WHAT IS THE BEST ANTENNA (ARRAY) FOR MS?
Part 1 - COMMENTS BY VE7BQH
(NOTE - this is based on tests done in the 1970s.
Be sure to see the updated comments at the end).
You have to keep E and H plane beamwidth clearly in your mind, NOT just
mixes of different antennas.
You certainly are clear when you talk about beamwidths in relationship with
what is good for MS.
Before I give you some thoughts on antennas, let me say I ran meteors with
Mike Staal for many months back about 1970. We both were using 160 el
collinears. End result was these were POOR antennas for MS. Yes, we got LOUD
pings but not much of them. The distance was optimum at 900 mi.
The old arguments about certain antennas were somewhat flawed as the Yagi
designs of the type you mention were not good. The collinear was very
successful in those days because it actually worked like it should. The
Yagis, W2NLY included were very so so compared to today's antennas.
Today that is not the situation. Yagi design IS perfected, PERIOD!
My conclusions were like others, you cannot use an antenna with too narrow a
beamwidth. You miss to much. So you have to strike a happy medium.
A box of 4 W1JR 8 el antennas (12') has 17+ dBd gain and a 18 X 20 degree
beam width. A single 7.7 WL Yagi (52') has less gain and a wider beamwidth.
So you can see by today's standards, the box of 4 is not low gain or wide
beamwidth. Gain and beamwidth are directly related.
The thing that I observed that worked the best for longer haul stuff was to
stack 2 X 3.6 WL - 4.0 WL Yagis in the H or vertical plane. This does NOT
lower the angle but it does concentrate the power in the main lobe. I saw
this arrangement used very effectively by stations looking out over 1100 mi.
In summary it is an age old struggle to offset gain vests beamwidth. It
would appear about a 4 WL Yagi or a M^2 2M5WL at max is as far as you can go
with the vertical stacking a good approach if you are wanting to "stretch
your legs". A 20 element CC collinear is interesting however, in that the
gain is only 12 dBd BUT the beamwidth is E = 48 and the H = 27. In other
words it is narrow vertically compared to very wide horizontally. This is
ideal for MS. A pair side by side would make excellent long haul MS array as
the gain would be 15 dBd and the pattern 24 X 27.
PART 2 -
The above was written by VE7BQH, based on his MS experience in the 1970s.
Since then, things have changed considerably!
Here are my comments on the current thinking concerning MS antennas.
About four years ago, as HSCW MS was becoming established over here, I queried
some of those who had been active on MS some years ago, and who had experimented
with antennas more than I have. The question was being asked again - which is better,
a lower-gain array with a broad front lobe, as has been recommended in the past, or go
for more gain with a narrow front lobe. They all agreed that the lower gain, broad lobe
array was best for MS.
But in the past few years, we've realized the problem with the old recommendation.
In the past, the only meteors usable were those that gave overdense (or very, very
good underdense) bursts. These are very infrequent, even during the peak of a major
shower; but they produce a strong reflection. So, for SSB operation during the peak
of a major shower, the lower-gain, wider-lobe array may still be best.
But for HSMS, which uses only the very tiny underdense pings of sporadics, the
opposite seems to be true. Since the typical ping is just above (or below!) the noise
level, another 3 dB of signal strength can make the difference between having a tiny
but usable ping and not having anything at all. There are lots and lots of those meteors
out there, so the number of them isn't that important most of the time. Even the lower-power
station will usually eventually get thru. But if you can increase the signal strength, the
number of detectable pings increases greatly.
You should hear the number of pings on W5UN and some of the other "big guns"
when they operate with their arrays on the horizon!
So which is better for you to use? This depends primarily on the modulation
mode you primarily use. If you are stuck with only SSB and/or slow CW which need
overdense bursts, you need to catch as many of these bursts as possible. Signal strength
is of secondary importance. So a broad front lobe is needed.
However, if you are using one of the high-speed meteor scatter modes, you are working
with the large number of very weak pings, right at the noise level. You can increase both
the strength of these pings, and also the number (by getting them above the noise) by
increasing your ERP. Thus, an array with higher gain, at the sacrifice of the broad front lobe,
(What is the best time for MS operation? Click and see).