| Author |
Message |
    
Motor_doctor
Junior Member
Username: Motor_doctor
Post Number: 14
Registered: 12-2005
| | Posted on Wednesday, August 29, 2007 - 4:31 pm: | 
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my 257 has modulation problems
on some freg. it modulates 100%
but on am reg cb channels the modulation is
only about 60 to 80% and power output seems to be
down also
i have done all the mods suggested here
it also seems to suffer badly with bleed over
and white noise
any ideas on what might cause this? |
Dale
Senior Member
Username: Dale
Post Number: 1114
Registered: 12-2002
| | Posted on Thursday, August 30, 2007 - 5:39 am: |
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are ya checking it weith a dummy load and
not your antenna into your meter?a mis tuned
antenna on a different bands will affect your
output.
what kind of antenna ya xusing?recieve sounds
likew its over tuned.think id send it back to
magnum for a alignment
dale/a.k.a.hotrod
cef426
cvc#64
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Hotwire
Senior Member
Username: Hotwire
Post Number: 2381
Registered: 1-2005
| | Posted on Thursday, August 30, 2007 - 12:39 pm: |
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You have a center resonant freq/channel that the antenna is tuned to so the radio will operate more effiently on that specific freq/channel. As you move further away from that channel the performance drops off a bit and if you go to far out of band radio performance gets poor really quick! Oh and those mod meters on Dosy's and many other cb watt meters are ridiculous. You need to look at you modualation on an oscilliscope to determine correct percentage.
What I like to do is tune to my favorite channel which is none other than 27.115 and tune my antenna there for lowest swr.
It is possible that the radio needs a professional tuneup. White noise is bad and unneccasary! Many high end radios if setup properly have almost no white noise at all. Sometimes it is hard to tell if my Connex 4800 is even on! Then sometimes a radio will have some white noise such as my Uniden. Just a little white noise, when it effects pulling in distant stations then it is unacceptable and needs fixed.
The ACR in the Magnum radios is supposed to be top of the line. If your on channel 19 within a few miles of a truck stop then your going to get somebleed over no matter what. Most of the time its not your radio causing the beedover but the other guys radio!!!
If your unhappy with your radio I would send it back in for diagnosis!
One more thing, a real good antenna and coax is worth its weight in gold!
Good luck and I hope I was able to help.73
KEEP IT REAL!
Kenny
cef491(27.115lsb)
2sf491(27.555usb)
Indiana
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Patzerozero
Senior Member
Username: Patzerozero
Post Number: 3915
Registered: 7-2004
| | Posted on Sunday, September 02, 2007 - 9:36 pm: |
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motor_doctor, i experienced the same thing on MY 257, but in reverse. i bought for 10 meter mobile use ONLY, but did the mod....just in case. 1st time i fired it up in the house on LSB 38, i got a bunch of replies form DX as to how good it sounded. went to 28.360 & couldn't get out. 10-15 watts & low audio on 10m, but 40 watts & loud on CB. opened it up again, cranked the power up FULL, got mid 50's plus on CB & 40 plus on 10m, with great audio. just what i was looking for. while i haven't used it mobile on 11m, i've talked to 6 or 7 CEF members on 10m DX, as well as nearly 100 other DX contacts. 40 watts in the mobile, no power, and while my predator antenna is tuned for 27.025, it shows 1.7 or so on 28.400, which may account for a bit less output. on xmit at least, i'm satisfied.
receive is another story. in the house, white noise was there more then any other radio i use, but it didn't cover anything up. mobile, well, i sure know when i'm getting near town, or a bad pole mounted power transformer! parked on the beach, and most parts of the highway, most audio gets over the white noise. in a 'loud' spot, even though 'noise' is only S1, it can be SO LOUD that it covers up an S5 signal! odd, yes, annoying, moreso. turn off the anl/nb & you cannot hear anything, so in that respect it does work really well. when the E skip was booming, i had no trouble copying any signal that i could hear. as it died out, there were a few tough contacts. ACR, i don't think mine is that bad at all. not grant xl, but more then satisfactory. overload of the frontend may be more of the problem then ACR. a local, less then 1000' from my house, running 250 watts PEP on CB & 10m, is totally unreadable when on the same freq. 100kHz each way is the same. even at 100 watts he sounds like he's crashing through my speaker. on the 257, not on my xl or ar3500 though. just get a mile or so away & things sound fine.
i think i got my 257 the day after copper got them-it's the blue, erf2030 powered model. for the $169 i paid for it, it is what it is! and that is a more then acceptable little radio. while my xl far outperforms it on CB, the 257 gets me on 10m & CB if in a pinch. i'd bet if they still made 'em, xl's would be near $250 today. |
Motor_doctor
Junior Member
Username: Motor_doctor
Post Number: 17
Registered: 12-2005
| | Posted on Tuesday, September 04, 2007 - 8:53 am: |
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thanks for the response guys!!!
i think im going to send it back to magnum
for a tune up
see ya
charliec |
Tech808
Moderator
Username: Tech808
Post Number: 14369
Registered: 8-2002
| | Posted on Tuesday, September 04, 2007 - 10:10 am: |
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Check to make sure that RV4 is adjusted ALL the way OPEN.
Hope this help's,
Lon ~ Tech808 ~ N9CEF
CEF#808 ~ CEF HAM#33 ~ CVC#002
Tech808@copperelectronics.com
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Motor_doctor
Junior Member
Username: Motor_doctor
Post Number: 18
Registered: 12-2005
| | Posted on Tuesday, September 04, 2007 - 1:34 pm: |
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hey Lon yes i have rv4 all the way open
i think it needs a tune up and alignment
thanks |
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