Hi Kevin,
Yes, this is very helpful. The equation and example you provided are exactly what I was looking for.
I really appreciate you taking the time to answer all of my questions today, as well as providing sources for the loop element and tuning capacitor. I think I'll build one of these mini loops.
Regards,
Gary
--- In ultralightdx@..., "Kevin S" <satya@...> wrote:

Hey Gary:

Here's a site:
http://en.wikipedia.org/wiki/LC_circuit
About halfway down, under "Resonance Effect", is the formula:
f = 1/((2*pi)*(sqrt(LC)))

I have found the following to be much easier to use, which is a simple rearranging of the above equation:
L*C*f*f = 25,330
f is in Mhz, L is uH (usually around 250) and C is in pf (usually 10-365 or some such). So, pick two of the values, and the third one pops out. For example, if L is 250 an you want to tune down to 530 khz, the require C value is 25,330/(250 * 0.53 * 0.53) = 361 pf.

For an average project, you can figure 20 or so pf for "distributed

capacitance" (i.e., the wires of the loop interacting with each other, acting as a capacitor). So, for a loop of say 250 uH with 20 pf distributed capacitance, in theory the cap would be 35 to 361, but with the 20 pf added capacitance of the loop, the required cap value would be 15 to 341. This is a typical range I've seen quoted.

I just checked my little loop in the green box, and I did link the two sections of the cap together to make 532 pf max capacitance. With all that capacitance, it tunes down to 440 khz, and easily reaches 1700 khz on the high end. The beauty of the Litz coil is that it has very little distributed capacitance owing to the winding pattern, so your high end (>1700 khz) is not endangered.

Hope this helps - Kevin

------------------------------------
Yahoo! Groups Links

Hi Kevin,

Yes, this is very helpful. The equation and example you provided are
exactly what I was looking for.

I really appreciate you taking the time to answer all of my questions
today, as well as providing sources for the loop element and tuning
capacitor. I think I'll build one of these mini loops.

Regards,
Gary

--- In ultralightdx@..., "Kevin S" <satya@...> wrote:

Hey Gary:

Here's a site:
http://en.wikipedia.org/wiki/LC_circuit
About halfway down, under "Resonance Effect", is the formula:
f = 1/((2*pi)*(sqrt(LC)))

I have found the following to be much easier to use, which is a simple
rearranging of the above equation:
L*C*f*f = 25,330
f is in Mhz, L is uH (usually around 250) and C is in pf (usually 10-365
or some such). So, pick two of the values, and the third one pops out.
For example, if L is 250 an you want to tune down to 530 khz, the
require C value is 25,330/(250 * 0.53 * 0.53) = 361 pf.

For an average project, you can figure 20 or so pf for "distributed

capacitance" (i.e., the wires of the loop interacting with each other,
acting as a capacitor). So, for a loop of say 250 uH with 20 pf
distributed capacitance, in theory the cap would be 35 to 361, but with
the 20 pf added capacitance of the loop, the required cap value would be
15 to 341. This is a typical range I've seen quoted.

I just checked my little loop in the green box, and I did link the two
sections of the cap together to make 532 pf max capacitance. With all
that capacitance, it tunes down to 440 khz, and easily reaches 1700 khz
on the high end. The beauty of the Litz coil is that it has very little
distributed capacitance owing to the winding pattern, so your high end
(>1700 khz) is not endangered.

Hope this helps - Kevin

----- Original Message -----

From: Tao Qu

To: ultralightdx@...

Sent: Friday, July 30, 2010 9:56 PM

Subject: RE: [ultralightdx] Re: PL-210 DSP or not?

 

Both the PL-210 and RP2100 are digital PLL based design, no DSP inside.

 

- Tao Qu

---

From: ultralightdx@yahoogroups.com [mailto:ultralightdx@yahoogroups.com] On Behalf Of farmerik
Sent: Saturday, July 31, 2010 7:55 AM
To: ultralightdx@yahoogroups.com
Subject: [ultralightdx] Re: PL-210 DSP or not?

