[1000mp] confused about mods

[Michael W Elliott]

Hey Bill
seems like all this got me confused also.  I like to work some contests but like the DXing also.
 
Sort of like I tried to tell someone - transceivers modified are great but no adequate antenna makes for no hearing; 
 
But 
 
what I have read it seems like you also need the optional filters installed in the rig to get the benefit. Can someone clear up this point or tell us the bare minimum you need in other filters.  Also does this work better with CW versus SSB???
 
Must be something to this new front end stuff if all the big guys are selling their IF mod boards.
  
Bill Tippett <btippett at alum.mit.edu> wrote:
W3JJ wrote:
>So how do I decide whether to buy the roofing filter mod or the IF mod?
If I don't really work contests but I want to work weak dx stations, then is
the IF mod the better choice? Or will the weak dx signal be buried by 3OIMD?
It seemed to me that my difficulty working VU4 was due to their weak signal
rather than 3OIMD. But then what does 3OIMD sound like if it is caused by
many signals up and down the band? The ARRL reviews says it sounds like
"junk" but I'm not sure exactly what this means.

On CW, IMD sounds like "bleeps and bloops"...like someone
sending CW in a different code than Morse. It is caused only
when both interfering CW signals are "ON", so it sounds very
strange like code with random length characters. On SSB, it
can be the by-product of just one strong SSB signal. Since
the signal is composed of signal components across a ~3 kHz
bandwidth, these components can mix with themselves to cause
IMD. Add 2 strong SSB stations and it gets worse. My "guess"
is IMD on SSB simply sounds like an increase in your noise
floor. A very quiet noise floor was the most striking thing
I noticed about my Orion the first time I used it in an SSB
contest, after using an MP the previous 5-6 years.

For the average DX-er, I would probably stick with the
original 70 MHz IF mod which decreases background hiss. For
low-band DX'ing or contesting, I would go with the roofing
filter. If you want the best of both worlds, you may need to
consider a different rig.

73, Bill W4ZV
_______________________________________________
1000mp mailing list
1000mp at mailman.qth.net
http://mailman.qth.net/mailman/listinfo/1000mp


Michael W. Elliott
THE INSIDE ADVANTAGE -
RETIREMENT - LEISURE, REST and ONLY ELECTRONIC MAIL PAYMENTS
Servant to Bridgett, Collin and all my Creditors
St. Louis County Missouri