Topband: 160 RX observations

[Tom Rauch]

> I live 14 air miles from the King of Topband, W8LRL.
> I have been on 160 using a C line, TS-830 FT-920 and now an
> FT-1000MP.  Each rig has had Fox Tango, Sherwood or Inrad filters
> based on who was in business at the time.
> Only with the FT-1000MP and Inrad filters can I be QRV on 160 while Wal is

Maybe we all miss the point. The R4C is a good platform to modify, 
but it requires the correct changes. 

Increasing the injection from the LO in the first mixer of the R4C 
will make the wide-spaced blocking DR range increase. THat 
simple change will increase the wide spaced blocking DR by 10 to 
20 dB. Without that change, the R4C it is certainly no better than 
any other above average quality modern rig for blocking DR just 
outside the BW of the roofing filter!

A narrow first IF filter (like the Sherwood 600 Hz filter or the 6kHz 
GUF filter) will increase the blocking DR ***outside*** the 
bandwidth of the new filter but ***less*** than the BW of the stock 
first IF filter. If the receiver has a 12 kHz stock filter after the first 
mixer and you replace it with a 8 kHz filter, things will get better 
only in the 4 kHz window change! You'll still have fits with people 4 
kHz up and down from you, or wider.

Many people make the mistake of adding a SSB compatible filter, 
and thing they are making a big change. That assumption simply 
isn't true, no matter who's name is on the filter. 

If you replace the first IF filter with a 600Hz filter, the "bad area" is 
reduced 11.4 kHz (more or less) in width. Now that's a worthwhile 
change, because only people within 300Hz of the center frequency 
will hit the very poor second mixer in the Drake. 

That's why SSB-capable first IF filters don't do much on CW. They 
are a waste of money for CW ops. They also have limited 
advantage on SSB, because they aren't that much narrower than 
the original filter.   

Without a 1st mixer mod an R4C is about ballpark with my FT-
1000 and 1000MP...which are about the same. That's why so 
many people report they don't see a difference!

If the receiver is under S/N 18700 or so (has no CW 1.5 position) 
throw it away or totally rebuild it. The second mixer is absolute 
junk, FT101 level performance.

73, Tom W8JI
w8ji@contesting.com



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