[R-390] R-390A On 160 Meters

[Tim Shoppa]

On 160M, sensitivity is really not the issue. The
issue is how the receiver deals with intermod from
local BCB stations and whether the filtering system
rings when hit by noise.

The 390A is certainly the winner in terms of
freedom from intermod thanks to the tuned front-end.

Modern ham crystal filters or DSP concentrate very heavily
on shape factor, which is great for SSB in crowded
conditions but can cause horrible horrible ringing
on CW on the low bands.

Not all crystal filters or DSP systems concentrate
only on good numbers for shape factor... but almost
all ham rigs do. That's a shame. A linear-phase crystal
filter doesn't have nearly the shape factor but is far
far better for CW listening in noisy conditions.

In my experience the 390A's crystal filter
(you didn't say what bandwidth you were using) has
a poor shape factor, which makes it look
not-so-good in a technical comparison of numbers
but makes it markedly superior for actually
listening to CW.

It is very possible that with some attenuation that
your solid state rigs could have done better on 160M.

12M, that's where noise floor starts mattering.

15M was surprisngly open to Europe this past weekend
for the ARRL DX CW contest.

Tim.

NA5DX writes:
>>> "Bill Breeden" <breedenwb at cableone.net> 2/23/2009 11:03:21 AM >>>
> I had an experience over the weekend that I thought I would share with the group.  I have a fine EAC R-390A from the 1967 production run that I purchased from Bill Neill a few years ago.  I have never performed an alignment on the radio, but have spot checked the sensitivity on various bands of interest with an HP 8640B and the sensitivity appears to meet or exceed the specifications everywhere I checked.  While listening to the K5D DXpedition on 160 meter CW this weekend, I found that my R-390A could hear K5D when my FT-920 transceiver and my NRD-525 receiver could not.  At the time, all three were sharing the same antenna via a Stridsberg MCA104 receiver multicoupler.  While I have made this type of comparison a number of times in the past, this is the first time in my experience that my R-390A has clearly outperformed the receiver in the FT-920.  My FT-920 has an excellent receiver and always outperformed my NRD-525.  I made the same comparison between the FT-920 and the R
 -390A on 12 meters yesterday afternoon, and the FT-920 may have had a slight edge there, but it wasn't as dramatic as the 160 meter comparison.  I realize that the alignment on the R-390A is a band by band issue, and looking back at my notes, I don't see that I have ever checked the sensitivity on 12 meters.