Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)
Dear Henry,
I don't know where you are in CZ. I'm on the boarder in DE near PL and CZ.
my former measurement (the one at YouTube, fairly good reception, winter)
has been done under Erzgebirge, Teplice, CZ. Now I moved near Sumava
(Boehmischer Wald), so tests may follow, if I will return to the topic.
The distance to DCF77 is about 450km and if I check the amplitude across 24h
I see considerable very deep fading effects! I think it is useless as a
phase-coupled time receiver. At least in specific positions. It will loose
phase at least for twice the day for approx. 2h ! That was the report for a
ferrite rod.
Thank you.
The other way would be a high-impedance FET-preamp vertical-wire antenna. I
think this will resist much more fading effects. But it is unchecked at the
moment. You're welcome to do it.
The benefit of a resonated ferrite rod is the good bandpass filtering for
local interferers like TV. The FET vertical wire will need heavily filtering
thereafter. All in the whole dynamice range, of course.
This was almost the only reason for ferrite rod -- simplicity and
attenuation of TVs, some LCDs, 50Hz etc.
Ferrites can be temperature controlled. They have big spreads in parameters
anyway! The production procedure is explained in the classical book about
Ferrites: Snelling "Soft Ferrites".
Thank you for your pointer.
Your idea of ferrite ovenization is cool.
Best regards,
Marek
The ferrite loop antenna receives the magnetic portion of the EM wave. It doesn't have to be a bandpass LC filter.
The Wellbrook loop antennas are one example of a broadband antenna that receives the magnetic portion.
-----Original Message-----
From: ehydra ehydra@arcor.de
Sender: time-nuts-bounces@febo.com
Date: Sat, 17 Mar 2012 16:10:48
To: Discussion of precise time and frequency measurementtime-nuts@febo.com
Reply-To: ehydra@arcor.de, Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)
Hi Marek -
I don't know where you are in CZ. I'm on the boarder in DE near PL and
CZ. The distance to DCF77 is about 450km and if I check the amplitude
across 24h I see considerable very deep fading effects! I think it is
useless as a phase-coupled time receiver. At least in specific
positions. It will loose phase at least for twice the day for approx. 2h
! That was the report for a ferrite rod.
The other way would be a high-impedance FET-preamp vertical-wire
antenna. I think this will resist much more fading effects. But it is
unchecked at the moment. You're welcome to do it.
The benefit of a resonated ferrite rod is the good bandpass filtering
for local interferers like TV. The FET vertical wire will need heavily
filtering thereafter. All in the whole dynamice range, of course.
Ferrites can be temperature controlled. They have big spreads in
parameters anyway! The production procedure is explained in the
classical book about Ferrites: Snelling "Soft Ferrites".
- Henry
Marek Peca schrieb:
That would be 36ns group delay variation if I did the math correctly.
OK
And in article P. Hetzel: Time dissemination via the LF transmitter
DCF77 using a pseudo-random phase-shift keying of the carrier, 2nd EFTF
Neuchatel, 1988., they conclude with timing results of about 2..10e-6 s
RMS over ~1000km distance.
However, I do not know what is the reality and whether such a
performance is limited by atmosphere/ground conditions, or whether it
could be better within LF band.
However, what material are you using for the ferrite? The material can
have a significant tempco.
In my project, I have used noname rod taken from within DCF77 alarm clock.
If I will recreate it, I will look for something defined at the store.
--
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gary wrote:
OK, assuming type 61, it is 0.1%/deg C.
IME, Type 78 is the usual choice for resonant antennas below 200 kHz
(tempco of initial permeability = 1.0%/deg C). I have seen Type 33
used for broadband LF/MF antennas (tempco of initial permeability =
0.1%/deg C). Type 61 is generally not used below 200 kHz.
Best regards,
Charles
Marek Peca schrieb:
This was almost the only reason for ferrite rod -- simplicity and
attenuation of TVs, some LCDs, 50Hz etc.
If you make the antenna about 10x bigger you can omit the whole ferrite.
The only benefit of a ferrite loaded coil is the size of it!
In ancient time radios had flat air coils like spider webs. In fact they
are named after spiders in german.
This air coil can be resonated too!
I can imagine a resonated vertical antenna. Never seen that but all it
requires is a low impedance pre-amp stage and a loading coil of very high Q.
- Henry
--
ehydra.dyndns.info
Check out "Observations on Ferrite Rod Antennas", QEX, 2008. Type 61 works better at low frequencies regardless of manufacturers guidelines.
-----Original Message-----
From: "Charles P. Steinmetz" charles_steinmetz@lavabit.com
Sender: time-nuts-bounces@febo.com
Date: Sat, 17 Mar 2012 12:01:36
To: Discussion of precise time and frequency measurementtime-nuts@febo.com
Reply-To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)
gary wrote:
OK, assuming type 61, it is 0.1%/deg C.
