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Hello,

I am planning on making a longwave loop antenna that uses 24 gauge
wire on the same frame. When I ran out of space on the sides
I had to rewind the wires backwards to get more on the loop. Also my
variable tuning capacitor is only useful for a value of 0 to 150 pF.
I was wondering can a wider range capacitor cover more of the longwave
bands than just the 0 to 150 pF cheap polyfilm type.

measurements are the usual 31 cm for the A side and B side is 7 cm.
I have used up to 81 turns it used to be 64 turns. measured 8 ohms
resistance. For now I am only using my cheap 0 to 150 pF capacitor
cause the old 480 pF capacitor crapped out. Anyways where can I
find a new 480 pF capacitor? since I am only using 24 gauge would
28 or 30 gauge help increase inductance?

Soon I am hoping to make bigger loops soon.

Thanks for your support

Adam E.

Looks like good stuff. But, wow, the prices.

Thanks for the helpful links, but is there anymore information why
you suggest these links? Also would smaller wire do better and is
there other things that I need to know about loops for longwave?

Adam E.

Hi Adam,
In the USA, this place carries parts for crystal radios, and has both single and dual section 365 pF variable caps.
Click on Radio Parts to see the caps for sale.


73,
Steve

I was wondering can a wider range capacitor cover more of the longwave
bands than just the 0 to 150 pF cheap polyfilm type.

Yes, that's the idea.

Without using any actual component values ... the loop has some inductance,
and some inherent capacitance. The L and C by themselves (no added cap)
resonate at some frequency, which will be the highest frequency you will be
able to get the loop to resonate, as it is currently wound.

Adding a variable capacitor lowers the resonant frequency. The larger the
capacitance added, the lower the frequency at which it resonates.

So, if 0 to 150 pF doesn't get you to a low enough frequency, add more. It
need not be all in the form of a variable capacitor. It could be a handful
of fixed (~100 to 150 pF) capacitors that you switch in as required.

This won't help to get the loop to a higher resonant frequency.

The antenna does receive at frequencies other than its resonant frequency.
Just not as well.

since I am only using 24 gauge would
28 or 30 gauge help increase inductance?

Wire gauge itself has very little effect on loop inductance, though it would
change the resistance and lower the Q.

Andy

How do I higher the Q?

Adam E.

--- In loopantennas@..., Andy <Andy.groups@...> wrote:

I was wondering can a wider range capacitor cover more of the longwave
bands than just the 0 to 150 pF cheap polyfilm type.

Yes, that's the idea.

Without using any actual component values ... the loop has some

inductance,

and some inherent capacitance. The L and C by themselves (no added cap)
resonate at some frequency, which will be the highest frequency you

will be

able to get the loop to resonate, as it is currently wound.

Adding a variable capacitor lowers the resonant frequency. The

larger the

capacitance added, the lower the frequency at which it resonates.

So, if 0 to 150 pF doesn't get you to a low enough frequency, add

more. It

need not be all in the form of a variable capacitor. It could be a

handful

of fixed (~100 to 150 pF) capacitors that you switch in as required.

This won't help to get the loop to a higher resonant frequency.

The antenna does receive at frequencies other than its resonant

frequency.

Just not as well.

since I am only using 24 gauge would
28 or 30 gauge help increase inductance?

Wire gauge itself has very little effect on loop inductance, though

it would

change the resistance and lower the Q.

Andy

Also, tubesandmore.com and radiodaze.com. But possibly the best source
is eBay.
Dave


--- In loopantennas@..., "Adam E." <gccengineering@...>
wrote:

Hello,

I am planning on making a longwave loop antenna that uses 24 gauge
wire on the same frame. When I ran out of space on the sides
I had to rewind the wires backwards to get more on the loop. Also my
variable tuning capacitor is only useful for a value of 0 to 150 pF.
I was wondering can a wider range capacitor cover more of the longwave
bands than just the 0 to 150 pF cheap polyfilm type.

measurements are the usual 31 cm for the A side and B side is 7 cm.
I have used up to 81 turns it used to be 64 turns. measured 8 ohms
resistance. For now I am only using my cheap 0 to 150 pF capacitor
cause the old 480 pF capacitor crapped out. Anyways where can I
find a new 480 pF capacitor? since I am only using 24 gauge would
28 or 30 gauge help increase inductance?

Soon I am hoping to make bigger loops soon.

Thanks for your support

Adam E.

How do I higher the Q?

and

Also would smaller wire do better and is
there other things that I need to know about loops for longwave?

Well, it is my understanding (take it with a grain of salt, this is theory)
that, all other things being equal, higher Q comes when the resistance is
lower. To get that, you need bigger wire (more copper cross-section) ...
not smaller. Bigger wire means smaller AWG number.

There might be ways to lower the effective RF resistance without necessarily
using fatter wire, but I am somewhat of a skeptic until it is shown to
actually be better; and a technique that works in one case, might not work
in another.

For longwire antennas, the frequencies may be low enough that skin effect is
not a significant factor and it is DC resistance that you need to worry
about.

Andy

--- In loopantennas@..., "Adam E." <gccengineering@...>
wrote:

For now I am only using my cheap 0 to 150 pF capacitor
cause the old 480 pF capacitor crapped out.

Hello Adam,

What went wrong with your old cap?

73,
Dave
KA3JGG