Rookie General is Confused

Discussion in 'General Technical Questions and Answers' started by KE5TCG, Mar 2, 2008.

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  1. N5USR

    N5USR Ham Member QRZ Page

    Well, Glen covered a lot of what I had originally typed...

    So, the rest of it is, around here it seems most of the always-listening "regulars" have moved off repeaters to simplex. While the repeaters sit idle except for brief periods and nets, it is likelier I'll find someone on simplex just about any time. Not sure if the same would go for Houston, but it's something to listen for. Of course, simplex can be tough over any distance with just an handheld.

    And yes, even though you can key a repeater on 1/2 watt, you can still be noisy at 5 watts. Not necessarily a weak signal, just a lot of noise. Many people don't like having to listen through the noise of a weak handheld, so just don't bother responding. They may be likelier to do so if you do as Glen mentioned and actually ask for someone to respond.
     
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Also...

    CTCSS frequencies for repeaters often change. I know here in the L.A. area, I have to go re-program almost every repeater in my "home station" rig's memory (199 channels) about once a year because that often, probably half the repeaters change the CTCSS tone they're using, for various reasons. So, what's "in the book" may not be what they're really using, today.

    And even if a repeater is only a few miles away doesn't mean it can really hear you, at least not well enough to repeat your modulation clearly. The difference between "keying up" a repeater and sounding good through the same repeater can be a lot more than 10 dB.

    "Full quieting" is usually about 25 dB for most FM receivers. But many of those can be "keyed up" with a signal that's only 6 dB above the noise; so the "difference" between "keying up" and "full quieting" can easily be 19 dB, which is a power ratio of nearly 100 to one.

    In my "mobile," I run 70 watts to a 5/8-wave whip installed on the center of the roof of my van, which is six feet above ground -- and I consider that "marginally sufficient" for most work. Lower power, a smaller antenna, or a lower height, is less than marginal, for me.

    WB2WIK/6
     
  3. K7JEM

    K7JEM Ham Member QRZ Page



    Glen-

    I thought that AD5MB's response was meant to be sarcastic, since he said "PLL tones", which do not exist. Oftentimes here we see OT ops ask newer ops questions like that, to jerk their chains.

    It is pretty obvious the original poster knows a little about electronics, from his proper calculation of dB, and the use of RCL.

    "PLL tones" probably sounded like "muffler bearings" to him.

    Joe
     
  4. KE5TCG

    KE5TCG QRZ Member

    OK...

    Thanks for the responses. I'm just a little disappointed and frustrated.

    I'm new to amateur radio, but not new to radio. I do need some help in getting up to speed in the amateur realm, and I only say this so that you won't waste your time explaining technical details. I do radio in all aspects for a living and have for a long time. I'm not concerned about the signal strength or S/N, or as you call it, SNR. In my original question I made it clear (or failed to) I was asking about procedure and protocol.

    The LID "PLL" question was a little condescending, if not misstated, and I assumed he meant "CTCSS" and not "phase-locked-loop." I hope that clears that issue up.

    On the other hand, the locals here and other personal ham contacts have been more than great. I'll use that asset as my primary source.

    I'm ready to take element 4 and my goals have now changed to CW DX.

    73 SK CL
     
    Last edited: Mar 2, 2008
  5. K7JEM

    K7JEM Ham Member QRZ Page

    Full quieting is usually a lot more than 25 dB. By definition, it would be the point at which any increase in signal strength causes no additional reduction in RX noise. This is generally around 45+dB of quieting. Most RX's will not reach this point until 10-50uV of RX signal level.

    20 dB of quieting is generally considered decent communications quality, but with a fair amount of noise. You can get the message through fine, but you wouldn't want to listen to it for extended periods.

    The other thing to remember is that near squelch threshold, the FM RX is quite non-linear in response. A 1 dB change in signal level might produce 2dB of change in quieting.

    An easy way to look at the 10 dB increase is to consider that it is very close to 3 times the voltage getting to the RX. If he had .15uV of signal at .5 watt, he would have .45 uV of signal at 5 watts. If .15uV is opening the repeater squelch, .45uV should be better than 20 dB quieting, and a fairly decent signal. I think this is what his test is showing.

    Probably what is happening is that people are just not responding, for whatever reason. The best thing to do would be to listen to the repeater for a while, and pick out an op that sounds like a decent guy. Give him a call after he signs off.

    "K6XXX this is KB6YYY, have you got just a second for a quick QSO?" or something similar should get a response. Also, listen to the protocols and procedures on the repeater, and try to follow them.

    If the repeater sounds like a bunch of jerks and losers, move to another frequency.

    Joe
     
  6. KE5TCG

    KE5TCG QRZ Member


    < It is pretty obvious the original poster knows a little about electronics,>

    Maybe a little.

    I majored in physics with a specialization in electro-optics. One interest of mine was in relativistic effects on polarized 10 GHz radiation through an oscillating diffractive aperture by analysis of planar field strength distribution represented by a J2 Bessel function.

    So, narrow band VHF is not a big mystery to me.
     
  7. AB9LZ

    AB9LZ Ham Member QRZ Page

    Yes, he was serious, pure stupidity is the root cause of most technical problems. Seeing how much experience you've had in the field of ham radio, it was a valid (and obvious) question to ask.

    73 m/4
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Being aware and educated is not equivalent to "experienced" in many cases.

    As I pointed out previously, understanding what CTCSS is and how to program the tones is not the same as understanding that repeaters often change them, and unless you're in the "inner circle" you won't know what the new ones are!

    Most places I've lived (from coast to coast) some of the very best, wide-area coverage repeaters don't ever publish their access tones simply because they don't want the general population to know them. In a few cases, I've been part of repeater groups using dual CTCSS tones: That is, the repeater's access is granted only to those using dual tones simultaneously, which is a feature most ham rigs don't have. We have one major local repeater here which uses a non-standard CTCSS tone (not part of the normal EIA library of tones), and another major local wide-area repeater that has a strange offset that is not programmable at all without knowledge aforethought.

    So, "you never know."

    But despite all that, the real fact is that VHF-UHF repeater operation isn't anywhere near as popular today as it was about 25 years ago, and I very much doubt that situation will reverse.

    WB2WIK/6
     
  9. K7JEM

    K7JEM Ham Member QRZ Page

    Your ignorance is showing, since there is no such thing as a PLL tone.

    It isn't a valid question to ask. If you're going to ask a question, or pose a response, it is best if you know what you're talking about.

    Too many hams on here assume every new op is someone who just fell off the turnip truck, and doesn't know a mike from an antenna.

    It was apparent to me from the first post that we are dealing with someone of a technical ability beyond what most OT hams will ever possess.

    Joe
     
  10. KE5TCG

    KE5TCG QRZ Member


    OK, knowledge: Check
    30 years professional experience: Check.

    Consider this. If I can rouse the repeater, wouldn't you say that the CTCSS tone is not an issue?

    I'm done here.

    [​IMG]
     
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