[PVRCNC] Jan/Feb NCJ

[Pete Soper]

Two things to add to this. Brian's example was for European DX with 80 
meters and for that a specific set of arrival/takeoff angles are 
important ("most of the time", as it's statistical of course). So what 
I've been doing is to focus on the differences between antennas within 
the range of "angles of interest." There are also "angles of extreme 
disinterest", so a huge difference between the 80m dipole or yagi 
relatively low to the ground is that there is a great deal of gain for 
high angle signals. For other antenna types there may be very low gain 
for high angles. So this means while you're trying to pick out the 
European station there may be very loud "local" signals with one antenna 
that are much quieter with the other antenna. So I guess this is a kind 
of signal to noise figure of merit, where we define noise in this 
particular case as "Joe and Bubba in Georgia discussing whatever."

Amen to Howie's bandwidth observation. The trouble with some of the 
"clever' wire antennas I've been studying is their bandwidth is unusable 
for contesting on 80.

I still have a coax stub for 15 meters that I used with that old Russian 
amateur satellite that transmitted on 10 and received on 15. Putting the 
15 meter stub inline with a receiver on 10 meters allowed listening 
while simultaneously transmitting on 15. It attenuated the 15m signal 
maybe 30-40db, enough to avoid blowing out the 10m receiver's front end. 
The sharpness of attenuation is directly related to the loss of the 
coax, so I guess a little piece of hardline would make the best filter.

I worked out a very interesting design recently that puts a 40 meter 
bobtail curtain inside an 80 meter halfsqure. I was amazed to find very 
little interaction, so this combo would play nicely together, according 
to eznec. I've managed to get a rope at 100' and am working on a second 
one at 75' and this would be perfect for this set of wires,  exactly 
broadside to you know where for DX contests from this area.

Then I thought of the people factors. I was OK for safety, as the high 
potential ends of the elements hanging down wouldn't be closer than 
maybe 12 feet up and the current maximums were all so far from the 
ground I figure field strength isn't an issue. But these two sets of 
wires would be over the front of my house and one mental image of the 
appearance in daylight made me realize neither Jenny or I would be happy 
with it. But according to eznec it would have been *killer* for DX. :-) 
So I'm falling back and regrouping and putting a 40/80 trapped dipole on 
the 100' end of the span while thinking what else I can do and looking 
for more out of the way trees. Of course wire on 80, even near 100', is 
much more of a local antenna and would be a good example of bad "DX 
signal to local noise" ratio. But we make the best of what we have.

-Pete