Narrow band antenna.
Artem
I'm looking how to make narrow band active antenna for 7 or 10.1mzh.
My idea: I will use magnetic antenna with one loop. A one-turn loop of
3.14m cupper pipe with diameter 15mm has 2.687uH. With Varicaps of
192pf it will have resonance frequency of 7MHz. I will load this LC
tank directly to Gate one of dual gate MOSFET.
http://homepage.eircom.net/%257Eei9gq/rx_circ.html
http://homepage.eircom.net/%257Eei9gq/mosifamp.GIF
Should it work? I'll never seen such schematics. Usually people use
transformers. But I will place this transistor directly inside gap in
the loop of cupper pipe. The Gate of MOSFET will add only additional
2pf to Varicaps and it will be very easy to compensate.
Sorry for English.
Tom Bruhns
> Hello all.
> I'm looking how to make narrow band active antenna for 7 or 10.1mzh.
> My idea: I will use magnetic antenna with one loop. A one-turn loop of
> 3.14m cupper pipe with diameter 15mm has 2.687uH. With Varicaps of
> 192pf it will have resonance frequency of 7MHz. I will load this LC
> Should it work? I'll never seen such schematics. Usually people use
> transformers. But I will place this transistor directly inside gap in
> the loop of cupper pipe. The Gate of MOSFET will add only additional
> 2pf to Varicaps and it will be very easy to compensate.
>
> Sorry for English.
You should probably download Reg Edwards' RJELoop3 and/or RJELoop1
programs, which will tell you that the conductor loss resistance of
your loop will be about ten times the radiation resistance, so not
even counting the relatively low Q of varactor diodes, you'll have
quite a bit of loss. On the other hand, even at 7MHz the atmospheric
noise is so high that the loss won't be a significant problem so long
as your amplifier is reasonably low noise. I'd recommend you use a
C0G ceramic or possibly silvered-mica capacitor for most of the tuning
capacitance, to keep the Q as high as possible (the losses as low as
possible). Reg suggests the Q for use at 7MHz will be around 2000, so
the bandwidth is quite narrow. If the Q really is that high (polish
the copper and coat it with a protective varnish or paint...), the
parallel resonant impedance will be up around 200k ohms, so it should
be a decent match to your FET amplifier. Make sure any loading at the
gap is well above 200k ohms resistive, to keep from introducing
significant additional loss. If you want the antenna to also do a
good job rejecting locally generated E field noise, you need to keep
things well balanced. But at 7MHz, this is probably of marginal
utility since any noise generators whose noise would be rejected would
have to be very close to the antenna--within a few tens of meters.
-- I've done similar amplifiers for multi-turn loops for LF, down
around 150kHz, using a balanced JFET design directly across the loop,
with good success.
You can find the suggested programs at http://www.zerobeat.net/G4FGQ/.
And you likely would get some additional replies if you cross-post to
rec.radio.amateur.antenna.
Cheers,
Tom
Artem
> On Mar 13, 9:35 am, Artem <artem.b...@gmail.com> wrote:
>
> > Hello all.
> > I'm looking how to make narrow band active antenna for 7 or 10.1mzh.
> > My idea: I will use magnetic antenna with one loop. A one-turn loop of
> > 3.14m cupper pipe with diameter 15mm has 2.687uH. With Varicaps of
> > 192pf it will have resonance frequency of 7MHz. I will load this LC
> > Should it work? I'll never seen such schematics. Usually people use
> > transformers. But I will place this transistor directly inside gap in
> > the loop of cupper pipe. The Gate of MOSFET will add only additional
> > 2pf to Varicaps and it will be very easy to compensate.
>
> > Sorry for English.
>
> You should probably download Reg Edwards' RJELoop3 and/or RJELoop1
> programs, which will tell you that the conductor loss resistance of
> your loop will be about ten times the radiation resistance,
How can calculate radiation resistance? resistance at 7MHz is
skin effect
http://circuitcalculator.com/wordpress/2007/06/18/skin-effect-calculator/
0.028mm.
for copper pipe 15mm in diameter:
octave:1> 15*3.14*0.028
ans = 1.3188mm^2
0.0155Om/m * 3.14m
ans = 0.048670 Om.
I think it's not bad.
> even counting the relatively low Q of varactor diodes, you'll have
> quite a bit of loss. On the other hand, even at 7MHz the atmospheric
> noise is so high that the loss won't be a significant problem so long
> as your amplifier is reasonably low noise. I'd recommend you use a
> C0G ceramic or possibly silvered-mica capacitor for most of the tuning
> capacitance, to keep the Q as high as possible (the losses as low as
> possible).
