Tuesday, 15 March 2011

4m Station Pre-Amp.

Recently I got a new Pre-Amp from Spectrum Communications. Model Type: RP4S.
Here are some details on the Pre-Amp:
STATION RECEIVE PREAMP, 125W through rated on transmit. RF & DC switched 10-26dB panel adjustable gain. 4m model use BF964 with noise figure under 1.5dB. Over-voltage and reverse voltage protected. Protected against transients and EMP at input and output ports.
PCB size 68 x 46 x 28mm. 
Purpose made box 76 x 70 x 38mm (Fitted with SO239 connectors. DC supply 13.5V 80mA.) Type: RP4S. PCB Kit £20.00, PCB Built £30.00, PCB & hardware kit £35.00, Boxed Built £57.00.

The unit itself is well made with a rotary knob for adjusting the amplifier gain and a switch for turning the amp on and off. There is a red led which glows low when on RX mode and goes bright when on TX. On the back there are 2 SO239 sockets, TX and RX as well as the red and black power lead.

Inside the circuitry is well put together, here is a photo of the inside.

I have tried it out on some of my 4m radios, Yaesu FT-847, Ascom SE-550 and the Anytone 5189.
I tested the 4m pre-amp last night and it is able to pull a signal out of the noise, for example can get a signal from where you could hear nothing..
I had Jim 2I0SBI on mobile 4m, I then put full attenuation on the FT-847 so that he disappeared, even with squelch open all I could hear was noise, no trace of a signal. As soon as I put the pre-amp on (on the minimum setting) he appeared out of the noise.
With pre-amp on full he was fully quiet.
The only thing is that with the pre-amp on, even at the low level it increases the floor noise level so that the squelch on the Ascom will not shut off, but squelch level can be adjusted on the Ascom. I noticed it more on the Yaesu FT-847 where the signal meter stays at Zero, when the pre-amp is at minimum but the signal meter rises to a Seven when on full.
The Anytone worked well with it as it seems to have a very low noise to signal ratio.
Having said that I would leave it on the minimum and only use full if needed.
So far I am impressed with it.

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