[NCARC] 6M Sporadic E propagation for the Summer, the FUN band!

[Dan W7RF]

Many of you have 6M capabilities as part of multi-band HF or VHF/UHF radios.
Some radios are all mode, some FM only.

Either way, there is LOTS of fun to be had using 6M when the band is 
open. The most common mode of propagation is Sporadic E. This is where E 
layer reflective "clouds" that reflect 6M and 10M (and sometimes 2M) 
form and dissipate. When they do form, they can provide incredible 
signals to distances from about 500-1000 miles away for "single hop" and 
more than that for "double hop".

Where to listen:
50.125 USB (this is the main SSB calling frequency)
52.525 FM (mail FM calling frequency
50.400 AM (main AM calling frequency, much lesser used than above)
50.300 FM (lesser used FM frequency, designed for use by those with more 
narrow bandwidth antennas)

Just put your radio on one of those top two frequencies and squelch out 
the background noise
Some other tips:
Locally we have been using mostly vertical polarization for line of 
sight propagation (remember that for local communication using the 
opposite polarization will result in a 20 dB "cross polarization" loss). 
Many locals have been heard and worked on 52.525 FM as well as 50.130 USB.
For any propagation mode other than local line of sight, polarization 
does not matter.
When the band opens, it is OK to make a few contacts on the calling 
channels but then establish a frequency above that and call CQ or answer 
someone else's CQ.
When the band opens there may be USB signals all the way up to 50.250 or 
more!
CW is generally below 50.125

There is no good way to predict an opening except being there. Listen 
and call CQ from time to time. Remember, the band MAY be open but we are 
all just sitting there listening!

When to listen? Almost ANY time of the day or night with a higher 
possibility of success in the early/middle afternoon to evening.

Antennas:
A simple dipole or vertical will work well.
I use a Yagi that is part of the SteppIr multi-band design. for best 
performance on 6M
I ALSO use a homebrew vertical dipole, Why a vertical dipole? It is 
vertically polarized for local work AND it is omni-directional (you 
never know WHERE the opening will be).
You could open your wallet and buy something but why not learn and BUILD 
your own?
Yagi's, verticals and dipoles (vertical or horizontal) are all very easy 
to build and lots of info on the web or in those old things called books!

Feedline: For 75 feet or less, use a minimum of RG-8X (mini-8). I use 
LMR-240 for the vertical dipole.
Connectors: Any RF type will be fine or no connector at all on the 
antenna end.

How high off the ground does my antenna need to be?
As high as possible for vertically polarized local work (line of sight)
For sporadic E (and F layer or Tropospheric ducting {tropo} propagation 
modes) about a half wave or more, a half wave is only 9.3 feet based on 
50.125.
Remember the formula to calculate a half wave dipole? 468/f in MHz = 
half wave in feet. So, 50.125 MHz is 9.33 total length (cut this half, 
put in a center insular and line isolator 1:1 balun (as we should for 
ALL dipoles and verticals and Yagi's, etc), then feed with 50 ohm coax.
Since a half wave is a bit less than 10 feet, I suggest at least 10 feet 
off the ground.
My vertical dipole is 20 feet off the ground to the center insulator. I 
use this when I am just listening for an opening and sometimes switch to 
the beam and sometimes just work the stations using that dipole.

Mounting:
When using the vertical dipole, one much take care to route the feedline 
away from the center at no less than 45 degrees downward slope. I mount 
mine just plugged into some schedule 80 PVC pipe to fit the outside 
diameter of the vertical dipole tubing.

A standard horizontal wire (or tubing) dipole is fine as well but will 
have a bit of a pattern broadside to the elements. A 1/4 wave or half 
wave or 5/8 wave vertical (or stacked versions) with proper impedance 
matching are also possible but a bit more work to build. If you build a 
horizontal dipole, orient the elements N-S for maximum E-W USA exposure.

NOW is the time to start listening and enjoying 6M!
The best seasonal times for sporadic E are May thru September (and again 
for about 6 weeks from Dec to Jan) with a peak of June and July.

If you have any questions, let me know. I also hope to be on the Tech 
net this coming Monday night.

Research and learn!


C U on the "magic band!


-- 
73, Dan W7RF