You recommended did hot use varistors? I'm thinking about
some kind
http://www.toshiba.com/taec/components2/Datasheet_Sync//273/1343.pdf
20 in parallel
--------------------------------------
Ultra low series resistance: rs = 0.20 Ω (typ.)
--------------------------------------
It will be 0.02 Om
Reg suggests the Q for use at 7MHz will be around 2000, so
> the bandwidth is quite narrow. If the Q really is that high (polish
> the copper and coat it with a protective varnish or paint...), the
> parallel resonant impedance will be up around 200k ohms, so it should
> be a decent match to your FET amplifier. Make sure any loading at the
> gap is well above 200k ohms resistive, to keep from introducing
> significant additional loss.
I'm thinking about soldering a box from FR4.
If you want the antenna to also do a
> good job rejecting locally generated E field noise, you need to keep
> things well balanced.
What you mean about balanced? Differential output? I should think
about it.
But at 7MHz, this is probably of marginal
> utility since any noise generators whose noise would be rejected would
> have to be very close to the antenna--within a few tens of meters.
> -- I've done similar amplifiers for multi-turn loops for LF, down
> around 150kHz, using a balanced JFET design directly across the loop,
> with good success.
>
> You can find the suggested programs athttp://www.zerobeat.net/G4FGQ/.
> And you likely would get some additional replies if you cross-post to
> rec.radio.amateur.antenna.
Thank.
Artem.
artem...@gmail.com
Sorry.
-----------------------------------------------
Hello all.
I'm looking how to make narrow band active antenna for 7 or 10.1mzh.
My idea: I will use magnetic antenna with one loop. A one-turn loop of
3.14m cupper pipe with diameter 15mm has 2.687uH. With Varicaps of
192pf it will have resonance frequency of 7MHz. I will load this LC
tank directly to Gate one of dual gate MOSFET.
http://homepage.eircom.net/%257Eei9gq/rx_circ.html
http://homepage.eircom.net/%257Eei9gq/mosifamp.GIF
Should it work? I'll never seen such schematics. Usually people use
transformers. But I will place this transistor directly inside gap in
the loop of cupper pipe. The Gate of MOSFET will add only additional
2pf to Varicaps and it will be very easy to compensate.
-----------------------------------------------
> Artem.
Tom Bruhns
> On Mar 13, 7:40 pm, Tom Bruhns <k7...@msn.com> wrote:
>
>
>
> > On Mar 13, 9:35 am, Artem <artem.b...@gmail.com> wrote:
>
> > > Hello all.
> > > I'm looking how to make narrow band active antenna for 7 or 10.1mzh.
> > > My idea: I will use magnetic antenna with one loop. A one-turn loop of
> > > 3.14m cupper pipe with diameter 15mm has 2.687uH. With Varicaps of
> > > 192pf it will have resonance frequency of 7MHz. I will load this LC
> > > tank directly to Gate one of dual gate MOSFET.http://homepage.eircom.net/%257Eei9gq/rx_circ.htmlhttp://homepage.eir...
> > > Should it work? I'll never seen such schematics. Usually people use
> > > transformers. But I will place this transistor directly inside gap in
> > > the loop of cupper pipe. The Gate of MOSFET will add only additional
> > > 2pf to Varicaps and it will be very easy to compensate.
>
> > > Sorry for English.
>
> > You should probably download Reg Edwards' RJELoop3 and/or RJELoop1
> > programs, which will tell you that the conductor loss resistance of
> > your loop will be about ten times the radiation resistance,
>
> How can calculate radiation resistance? resistance at 7MHz is
> 0.028mm.
> for copper pipe 15mm in diameter:
> octave:1> 15*3.14*0.028
> ans = 1.3188mm^2
>
> 0.0155Om/m * 3.14m
> ans = 0.048670 Om.
> I think it's not bad.
See http://personal.ee.surrey.ac.uk/Personal/D.Jefferies/antennexarticles/cloops.htm
for info on calculating the radiation resistance. I believe that will
be helpful. I assume Reg's RJELoop1.exe uses essentially the formula
you'll find there. For your loop, that program says inductance is
2.69uH, conductor loss resistance is 46.2 milliohms, and radiation
resistance is 5.7 milliohms. Although the conductor loss resistance
(essentialy the same as you calculated above is "not bad," you need to
consider it with relation to the very low radiation resistance. A
current in the loop will dissipate far more power in the resistive
loss than in the radiation resistance. You ideally will keep the loss
resistance small compared with the radiation resistance, though for
receiving (because of the very high level of atmospheric noise on HF
and lower frequencies) it matters not nearly so much as for
transmitting. When transmitting, you want your power to go into radio
waves, not heat. When receiving you only need signal greater than
noise, and it is relatively easy to make an amplifier with low enough
noise figure that even an inefficient antenna will result in an
amplifier output whose noise is dominated by the atmospheric noise
received by the antenna.
