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AO40 lids?



Ed AL7EB wrote:

Why some stations persist in running too close to the MB level is hard to
say (maybe they can't hear well, maybe they don't care, maybe it hasn't
been sufficiently explained to them).

Wayne W9AE replies:

I think the major reasons are TREES and INTERFERENCE.  Listening to conversations on AO40, it is very common for at least ONE station in a 2-way QSO to be pointing through a tree and/or getting significant interference from a cordless phone.  My location has many trees, but cordless phones are far enough away that my noise blanker reduces the interference to "barely audible".  My most recent portable operation was at a location where the noise blanker was only able to reduce the cordless phone pulses to the level of the AO40 beacon.  Setting the receiver AGC to "fast" helped a little bit, but raised the noise floor.

Big dishes have enough gain to hear through some trees.  But big dishes are usually mounted close to the ground where tree and building obstruction is much worse than a rooftop or tower location.  Not necessarily a net improvement compared to a small rooftop or tower mounted dish.  Some people solve that problem by using a both a "big low dish" and a "small high dish".

For many of us, the best solution is a V or U downlink.  I look forward to the V downlink on P3E.  Trees won't affect me, and I won't have perpetual interference from cordless phones.  V and S downlinks are very complementary because they have "opposite" advantages and disadvantages.  V-band requires a long antenna, but the antenna has a small wind load, the radio equipment is simple, and there is no tree attenuation.  S-band allows a "small" antenna, but has large wind loading, significant tree attenuation, and significant interference from unlicensed devices.  Each person assigns a different value to each of these characteristics.  People with big trees and no tower usually prefer a V or U downlink.  Apartment dwellers usually prefer microwaves.  But the recent proliferation of unlicensed devices has made S-band an undesirable downlink for almost everybody.

Wayne Estes W9AE
Mundelein, IL, USA
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