.) Basically what you want is the squelch to CLOSE no matter what, so you CAN turn off CTCSS if necessary. Or worse, if your CTCSS board were to fail in such a way as to convince the controller that CTCSS was always present, that the repeater would stay quiet. What the noise floor is, at what point the squelch closes, and the receiver sensitivity -- are all just measurements you make, and try to make it better... but playing with the squelch knob won't do anything to improve real receiver performance. (And I'm leaving out the benefits of bi-level squelches -- fluttery/in-and-out signals can benefit from those when a station is mobile and right on the edge of the repeater coverage.) Nate WY0X