>
> > even counting the relatively low Q of varactor diodes, you'll have
> > quite a bit of loss. On the other hand, even at 7MHz the atmospheric
> > noise is so high that the loss won't be a significant problem so long
> > as your amplifier is reasonably low noise. I'd recommend you use a
> > C0G ceramic or possibly silvered-mica capacitor for most of the tuning
> > capacitance, to keep the Q as high as possible (the losses as low as
> > possible).
>
> You recommended did hot use varistors? I'm thinking about
> some kindhttp://www.toshiba.com/taec/components2/Datasheet_Sync//273/1343.pdf
> 20 in parallel
> --------------------------------------
> Ultra low series resistance: rs = 0.20 Ù (typ.)
> --------------------------------------
> It will be 0.02 Om
So 0.02 ohms sounds like a small amount, but it's almost half as much
as the resistance of the copper loop. This may not be a bad thing,
because the Q is so high that the bandwidth will only be about 3.5kHz
assuming a lossless capacitor, and with the added loss the Q will be
lowered to perhaps 1400, allowing a slightly wider bandwidth. With so
narrow a bandwidth you need to be concerned about the stability of the
varicap diodes' capacitance. Still, I would think a very high Q fixed
capacitor supplying most of the total capacitance would be a good
thing. Use only enough varicap to cover the tuning range you want.
So for example, with 2.69uH inductance, if you want to cover 7.00MHz
to 7.30MHz, you need 192.2pF at the low end and 176.7pF at the high
end, a range of a little less than 16pF. You should be able to do
that easily with two of your suggested varicap diodes, perhaps a
couple of fixed 82pF high Q caps, and a high Q trimmer such as a
piston trimmer to trim the center of the range.
>
> > Reg suggests the Q for use at 7MHz will be around 2000, so
> > the bandwidth is quite narrow. If the Q really is that high (polish
> > the copper and coat it with a protective varnish or paint...), the
> > parallel resonant impedance will be up around 200k ohms, so it should
> > be a decent match to your FET amplifier. Make sure any loading at the
> > gap is well above 200k ohms resistive, to keep from introducing
> > significant additional loss.
>
> I'm thinking about soldering a box from FR4.
>
> If you want the antenna to also do a
>
> > good job rejecting locally generated E field noise, you need to keep
> > things well balanced.
>
> What you mean about balanced? Differential output? I should think
> about it.
It has more to do with the symmetry of the way the antenna is
mounted. You want to make sure that the capacitance to ground from
each side is as nearly the same as possible. You need to put the gap
in the loop (the feedpoint) either at the top or at the bottom of the
antenna, and for mounting it's often easier to put it at the top.
That way you can clamp onto the middle of the bottom of the loop to
mount to a pole... But if you have a balanced amplifier at the
bottom and bridge the gap symmetrically across the box that amplifier
is mounted in, it should also work well. I recommend to you the
discussion about small loop antennas in King, Mimno and Wing's
"Transmission Lines, Antennas and Waveguides."
>
> > But at 7MHz, this is probably of marginal
> > utility since any noise generators whose noise would be rejected would
> > have to be very close to the antenna--within a few tens of meters.
> > -- I've done similar amplifiers for multi-turn loops for LF, down
> > around 150kHz, using a balanced JFET design directly across the loop,
> > with good success.
>
> > You can find the suggested programs athttp://www.zerobeat.net/G4FGQ/.
> > And you likely would get some additional replies if you cross-post to
> > rec.radio.amateur.antenna.
>
> Thank.
>
> Artem.
Cheers,
Tom
Artem
> for info on calculating the radiation resistance. I believe that will
> be helpful.
I assume Reg's RJELoop1.exe uses essentially the formula
> you'll find there. For your loop, that program says inductance is
> 2.69uH, conductor loss resistance is 46.2 milliohms, and radiation
> resistance is 5.7 milliohms. Although the conductor loss resistance
> (essentialy the same as you calculated above is "not bad," you need to
> consider it with relation to the very low radiation resistance. A
> current in the loop will dissipate far more power in the resistive
> loss than in the radiation resistance. You ideally will keep the loss
> resistance small compared with the radiation resistance, though for
> receiving (because of the very high level of atmospheric noise on HF
> and lower frequencies) it matters not nearly so much as for
> transmitting. When transmitting, you want your power to go into radio
> waves, not heat.
No transmitted. Only received.
When receiving you only need signal greater than
> noise, and it is relatively easy to make an amplifier with low enough
> noise figure that even an inefficient antenna will result in an
> amplifier output whose noise is dominated by the atmospheric noise
> received by the antenna.
Is the BF981 will be good enough for this?
