| Author |
Message |
    
Jamie4aday
New member
Username: Jamie4aday
Post Number: 3
Registered: 4-2005
| | Posted on Friday, April 29, 2005 - 5:16 pm: | 
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I have a palomar dx250b base amplifier. When i turn on the preamp, it pegs the needle and is just a bunch of noise then sounds like it is tuning to an am shortwave or am radio broadcast station. This aint right, help. |
Bruce
Senior Member
Username: Bruce
Post Number: 2542
Registered: 9-2003
| | Posted on Saturday, April 30, 2005 - 10:23 am: |
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HUMMMMM????
Could it be your preamp is wideband enough to go down to 15 mhz...... Just maby its sneeking on the other mixer (image) which would be 27 mhz - 10.7 mhz. |
1861
Intermediate Member
Username: 1861
Post Number: 161
Registered: 2-2004
| | Posted on Saturday, April 30, 2005 - 11:18 am: |
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I use a palomar 250 mobil and alot of time when i turn on pre amp , i pick up a radio station out of Canada . I have no idea why , but it is the same station every time . |
Yankee
Intermediate Member
Username: Yankee
Post Number: 492
Registered: 7-2003
| | Posted on Saturday, April 30, 2005 - 10:29 pm: |
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I have this problem with just a regular 35DB gain receive preamp somewhere around channels 30-32. I tend to agree with Bruce's answer. I think I'm receiving a Voice Of America station. Nothing wrong with your radio or amp. |
Sg569
Intermediate Member
Username: Sg569
Post Number: 156
Registered: 12-2004
| | Posted on Friday, July 01, 2005 - 6:47 pm: |
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I pick up european shortwave on 38 mexican on 20 or there abouts.
Is there any way to eliminate this prob. I try to find weak ssb on 38 at night and that shortwave screws it all up |
Bruce
Senior Member
Username: Bruce
Post Number: 2910
Registered: 9-2003
| | Posted on Friday, July 01, 2005 - 7:51 pm: |
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most preamps are untuned and depend on the bandpass of the antenna and radio.....Now you turn on the preamp + 30 db gain a VOLTAGE gain of more than 13 to 1 your protection diodes could be reaching conduction ( .4-.7 volts signal ) and if so will act as a conveter as well as a preamp generating lots of mixing products allowing you to hear things far away from the normal cb frequencys! |
Sg569
Intermediate Member
Username: Sg569
Post Number: 157
Registered: 12-2004
| | Posted on Friday, July 01, 2005 - 8:56 pm: |
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In other words, No, I will not be able to fix it very easily(except to not use the pre-amp).
Ok, I just thought that I would ask.
Thanks Bruce. |
Bruce
Senior Member
Username: Bruce
Post Number: 2911
Registered: 9-2003
| | Posted on Friday, July 01, 2005 - 10:11 pm: |
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if you can put a bandpass filter in frount of it that should work also a tightly tuned preamp would work such as the one copper used to sell or the LNK-28 by hamtronics ( http://www.hamtronics.com/ )
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Sg569
Intermediate Member
Username: Sg569
Post Number: 162
Registered: 12-2004
| | Posted on Saturday, July 02, 2005 - 1:18 pm: |
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I will have to try one of those. Thanks Bruce.
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Bruce
Senior Member
Username: Bruce
Post Number: 2917
Registered: 9-2003
| | Posted on Sunday, July 03, 2005 - 8:05 am: |
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make a band pass filter first its just a few coils and caps .... |
Hollowpoint445
Intermediate Member
Username: Hollowpoint445
Post Number: 479
Registered: 6-2004
| | Posted on Sunday, July 03, 2005 - 2:35 pm: |
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Why not just keep the preamp off? They add more noise to the receiver chain and they're rarely as good as the amplification in the front end of your radio.
Besides, if you can't hear them with your radio you won't be able to work them anyway - regardless of how much power you use. |