 

I noticed a seller who claimed the PL-210 and the RP-2100 are both DSP radios. I think it is an error in translating. The PL-200 wasn't DSP and the RP-2100 isn't either, but they are digitally tuned or at least have a digital frequency read out. - FARMERIK

--- In ultralightdx@yahoogroups.com, "surveyor6180" .> wrote:
>
> There seems to be be conflicting information regarding the 210.
> Does anyone know for sure if it has DSP or not?
> It looks like it could be an interesting radio and I am curious if it in fact does have DSP capability.
> Thanks everyone, Harold
>

Thanks for the info, Kevin.

Pardon my ignorance, but where does the 90,175 pf*uH come from? Do you
have any web sites that discuss this?

--- In ultralightdx@..., "Kevin S" <satya@...> wrote:

I think that's correct - I must have tied the two sections together to
make a 532 pf lower end. Multiplying inductance times cpaacitance, you
need about 90,175 pf*uH. Since the inductance of the coil is around
266 uH, that leaves 339 pF needed to get down to 530 khz.

Since there is so little distributed capacitance in the Litz coil, tying
the two cap sections together means that you should still be able to
tune the top end.

Kevin

Thanks, I gave him those numbers, and asked for a quote for both. He mentioned an OD of 9,25 inches. I wouldn't expect this to be a long distance DXing antenna when it is so small, but it should be interesting. If anyone else is interested, we might get a better price if he sets up and makes several, or maybe not. If I get them, I'll report how they work on the PL-360, and I have a suitable cap to tune them for other radios too. - FARMERIK



--- In ultralightdx@..., D1028Gary@ wrote:

Hi Farmerik,

Good luck on the purchase of AM and LW coils from the eBay seller. If he
asks for inductance values, the PL-360 AM 7.5" plug-in loopstick uses an
inductance of 350 uh, and tracks very well across the MW spectrum. The current
PL-360 LW 7.5" plug-in loopstick (the first of several planned test models)
has a coil inductance of 2000 uh (composed of a 40/44 LItz wire coil on a
type 33 ferrite bar), and had excellent LW-TP chasing results during the
past Oregon DXpedition in the PL-380, logging 3 Russian LW stations in the
Far East.

After completion of the recent DXpedition report, more LW coil tests (and
construction of 7.5" LW plug-in loopsticks for you and others) is planned.
Have fun tinkering around, Richard!

73, Gary D.


In a message dated 7/30/2010 12:45:15 P.M. Pacific Daylight Time,
farmerik@ writes:




I just sent the coil seller a message through Ebay to ask about making AM
BCB and LW BCB coils for the PL-360. Don't worry Gary, I will want the long
ferrite model you plan to offer too. If he asks, what inductance would the
radio want for these two bands? - FARMERIK

--- In _ultralightdx@... (mailto:ultralightdx@...)
, "farmerik" <farmerik@> wrote:

It should connect to the PL-360 as is, and It would be great if he could

optimize by making it larger for a little more signal pick up, and offer
one for LW BCB. He has a number of choices of wire, and can make these up to
or larger than 6 inches OD. HMMMM... - FARMERIK

--- In _ultralightdx@...

(mailto:ultralightdx@...) , "gkinsman1" <gkinsman@> wrote:

Thanks for the info, Kevin.

What is a good variable capacitor to use with this coil? Any links

would be appreciated.

--- In _ultralightdx@...

(mailto:ultralightdx@...) , "Kevin S" <satya@> wrote:

Hi Gary:

The only thing I can think of is where I took a 4" coil which was

wound for a crystal radio and connected it to a mini variable capacitor. It
provided a good little boost for its size, and the Litz coil and special
basket weave meant that the Q, or tuning sharpness, was very high. The seller
on ebay currently has a similar coil (see ebay item 330448576470).

Hope this helps - Kevin

Hi Kevin,

I recall that you built a very small loop antenna of about 4"-5"

diameter.

Is there an article describing the construction of this antenna? I

> > couldn't find it on www.dxer.ca with all of the other ULR antenna

files.

