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Author Topic: Playing around with preamps...  (Read 290 times)
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dale661
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« on: April 28, 2017, 12:44:00 AM »

Well, I've had some fun over the past week or so messing around with my antenna setup.  I'm kind of crazy when it comes to certain things, but I love to tinker.  The two culprits are the RCA preamp you can pick up at Lowe's for around $30 and Radio Shack's supposed 33 db preamp. 

When I first installed my antenna, I used the RCA preamp, and it worked very well.  While moving things around, I stripped one of the ports off the PCB.  I replaced it with another RCA preamp.  Well, the same thing happened to it as well.   Angry 

For those of you that may not know, Radio Shack is closing a lot of stores throughout the country.  All of the ones on the outskirts of Houston and closing up shop and slashing prices up to 90% on some items.  Most of the stuff is marked down about 60%.  I kind of laughed at what they were charging for diplexers, but that is a story for another day.  LOL!

Anyway, the RCA preamp has performed very well for me.  I have just learned I have to be careful when tightening connectors to its ports.  Other than that, it performs extremely well for my setup.

Enter in the Radio Shack unit... I figured I could get by with the extra supposed gain.  I got it all hooked up, scanned the channels and lost 27 of them.  I looked at the signal, and the amplification was all over the place.  Also, it wasn't doing much on the VHF side.  CBS is VHF here.  The FM trap was killing CBS.  On a scale to 100, CBS normally comes in at about 50 with no preamp connected to my Clearstream 2v.  The FM trap was knocking it down to 5 to 0.  I also noticed the power levels weren't very consistent.  They were jumping a lot.  Then, the amplification was very sporadic throughout the spectrum.  Some would be juiced up, and some were about on par with the RCA.  I may have seen a 5 db improvement on some of the channels, but it wasn't worth it in the end.

Needless to say, I purchased my last RCA preamp again this morning.  I hooked it up, and everything is back to normal.  When this one goes, I'm going to throw a little more money toward a Kitz preamp, but it's going to have to either burn up or get struck by lightning for that to happen.  We shall see how it makes it through the summer months down here. 

As Forrest Gump says, "That's awl I gawt tuh say about that!"
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mopat
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« Reply #1 on: April 28, 2017, 07:14:41 AM »


I don't know what your TV Fool report looks like so you may or may not need all the gain the KT-500 can provide.

Try tightening coax connectors just by hand--a 7/16" wrench can break most soldered connections pretty easily.

Over amplification can wipe out a lot of channels--too strong of a signal saturates the receiver's tuner and you'll soon get next to nothing.

The Kitz amp does have variable gain but it is pricey and doesn't sound like it's needed at your locale.
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WS9036 dish, Spitfire Lnb, Powermax SG9120 rotor, .
10' solid dish with C1-PLL, TBS6982 card running SmartDVB
dale661
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« Reply #2 on: April 28, 2017, 08:46:52 AM »


I don't know what your TV Fool report looks like so you may or may not need all the gain the KT-500 can provide.

Try tightening coax connectors just by hand--a 7/16" wrench can break most soldered connections pretty easily.

Over amplification can wipe out a lot of channels--too strong of a signal saturates the receiver's tuner and you'll soon get next to nothing.

The Kitz amp does have variable gain but it is pricey and doesn't sound like it's needed at your locale.

Thanks.  It's all good now.  I'm all about learning and experience.  If I lose 60 bucks in the process, that's okay.  I probably didn't need the McDonald's.   tongue
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Jeff S.
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« Reply #3 on: May 10, 2017, 02:12:05 PM »

If designed properly, FM traps should have no effects on signal quality or station degradation. The RCA unit is OK, but there are better units out there.

Amps with variable gain are crap in most cases because it adds noise to the unit. Along with units that have multiple outputs. Noise is the big killer in these units. I would stay in most cases that a 16db amp is more than enough. At a noise level of less than 2db. is required.

Most problems happen in the installation. The closer the pre-amp to the antenna the better. If you have the Pre-Amp less than 1m from the antenna the better response you will get. But not to close, then you interfere with the antenna.

Good luck,

Jeff Schumann
Manhattan-Digital



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jess73
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« Reply #4 on: May 10, 2017, 06:24:35 PM »

I'm using  an RCA pre-amp[1z] that has separate VHF and UHF connections .  This model can be "set" by removing the rubber plugs to set for combined or separate antennas, and also to turn on/off an FM trap.  I have mine set with the trap on and to combine a UHF yagi and a HI-VHF yagi.  Those are pointed toward Fresno, Ca.  The transmitters are approx. 90 mi away with the exception of  one transmitter at 130 mi.  The ones at 90 are solid, and the one at 130 will drop at times.  I dis salvage my old radioshack antenna that came down during a tree removal.  I removed the LO-VHF part of the antenna, so just the UHF and the HI-Vhf is all that remains. I have that coupled with a Winegard[200] pre amp pointed to San Francisco..  Both antennas ore only about 10 feet above the roof.   I have more TV off air.  It is also FREE!  Jess out in California   
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dale661
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« Reply #5 on: May 11, 2017, 12:41:36 AM »

If designed properly, FM traps should have no effects on signal quality or station degradation. The RCA unit is OK, but there are better units out there.

Amps with variable gain are crap in most cases because it adds noise to the unit. Along with units that have multiple outputs. Noise is the big killer in these units. I would stay in most cases that a 16db amp is more than enough. At a noise level of less than 2db. is required.

Most problems happen in the installation. The closer the pre-amp to the antenna the better. If you have the Pre-Amp less than 1m from the antenna the better response you will get. But not to close, then you interfere with the antenna.

Good luck,

Jeff Schumann
Manhattan-Digital


Hey, Jeff!  Thanks for chiming in!  The one on the Radio Shack must not have been designed very well.  My preamp is mounted to the mast below the antenna. 
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dale661
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« Reply #6 on: May 11, 2017, 12:44:30 AM »

I'm using  an RCA pre-amp[1z] that has separate VHF and UHF connections .  This model can be "set" by removing the rubber plugs to set for combined or separate antennas, and also to turn on/off an FM trap.  I have mine set with the trap on and to combine a UHF yagi and a HI-VHF yagi.  Those are pointed toward Fresno, Ca.  The transmitters are approx. 90 mi away with the exception of  one transmitter at 130 mi.  The ones at 90 are solid, and the one at 130 will drop at times.  I dis salvage my old radioshack antenna that came down during a tree removal.  I removed the LO-VHF part of the antenna, so just the UHF and the HI-Vhf is all that remains. I have that coupled with a Winegard[200] pre amp pointed to San Francisco..  Both antennas ore only about 10 feet above the roof.   I have more TV off air.  It is also FREE!  Jess out in California   

I have the same exact preamp you're talking about, Jess.  I made sure the FM trap was off when I installed the last one.  I haven't messed with it since then, as the wife gets mad when I start tinkering with things.   grin
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