> > You recommended did hot use varistors? I'm thinking about
> > some kindhttp://www.toshiba.com/taec/components2/Datasheet_Sync//273/1343.pdf
> > 20 in parallel
> > --------------------------------------
> > Ultra low series resistance: rs = 0.20 Ù (typ.)
> > --------------------------------------
> > It will be 0.02 Om
>
> So 0.02 ohms sounds like a small amount, but it's almost half as much
> as the resistance of the copper loop. This may not be a bad thing,
> because the Q is so high that the bandwidth will only be about 3.5kHz
> assuming a lossless capacitor, and with the added loss the Q will be
> lowered to perhaps 1400, allowing a slightly wider bandwidth. With so
I'm interesting in QRSS receiving. So narrow bandwidth is very useful
because it will help suppress noise from PC with I will connect to
radio.
> narrow a bandwidth you need to be concerned about the stability of the
> varicap diodes' capacitance. Still, I would think a very high Q fixed
> capacitor supplying most of the total capacitance would be a good
> thing. Use only enough varicap to cover the tuning range you want.
> So for example, with 2.69uH inductance, if you want to cover 7.00MHz
> to 7.30MHz, you need 192.2pF at the low end and 176.7pF at the high
> end, a range of a little less than 16pF. You should be able to do
> that easily with two of your suggested varicap diodes, perhaps a
> couple of fixed 82pF high Q caps, and a high Q trimmer such as a
> piston trimmer to trim the center of the range.
Understand. Its uneasy to find high stable capacitor at this range.
But maybe I can find vacuum capacitors or something like this.
>
> > What you mean about balanced? Differential output? I should think
> > about it.
>
> It has more to do with the symmetry of the way the antenna is
> mounted. You want to make sure that the capacitance to ground from
> each side is as nearly the same as possible. You need to put the gap
> in the loop (the feedpoint) either at the top or at the bottom of the
> antenna, and for mounting it's often easier to put it at the top.
I think that gap at the bottom add more mechanical strength. And it
should be easy to connect coaxial cable.
> That way you can clamp onto the middle of the bottom of the loop to
> mount to a pole... But if you have a balanced amplifier at the
> bottom and bridge the gap symmetrically across the box that amplifier
> is mounted in, it should also work well.
It's mean two transistors ans transformer for connect this to the
cable.
Thank.
Mark
 I'd recommend you use a
> C0G ceramic or possibly silvered-mica capacitor for most of the tuning
> capacitance, to keep the Q as high as possible (the losses as low as
> possible). Â Reg suggests the Q for use at 7MHz will be around 2000, so
> the bandwidth is quite narrow. Â If the Q really is that high (polish
> the copper and coat it with a protective varnish or paint...),
Do you have any solid evidence or citation that polishing really helps
at 7 MHz?
Mark
Artem
At this frequency skin effect 0.028mm.
It's uneasy to explain for me because my English is not enough. But
It's more short way by plane territory that through mountains. For RF
if very simply: mountains must be no more than 0.028mm at 7MHz. IMHO.
>
> Mark
K7ITM
... (snipping out a lot to keep this a reasonably length...)
>
> No transmitted. Only received.
I understand, but my point is that an antenna is reciprocal: there is
the same percentage loss in the copper resistance whether receiving or
transmitting.
...
>
> Is the BF981 will be good enough for this?
I would think almost any modern RF mosfet would be fine. You do not
need very good noise figure for HF reception, even with an antenna
with modest efficiency. Just make sure the amplifier input has high
effective shunt resistance at the operating frequency-- greater than
200kohms--to preserve the high Q.
...
> Understand. Its uneasy to find high stable capacitor at this range.
> But maybe I can find vacuum capacitors or something like this.
It should not be that bad. C0G dielectric (also called NPO)
capacitors have a _maximum_ temperature coefficient of 30ppm/C. The
diameter of the loop itself, and therefore its inductance, will change
with temperature in the same range, I believe. C0G capacitors,
especially surface mount type, also have extremely low effective
series resistance. I've found some C0G SMT caps that seem to have
very close to zero temperature coefficient--it varies from lot to lot,
apparently depending on the exact mix of the dielectric. What do you
suppose the temperature coefficient of the capacitance of varactor
diodes is? Note: 100ppm change in capacitance causes 50ppm change in
resonant frequency. That's 350Hz at 7MHz. You probably wouldn't even
notice that. It's only about 10 percent of the 3dB bandwidth of the
antenna.
