[TowerTalk] Mosley Antenna Question

[Jim Brown]

On Sat,2/21/2015 11:08 AM, Rick Stealey wrote:
> We can see there is still a lack of consensus as to the value of a few db, for one thing.

There is no question that 2dB matters when conditions are marginal. I 
have personally verified dozens of examples during contests.

> And, at least obvious to me, it is nearly impossible for a lone ham, with only one tower, to judge the gain of two yagis - one that he owns now and one he previously owned.

Correct. The only way to do this is with some sort of rigorous testing. 
K7LXC and N0AX did that around 2000, and we can buy and study their 
report. Or we can bury our heads in the sand, and wear ourselves out 
patting ourselves on the back for the wonderful buying decision we made 
on buying X antenna on which we works Y number of countries.

> Not taking issue with the results of the yagi comparison that has been referred to here.  In fact, let's assume for sake of discussion some yagi is on the market that DOES have some deficiency that results in loss amounting to something like 2 db.  IS IT POSSIBLE that not just one, but a very large number of users would not know this from on-the-air results?

The only practical way to know this is with some disciplined sort of 
measurement. Few hams even understand how to do this, let alone have the 
resources to do it.

> Another example, so you might see where I'm going with this - say something happened and your 1500 watt amp was only putting out 1000 watts for the last month but you didn't know it.  That's about the same as a 2 db loss.  Do you think you, and 5,000 other hams with a similar situation would have still worked K1N?  And the Cocos group?

There is more to ham radio than a DX pileup.  The ARRL CW DX contest is 
on, and I wanted to see what I could do with the 2-el 80M wire Yagi that 
I had just raised to 135 ft. From my QTH just south of San Francisco, EU 
is tough for me, so that's where my wire Yagi is pointed. Modeling told 
me that the increased height was worth about 2dB, and the reflector 
about 3 dB.

I worked a couple of EU stations around their sunrise -- CT3, EA5 -- 
then went to bed and set the alarm for an hour before my sunrise, hoping 
to catch a long path opening to northern EU. For long path, I switch in 
a stub on the reflector that disables it, making the antenna a dipole.  
I started calling CQ, and at first worked JAs and UA0. The effort paid 
off -- three EU Russians, all three of which I could barely hear, and 
could definitely not have worked with even one dB less.

Here's a rule of thumb for you -- any time you work a station that you 
can barely hear, or who can barely hear you (perhaps due to his local 
noise), you probably would not have worked him with 2dB less signal.

73, Jim K9YC