Thanks,

> Gary

There seems to be be conflicting information regarding the 210.
Does anyone know for sure if it has DSP or not?
It looks like it could be an interesting radio and I am curious if it in fact does have DSP capability.
Thanks everyone, Harold

Hi Farmerik,

Good luck on the purchase of AM and LW coils from the eBay seller. If he
asks for inductance values, the PL-360 AM 7.5" plug-in loopstick uses an
inductance of 350 uh, and tracks very well across the MW spectrum. The current
PL-360 LW 7.5" plug-in loopstick (the first of several planned test models)
has a coil inductance of 2000 uh (composed of a 40/44 LItz wire coil on a
type 33 ferrite bar), and had excellent LW-TP chasing results during the
past Oregon DXpedition in the PL-380, logging 3 Russian LW stations in the
Far East.

After completion of the recent DXpedition report, more LW coil tests (and
construction of 7.5" LW plug-in loopsticks for you and others) is planned.
Have fun tinkering around, Richard!

73, Gary D.


In a message dated 7/30/2010 12:45:15 P.M. Pacific Daylight Time,
farmerik@... writes:




I just sent the coil seller a message through Ebay to ask about making AM
BCB and LW BCB coils for the PL-360. Don't worry Gary, I will want the long
ferrite model you plan to offer too. If he asks, what inductance would the
radio want for these two bands? - FARMERIK

--- In _ultralightdx@... (mailto:ultralightdx@...)
, "farmerik" <farmerik@> wrote:

It should connect to the PL-360 as is, and It would be great if he could

optimize by making it larger for a little more signal pick up, and offer
one for LW BCB. He has a number of choices of wire, and can make these up to
or larger than 6 inches OD. HMMMM... - FARMERIK

--- In _ultralightdx@...

(mailto:ultralightdx@...) , "gkinsman1" <gkinsman@> wrote:

Thanks for the info, Kevin.

What is a good variable capacitor to use with this coil? Any links

would be appreciated.

--- In _ultralightdx@...

(mailto:ultralightdx@...) , "Kevin S" <satya@> wrote:

Hi Gary:

The only thing I can think of is where I took a 4" coil which was

wound for a crystal radio and connected it to a mini variable capacitor. It
provided a good little boost for its size, and the Litz coil and special
basket weave meant that the Q, or tuning sharpness, was very high. The seller
on ebay currently has a similar coil (see ebay item 330448576470).

Hope this helps - Kevin

Hi Kevin,

I recall that you built a very small loop antenna of about 4"-5"

diameter.

Is there an article describing the construction of this antenna? I

> > couldn't find it on www.dxer.ca with all of the other ULR antenna

files.

Thanks,

> Gary

I think that's correct - I must have tied the two sections together to make a 532 pf lower end. Multiplying inductance times cpaacitance, you need about 90,175 pf*uH. Since the inductance of the coil is around 266 uH, that leaves 339 pF needed to get down to 530 khz.

Since there is so little distributed capacitance in the Litz coil, tying the two cap sections together means that you should still be able to tune the top end.

Kevin

Thanks, Kevin.

I believe the coil seller said 365 pF is needed to tune down to 500 kHz.
Perhaps your coil needed less capacitance than the one he currently
offers.

--- In ultralightdx@..., "Kevin S" <satya@...> wrote:

I wanted a compact set-up, so I used a 2x266 mini variable capacitor
from "zlowe7", ebay item # 150275619877. As I recall I only needed to
use one of the 266 pf sections to resonate the whole band. I think
these are the same capacitors that are used in the Quantum Stick
antenna. If you go this route, make sure you get the stems and knobs (I
heartily recommend the large knobs, item #150275619937, for better
fine-tuning control).
I've ordered stuff from this guy a few times, and he ships quickly. He
combines shipping, so ask for a final invoice amount if you order
multiple items!