Cheers,
Tom
Artem
>
> It should not be that bad. C0G dielectric (also called NPO)
> capacitors have a _maximum_ temperature coefficient of 30ppm/C. The
> diameter of the loop itself, and therefore its inductance, will change
> with temperature in the same range, I believe. C0G capacitors,
> especially surface mount type, also have extremely low effective
> series resistance. I've found some C0G SMT caps that seem to have
> very close to zero temperature coefficient--it varies from lot to lot,
> apparently depending on the exact mix of the dielectric. What do you
> suppose the temperature coefficient of the capacitance of varactor
> diodes is? Note: 100ppm change in capacitance causes 50ppm change in
> resonant frequency. That's 350Hz at 7MHz. You probably wouldn't even
> notice that. It's only about 10 percent of the 3dB bandwidth of the
> antenna.
Thank you very much. About about transformer (for connect coaxial
cable). I can use any ferrite with small permeabilty?
Tom Bruhns
Citation would be an article written by an engineer at Andrew and
published 10-15 years ago that I unfortunately can't find.
"Polishing" (implying a mirror-like finish) certainly isn't necessary,
but I do think it's worthwhile getting it reasonably clean and then
protecting it so corrosion doesn't set in. In the case of the antenna
presented here, the copper resistance is about ten times the radiation
resistance, so there is some incentive to keeping it as low as
practical. In the case of a typical resonant dipole, the copper
resistance is such a small percentage of the radiation resistance that
it's much less concern.
Cheers,
Tom
Tom Bruhns
Yes, that should be fine. I suppose a transformer will be a
convenient way to better match the FET amplifier output to a
transmission line. The transformer can be physically quite small.
MiniCircuits and some others (CoilCraft; M/A-Com; ...) sell
appropriate transformers, and of course they are easy to make if you
have an appropriate core. Also you can feed power to the amplifier
through the transmission line. The transformer secondary can return
to a bypass capacitor instead of directly to ground, and your DC feed
appears across that capacitor. The circuit I used for 150kHz loops
used a shunt voltage regulator in the amplifier, and by feeding the
other end with a controlled variable current, I could avoid problems
with uncertain voltage drop in the line plus connectors, and also use
the current through the regulator to control the tuning voltage on the
varicap diodes. So everything was done through the transmission line.
Cheers,
Tom
Artem
> On Mar 14, 9:20 am, Artem <artem.b...@gmail.com> wrote:
>
>
>
> > On Mar 13, 11:38 pm, K7ITM <k7...@msn.com> wrote:
>
> > > It should not be that bad. C0G dielectric (also called NPO)
> > > capacitors have a _maximum_ temperature coefficient of 30ppm/C. The
> > > diameter of the loop itself, and therefore its inductance, will change
> > > with temperature in the same range, I believe. C0G capacitors,
> > > especially surface mount type, also have extremely low effective
> > > series resistance. I've found some C0G SMT caps that seem to have
> > > very close to zero temperature coefficient--it varies from lot to lot,
> > > apparently depending on the exact mix of the dielectric. What do you
> > > suppose the temperature coefficient of the capacitance of varactor
> > > diodes is? Note: 100ppm change in capacitance causes 50ppm change in
> > > resonant frequency. That's 350Hz at 7MHz. You probably wouldn't even
> > > notice that. It's only about 10 percent of the 3dB bandwidth of the
> > > antenna.
>
> > Thank you very much. About about transformer (for connect coaxial
> > cable). I can use any ferrite with small permeabilty?
>
> Yes, that should be fine. I suppose a transformer will be a
> convenient way to better match the FET amplifier output to a
> transmission line.
I mean that I will use you suggestion about balanced amplifier. I'll
use two FETs. I'll place one more tube from middle of the loop to the
gap. And I will use this point as ground point for balanced amplifier.
In this case I will have differential signal at FET Drains and I will
need transformer for put this signal to coaxial cable.
The transformer can be physically quite small.
> MiniCircuits and some others (CoilCraft; M/A-Com; ...) sell
> appropriate transformers, and of course they are easy to make if you
> have an appropriate core. Also you can feed power to the amplifier
> through the transmission line. The transformer secondary can return
> to a bypass capacitor instead of directly to ground, and your DC feed
> appears across that capacitor. The circuit I used for 150kHz loops
> used a shunt voltage regulator in the amplifier, and by feeding the
> other end with a controlled variable current, I could avoid problems
> with uncertain voltage drop in the line plus connectors, and also use
> the current through the regulator to control the tuning voltage on the
> varicap diodes. So everything was done through the transmission line.
My cable only 10m long. So I this it would be unnecessary. And I will
operate with three signals:
1. Varicaps voltages.
2,3 - voltages at secondary FETs gates.
>
> Cheers,
> Tom
K7ITM
> use two FETs. I'll place one more tube from middle of the loop to the
> gap. And I will use this point as ground point for balanced amplifier.
> In this case I will have differential signal at FET Drains and I will
> need transformer for put this signal to coaxial cable.
