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Audioman
Junior Member
Username: Audioman
Post Number: 29
Registered: 2-2004
| | Posted on Tuesday, October 12, 2004 - 3:28 pm: | 
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I have several radios.
RCI 2990, RCI 2990DX, Galaxy 2517, Galaxy 2527 to name a few.
All of these radios have some kind of swing mod.
However, I have a RCI 2985DX with no mods at all.
When driving any of them into my KLV 400 or my KLV 1000, they all sound great.
In fact my RCI 2985DX (no mods) sounds just as loud, powerful & clear as any of the other radios with their swing mods.
If I use my RCI 2985, I get a bigger dead key & of course a bigger dead key out of the linear then any of the others. True, it does not swing like the others but does it matter?
Those on the other end report that they all are killers.
The combo of the RCI 2985 (no mods) & the KLV 1000 produce a 500 watt or better dead key with peaks to 900 on AM.
The others (with swing mods) produce about 150 watts out of the KLV 1000 with a swing to 900.
Those on the other end report that they all sound about the same. In fact, the RCI 2985 (no mods) produces the biggest overall sound. I floor their meters & blow their ears off.
So I ask, why does the swing really matter?
Please explain why I sacrifice output power for swing?
Another thing I noticed is that others see little actual swing on their end no matter what I do. It NEVER swings on their end like it does at my end.
If I dead key I can give another a 20db on the meter with my 2985 (no mods) & the KLV 1000.
On my other radio (with swing mods) I give them a 10db that swings up to around 20db.
I would think it is better to give them A nice big signal all the time?
Does this make sense to you??
I really need to know as I loose sleep over this.
Thanks
Audioman.
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Highlander
Advanced Member
Username: Highlander
Post Number: 626
Registered: 12-2001
| | Posted on Tuesday, October 12, 2004 - 7:32 pm: |
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Radios that don't have a swing mod, but are tuned correctly will sound loud and clear because the AMC circuit is intact and operating as designed--this causes a little bit of compression as your peaks approach 100 percent modulation. Not only does it sound loud, the signal will be much cleaner, less splatter and harmonics, which your amplifier will dutifully amplify along with you actual signal as in the case of the swing modded radios.
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Kilowatt
Member
Username: Kilowatt
Post Number: 55
Registered: 2-2004
| | Posted on Tuesday, October 12, 2004 - 9:24 pm: |
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From a CBer standpoint, lots of swing looks impressive on a meter and exercises the other guy's radio's needle. It also causes lots of bleedover and TVI, and some folks consider that a good thing.
From an engineering standpoint, what you want is high-level AM modulation that doesn't exceed 95 to 100 percent on peaks (on a scope). This way, your signal is clear and loud even though it may not show a lot of swing on a wattmeter.
All that swing you see is mainly harmonic distortion (if you have disabled the AMC circuit). Most of it consists of rf spikes on frequencies other that what you are intending to operate on. Your wattmeter just adds the "spike wattage" to the wattage you are producing on the channel you are operating on. Hence, the big swing...
In other words, if folks can hear you "bleeding" onto other channels, you have a problem. That is unless you are very close to them...
You would agree that you want all of your power on one channel, wouldn't you? If so, then don't mess with the AMC unless you have access to a scope.... Trust me on this, you'll sound MUCH better.
Even better- have the Copper techs tune your radio when you buy it from them. They have the equipment to do it right!
Radios using high-level AM modulation - Almost any CB EXCEPT some of the "10 meter SSB radios." Radios like the President HR 2510 use low-level modulation as do most ham radios. This is because AM is not considered to be a mode used by many hams. Therefore the AM quality of these radios isn't extremely good.
Oh well, just my two cents... You mileage may vary.
