[50mhz] 6m Point-to-Point Distances?

[Chris Boone]

My answers below without leading > ...

-----Original Message-----
>> Questions:
>> 
>> What's a reasonable expectation of 6m mobile-to-mobile
>> direct communications @ 25w - 50w?
>
>  If they're both running 1/4 whips, I'd say 25 miles in mostly-open terrain.

Depending on noise levels, less than 25 miles...10-15 max in flat open terrain in my experience. Even with 100 watts and a noise blanker is highly recommended even on FM...though most ham FM rigs on 6 does not have such, yet their commercial counterparts DO!..go figure.
 
>> How does that change if one station is fixed and the
>> antenna is at 30-35'?
>
>  Probably out to 40-50 miles...
>
>> What about two fixed locations w/antennas both at 30-35'?
>
>  If they are DB-201 antennas, which are 1/2 wave folded-down
>ground-plane antennas, 50 to 60 miles.. if the're running yagis,
>might be up to 100 miles.. better with SSB than with FM, though..

30-35 ft and a DB201 wont cover 50-60 miles base to base; maybe 40 miles if that. Neighbor across the street from me (WA5EFI) when I 1st got licensed had 40ft of tower with a DB201 on top....he and a coworker tried 6m simplex over a 50 miles path...never made it on regular basis

The DB201 is a 1/4 folded monopole groundplane; a folded monopole is a 1/4wl antenna with a second downlead conductor which goes to ground...this provides a ground return since overall length is from the feedpoint is 1/2wl and thus the feedpoint is still a 50 ohm feed and does not see the short to ground but the top of the antenna now sees a DC ground; this method is also used in AM broadcast station on grounded towers but in reverse with an outside skirt around the tower as the driven/insulated feedpoint and the tower, which is the support for the skirt, is grounded for lightning and also allows other antennas/feedlines to be mounted on the tower without causing issues with the AM operation or need of an isocoupler on every other feedline!

A DB212-3 at 300 ft fed by 7/8 Heliax and 100 watt MICOR got more than 70 miles in the main lobe...side (90deg) coverage was maybe 40-50 miles.

Always better with SSB than FM since FM is not a weak signal mode..especially on 2m....you can get easily 20-300 miles on 6SSB with a 50 ft high yagis at each end and 100w...FM is much less due to capture effect and FM not being a weak signal mode.

>> I've read about repeaters using 6m as a backbone but what
>> about control signals and/or digital modes, must that be
>> at 220 or higher?
>
>  As far as I know, you can still run digital on 6m, but hardly anyone
>else runs digital on 6m... and yes, control should be at 220 or higher...

6m is the lowest band 'certain' digital PHONE modes are allowed such as P25 or the C4FM mode by Yaesu (The emission designator Yaesu uses for C4FM, F7W, is NOT legal below 50.1 MHz under current FCC Part 97 rules). Also 9600 baud packet can only be used 50.1 and above..97.3(c) and 97.307 and 97.308 cover what can and cannot be used where. NOTE any emission that carries VOICE is considered PHONE..even if digital so those modes only allowed by 97.3(c)(5) are allowed in subbands designated PHONE and C4FM is not listed as a legal PHONE mode. There is no "Digital/Analog" mention in Part 97...only Data, Image, Voice, etc. in Part 97.3.

6m cannot be used for AUX linking (backbone) on voice systems....and is not recommended...hell the normal rptr subband is not even standard across the US...thanks to 1960s thinking by the ARRL VRAC in the 1990s....for packet backbone, it would be great at 50.6-50.7!! Much longer path than 220 or 440..and you can run 9600 baud. 

As to control (which falls under the AUX rules), 144.5-145.5 and 146.0-148 IS now allowed (has been for couple of years...Kenwood pushed for it to allow their SkyCommand to be legalized).

222.15 and above (except 431-433 and 435-438) are the other bands allowed for AUX/CONTROL/LINK...a 6m rptr cannot be controlled on its input legally...now a 2m can be as well as 220 and above rptrs..

222.0-222.15 is reserved for SSB/CW/data/etc. Rptr inputs are not allowed there and no AUX use is allowed there either (same with 144.0-144.5 and 145.5-146 and 219-220 which are also offlimits for rptrs and aux use)


Chris
WB5ITT