Any preamp fans out there?

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rbm

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I saw a preamp on Ebay today that caught my eye.
It's the same as some that I've used for a while and I thought I should pick up a spare.

So, I took an inventory of some of my spares.
It turns out that I didn't need another of that type. ;)

Here's a photo of just a few of my spares.

I have another 11 or so in constant use.
Mostly LNA-1000's from RF Bay, Inc.
You can see from the discoloration that I've used a few and had to swap them out when they took ESD hits.
Then I repair them for future 'swap outs'.

I used to have seven of the Jim M-75 preamps but lost five of those (and others) to a nearby lightning strike back around 2007.

Rich

 

aggie72

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I'm using this to provide output to 4 scanners without loss of signal. I built a box to switch several antennas into the preamp. Works very well!
 

rbm

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Which of those works well for aircraft band monitoring (civilian a/c band), if you monitor those freqs?
If you have no very strong nearby signals ......................

I use the LNA-580 for air, MilAir, and SatCom frequencies and it works great.
It's somewhat expensive though.

They're around $165 but the noise figure is only around 0.7 dB and gain is around 23 dB.
RF Bay, Inc has listings for them on Ebay.
Specs are here:
http://www.rfbayinc.com/upload/files/lna/lna-580.pdf

That's a little overkill for most people.
One thing that could be a problem for some MilAir fans is that the SatCom frequencies come in so well in the 200-300 MHz range that they can actually be a bit annoying at times if all you want to hear is MilAir.

For a total outlay of less $15-$20 for the preamp, power inserter, and DC Block, the Holland LA-520 may be sufficient for your needs.

You can refer to this earlier post of mine describing it.
http://forums.radioreference.com/scanner-receiver-antennas/228728-so-i-bought-antennacraft-st2-scantenna-5.html#post2015393

Rich
 

zz0468

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The RFBay preamps are decent quality, about comparable to Mini-Circuits. The caveat for both is going to be the rather low IP3 or third-order intercept specification on most of their preaamps. These preamps are quite susceptible to overload, so some sort of filtering is usually needed in front of them.

Look at the specifications for noise figure, gain, and IP 3. The lower the NF, the better. The higher the IP3, the better.

At a minimum, I would run a low pass filter in front of it to keep cellular signals out. Even if the preamp is only specified for 500 MHz or below, it's quite possible for 1.9 GHz PCS to cause it to overload, so watch for that.

Anything over about 10 db gain is overkill unless you're also driving a lossy splitter for multiple receivers. When you order your 23 db gain preamp, order a 10 and a 3 db attenuator pad to go with it. Put the pad on the OUTPUT side of the preamp.
 

doublescan

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Thanks Rich, have read that thread before, I'll revisit it. I find sometimes that re-reading some of these threads helps the super-technical stuff sink in! Trying to overcome the loss from 150' cable, doing ok with a tv amp, but I think it could be better. Likely would be less complex if I would just move the tower closer to the house!
And thanks zz for the info, man this stuff really gets complicated, lol.
 
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