>
> The transformer can be physically quite small.
>
Yes...very good. That should help keep the loop nicely balanced,
especially if you build it all very symmetrical. That one more tube
can also then help support the loop mechanically. Good luck with your
project!
Cheers,
Tom
Mark
>
> > Do you have any solid evidence or citation that polishing really helps
> > at 7 MHz?
>
> At this frequency skin effect 0.028mm.
> It's uneasy to explain for me because my English is not enough. But
> It's more short way by plane territory that through mountains. For RF
> if very simply: mountains must be no more than 0.028mm at 7MHz. IMHO.
>
>
Yes I understand the radiation resistance is low so loss resistnce is
very critical.
Isn't 0.028mm still pretty rough as far as surface finishes go?
I can understand surface finish can vbe significant at a few GHz, but
7 MHz????
Mark
mi...@sushi.com
> I'm looking how to make narrow band active antenna for 7 or 10.1mzh.
> My idea: I will use magnetic antenna with one loop. A one-turn loop of
> 3.14m cupper pipe with diameter 15mm has 2.687uH. With Varicaps of
> 192pf it will have resonance frequency of 7MHz. I will load this LC
> Should it work? I'll never seen such schematics. Usually people use
> transformers. But I will place this transistor directly inside gap in
> the loop of cupper pipe. The Gate of MOSFET will add only additional
> 2pf to Varicaps and it will be very easy to compensate.
>
> Sorry for English.
The ARRL has a few such designs in their antenna handbook.
Most receive antenna designs use a 2nd loop to connect the
amplifier.
JosephKK
wrote:
In the HF MHz range (3 to 30 MHz) Litz wire is a better improvement to
RF signal conduction than pipe. Pipe does not become all that useful
until VHF and over 100 MHz, and becomes very much less helpful by 500
MHz.
Two or three turns may be better as well.
Artem
> On Mar 14, 2:15 pm, Artem <artem.b...@gmail.com> wrote:
Yes...very good. That should help keep the loop nicely balanced,
> especially if you build it all very symmetrical. That one more tube
Hi. I have some problem. I can't receive nothing except noise And self
oscillation frequency.
I have some photos. Could any give me some suggestions?
Antenna:
http://artembond.no-ip.info/apache2-default/DSC_9427.JPG
Chematics:
http://artembond.no-ip.info/apache2-default/DSC_9431.JPG
Amplifier:
http://artembond.no-ip.info/apache2-default/DSC_9426.JPG
GregS
I think you need to narrow band those photos.
greg
Artem
> In article <9b9f8451-c293-4be2-ad02-8c6e606dc...@e10g2000prf.googlegroups.com>, Artem <artem.b...@gmail.com> wrote:
>
>
> I think you need to narrow band those photos.
>
Martin Griffith
Joerg
I remember the pain in my wrists from polishing load coils and such.
Yes, it did make a difference and if you slacked off for too long the
stuff would actually become hot when exposed to a few hundred watts.
So, I learned to develop enough dexterity in my left hand in order to
switch wrists from time to time. Many tubes of Wenol polishing paste
have gone into this effort over the years.
--
Regards, Joerg
Richard Clark
wrote:
>Hi. I have some problem. I can't receive nothing except noise And self
>oscillation frequency.
Try choking both what are labeled "RF Out" and "Shield Cable."
73's
Richard Clark, KB7QHC
K7ITM
:-) I saw the comment about "narrow-banding" the images. They were
perhaps a little more than we needed, but it was nice to have
something we could actually see. They did not take very long to
download here, but someone with a slow connection may have troubles.
One comment: usually you do not need much voltage gain. It is enough
to get power gain with the FETs. That is, the received signal voltage
across the gap of the loop, as resonated by the capacitors, should be
high enough to be used with a good receiver. The problem is that the
impedance is very high there. But that same high impedance makes for
easy oscillation. From what you posted, it sounds like maybe you have
identified an oscillation. If the AGC voltage is low enough, does the
oscillation stop? The amplifier I built used two stages, an FET input
stage and a buffer stage, and it had very low voltage gain--I am
remembering about 3:1 or only 10dB, and maybe only 1:1 or 0dB
including the output transformer, but quite a bit of power gain since
it transformed the high loop impedance down to 50 ohms for the
feedline.
Also, there should be no need for the RF chokes from the gate-1 to
source, if the loop is grounded at the bottom. If the loop is
grounded at the bottom, the loop plus the RF chokes will short out the
source-to-ground resistor. Maybe there is not a need to raise the
source voltage above DC ground potential anyway. Also, it may help to
NOT bypass the sources to ground, to allow some negative feedback.
That may help stabilize the amplifier.
If other things occur to me, I will post them...
