Wideband pre-amplifier II

Medium & long wave antenna discussion
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daveB
Posts: 1239
Joined: 07 Oct 2014 16:49

Wideband pre-amplifier II

Post by daveB » 27 Feb 2018 00:16

Here is another wideband preamplifier - available from cosycave.co.uk. Spec is 17-19 dB gain, 0.7 to 1.44 dB n/f and "it works well from 1 MHz to 2.5 GHz. Using my short horizontal dipole it gives a good boost to signals all the way down to 153 kHz on my SDRPlay RSP1. If I run the dipole barefoot I get overload from strong out of band signals when I up the gain to bring Norway on 153 kHz out of the noise. With the preamp in line and the gain pulled back on the SDRPlay 153 kHz comes through without spurious signals.

Here is the preamp in my test bed diecast box. Lots of connectors/adapters. I decided that soldering on the SMA connectors provided and using adapters would be better for amplifier stability nhan short bits of wire ad earthing points. In order to feed the power up the coax cable I have added a 470uH inductor between Vcc and the preamp output. Checking all the way to 1 GHz there doesn't appear to be any sign of instability.
CosyCave PAS4-5043 preamp.jpg
Note: diecast boxes are blooming expensive I managed to get 2 x Hammond 1590A 90 x 35 x 30 approx from China at £2.48 each to be used on a final version of a preamp project.

David
SDRPlay, AirSpyMini, RTL dongles, SB920s, Yamaha TX930. 5 ele compact yagi on rotator at 18ft agl. FM5 facing east, FM5 facing south, FM3 facing NE, OIRT dipole, 3-ele Moxon vertical facing east.

pe1etr
Posts: 1347
Joined: 07 Oct 2014 00:40
Location: Bangkok, Thailand

Re: Wideband pre-amplifier II

Post by pe1etr » 27 Feb 2018 08:27

I got a Cosycave preamp as part of an RTL-SDR package. I could get it to work well. I left all of the Cosycave set in the UK so I can't try it your way.

Peter

daveB
Posts: 1239
Joined: 07 Oct 2014 16:49

Re: Wideband pre-amplifier II

Post by daveB » 27 Feb 2018 13:23

Some follow up information and data.

This pre-amp uses the same chip as the LNA4ALL - but costs £6.45 compared to 20 euros (about £17). It is amazingly simple to add a 470uH inductor to provide power up the coax - I presume because the on-board voltage regulator circuitry does any decoupling there is no instability.

Comparing low frequency performance with the other preamp - based on the INA-20186 which is advertised as covering the range 100kHZ - 2 GHz, the cosycave preamp gives a much better performance on the short dipole I am using.

SDRPlay RSP1 - SDR# build 1361. LNA off, system gain reduction -78dB. [Running the LNA with a high gain external pre-amp will cause overload/images]

On RTE 252 kHz
cosycave PSA4-5043: -40 to - 35 dB, noise floor around -78 dB. S/N ratio around 40 dB
INA-20186 preamp : -50 to -55 dB, noise floor around -78 dB. S/N ratio around 20 dB

This morning around 10:30 am I was listening to Algeria Chaine 3 on 252 kHz which was over the top of RTE.

I can't be bothered to do loads of comparison at this time because I have to swap over the circuit boards - but I shall certainly be testing it with the planned shielded loop. I suspect, based on all the stuff I read that the PSA54-5043 chip has a much higher impedance at low frequencies. It's design range for 50 ohm impedance, without external matching, is 50 MHz to 4 GHz
SDRPlay, AirSpyMini, RTL dongles, SB920s, Yamaha TX930. 5 ele compact yagi on rotator at 18ft agl. FM5 facing east, FM5 facing south, FM3 facing NE, OIRT dipole, 3-ele Moxon vertical facing east.

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