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Message |
    
Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 342
Registered: 4-2006
| | Posted on Friday, April 27, 2007 - 8:21 pm: | 
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OK, I am getting reports that on SSB I am way too loud. Even with the Grant XL mic gain at 12:00 o' clock, and my D104 minuteman 2 barely on the number 1 (Around 8:00). But on AM, I sound fine when the XL mic gain is up all the way, and the mic is at about 1:00. Any ideas? My radio is basically set to dead key at 3 watts and swing to 4. Driving a 667V. Thanks. |
Tech808
Moderator
Username: Tech808
Post Number: 13576
Registered: 8-2002
| | Posted on Friday, April 27, 2007 - 9:34 pm: |
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Try adjusting VR7 the AMC control.
You should have full audio with the mic gain set no higher than 1/2 way (12 oclock).
Find someone with a scope and and you will be able to see where you have a perfect wave pattern and 100% modulation.
I honestly have never seen any radio that needs the mic gain set over 12 oclock for 100% clean clear audio.
Lon ~ Tech808 ~ N9CEF
CEF#808 ~ CEF HAM#33 ~ CVC#002
10-10 International #61493 ~ 10-10 VP#2688
Tech808@copperelectronics.com
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Jameslarson
Intermediate Member
Username: Jameslarson
Post Number: 343
Registered: 4-2006
| | Posted on Friday, April 27, 2007 - 10:13 pm: |
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Actually, I was thinking of getting a scope for myslef. Any recomendations? brands? models? Etc... Thanks |
Hollowpoint445
Senior Member
Username: Hollowpoint445
Post Number: 1486
Registered: 6-2004
| | Posted on Saturday, April 28, 2007 - 9:18 am: |
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I agree that you don't need much microphone gain to get 100% modulation - even with the stock microphone.
The way I read your post, SSB was too loud and AM was fine. I'd adjust the ALC to dial back SSB a bit. Of course a scope is the best way to go, and ultimately the only accurate way.
I don't own a service oscilloscope because I'm not a tech - I'm a power user. Instead, I own a station monitor that incorporates a basic oscilloscope, two tone audio generator, and a device called a panadapter that allows me to look at a swath of bandwidth around the frequency I'm receiving. I'm sure it does more, but that's all I really bother with. It does a great job adjusting AMC/ALC on CBs, and it allows me to look at my waveform while transmitting with either my CBs or HF rig.
Heathkit made a good one, and there are lots of matching station monitors out there for amateur HF rigs. Some are downright cheap! I believe there were even some made/marketed to serious CBers back in the late 70s and early 80s. I know that Wawasee made a modulation scope for CB that matched their other products.
Aack! - Bill the cat
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Dale
Advanced Member
Username: Dale
Post Number: 807
Registered: 12-2002
| | Posted on Saturday, April 28, 2007 - 6:10 pm: |
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is your audio limiter clipped/cut out.cause that
definately will overmodulate on ssb.not
always on am.if its still intact the mod list
says vr7 is the audio adjustment this maybe
turned up all the way if so back it off a hair
dale/a.k.a.hotrod
cef426
cvc#64
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Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2510
Registered: 9-2004
| | Posted on Saturday, April 28, 2007 - 10:02 pm: |
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i agree with dale,
jameslarson, check TR24. is it there?
it is hard to find. it is in the front right part of the radio, right near R131.
if TR24 is removed, or altered, it will cause distortion on SSB.
if you find it missing, replace it with a 2SC945 transistor, or any other applicable sub.
VR7 is probably ok to be turned up all the way. just use the mic gain on the front panel.
VR11 for SSB is the same case, but dont set it for anything over about 15 watts.
i really think TR24 is your problem.
matt
anyone wanting a "clean signal", just look to the left and build one of these!!!
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Dale
Advanced Member
Username: Dale
Post Number: 808
Registered: 12-2002
| | Posted on Saturday, April 28, 2007 - 11:14 pm: |
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kv i just got a grantxl on ssb its fuzzy sounding cant understand a word.i had 2 locals
trying to tune me in 1 was on a 2950 the other
a yeasu 101 neither could tune me in or even get close to understanding me.i know this is off topic sorry about that but was wondering should i check limiter?cause this isnt your normal warble or overmodulated.also on mods list off to left of this post r-131 is listed.i thought it
was tr24 am i missing something here
dale/a.k.a.hotrod
cef426
cvc#64
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Im4jc
Intermediate Member
Username: Im4jc
Post Number: 235
Registered: 11-2005
| | Posted on Sunday, April 29, 2007 - 12:14 am: |
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Dale, yes, "cut R131" is listed in the modification list for both the Cobra 148 and the Uniden Grant, but it shouldn't be there because it garbles sideband. They should remove it from the modifications list promptly. I don't think they will because it's been there forever and has been the source of confusion for many on this forum and many other forums.
