[TowerTalk] Perfect Field Day beam?
Guy Olinger, K2AV
Mon, 03 May 1999 17:14:03 GMT
We possibly into this pink db, green db thing? Doesn't K7LXC practice
dbd ala Force 12, etc?
If the 1.3 db referred to db is over a dipole at similar height, we
are not talking about a lot of loss. What we have is front to side
like a dipole, and some very minimal FB or FB that is rather narrow if
looked at in a 3D pattern such as EZNEC-2.
The interpretation is that it is only slightly better than a dipole
with nothing approaching a broad, decent F/B and without any huge
forward gain. The point made was that the aggravation of beam,
rotator, mast, etc hardly seem worth the effort just to get 1.3 db
more, 1.3 db being imperceptible to most people.
Other tribanders show 4.5 db over a dipole at similar height. That can
HOWEVER, thinking field day, one of the helpful aspects of a triband
beam, even a wimpy 1.3 db beam, is that it has three bands in one
place and is really horizontally polarized (not completely so some
field day dipoles I have seen), which means you can put up a m/b
vertical for the novice/tech station and take advantage of the
cross-polarization isolation to keep from driving each other off the
Having operated f/d on a saltwater beach on the east side of
Cheasapeak Bay, looking across saltwater to the rest of the US, I can
say from experience that the difference between a wimp beam and a
substantial one there is totally blown away by the superior location.
After all, the most important factors in a field day setup, in order
4) Good food
5) More than one generator
7) More than one rig
9) Using feedline between antennas and rigs.
10) Operator that can do CW
12) Less than 20 miles to a 24 hour gas station (subheading to
13) Other stuff
On Mon, 03 May 1999 12:31:51 -0400, you wrote:
>At 10:57 AM 5/3/1999 -0400, Tom Rauch wrote:
>>> >Somewhere almost 5 dB (69%) of the applied power is missing.
>>> Does this necessarily follow? Trap losses surely aren't the only
>>> mechanism at work here. I suspect I could all too easily build a monoband
>>> yagi that would work just as well (or badly) as a TA-33. Why couldn't
>>> element spacing compromises, real-world traps, etc., all lead to a net
>>> deterioration in both pattern and F/B?
>>If an antenna had no noticeable F/B, and the same F/S as a dipole,
>>then we can reasonably expect the system to have very little gain.
>>I certainly know that isn't the case with a properly functioning TA-
>>You be amazed at how hot an inductor gets (especially in a closed
>>cylinder) with even 30-40 watts of heat!
>Tom, I'm certainly not arguing the old "trap losses" line, nor am I
>suggesting that ohmic losses account for the TA-33's behavior. What I am
>suggesting is that cancellation effects resulting from incorrect spacing or
>other design factors could lead to an antenna that has both F/B and minimal
>forward gain, without having to blame it on low efficiency. If not, why not?
>73, Pete N4ZR
>Loud is good
Guy Olinger, K2AV
Apex, NC, USA
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