75 or 80m?

[k4kyv]

Ever since the band was expanded, there seems to be a question of where 75m ends and 80m begins.  Some say all the phone band is 75m and what's left of the CW band is 80m.  Others say there is some arbitrary frequency that forms a dividing line between the two. I frequently hear the "old" phone band from 3800-4000 referred to as "75" and the expanded portion down to 3600 as "80".

Wavelength is calculated in metres by dividing the frequency in megacycles/second into 300.  75m is exactly 4 mc/s.  3.5 mc/s is 85.7m.  So the bottom end could just as easily be called 85m as the top end is called 75. 80.0m would be the exact wavelength at 3.75 mc/s, the exact midpoint of the band.

So logically, one might say that 75m is the part of the band above 3750 kc/s and 80m is the part below.  But we need to look into the historical aspects.  Originally, the phone band was only 50 kc/s wide, and was down at the low end.  That was a few years before my time, but I remember reading that it was 3500-3550 (or was it 3550-3600?).  Then sometime in the early to mid 30's it was moved up to 3950-4000.  It makes perfect sense that it would have been called the "75m" band following the move, since the entire phone band was so close to that wavelength.  Over the years, the phone band  has expanded, until it now occupies the range of wavelengths from 75.0m to 83.33m.  The CW band now runs from 83.33 to 85.7m. This is almost an exact mirror image of the situation in the late 20's/early 30's, so maybe to strictly follow historical precedent, the phone band should now be referred to as 80m and the CW band, 85m.

OTOH, the guys in Europe refer to the whole band as "80m", but the vast majority of their allocation is below 3750.  I tend to call the whole phone portion "75m" particularly since I have only one automatic CQ recording that says "CQ 75" and none that says "CQ 80".

Call it what you like, but since "85m" sounds a little strange, most people will probably continue to call the phone band 75m and the CW band 80m.  I believe that is how the FCC lists it in their frequency table.  

This urgent, earth-shaking issue is a good topic of discussion for those with time on their hands, or a good for a "dead band" activity when the band is filled with QRN as it is right now with T-storms extending all the way from Florida to the Great Lakes.

[WD8BIL]

Now I can sleep at night Don. Thanks!

Seriously, I always refer to anything below 3750 as 80M !

[K5UJ]

Now I can sleep at night Don. Thanks!

Seriously, I always refer to anything below 3750 as 80M !

I did that at first when CW and data exclusivity started ending at 3600 but now I just refer to everything from 3600 on up as 75 m.  to me 75 means phone.  I don't attach much exact frequency meaning to it because I knew if you did the wavelength calculation you'd find 3.5 to 4 MHz no where near 80 or 75.  Well, 4 MHz is 75 m. but 3.5 is around 85 m.   7 MHz is close to 43 meters.  I happen to like 159.151 meters 

[KX5JT]

   Deja Vu Don

[The Slab Bacon]

But what does it REALLY matter?? Most of us just simply call "CQ AM phone" and simply announce what frequency we're on. I have never lost even one second of sleep worrying about it.    

Don,
       You need to go back to work, you just have too much free time on your hands.
Or your wife cant find enough "honey do's" for you. Doesnt the shed still need painting??
    

                                                  The Slab Bacon

[K9ACT]

I don't have a whole lot of experience with commercial equipment but I don't recall ever seeing 75 on a front panel.

For another factoid, I had never even heard the expression "75 meters" before getting back into the fold about 5 years ago.

I see no more value in differentiating between 75 and 80 than in reverting back to wavelengths to describe where we are transmitting or listening.

The 80 meter band is twice the frequency of the 160 meter band and half that of 40 meters.  75 meters is a strawman that serves no useful purpose.

js