3816Re: Tranmitting Loop for 6m & 10m
- Aug 1, 2007At 1:21 pm ((PDT)) Tue Jul 31, 2007, in Digest 882, W2XJ wrote:
>I agree that the loop is too large. The circumference needs to be lessOnly if it is to be a "small" receiving loop: it is marginal as
>than 1/4 wave.
a "small" transmitting loop; and there is no restriction on
(approx) multiple half-wavelengths being used in a large loop.
For example, see "The Loop Skywire" and the following
"7-MHz Loop" in ARRL Antenna Book chapter 5, both of
which have multiple modes above their fundamental (and
the Skywire as a top-hat loaded vertical too).
>With 47 cm diameter, you are right at 1/4 wave lengthBoth MLOOP31 and RJELOOP1 say it should tune 50MHz
>before you consider velocity and loading.
and work with good efficiency with a 25mm conductor...
>If you go to a diameter... with about 8pF or 9pF respectively, though we know
>slightly less than 40 CM, it should tune on 6 M and be about 60 %
>efficient on 10 M if you use around 1 inch (25mm) tubing. Also, your
>capacitor is to large. You need about 26 pf for 10 m and half that on 6.
this value must be marginal for Dexter's variable capacitor.
(RJELOOP1 says only 4.4pF with a 1mm conductor.)
For 10MHz, RJELOOP1 predicts 29.3pF.
> With a capacitor 10 times too large, tuning at the bottom of the rangeThere are many specific details Dexter hasn't given us,
>could be difficult. What kind of match are you using - gamma match or
>loop coupling? How much power do you plan to use?
(though I see there are some later in this Digest)
probably because he doesn't understand them himself yet
or have enough information to reach a decision.
I suggest it is time for Dexter to do his own legwork and at least
play with RJELOOP1 (or MLOOP31) until he gets a feel for the
numbers and preferably also read chapter 5 of ARRL Antenna Book
to get a handle on the theory and some specific designs.
And would contributors please _not_ quote most of the history
of this thread into their messages - especially top-posted into
reverse or higgledy-piggledy order. I can't easily follow much
of the quote in your message and I see I wrote most of it!
Quotes should give _context_ - and they need to be come before
the reply to do that - not _history_ - we have an Archive for that.
If you are sending a reply to a message... be sure you summarize the
original at the top of the message, or include just enough text of
the original to give a context. This will make sure readers under-
stand when they start to read your response.... Giving context helps
everyone. But do not include the entire original! (rfc1855)
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