Cheers,
Tom
JosephKK
Hunh? WTH? I have had loading coils, tuning coils, etc. go for
years without polishing at 1 KW in regular use. An HF transceiver to
be sure, but what is the difference here?
Artem
> On Mar 20, 12:58 pm, Artem <artem.b...@gmail.com> wrote:
>
> :-) I saw the comment about "narrow-banding" the images. They were
> perhaps a little more than we needed, but it was nice to have
> something we could actually see. They did not take very long to
> download here, but someone with a slow connection may have troubles.
I'm move images to ImageShack
http://img524.imageshack.us/my.php?image=dsc9427ib7.jpg
http://img262.imageshack.us/my.php?image=dsc9431tv9.jpg
>
> One comment: usually you do not need much voltage gain. It is enough
> to get power gain with the FETs. That is, the received signal voltage
> across the gap of the loop, as resonated by the capacitors, should be
> high enough to be used with a good receiver. The problem is that the
> impedance is very high there. But that same high impedance makes for
> easy oscillation. From what you posted, it sounds like maybe you have
> identified an oscillation. If the AGC voltage is low enough, does the
> oscillation stop?
Yes. It's stop. my main reason for this antenna is make very narrow
antenna for city. I can't receive to my receiver almost nothing by big
nose from computers, lamps and other things. But looks like this
antenna did not help. Its amplify narrow-band noise. And even add more
noise when oscillated.
The amplifier I built used two stages, an FET input
> stage and a buffer stage, and it had very low voltage gain--I am
> remembering about 3:1 or only 10dB, and maybe only 1:1 or 0dB
> including the output transformer, but quite a bit of power gain since
> it transformed the high loop impedance down to 50 ohms for the
> feedline.
>
> Also, there should be no need for the RF chokes from the gate-1 to
> source, if the loop is grounded at the bottom.
Source is not grounded for DC. For better transistors matching and
overcurrent protection.
If the loop is
> grounded at the bottom, the loop plus the RF chokes will short out the
> source-to-ground resistor. Maybe there is not a need to raise the
> source voltage above DC ground potential anyway. Also, it may help to
> NOT bypass the sources to ground, to allow some negative feedback.
> That may help stabilize the amplifier.
>
Sources is not grounded.
Artem
> On Thu, 20 Mar 2008 12:58:02 -0700 (PDT), Artem <artem.b...@gmail.com>
> wrote:
>
> >Hi. I have some problem. I can't receive nothing except noise And self
> >oscillation frequency.
>
> Try choking both what are labeled "RF Out" and "Shield Cable."
>
cs_po...@hotmail.com
wrote:
> I remember the pain in my wrists from polishing load coils and such.
> Yes, it did make a difference and if you slacked off for too long the
> stuff would actually become hot when exposed to a few hundred watts.
>
> So, I learned to develop enough dexterity in my left hand in order to
> switch wrists from time to time. Many tubes of Wenol polishing paste
> have gone into this effort over the years.
Can you use a cotton strip looped around the conductor and saw it back
and forth?
Called "ragging" very common in musical instrument business going back
hundreds of years.
K7ITM
> On Mar 21, 2:56 am, K7ITM <k7...@msn.com> wrote:
>
> > On Mar 20, 12:58 pm, Artem <artem.b...@gmail.com> wrote:
>
> > :-) I saw the comment about "narrow-banding" the images. They were
> > perhaps a little more than we needed, but it was nice to have
> > something we could actually see. They did not take very long to
> > download here, but someone with a slow connection may have troubles.
>
Yes, unfortunately noise that is generated more than one or two
wavelengths away from your antenna will be almost entirely
electromagnetic by the time it reaches your antenna. Antennas do not
differentiate between "electrically generated" and "magnetically
generated" noise, when you are far enough that the electromagnetic
field dominates over any near-field electric or magnetic field. The
balanced small loop is good for rejecting electric-field noise only if
(1) the noise is generated close to the antenna and (2) the antenna is
close to the ground (so the electric field is guaranteed to be nearly
vertical) -- -- where "close" means relative to a wavelength. So the
small balanced loop is especially good for LF and VLF work.
Perhaps someone else will have suggestions about what else you might
try.
Cheers,
Tom
Artem
> On Mar 21, 3:08 am, Artem <artem.b...@gmail.com> wrote:
>
> > Sources is not grounded.
>
> Yes, unfortunately noise that is generated more than one or two
> wavelengths away from your antenna will be almost entirely
> electromagnetic by the time it reaches your antenna. Antennas do not
> differentiate between "electrically generated" and "magnetically
> generated" noise, when you are far enough that the electromagnetic
I did not hear nothing about electrically or magnetically photons.
It's just photons.
