Topband: Re: 160m RX

[Tom Rauch]

> W8JI claims:

Not claims, measurements.
 
> >I have an R4C modified with balanced mixers and solid-state IF
> >amplifiers that overloads at 23 dBm (2-1/4 volts) input, yet has -145 dBm
> >noise floor (12.6 nanovolts). It's still triple conversion. The design
> >was just converted using modern mixer and amplifier technology.
> 
> I wonder why one needs 12,6 nV sensitivity up to 50 MHz?  Using wrong
> oversensitive semiconductors for GHz range?

What does it matter where the noise floor is, when the upper end is 
better than anything else you can purchase? All that means is the 
receiver is very very quiet when the antenna is disconnected yet 
still has enough gain.

Any reduction in gain can easily be accomplished by adding an 
attenuator pad when needed, but you can't fix a overload prone or 
phase noise limited receiver with a pre-amp. 
 
> G3RPB explained the relation between IMD and phase noise in QEX letter.
> FT-1000MP satisfies these criteria at +30dBm IMD with all the gadgets
> added.

I'm not sure I understand what you are saying by "relationship 
between phase noise and IMD" and "all the gadgets added". Was it 
a recent QEX?

My 160 meter requirements are more taxing than most other 
bands, because of the system I'm using and where I'm located. I 
have to receive some very weak signals right next to very strong 
transmitters with my antennas pointed right at the strong stations.

Other people probably have the same situation, because first hop 
160 meter signals are pretty strong at times...and DX signals pretty 
weak. It sure used to be better when the DX worked split!

73, Tom W8JI
w8ji@contesting.com



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