Moderator Note!
It will not be removed as it is an "OPTION" only to properly adjusting VR7 in the radio but most people do not have the proper equipment or specifications to properly adjust a radio.
And it also depends on WHAT Model of Grant you have and WHAT country it was manufactured in ie: China, Philippines or Taiwan.
If you clip or remove R131 and it does not improve the radio's audio it can be reinstalled.
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Unit199
Intermediate Member
Username: Unit199
Post Number: 464
Registered: 8-2003
| | Posted on Sunday, April 29, 2007 - 2:43 am: |
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R131 is what you clip for modulation.If you need to replace it, it is a 4.7k resistor. The CHINA made with front mic connectors are different from the other ones. They are not anything like the ones made in the Philipines and Taiwan. Some of the parts are different values and some are not even there. Do not let anyone convince you that they are the same radios, because they are not. This is how radios end up in the junk pile, because people are given wrong info on these radios.
HARVE
UNIT199
CEF210
CVC18
KB0YVK
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Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2512
Registered: 9-2004
| | Posted on Sunday, April 29, 2007 - 11:00 pm: |
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hi all,
tried to post this three times, and my comp. keeps locking up. grrrr!
ok, removing R131 will not affect the SSB.
removing or adding resistance to TR24 will cause distortion on SSB. (usually)
stock value of R131 is 10k ohms. replacing it with a 4.7k as harve suggests is a good idea IMO, as it gives a slight modulation increase.
removing R131 will work in ALL versions of this chassis, new 148's included.
will it sound as good on the new ones?
maybe, maybe not. really poor voltage regulation on the new ones makes it hard to get high modulation peaks without distortion.
cant turn up SSB power in these much at all.
dale, and anyone else experiencing severe distortion/ "cant clarify or be clarified" symptoms:
if TR24 does not end up being your problem, look at the 7.8mhz IF coils/ variable cap.
if these are misadjusted, SSB can be rendered useless.
here is the alignment info for the 148/2000gtl, and the grantXL, the grant LT is a bit different. not much, but a bit.
radio to ch.19, clarifier centered.
freq. counter probe to TP3. (just in front of final and driver)
set radio to USB mode, and adjust CT2 for 7.8015mhz.
set radio to LSB mode, and adjust L30 for 7.7980mhz.
set radio to AM mode, turn mic gain all the way down, key mic and adjust L31 for 7.8000mhz.
to center the clarifier:
radio to ch.1, clarifier centered. (dont bump it!)
freq. counter probe to TP1. (near L20, by VCO)
radio to AM mode, adjust L23 for 34.7650mhz.
radio to USB mode, adjust L59 for 34.7665mhz.
radio to LSB mode, adjust L22 for 34.7635mhz.
if your clarifier is unlocked, you are done.
if not, move the freq. counter probe to the antenna input, turn the mic gain all the way down, key the mic, (ch.1) and adjust VR5 for 26.9650mhz.
if you unlocked the clarifier, VR5 is out of the circuit, and adjusting it wont do anything.
your TX freq. was aligned by aligning the other cans.
best of luck to all,
matt
anyone wanting a "clean signal", just look to the left and build one of these!!!
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Dale
Advanced Member
Username: Dale
Post Number: 821
Registered: 12-2002
| | Posted on Monday, April 30, 2007 - 8:05 pm: |
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ok my clarifer is locked can i use just vr5
to put it on freq. or will i need to tune
other cans ya listed.also adjusted vr7 modulation
adjustment didnt make much of a difference if any
now heres were it gets confusing.most radios that been clipped has a high/wild swing this one doesnt.dk=4-pep 10watts.im still hunting for limiter as im typing this
dale/a.k.a.hotrod
cef426
cvc#64
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Kid_vicious
Senior Member
Username: Kid_vicious
Post Number: 2517
Registered: 9-2004
| | Posted on Friday, May 04, 2007 - 12:23 am: |
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R131 is near TR26, in front of L2 i think.
yes, if you just want to adjust your TX freq. use VR5 with a freq. counter to the antenna input.
if the others are off, you'll just have to turn your clarifier to tune others in.
you will be TXing on freq.
if you are doing 4 swinging to 10 watts, i would be very happy, as that is a good sounding setup.
matt
anyone wanting a "clean signal", just look to the left and build one of these!!!
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Dale
Advanced Member
Username: Dale
Post Number: 833
Registered: 12-2002
| | Posted on Friday, May 04, 2007 - 8:19 pm: |
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thank you kv i ask cause i seen 3 other cans/pots labeled
usb
am
lsb
just adjust vr5 to adjust transmit frequ.seems ok on am but on lsb its off dont know about usb
dale/a.k.a.hotrod
cef426
cvc#64
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