| Author |
Message |
    
Wendy
Member
Username: Wendy
Post Number: 61
Registered: 6-2004
| | Posted on Tuesday, August 24, 2004 - 9:28 pm: | 
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Can anyone explain to me what a preamp is? What does it do? How does it work? Why do I need one?
Thanks Wendy |
Tech808
Moderator
Username: Tech808
Post Number: 3388
Registered: 8-2002
| | Posted on Tuesday, August 24, 2004 - 10:15 pm: |
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Wendy,
A Pre-Amp will give you up to 27 to 30 or more DB gain on Receive.
If you can just barely hear someone in the distance you can flip your pre-amp on and bring them in Much Cleaner & Clearer, up to several S units.
Lon
Tech808 |
Hollowpoint445
Intermediate Member
Username: Hollowpoint445
Post Number: 282
Registered: 6-2004
| | Posted on Wednesday, August 25, 2004 - 6:04 am: |
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They have a downside too. They amplify everything including the noise. If it's noisy a receive amplifier won't do anything for you except make the noise louder. Generally speaking, most CB radios are sensitive enough that you don't need a receive amplifier.
Scannists use them because higher frequency signals are attenuated more by coax. If you amplify the signal right at the antenna you can overcome the coax loss and even hear signals you wouldn't hear without the amplifier.
It's useful to have a variable gain control so you can turn it up or down as needed. Strong signals can cause the amplifier to do weird things (oscillate) and make it impossible to listen to anything at all unless you can cut the gain back.
For a 2 way radio you'd need one that can switch in an out when you transmit. |
Hatchet
New member
Username: Hatchet
Post Number: 6
Registered: 7-2004
| | Posted on Wednesday, August 25, 2004 - 7:19 am: |
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It also amplifies the noise the same amount as the signal. So 98% of the time you still cant hear them because of all the noise. Ive never seen a preamp that cleans up the signal and dosent amplify the noise
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Highlander
Advanced Member
Username: Highlander
Post Number: 595
Registered: 12-2001
| | Posted on Wednesday, August 25, 2004 - 3:32 pm: |
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Just turn up the volume on the radio, same effect! |
Bc910
Member
Username: Bc910
Post Number: 95
Registered: 7-2004
| | Posted on Wednesday, August 25, 2004 - 6:45 pm: |
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Highlander;
I have never agreed with any one more in my entire life! |
Bruce
Senior Member
Username: Bruce
Post Number: 1507
Registered: 9-2003
| | Posted on Wednesday, August 25, 2004 - 7:18 pm: |
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NOW preamps DO have a use if your in a VERY quite location. Some older CB radios like STOCK Lincolns CAN use a bit of help. However when the skip rolls all the preamp is going to do is give you a higher "S" meter reading. The only preamp that REALY works good is a mast mounted one feeding a VERY long coax ....... This is done on bands like 2 and 3/4 meters and can make a 10 or more DB ( 3 times or more sensitivy ) difreance in copying a signal. In some radios changing the RF amp stage is a worth while change ..... a recomended mod for a lincoln. |
Wendy
Member
Username: Wendy
Post Number: 62
Registered: 6-2004
| | Posted on Wednesday, August 25, 2004 - 9:27 pm: |
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Thank you all for the advice.
Wendy |
Tech548
Moderator
Username: Tech548
Post Number: 264
Registered: 5-2004
| | Posted on Wednesday, August 25, 2004 - 9:36 pm: |
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Hey guys.
Speaking of Pre-amps and noisey receivers, ever play with a tunable DSP filter? It's a great way to get rid of atmospheric hash and trash.
My personal favorite is the MFJ-784. A bit pricey but very versitale
Jeff
Tech548 |
Bruce
Senior Member
Username: Bruce
Post Number: 1509
Registered: 9-2003
| | Posted on Thursday, August 26, 2004 - 7:18 am: |
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I have DSP built in to my FT-100D and a Radio Shack DSP for my FT-840 also i use a audio filter on the Grant LT it works good To. As for preamps i use a preamp sold by copper on the grant again when things are dead it does help. |
Drcat
New member
Username: Drcat
Post Number: 8
Registered: 7-2004
| | Posted on Tuesday, December 07, 2004 - 10:53 pm: |
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Is their a device that could separate noise from signal?
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Tech291
Moderator
Username: Tech291
Post Number: 3
Registered: 11-2004
| | Posted on Tuesday, December 07, 2004 - 11:03 pm: |
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DrCat,
a dsp or digital signal processor is about as close as you can get to that. |
Drcat
Junior Member
Username: Drcat
Post Number: 13
Registered: 7-2004
| | Posted on Saturday, December 11, 2004 - 5:38 pm: |
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Hi: Where could I see a picture and read more about them?
73 |
