Text 1953, 73 rader
Skriven 2007-11-19 13:05:39 av Richard Webb (1:116/901.0)
   Kommentar till text 1951 av mark lewis (1:3634/12.0)
Ärende: yagi cantenna building...
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mark lewis wrote in a message to Richard Webb:

ml> the question is, will the 1.5inch washers work or must i get some
ml> 1inch ones? 

 RW> I'd think if the washers are the reflectors themselves that the
 RW> larger washers would have a lower resonant frequency.  Might screw
 RW> up your pattern a bit. 

ml> my biggest problem is figuring out what part the washers play in the
ml> whole thing... i know their spacing is 1.2 inches... should they
ml> also be 1.2 inches in diameter?

TOugh question, especially when we don't know if they're actually supposed to
be elements.  Plug the term yagi into your favorite search engine you'll  find
all sorts of dimensions for yagis and the formulae to derive them for your
frequencies of interest.  THat might help you. Iirc and I am doing this pre
coffee the reflectors are usually behind the driven element, and often a bit
longer.

ml> i might have to look them up... as it is, i'm going to have to go
ml> online to get some RP-SMA male connectors... either that or RP-SMA-M
ml> to BNC adapters... i've seen RP-SMA to TNC (TNA?) adapters as well
ml> as the more common RP-SMA to N stuff... i'd have to rip things apart
ml> and get another can to use an N connector with... that and gut an
ml> old CB radio or possibly see if i can rip one off of an old antenna
ml> laying about :?

Yah they mioght use an N somewhere in an older cb.  I know the connections to
the antenna aren't usually N connectors however but the old "uhf" connector.
Now that's a misnomer if I ever heard one.
THose "uhf" connectors are more commonly known as so-239 btw. IN fact of the
two types I happen to like bnc quite a bit better than the sma.  Sma is a bit
smaller and fits in a tighter space though so it's become quite popular with
portable two-way equipment.

ml> i went and looked at lowes today to see if i could find some 3/16ths
ml> x 1 inch and they didn't have any... they did have 1.25s and .75s
ml> but not the 1's in a 3/16ths hole... heck, i might just go ahead and
ml> break down and buy some 1/8th inch all-thread and the washers to fit
ml> that with some tubing, too... all total, it would be less than $10
ml> :)

Yah I think I would so that it'll work as advertised, especially if it's to
link something into your network.  REmember this thing has to transmit too, and
even though it's low power the transmitter will be much happier seeing the
proper 50 ohm impedance etc. AT these frequencies you're dealing with low
tolerances and any loss is bad.  ESpecially from your home to the neighboring
rv, both metal skins iirc.


ml> but then again, free is better :lol:  i wonder what king of blast
ml> i'd get by hooking up this old three legged scanner antenna that's
ml> up on the roof ;) 

I'd say not near as good.  THat old antenna went into uhf but not into that
range. I'd guess its top range would be around 512 mhz.  Also your feed line
loss is probably going to be pretty huge. I'm mostly an old school high
frequency guy so others who dabble in the microwave stuff could advise you a
bit better, but that's my take on this  thing anyway. My vhf/uhf setup here at
the house is less than optimum in some respects.  I've got a hundred foot run
of rg-8 feeding a j pole 60 foot up in a big old oak tree.  NOw the problem is
line loss, as there's a barrel connector connecting two runs of coax to make it
that far. WERe i Really going to do it right I"d get some 7/8 inch hard line to
run to that antenna. I still can hit just about anything I want, from 30 miles
east of MEmphis Tn. I can hit the Jackson Tn. main repeater system reliably any
time I need to. THat's with 50 watts.


Regards,
           Richard
--- timEd 1.10.y2k+
 * Origin: Radio REscue net operations BBS       (1:116/901)