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CPI Range Plus Preamp Review

Wire Weasel

Wire Weasel

Senior Moment
Dec 13, 2008
3,185
841
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I guess I lucked into a brand new old stock mint Communications Power Inc (CPI) Range Plus Base/Mobile Preamp at a swap meet. With factory box. Guy was asking $70 and he later accepted my offer of $60. A local friend got one off of eBay recently and has been raving about it.

These are dual power units. 110V plug in the wall for base use and has 12V terminals on rear for mobile use.

Is variable gain with knob on front. Functions as attenuator as well as preamp. Mine didn't have any paperwork but the friend says it's rated 25db up and down.

I am shazzam impressed with the performance. VERY low noise increase, just big boost to signals. Will take an S 3 reading up to a 15. Attenuator will take an S 5 down to a zero.

I've been looking for a good quality outboard preamp for awhile so I'll be glad I ran across this one.

You will see used ones in less than mint condition for sale for less money on eBay. I don't think I'd want to pay $60 for one in less than pristine condition. I suppose I got a fair deal on this NOS unit.

Anyone know what they retailed for back when they were being sold?
 
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Update. The gain specs appear to be 25db down on attenuation and 13db up.

Brought another station about 35 miles away up from an S 2 to S 14. Sweet
 
What
Wire Weasel said:
Update. The gain specs appear to be 25db down on attenuation and 13db up.

Brought another station about 35 miles away up from an S 2 to S 14. Sweet
Click to expand...

But irrelevant.

I'm massively cynical about the use of preamps on HF. What is the noise level at your location without the pre-amp on and no signals being received? All a pre-amp does on HF is usually make the signal to noise ratio worse so whilst it reads stronger on the S meter it is at best no more intelligible but usually worse. But hey, it makes the meter read higher so it must be good. You should be judging by your ears or with the use of a SINAD meter, not the S meter on the radio. It is all about the signal to noise ratio, not the S meter readings.

If the noise level at your location is above S0, you shouldn't be using a preamp. And given that on 11m the noise level of every single person on the entire planet is going to be at least S1, due to the fact that in absence of all other noise sources the very galaxy itself produces S1, the only way to get S0 is a lossy antenna. Sorting out a better antenna would be more beneficial than using a pre-amp as you would benefit on TX as well.
 
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M0GVZ said:
What


But irrelevant.

I'm massively cynical about the use of preamps on HF. What is the noise level at your location without the pre-amp on and no signals being received? All a pre-amp does on HF is usually make the signal to noise ratio worse so whilst it reads stronger on the S meter it is at best no more intelligible but usually worse. But hey, it makes the meter read higher so it must be good. You should be judging by your ears or with the use of a SINAD meter, not the S meter on the radio. It is all about the signal to noise ratio, not the S meter readings.

If the noise level at your location is above S0, you shouldn't be using a preamp. And given that on 11m the noise level of every single person on the entire planet is going to be at least S1, due to the fact that in absence of all other noise sources the very galaxy itself produces S1, the only way to get S0 is a lossy antenna. Sorting out a better antenna would be more beneficial than using a pre-amp as you would benefit on TX as well.
Click to expand...

Hello yeah I am aware of all you say but if the signal to noise level is nice, it works for me ! Appriciate your input ...
 
Pre-Amps are worthless. They amp the noise as well. Notching and active filtering are the way to go if you feel the need.

People rav about all kinds of stupid stuff that does not make it credible or based in fact. People rave about magnets on their fuel lines of that craptastic Vornado Air Intake stamped steel marvel! LOL It just shows peoples ignorance and how trendy they can be! Any remember the "Pet Rock" or how the Germans love David Hasselhoff? LOL

Oh and lets not forget how rednecks the land over just love them some echo and rave about it! LOL

Mouthballs in the fuel tank and acetone to improve fuel economy and on and on and on.....
 
I'm pretty certain that the CPI unit is not your typical Audio pre-amp.

Back in the day (1977), a company called DX PRODUCTS produced what they called the DP2112A "Phase-Coherrent Low Pass Filter." It was a denoising circuit based on the theory of audio compression and expansion. The audio signal from the receive detector was fed into the 2112, and the output was fed to the receiver's volume control. There was a "peaking control" that was used to adjust the circuit for maximum voice recovery/ minimum noise. I bought one to try out, and was amazed at how it was able to pull weak signals out of the "mud." When I went to buy a few more, their phone had been disconnected. I could see that they used the Signetics NE570 chip as the basis for their circuit. But they covered most of the board in hard epoxy. I was afraid trying to remove it would destroy the board. I was never able to reproduce their circuit. Too bad.

The point I'm trying to make is that not all "receive boosters" are created equal.

- 399
 
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