Posts by G4KCM

Hi All, Following this with interest and would like to add a few thoughts...

Currently I use the 30W Spectrian module which is probably not much more than 20W at 2.4Ghz. Due to its class A operation it spends most of it's life keeping the shack warm so I am considering a replacement in due course. Whilst I am an avid constructor my test equipment presently tops out at 1.5GHz and being an LF guy by profession I'm afraid I don't have the skills to design a 13cm amplifier board from grassroots. So I am pleased to see this discussion develop.

I agree with the comments that the SG Labs amplifier looks excellent value for money and as it stands it seems hard to beat for overall value once you factor in the cost of a nice enclosure. The amplifiers mentioned earlier in this thread would be great for the Amsat-DL up-converter and transverters with outputs in excess of 25dBm. I think though that there is a bit of a market gap for an amplifier designed to be driven by small SDRs like the Pluto, LimeSDR or HackRF all of which really need some decent 2.4GHz filtering on their outputs, ideally bandpass but at least lowpass as they are by design wideband devices.

I currently use a SAW filter and Gali-84+ combination in front of the Spectrian as the LimeSDR mini only delivers circa 0dBm at 2.4GHz. I have yet to see any of the Chinese preamplifier modules that many people use to boost SDR output with any bandpass or lowpass filters as they are mostly designed to be broadband. The exception being the rather expensive Analog Devices CN0417 2.4GHz evaluation board that I see some are using which does have an input bandpass filter which is ideal but costly. Whilst modern LDMOS devices such as the MW7IC2725N have on board matching and tailored response is still better to drive them with a clean signal.

So I feel there is a need for a 0dbM input level amplifier with filtering for SDR drive and possibly also for a pre-amplifier type board with some front end filtering for existing power amplifiers. After starting with a mini-kits transverter I'm now rebuilding my Spectrian amplifier enclosure to contain the filtered pre-amp (I'm using a Murata SF2124E with Gali-84+) and USB PTT switching that I use with SDR Console and the limeSDR mini as I personally prefer the SDR route.

I'm also looking forward to the LimeRFE :- https://www.crowdsupply.com/lime-micro/limerfe

73 de Clive, G4KCM

Agree with all previous comments. I have had good luck thus far with Chinese power attenuators but always check them and also allow a 50% safety margin when it comes to power ratings!

As stated Ebay is a good source of ‘professional’ items. I have found a US seller that has some good value items even after adding shipping and duties... Have a look at prestige-test-equipment.

Best Regards

Clive, G4KCM

Hi, Adding a TCXO in the LNB and then a down converter to bring the final signal to 144MHz is a solution I’m very interested in trying. I haven’t opened my Octagon LNB yet so I’m not sure if it is of the 27 or 25MHz xtal variety but see that both frequencies are off the shelf D75F from Digi-Key.

Having only recently rejoined AMSAT-UK I don’t have access to David’s design for the down converter. I would certainly be interested in purchasing a PCB from Luciano if there are any spare and would also appreciate a copy of the original article/schematic.

Clive G4KCM

Hi all, just registered here. Happily my retirement is giving some time to focus on amateur radio. Had a long time interest in satellites but not having any chance to operate for many years. Construction has always been a passion.

73 de Clive