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Message |
    
Vanillagorilla
Junior Member
Username: Vanillagorilla
Post Number: 39
Registered: 4-2005
| | Posted on Friday, May 20, 2005 - 8:30 pm: | 
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Another easy question for you guys. I understand the "basic" diff between RMS and Peak watt reading but which do I want to tune my radio to?
I borrowed a Dosy from a friend to help me tune my Grant and am a little tossed here.
On the peak reading I'm DK 8 swing to 14..on the RMS scale I DK 9ish and swing DOWN a watt.
I'm quessing I'd look to maintain a steady RMS for best performance? Or should I lower the DK to get a forward swing on RMS? I've been told its the swing that makes you loud but would hate to think I'm overdriving the rig. The rear chassis NEVER gets warm and I have more VR to go if I wanted. Its just that if I do then I REALLY will swing backward on RMS scale.
Please break this down for me in basic terms?
BTW I know the middle leg of "Q" was clipped before I got it..no splatter with the D104M6C or recently purchased DM452...(BTW..the reports are better with the 452  )I always have the mic gain set to just "tickle" 100% mod with whichever mic I use. Just wanna be sure I'm being as efficient as possible and still be clean.
BTW this rig is staying barefoot as long as I have it. I'll run heat on another radio in the base. Bottom line...what should I shoot for before I return the Dosy?
Thanks in advance! (and yes I tried the search first...just didn't find what I was looking for )
Hank LI NY
'905 / CEF-559 |
Iluvrf
Member
Username: Iluvrf
Post Number: 84
Registered: 2-2005
| | Posted on Friday, May 20, 2005 - 8:58 pm: |
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Lower your deadkey and you will stop swinging down on RMS. Your deadkey should be the same no matter if its RMS or peak. |
Vanillagorilla
Junior Member
Username: Vanillagorilla
Post Number: 40
Registered: 4-2005
| | Posted on Saturday, May 21, 2005 - 8:50 am: |
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Thanks..I knew that it would just wondering which scale was more important to follow. Either way I suppose it makes sense not to swing backward on either.
Thanks
Hank CEF 559 |
Hollowpoint445
Intermediate Member
Username: Hollowpoint445
Post Number: 286
Registered: 6-2004
| | Posted on Saturday, May 21, 2005 - 6:13 pm: |
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It's far more important to have the the AMC/ALC working and adjusted properly than to wring the last watt out of the poor radio. Personally, I'd much rather have a 3 watt radio with AMC/ALC adjusted to 100% max modulation than an 8 watt radio with only 75%.
These radios will only key maybe 6 or 7 watts and still hit 100% modulation on peaks, and it's like flooring your car everytime you key the mic. I have heard of some extensively modified radios that actually key 10 watts and still hit 100% modulation, but it's just not worth it in my opinion.
Find a decent local tech who has (and knows how to use!) an oscilloscope. Pay him to fix the AMC/ALC and to do a full alignment on the radio. It'll sound good, won't splatter, and it should last a looooong time.
Don't forget to get a 7.8MHz Channel Guard. It's worth every penny if you hate bleedover even 1/2 as much as I do.
BTW - I applaud your effort to have a clean signal, but there's no way you aren't splattering if the radio's meter reads 100% modulation with a disabled limiter. That's the very reason limiters are designed into radios - to prevent voice peaks from becomming splatter. If the meter shows 100% on your voice peaks you can be sure that you're hitting way over 100% on those peaks. The circuitry that drives the meter has a certain timebase that averages out the input, and that's what you're actually seeing. It can't show modulation levels at an audio rate - it's just too slow. |
Bruce
Senior Member
Username: Bruce
Post Number: 2648
Registered: 9-2003
| | Posted on Saturday, May 21, 2005 - 6:36 pm: |
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AMENT on that channel guard! and another well worth mod is to change the 2sc1674 rf stage to a 2sc2999. Nothing beats a clean sounding radio! |
Vanillagorilla
Junior Member
Username: Vanillagorilla
Post Number: 41
Registered: 4-2005
| | Posted on Saturday, May 21, 2005 - 6:39 pm: |
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Gotcha...both you guys..thanks.
I was in the cave this afternoon and played with it a little. What I ended up with was a 3w DK swing to 13 peak and 3DK w/swing to 6 RMS. A local I modulate with said it sounded cleaner not that is was bad before but "certainly cleaner". I had to smile
I CANNOT reach in there and re-solder that middle leg so I'll live with limiting my gain as needed. I have it marked at max without ANY distortion and she sounds clean as a whistle. (with a hint or 452 echo)
I hear you on the "Good Tech" search. I had a great deal of respect for my local but when I found they were "clippers" I kinda decided to take it upon myself to learn more. I have no scope but will keep looking for a good tech..anyone have a contact on LI? Hey "Zerozero" you got yer ears on?
Thanks a bunch again...owe ya's a cold one!
Hank '905
LI NY |
Hollowpoint445
Intermediate Member
Username: Hollowpoint445
Post Number: 289
Registered: 6-2004
| | Posted on Saturday, May 21, 2005 - 7:43 pm: |
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A 3 watt d/k to 6 watts RMS on modulation is much more than 100% modulation. By definition, an AM carrier that is 100% modulated shows 50% more average output than the carrier alone.
Just because you sound clean doesn't mean that you're not overmodulating. By the time you notice distortion you're overmodulating a great deal.
Overmodulation creates additional sidebands which is what people hear as splatter on neaby frequencies. Initially it's just voice peaks, but it's possible to drive a radio so that average voice levels create overmodulation - and that's about when you start to hear distortion.
If you can't find a decent CB tech locally hunt down a ham. Most hams who like to tinker will have a station monitor they can use to adjust your modulation limiters properly. I do. |
Vanillagorilla
Junior Member
Username: Vanillagorilla
Post Number: 42
Registered: 4-2005
| | Posted on Saturday, May 21, 2005 - 11:26 pm: |
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Point taken...thanks for all the input. I'll look into that channel guard. Always wondered what they were about. Not to sound stupid or anything but sounds like I could use one. I'll see if I can find one here on Copper~
Hank~learning more every day |
Tech808
Moderator
Username: Tech808
Post Number: 5814
Registered: 8-2002
| | Posted on Saturday, May 21, 2005 - 11:55 pm: |
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Vanillagorilla,
Click on the LINK below.
Channel Guard Filters 7.8 MHZ
Hope this helps,
Lon
Tech808
CEF808
N9OSN
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Vanillagorilla
Junior Member
Username: Vanillagorilla
Post Number: 43
Registered: 4-2005
| | Posted on Sunday, May 22, 2005 - 9:52 am: |
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Thanks 808,
I used the search after Bruce and Hollowpoint445 recommeded it. Quite a few good threads on that..
That skip will bleed 3 channels away sometimes totally drowning out 15mi away local contacts!
Thanks to all~
Hank '905
CEF 559 |
