[Premium-Rx] New Membe/Cubic R-3030A

[w3jn]

Hi list, as a new member I'd like to introduce myself.  I've been a ham since '75; my original call was WB0POZ but I'm now W3JN.  I've been messing with receivers since my first (a National NC-173) when I was 14.  Collection now consists mostly of boatanchors, but I have several premiums including a 651S-1, a Racal 6790/GM, and the subject Cubic that just arrived on the doorstep last night.  I'm an electronics engineer for the US Department of State.

With those banalities out of the way, I've read a number of threads on the R-3030A on the archives (which is what prompted me to apply to the list).  My obsevations after a few hours on this radio:

1)  Yup, it has keyboard debounce problems.  First thing I'm gonna fix, thanks to the fine work researching this problem by the Premium-RX members.

2)  Audio hiss on AM only.  What's up with THAT?  I see no obvious reasons for it looking at the schematic- and both receivers have that problem

3)  Don't mount this above another radio with an active power xformer.  Found out the hard way that the synthesizer VCOs will nicely FM with coupled AC.

4)  Wonderful sensitivity, decent selectivity, and it has passband tuning (a rarity in a professional receiver!).  I don't find the ergonomics all that awkward.

5)  Picks up noise from the keyboard.  Mine is missing the top cover; presumably, this will help as will hooking it to a real antenna instead of a wire slung along the floor.

6)  Not the quietest receiver I've ever used.  Looking at the synth schematic, there's a bunch of voltage regulators that are either inadequately bypassed, or arent bypassed at all (the 78L? feeding the D/A converter Vref has no bypassing at all - and all that noise goes right to the VCO).  ANother poor design choice is using clipper diodes on the VCO.  Ulrich Rohde compared VCOs with and without clipper diodes in his book on synth design - there's at least a 20 dB difference in SSB phase noise.  I'm awfully leery about removing the diodes, though, because this could cause the FET oscillator to exceed its Vgs.

Overall, I'm pretty happy, especially considering what I paid for it, and it was advertised as-is.  

I'd sure like to hear any comments from members that have cured the AM hiss problem and worked on reducing the synth phase noise on this great radio.

73 John - W3JN 
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