IME, Type 78 is the usual choice for resonant antennas below 200 kHz
(tempco of initial permeability = 1.0%/deg C). I have seen Type 33
used for broadband LF/MF antennas (tempco of initial permeability =
0.1%/deg C). Type 61 is generally not used below 200 kHz.
Best regards,
Charles
time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.
In the end every antenna receives the EM wave! The EM-wave is the far
field. The antenna works in the near field where a dominant component
can be the E or M. That depends on the antenna. Between the near and the
far field the field is "converted" and local Z0 highly complicated.
As far as I know every antenna declared as whole EM-capable wasn't it
and I think it is maybe just impossible to couple directly EM to a
antenna <at least if the antenna should be "engineered" which means
simple and cheap>.
The ferrite antenna couples the M component. The vertical capacitive
antenna the E component!
Both can be resonant or broadband.
The ferrite antenna is highly nonlinear and therefor not suitable as
transmitter. As we don't have a "reverse" component for FETs this is
even true for the vertical capacitive antenna.
And a wire antenna in the classical way is a M component antenna. No
ferrites and low Z0 means it can be effectivly used as a transmitting
device.
- Henry
lists@lazygranch.com schrieb:
The ferrite loop antenna receives the magnetic portion of the EM wave. It doesn't have to be a bandpass LC filter.
The Wellbrook loop antennas are one example of a broadband antenna that receives the magnetic portion.
--
ehydra.dyndns.info
Wouldn't the difference be directly proportional to the relative permeability? If so, the difference would be more like 125, not 10, depending on core material.
-----Original Message-----
From: ehydra ehydra@arcor.de
Sender: time-nuts-bounces@febo.com
Date: Sat, 17 Mar 2012 21:22:17
To: Marek Pecamarek@duch.cz; Discussion of precise time and frequency measurementtime-nuts@febo.com
Reply-To: ehydra@arcor.de, Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)
Marek Peca schrieb:
This was almost the only reason for ferrite rod -- simplicity and
attenuation of TVs, some LCDs, 50Hz etc.
If you make the antenna about 10x bigger you can omit the whole ferrite.
The only benefit of a ferrite loaded coil is the size of it!
In ancient time radios had flat air coils like spider webs. In fact they
are named after spiders in german.
This air coil can be resonated too!
I can imagine a resonated vertical antenna. Never seen that but all it
requires is a low impedance pre-amp stage and a loading coil of very high Q.
- Henry
--
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and follow the instructions there.
Hi:
The material permeability gets reduced to effective permeability depending on the rod length / diameter radio (you would
like it to be >= 100) to realize the material permeability).
For example: http://www.magneticsgroup.com/pdf/erods.pdf
More on ferrite loop sticks at:
http://www.prc68.com/I/Loop.shtml
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/Brooke4Congress.html
lists@lazygranch.com wrote:
Wouldn't the difference be directly proportional to the relative permeability? If so, the difference would be more like 125, not 10, depending on core material.
-----Original Message-----
From: ehydraehydra@arcor.de
Sender: time-nuts-bounces@febo.com
Date: Sat, 17 Mar 2012 21:22:17
To: Marek Pecamarek@duch.cz; Discussion of precise time and frequency measurementtime-nuts@febo.com
Reply-To: ehydra@arcor.de, Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: Re: [time-nuts] WWVB BPSK Receiver Project? (fwd)
Marek Peca schrieb:
This was almost the only reason for ferrite rod -- simplicity and
attenuation of TVs, some LCDs, 50Hz etc.
If you make the antenna about 10x bigger you can omit the whole ferrite.
The only benefit of a ferrite loaded coil is the size of it!
In ancient time radios had flat air coils like spider webs. In fact they
are named after spiders in german.
This air coil can be resonated too!
I can imagine a resonated vertical antenna. Never seen that but all it
requires is a low impedance pre-amp stage and a loading coil of very high Q.
- Henry
No, there is a geometric saturation. You can't use the better
permeability in reality.
The optimum length to width relation is about 6 to 10 for ferrite rods.
Here is a diagram:
http://ehydra.dyndns.info/NG/time-nuts/Pettengill%20002.jpg
This is one of the classics in my link list:
http://www.bentongue.com/xtalset/29MxQFL/29MxQFL.html
- Henry
lists@lazygranch.com schrieb:
Wouldn't the difference be directly proportional to the relative
permeability? If so, the difference would be more like 125, not 10,
depending on core material.
--
ehydra.dyndns.info
In message 4F64F279.4040208@arcor.de, ehydra writes:
Marek Peca schrieb:
This was almost the only reason for ferrite rod -- simplicity and
attenuation of TVs, some LCDs, 50Hz etc.
If you make the antenna about 10x bigger you can omit the whole ferrite.
I have used two antennas, an unloade air-coil, actually plastic-lid-coil:
http://phk.freebsd.dk/loran-c/Antenna/
and a vertical monopole based on a Chris Trask design I can highly
recommend:
http://home.earthlink.net/~christrask/Complementary%20Push-Pull%20Amplifiers.pdf
In my implementation, it covered DC to 200MHz until I low-pass'ed it.
--
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