Kevin

If you want to see what the finished product looks like, download the "Using Passive Loop Antennas" article and look for the picture of a little green box on page 5. I put it into a green plastic computer diskette filing box. The article is here on the group, and also here:
www.am-dx.com/passiveloops.pdf

Kevin

I wanted a compact set-up, so I used a 2x266 mini variable capacitor from "zlowe7", ebay item # 150275619877. As I recall I only needed to use one of the 266 pf sections to resonate the whole band. I think these are the same capacitors that are used in the Quantum Stick antenna. If you go this route, make sure you get the stems and knobs (I heartily recommend the large knobs, item #150275619937, for better fine-tuning control).
I've ordered stuff from this guy a few times, and he ships quickly. He combines shipping, so ask for a final invoice amount if you order multiple items!

Kevin

Thanks for the info, Kevin.

What is a good variable capacitor to use with this coil? Any links would
be appreciated.

--- In ultralightdx@..., "Kevin S" <satya@...> wrote:

Hi Gary:

The only thing I can think of is where I took a 4" coil which was wound
for a crystal radio and connected it to a mini variable capacitor. It
provided a good little boost for its size, and the Litz coil and special
basket weave meant that the Q, or tuning sharpness, was very high. The
seller on ebay currently has a similar coil (see ebay item
330448576470).

Hope this helps - Kevin

Hi Kevin,

I recall that you built a very small loop antenna of about 4"-5"

diameter.

Is there an article describing the construction of this antenna? I
couldn't find it on www.dxer.ca with all of the other ULR antenna

files.

Thanks,
Gary

Thanks for the info, Kevin.

What is a good variable capacitor to use with this coil? Any links would
be appreciated.

--- In ultralightdx@..., "Kevin S" <satya@...> wrote:

Hi Gary:

The only thing I can think of is where I took a 4" coil which was wound
for a crystal radio and connected it to a mini variable capacitor. It
provided a good little boost for its size, and the Litz coil and special
basket weave meant that the Q, or tuning sharpness, was very high. The
seller on ebay currently has a similar coil (see ebay item
330448576470).

Hope this helps - Kevin

Hi Kevin,

I recall that you built a very small loop antenna of about 4"-5"

diameter.

Is there an article describing the construction of this antenna? I
couldn't find it on www.dxer.ca with all of the other ULR antenna

files.

Thanks,
Gary

It should connect to the PL-360 as is, and It would be great if he could optimize by making it larger for a little more signal pick up, and offer one for LW BCB. He has a number of choices of wire, and can make these up to or larger than 6 inches OD. HMMMM... - FARMERIK

--- In ultralightdx@..., "gkinsman1" <gkinsman@> wrote:

Thanks for the info, Kevin.

What is a good variable capacitor to use with this coil? Any links would be appreciated.

--- In ultralightdx@..., "Kevin S" <satya@> wrote:

Hi Gary:

The only thing I can think of is where I took a 4" coil which was wound for a crystal radio and connected it to a mini variable capacitor. It provided a good little boost for its size, and the Litz coil and special basket weave meant that the Q, or tuning sharpness, was very high. The seller on ebay currently has a similar coil (see ebay item 330448576470).

Hope this helps - Kevin

Hi Kevin,

I recall that you built a very small loop antenna of about 4"-5" diameter.
Is there an article describing the construction of this antenna? I
couldn't find it on www.dxer.ca with all of the other ULR antenna files.

Thanks,
Gary

Thanks for the info, Kevin.

What is a good variable capacitor to use with this coil? Any links would be appreciated.

--- In ultralightdx@..., "Kevin S" <satya@> wrote:

Hi Gary:

The only thing I can think of is where I took a 4" coil which was wound for a crystal radio and connected it to a mini variable capacitor. It provided a good little boost for its size, and the Litz coil and special basket weave meant that the Q, or tuning sharpness, was very high. The seller on ebay currently has a similar coil (see ebay item 330448576470).

Hope this helps - Kevin

Hi Kevin,

I recall that you built a very small loop antenna of about 4"-5" diameter.
Is there an article describing the construction of this antenna? I
couldn't find it on www.dxer.ca with all of the other ULR antenna files.

Thanks,
Gary