Pre-Amplifier
Pre-Amplifier
I'm looking at getting a pre-amp to boast fringe signals around the 400MHz area, but don't know what I should be looking for or what price.
There is heaps of info available on the net, but was hoping somebody on here could give me info about what I should look for and what a reasonable price is. Am I wasting my time getting one to use it with modern Uniden scanner - some seem to think so? I don't want to go overboard on features (or price), just looking for something that will work.
Thanks,
Scott
There is heaps of info available on the net, but was hoping somebody on here could give me info about what I should look for and what a reasonable price is. Am I wasting my time getting one to use it with modern Uniden scanner - some seem to think so? I don't want to go overboard on features (or price), just looking for something that will work.
Thanks,
Scott
- Bigfella237
- Posts: 1897
- Joined: Fri Feb 26, 2010 3:11 pm
- Location: In geosynchronous orbit above the Far South Coast of NSW, Australia
Re: Pre-Amplifier
+1 for me too
I already have pre-amps in the multi-couplers but was thinking about adding a pre-pre-amp to try and get a better decode with Unitrunker on a few of the more distant GRN sites?
I would prefer something that can be run off mains power (through an adapter)... changing batteries sucks!
Thanks in advance,
Andrew
I already have pre-amps in the multi-couplers but was thinking about adding a pre-pre-amp to try and get a better decode with Unitrunker on a few of the more distant GRN sites?
I would prefer something that can be run off mains power (through an adapter)... changing batteries sucks!
Thanks in advance,
Andrew
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- Posts: 672
- Joined: Thu Aug 14, 2008 8:22 pm
Re: Pre-Amplifier
I'm using the JIM M-75. Cant beat it I rekon. Variable gain, battery or 12V, filters.
Really pulls the signals out of the grass.
Good to get them from the USA now while the dollar is up http://www.scannermaster.com/Pre_Amplifiers_s/45.htm
Mike
Really pulls the signals out of the grass.
Good to get them from the USA now while the dollar is up http://www.scannermaster.com/Pre_Amplifiers_s/45.htm
Mike
- Bigfella237
- Posts: 1897
- Joined: Fri Feb 26, 2010 3:11 pm
- Location: In geosynchronous orbit above the Far South Coast of NSW, Australia
Re: Pre-Amplifier
I forgot to say thanks Mike,
Jim looks like he may be just the ticket... unless anyone else has a favorite pre-amp they'd like to put up against Jim?
The only thing I'm not that impressed about is the male/female BNC connectors, I would prefer N-type both ends but it's nothing a bit of creative cabling can't get around!
Andrew
Jim looks like he may be just the ticket... unless anyone else has a favorite pre-amp they'd like to put up against Jim?
The only thing I'm not that impressed about is the male/female BNC connectors, I would prefer N-type both ends but it's nothing a bit of creative cabling can't get around!
Andrew
Re: Pre-Amplifier
Andrew, it would be better if you could mast mount the preamp... preamps don't perform miracles- they can only amplify what is there (including noise) so by mast mounting it you will get a better result. Cascading amps is very dangerous... every amp adds noise so cascading will also amplify the noise generated by the first preamp.
Cheers,
Richard
Cheers,
Richard
- Bigfella237
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- Joined: Fri Feb 26, 2010 3:11 pm
- Location: In geosynchronous orbit above the Far South Coast of NSW, Australia
Re: Pre-Amplifier
Thanks Richard, good to know!
Assuming Jim would be better (or at least more adjustable) than the pre-amps in the multi-couplers, I will have a look to see if the latter can be "bypassed" so that Jim (or whichever amp I end up buying) is the only one in-line, this may be as simple as removing the power feed to the M/Cs, I think they revert to being "passive" without DC?
Andrew
Assuming Jim would be better (or at least more adjustable) than the pre-amps in the multi-couplers, I will have a look to see if the latter can be "bypassed" so that Jim (or whichever amp I end up buying) is the only one in-line, this may be as simple as removing the power feed to the M/Cs, I think they revert to being "passive" without DC?
Andrew
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Re: Pre-Amplifier
Normally, an amp without DC will turn into an attenuator, that of course is passive with loss! Only if it has bypass arrangements will it revert to no loss / no gain so you you would need to test it. Be careful also of intermodulation products cuased by strong signals / tx nearby. The best use of a preamp would include a preselector filter. Not common in the scaning fraternity though.
Re: Pre-Amplifier
Seems like an amplifier might not be the way to go then. Thanks to all for your feedback and advice. I can probably get my antenna about 2-5 metres higher...that might just make the difference for me.
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Re: Pre-Amplifier
Height is might ....Scotty wrote:Seems like an amplifier might not be the way to go then. Thanks to all for your feedback and advice. I can probably get my antenna about 2-5 metres higher...that might just make the difference for me.
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Re: Pre-Amplifier
For what it's worth, I haven't had an issue with the Jim M75. I'm using it at the end of a 10m run of RG213 connected to a Diamond X50 antenna. It pulls faint P25 transmissions out of the noise floor with no degradation in the decoded audio. It uses a low noise GaAs FET pre-amp and the 3 selectable band-pass filters reduce the chance of RF overload. I also like the variable gain which allows attenuation as well, handy for targeting local signals only.Scotty wrote:Seems like an amplifier might not be the way to go then. Thanks to all for your feedback and advice. I can probably get my antenna about 2-5 metres higher...that might just make the difference for me.
Sure, a masthead amp is the best technical solution, but you just don't have the ease of control the M75 gives you in the shack.
Mike