[Fourlanders] 2m Antenna comparison

[Sherman Banks]

I would think the take off angles to be more significant at 6M than at 2M. Remember my analysis was at 6M.

For those interested, the analysis of Bob's QTH that I gave at the 6M BBQ can be downloaded at aa4xg.com.



> On Dec 30, 2014, at 11:25 AM, Ron Rogers <ww8rr at charter.net> wrote:
> 
> OK...here's my initial thoughts without further facts to confirm or refute.
> 
> The only way to truly compare antenna performance is by using the same feed
> line for testing of both antenna sets. I would say that the majority of the
> signal difference is due to differences in feed line loss of both antenna
> arrays.
> 
> If I remember correctly, the feed line going to the horizontal antennas on
> Blackhawk is made up of about 150' of LDF4-50 (2 pieces with a jumper),
> 50-60 feet of untested RG-8 "something" from the hard line up to the
> antennas, another short jumper in the shack, etc. If everything was perfect
> and met specs, that's at least (theoretical) 3.8 db loss in the feed line
> run at 144 MHz. and that's significant !
> 
> Until you actually measure under some power with a pair of calibrated Bird
> 43 meters at each end of the individual feed lines you will not know what
> your true system losses really are.
> 
> At this point I would have to say that the EME antennas having much shorter,
> and newer feed line give them the real advantage, no matter what the height
> is.
> 
> Ron
> WW8RR
> 
> -----Original Message-----
> From: Fourlanders [mailto:fourlanders-bounces at contesting.com] On Behalf Of
> w4zst at windstream.net
> Sent: Tuesday, December 30, 2014 10:43 AM
> To: fourlanders at contesting.com
> Subject: [Fourlanders] 2m Antenna comparison
> 
> Here's some interesting results for the group to ponder on.
> 
> Johnnny's 2m EME antennas have been up here at my QTH for about 3 months
> now.  They are two M2 2MXP20 cross-polarized antennas mounted on his tower
> trailer with an AzEl rotor, 12' separation on a horizontal boom (fiberglass
> extensions).
> 
> We have used them exclusively on horizontal polarization so far for all the
> EME Q's we've made, because I was using my transverter with common output
> rather than his with separate RX and TX connections.  This was done for
> trouble-shooting purposes as we had some problems with his preamp and
> transverter and I had bypassed the H-V relay for convenience.
> 
> Last week, Johnny and I put up the club 2m beams for the contest.  The pair
> of M2 2M9SSB antennas that we have been using on the BlackHawk tower trailer
> stacked vertically and at about 45 feet right now.
> 
> What I found interesting and would like your observations on were the
> results I had on last weeks Monday night 2m net.  I had an AB switch from
> the 2m station to be able to switch between the contest antennas and the
> horizontal EME antennas.  Note that the EME antennas are only about 20'
> high.
> 
> I followed the net control stations directions and copied almost every
> station that checked in from EL96 to EM77 and couldn't tell any difference
> switching between the two set of antennas.  The only two net check-ins that
> I couldn't hear were uncopyable on both sets of antennas.  those stations
> were North of Charlotte.  Of course, since net control is about 65 miles
> East of me, there would be times that stations pointing toward him might not
> have been optimum for me.
> 
> Anyway, I was pretty surprised that the much lower EME antennas performed so
> well here.  Maybe it has to do with the pretty rapid dropoff of terrain from
> the hilltop.  That's what Sherman said was the reason he recommended the
> height for the 6m antennas, both here and from the mountain.  All the leaves
> are off the trees right now too, so that may also be a factor, but I've had
> Johnny's antennas on for the monday night 2m net many times in the last 3
> months before they started falling.
> 
> I have copied the FL checkins to the net off the side of the EME antennas,
> copied stations in central AL off the back and even the station in EM77 in
> KY off the back of the antennas.
> 
> I am planning to leave the 2m EME antennas and station set up for the
> contest as it is expected to be a good condition EME weekend and we may be
> able to get some good multipliers out of it.  I also plan to listen with
> that station while Kos is on 2m with his station and the contest antennas,
> just to make some futher comparisons.
> 
> I also copied K8TQK last night 59 on the EME antennas, pointed right in to
> the house!!
> 
> Either the 2m EME antennas are magic or the height is special.  It does make
> me want to get a pair of them for myself to set up here permanently for both
> EME and terrestrial!!  And actually so far, they've only been used with
> H-pol.  I did change them last night to V-pol when I had about 50+ degrees
> elevation and sigs off the moon were stronger with V-pol.
> 
> Let me know what you think about this antenna situation.
> 
> Thanks, Bob
> 
> 
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