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Sparkyscb
New member
Username: Sparkyscb
Post Number: 7
Registered: 5-2003
| | Posted on Wednesday, October 13, 2004 - 12:35 am: |
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Kilowatt...I take my hat off to you!!! In 25+ years in this foolish radio hobby, that was the BEST explanation I have ever read concerning "Swing" and the proper alignment of transmitters without defeating the AMC circuit. I see far too many radio thru here where guys thought resistors/diodes were wire ties and just started clipping them out!! We have a few "Shadetree" techs around here that are good guys, but a bit mis informed. I have tried to sell them for years...instead of buying the latest power microphone, spend the money on a good, used scope. Many decent old 10-15MHZ scopes can be bought for less than $100.00 and while they are not useable to monitor the 30MHZ signal they ARE perfectly useable for modulation adjustments. just My 2 cents worth. |
Stepchild
Intermediate Member
Username: Stepchild
Post Number: 135
Registered: 11-2002
| | Posted on Wednesday, October 13, 2004 - 9:52 am: |
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I have a Galaxy 99 and had a guy in Houston talk me into a"Super Mod KIT".He said it would make my 99 swing on AM what it does on SSB and it does.It also swings the same with the RF PWR at max or min on AM.The problem is I have a Silver Eagle 350 amp I'd like to put on it but I'm afraid that much swing will dammage my amp.The radio on low dead key's 3.5w and swings 45w and on high dead key's 12-15w and swings 45-50w.Also it doesn't sound as clear and well defined as it did before,but I think my RK-56 is worn out(15+yrs old)Should I have the mod kit removed or not??? Stepchild |
Kilowatt
Member
Username: Kilowatt
Post Number: 58
Registered: 2-2004
| | Posted on Thursday, October 14, 2004 - 3:31 am: |
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Hi Sparky!
Thanks - I appreciate the good word! I give credit to the US Army Signal Corps for all of the good knowledge they imparted unto me!
My hat is off to you for recommending that folks buy a scope! They are very handy instruments, and will really help folks set up their modulation correctly. A good scope is definitely money well spent!
I can hardly wait to use my scope to check out my "new to me" Grant Classic as soon as it gets in :-)
Stepchild, I would definitely have the mod kit removed. If you could find a tech with a scope, he should be able to set your radio up to do its best. He could check the roadking for proper operation, too. |
Stepchild
Intermediate Member
Username: Stepchild
Post Number: 136
Registered: 11-2002
| | Posted on Saturday, October 16, 2004 - 9:22 pm: |
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Thanks Kilowatt,
I haven't made up my mind yet about the kit but I want to check my mic first.As far as the scope goes I don't know the first thing about one although I would like to learn. Thanks again Stepchild
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Kilowatt
Member
Username: Kilowatt
Post Number: 62
Registered: 2-2004
| | Posted on Sunday, October 17, 2004 - 6:03 am: |
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Sure thing, Stepchild!
A scope is a piece of test equipment that looks vaguely like a TV with lines drawn up and down and sideways across the screen. A tech will use one of these to enable him to set your CB's modulation to the greatest point below the area where distortion occurs. That's all...
Those Road Kings are good microphones. I used one in my mobile for a long time. Maybe yours just needs a good spraying of it's contacts with some contact cleaner? I know that mine needed this every couple of years.
Anway, good luck with everything. Those Galaxies are good radios! |
Inspector
Member
Username: Inspector
Post Number: 95
Registered: 12-2001
| | Posted on Sunday, October 17, 2004 - 8:56 am: |
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Kilowatt, I agree. Those mods have become a "Wattage" thing and the over-kill swing defeats the purpose and generates RFI. When done right (with the AMC intact), the NPC can work the way it was supposed to: low RFI amd low harmonic distortion; the impression of higher than 100% modulation; and a 4:1 or 5:1 carrier to swing ratio...no more than that. And yes, a scope is a necesity to do it right.;-) |
Stepchild
Intermediate Member
Username: Stepchild
Post Number: 139
Registered: 11-2002
| | Posted on Monday, October 25, 2004 - 6:13 pm: |
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Thank you all,I now know what must be done.
Stepchild |
Keithinatlanta
Intermediate Member
Username: Keithinatlanta
Post Number: 428
Registered: 3-2003
| | Posted on Tuesday, October 26, 2004 - 7:41 am: |
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Hi guys. My two cents worth here. AS a CB'r since 1973, let me tell you what I listen for when talking to someone on the cb radio. How clear is your transmission? Can I understand you? I could care less about anything else, because if I cannot hear you clearly, how can I carry on a conversation???? Like mentioned above, some shops will promise you everything under the sun with your radio. Sometimes, I will stop at a shop and play Mr. Dumb, just to see what they will tell me and you would not believe some of the stuff I hear. No, I am not a tech, but I have been around enough to understand and know what can be done to a radio for it to work or not work properly. Thanks for giving the advice above to the young man to get a scope. I read so many times on here where someone posts about how to do something, but they have no equipment to measure it with. That is like when I go into a kitchen in a restaurant to sell biscuits, ask for an oven to bake them in, and then have no temperature gage to set oven to proper temp for baking. Talk about guessing!!! Guess how good my biscuits are gonna be!!
In meantime, all you folks who help out and guide with your knowledge on this forum, I say a major
THANK YOU to all of you. As a member of this forum, it is nice to have a place where I can come and enjoy the hobby and learn as well!!
Keith in Atlanta
CEF 150 |
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