On Sat, 22 Nov 2003 10:23:52 +0500, "John Doty" wrote:

|In article , "Wes Stewart"
wrote:
|
| Heh heh. When the guys from MIT come out to argue with you, you know
| you're in trouble. But fools rush in...
|
| I have made thousands of measurements in anechoic antenna ranges and I
| have never seen a difference between measuring s21 and s12. (Without the
| circulators, and accounting for mismatch effects of course)
|
| Where did I go wrong?
|
|You didn't ionize the air in the range :-)
|
|Seriously, for your purposes you did nothing wrong. Just don't call
|reciprocity a "law", OK? It's a useful idea of wide applicability, but
|physics does not require it in general. Calling it a law confuses people.

I never made that statement.

[snip]
|
|Directivity matters equally for receiving and transmitting. Was your wet
|string as directive as your other antenna?

I don't know. Remember I live in the desert; I couldn't keep the
string wet long enough to find out.

|2 meters is also quiet enough
|that there's not much room for inefficiency: in some directions the sky
|temperature is 200K.

Yep. Love that quiet sky.
|
|
| I have observed the same on 20 meters. My Yagi at a modest height of
| 50 feet is *always* better than an indoor wire.
|
|Throw a thin wire with dark brown insulation over a tall tree, up over one
|side, partway down the other (shaped like a "?"). Tie it in place with
|nylon fishing line. It will be invisible unless you're very close. Couple
|to coax with a grounded 9:1 broadband matching transformer. Bury the coax
|run to the house.

Tall tree? What's a tall tree? The best I have is some 35 foot tall
Saguaro cactii. They're a bitch to climb, although when the coyotes
went after the cat, she managed. Let's see, I could tie a string to
the cat's tail and find a coyote.....

[snip]

| In the general sense of h-f to microwave, I stand by my claim.
|
|For the special case of confinement to a small number of narrow bands (as
|in ham radio), you are reasonably correct above 10 MHz. To me as a
|hobbyist listing to LW/MW/SW, that isn't the general case. Of course the
|game changes when I'm operating a satellite, but that isn't my *hobby*.

See, one of the groups this got cross-posted to is an *Amateur Radio
Antenna* group. I'm reading and writing it from this group and
commenting from that perspective. I normally don't cross post but did
the first one by accident and since I've developed such a loyal
following I didn't want to lose anybody G.

Regards,

Wes Stewart, N7WS

Wes Stewart ...

^ Tall tree? What's a tall tree? The best I have is some
^ 35 foot tall Saguaro cactii.

That might serve as a 40m vertical if the roots are dry and shallow.

Frank

In article , "Wes Stewart"
wrote:

|Seriously, for your purposes you did nothing wrong. Just don't call
|reciprocity a "law", OK? It's a useful idea of wide applicability, but
|physics does not require it in general. Calling it a law confuses
people.

I never made that statement.

Oops, you're right.. It was "w4jle". But you took his side :-)

See, one of the groups this got cross-posted to is an *Amateur Radio
Antenna* group. I'm reading and writing it from this group and
commenting from that perspective. I normally don't cross post but did
the first one by accident and since I've developed such a loyal
following I didn't want to lose anybody G.

But we were discussing Frank's observation:

It's been my experience that an antenna used for receiving will function
satisfactorily over a much broader range of conditions (environment,
antenna length, etc.) than it will if used for transmitting under those
same conditions.

Certainly below 30 MHz this is represents a correct observation,
verifiable both by calculation and experiment. Why should this reality
change with the newsgroup?

Tall tree? What's a tall tree? The best I have is some 35 foot tall
Saguaro cactii. They're a bitch to climb, although when the coyotes
went after the cat, she managed. Let's see, I could tie a string to the
cat's tail and find a coyote.....

Sounds like you're in "Beverage on the ground" territory. That works too,
I'm told (I live next to a swamp, so the tall maples are my friends :-).
I've never tried a Beverage on the ground, although I have used a long
skinny island as a slot antenna (worked very well from longwave through
tropical bands, useless above 10 MHz).

--
| John Doty "You can't confuse me, that's my job."
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