[MAMS] MAD weekend, July 2nd

[Dr. Gerald N. Johnson]

When using the Direct TV dish on 24 GHz where it gets hard to point if 
its all used, there's no law that says you have to feed the whole dish. 
Go to a larger aperture feed horn and underfeed it to keep the beamwidth 
manageable. Design the feed horn for a dish of that focal length and 
half the diameter. It will have even fewer and weaker sidelobes (and 
backlobe) and be easier to aim. At a cost of 6 dB signal gain. Aiming 
error and changes in path may easily cost more than that.

73, Jerry, K0CQ

On 6/29/2011 5:28 PM, Lloyd Ellsworth wrote:
> Zack,
>
> My experience, going from one band up to the next. Has been great over
> the years. 1971, 1296 about a watt. APX6. Wow, really great results.
> 24 GHz, became a major difference. Much more of a challenge. 47 GHz
> being about the same. Here in the Midwest, On 24 GHz it seems like
> everything is fighting you. Everything has more losses. Getting good
> power, well, more difficult, more expensive. Finding parts that work.
> WR42, scarce, and expensive. The whole secret seems to be power. As
> W9ZIH says, "power at the microwaves, is not a luxury. It is a
> necessity." Plus, as I will add, test everything. Amazing what decides
> to not work. Best not to assume it is working. Far as propagation, and
> tricks. Well, still learning. What I have observed, 10-20 mile paths,
> are fairly easy, quick. 50 miles with say, 100mW or so, foot or two
> dish, reasonable pre amp, are routine. Two, one watt 24 GHz stations.
> 2 ft dishes, routinely going to make the 60 to 70 mile path across
> Lake Michigan, with good signals. Across the Lake and inland, another
> story. Maybe. Over water is pretty darn good. Water, humidity, can be
> routine problems. However, Rain and snow scatter work. In general, 24
> GHz seems more a noon, Afternoon band, than a morning sunrise or night
> band. Unlike the lower bands. 24 GHz, appears the path has to dry out
> a bit first. At times, many of us have found that signals on 24 GHz
> were better than on 10 GHz, or lower. If you did not or don't try it,
> or just assume, you don't know. Comparison, 10 GHz I would consider
> 100mW 18-24 inch dish, to be good for, oh, 100 miles. 10 GHz is pretty
> forgiving about paths. Plus, you really want to be on at sunrise for
> best results. Lots more things are more easily done on 10 GHz than 24
> GHz. Vegetation is a serious concern at 24 GHz. 47 GHz also. Not
> forgiving. Dish aim can be a concern, but normally, has not proven to
> be a bother for me. Oh, those dish network satellite dishes. They work
> just fine on 24 GHz. Just avoid the ones that came down rough. Too
> many, were used as a "Frisbee" when taken down. Wind up getting bent
> out of shape.
>
> Another reminder comment. Path conditions change. Try to make a
> contact on a path that should work. Is not. Results in a given 15
> minute run, might be poor to non existent. Try, and try again. Things
> change. Half hour, hour later, you might find the band open. No
> problem. Unless you are close, the 30 second 24 GHz contact, is
> unlikely. Expect to take some time. What Don WW8M and I used to do.
> The routine, was first, get within range, and make a contact. Prove
> things are working, first. Then, stretch that string between dishes.
> It is kind of rough, trying to make a 50 mile plus contact, and later
> find the real problem. Something in the radio decided not to work.
> Microwave Activity Day, in part, exists, to try and keep using
> equipment. Find problems before the contest. Make activity. Learn how
> paths work.
>
> July MAD, if there is anyone in range from EN74at, I can be on.
> Otherwise, will save the fuel for the next adventure. Zack, front Ball
> Joints. Yep, looks like Rover here has some similar issues. So long
> trips are off for a while. Need to save up some repair funds.
>
> As gets said. If it was easy, everyone would have already done it. Me,
> I am still learning.
>
> 73, Lloyd NE8I/r
> EN74 etc
>
>