Repeater Basics

Discussion in 'Becoming an Amateur Radio Operator/Upgrading Privi' started by KF7EIF, Aug 25, 2009.

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  1. W7MRN

    W7MRN Ham Member QRZ Page

    Hey, just heard you at about quarter after 12, but I was in the midst of an exchange here, so I could only quickly reply as 'monitoring' after the other fellow came back to you.

    Your signal sounded good and loud up here near ASU. :)
     
  2. KF7EIF

    KF7EIF Ham Member QRZ Page

    You are probably right. He did mention amateur TV when we talked this morning. Thanks

    I got a reply closer to 11:30 saying I was a bit faint, but audible on the Mt Lemmon repeater. I'm really new at this, but that seems like a pretty good hop for a handheld on a little mag antenna to go from Tempe to Mt Lemmon (about 100 miles). Good and loud to ASU is also great to know. I was on my way back to work and think I was on the Superstition repeater at that point.

    Thanks for the shout out.
     
  3. W7MRN

    W7MRN Ham Member QRZ Page

    Yep, on 147.112 - one of the 162.2's that I can operate on. I even have to hit the high-power switch to hit it due, I think, to the way my antenna is situated in relation to nearby structures, but you sounded fine on that HT, and were just shy of pegging the LED's into the red.
     
  4. K7JEM

    K7JEM Ham Member QRZ Page

    Was he pegging your meter, or the repeater?
     
  5. W7MRN

    W7MRN Ham Member QRZ Page

    :)... I see my mistake, here!

    His signal from the repeater (147.12 - typo in the last post!) had my meter at just about S9. His clarity and audio were both quite good. I didn't check the input frequency to see how he was doing, though, so I can't say much about how the signal would have been if we were trying to talk simplex. So, it's a foregone conclusion that his signal strength as regards the carrier would be good regardless, which I forgot about when I wrote the last post.

    This leads to a question that I never really thought about, actually, since I'm almost never on VHF. Maybe you can shed some light on this ...

    Since the repeater output should always be at the same relative strength, as far as how I hear it at my qth, then EIF can ride all over the Valley metro area, and as long as he hits the repeater, his signal will look the same to my meter, since the meter is reading the carrier of the repeater with no effect from the relative audio, yes (iow, only the carrier strength is read by the meter, or does some modulation affect the reading to a degree)? Yet, his audio quality will suffer or his audio level will grow quieter when he is moving close to his maximum distance from the repeater, and in those cases, even though the repeater carrier will be strong, EIF's audio will be less than optimal, correct?

    Seems basic, but I'm not 100% sure if this is the best technical way to describe this, and I've never really paid enough attention to the meter to see how it is affected between weaker and stronger audio on the same repeater output frequency. I've only really ever used HF with any regularity, and cw at that, from back when I was first licensed (then went almost three decades between active licenses), and need a reminder about these things at times. Or, perhaps I need to use the VHF set more often!
     
  6. K7JEM

    K7JEM Ham Member QRZ Page

    Your meter will always read the same. You are only seeing the signal from the rpt tx to your rig.

    The input signal will not necessarily change in audio level, it will change in quality. As the signal gets weaker, it gets more noise on it. A signal that is good will be "fully quieted" to the RPT RX, IOW there will be no background hiss other than what is coming through the mike.

    With FM, once the signal becomes "full quieting", all the additional power in the world won't make it better. Full quieting usually starts at around 30-50 uV or so. If you have a handheld that is a mile away from the rpt, it might be 50uV of signal on low power. Switching to high power won't make any difference. If your signal is only .5uV to the repeater, it will be noisy, and switching to higher power will make an improvement in the quieting, and quality of the signal.

    Joe
     
  7. W7MRN

    W7MRN Ham Member QRZ Page

    OK, then - this is what I suspected. I never have paid much attention to the 'meter' (just an LED row) on the IC-25H, so never really thought about if there would be any s-unit change due to improved quieting once the repeater had been engaged regardless.

    I'm so used to relating to signal strength in an HF, 'simplex' sort of way that the added factor of the repeater completely slipped my mind when I made my earlier comment. :)
     
  8. KL7AJ

    KL7AJ XML Subscriber QRZ Page

    Here's an absolute sure-fire test. Beg, borrow, or steal another hand held and see if you can talk to yourself through the repeater....both directions, from the same location.

    Eric
     
  9. K7JEM

    K7JEM Ham Member QRZ Page

    That usually won't work well, since you will probably desense your own RX.

    I see that problem all the time. "I couldn't talk to the other guy through the repeater, and we were sitting right next to each other in the parking lot! But it worked great when he drove away."

    Joe
     
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