> field dominates over any near-field electric or magnetic field. The
> balanced small loop is good for rejecting electric-field noise only if
> (1) the noise is generated close to the antenna and
Yes. Computer, lamps etc close to antenna.
> (2) the antenna is
> close to the ground (so the electric field is guaranteed to be nearly
15 floor of 16-floor building. But I think that in this case "ground"
are building walls.
> vertical) -- -- where "close" means relative to a wavelength. So the
> small balanced loop is especially good for LF and VLF work.
my reason was make narrow-band antenna. For reject all out of band
noise.
Artem
> Yes, it did make a difference and if you slacked off for too long the
> stuff would actually become hot when exposed to a few hundred watts.
John Ferrell
>
>my reason was make narrow-band antenna. For reject all out of band
>noise.
>
intermod noise and the sooner you can stop it, the better.
In my youth I recall calling CQ on 42 mhz for a couple of weeks.
Fortunately, a very sharp yagi and very low power saved me from a
violation.
John Ferrell W8CCW
Beware of the dopeler effect (pronounced dope-ler).
That's where bad ideas seem good if they come at you
fast enough.
K7ITM
> On Mar 21, 6:26 pm, K7ITM <k7...@msn.com> wrote:
>
> > On Mar 21, 3:08 am, Artem <artem.b...@gmail.com> wrote:
>
> > > Sources is not grounded.
>
> > Yes, unfortunately noise that is generated more than one or two
> > wavelengths away from your antenna will be almost entirely
> > electromagnetic by the time it reaches your antenna. Antennas do not
> > differentiate between "electrically generated" and "magnetically
> > generated" noise, when you are far enough that the electromagnetic
>
> I did not hear nothing about electrically or magnetically photons.
> It's just photons.
:-) Oh, no, not photons again! When you are near to a source -- to a
transmitting antenna or to a computer radiating noise -- the fields in
general have not developed fully into electromagnetic waves -- photons
if you wish. It is quite usual that, close to the source, either the
electric or the magnetic field will dominate. Often from noise
sources, the near field is predominantly electric, and a properly done
loop antenna will reject that, responding only to the, um, photons.
>
> > field dominates over any near-field electric or magnetic field. The
> > balanced small loop is good for rejecting electric-field noise only if
> > (1) the noise is generated close to the antenna and
>
> Yes. Computer, lamps etc close to antenna.
>
> > (2) the antenna is
> > close to the ground (so the electric field is guaranteed to be nearly
>
> 15 floor of 16-floor building. But I think that in this case "ground"
> are building walls.
There is a hint here: it is common that tall buildings incorporate a
lot of steel, and that will likely act as a shield. I hope this
antenna is not mounted inside!
>
> > vertical) -- -- where "close" means relative to a wavelength. So the
> > small balanced loop is especially good for LF and VLF work.
>
> my reason was make narrow-band antenna. For reject all out of band
> noise.
A reasonable thing to do, though a good receiver with a low-distortion
and fairly narrow-band front end should not have trouble with out-of-
band signals (noise). Do you have a quantitative measure of just how
strong this out of band noise is? I'd personally much rather use a
preselection filter separate from the antenna, and close to my
operating position, to reject out-of-band signals. Even though the
antenna you have described has very high Q, I believe I could do
better with a two or three resonator filter running at lower Q, since
the slope of the attenuation versus frequency is much greater. Unless
there was some especially strong signal in the band, I would at least
consider a fixed-tuned bandpass filter that covered my band of
interest, assuming that band is fairly narrow such as 7.0-7.1MHz.
Can you tell that you are getting the expected antenna bandwidth,
about 3kHz at the 3dB points at 7MHz?
If the amplifier at the antenna has a tendency to oscillate, it very
likely also has poor intermodulation performance. Be careful that it
doesn't destroy the benefits you are trying to obtain.
Cheers,
Tom
Artem
>
> > 15 floor of 16-floor building. But I think that in this case "ground"
> > are building walls.
>
> There is a hint here: it is common that tall buildings incorporate a
> lot of steel, and that will likely act as a shield. I hope this
> antenna is not mounted inside!
It's not mounted at all. But for tests I'm put this antenna outside.
>
>
>
> > > vertical) -- -- where "close" means relative to a wavelength. So the
> > > small balanced loop is especially good for LF and VLF work.
>
> > my reason was make narrow-band antenna. For reject all out of band
> > noise.
>
> A reasonable thing to do, though a good receiver with a low-distortion
> and fairly narrow-band front end should not have trouble with out-of-
> band signals (noise). Do you have a quantitative measure of just how
> strong this out of band noise is?
Not. Just not received.
I'd personally much rather use a
> preselection filter separate from the antenna, and close to my
> operating position, to reject out-of-band signals. Even though the
> antenna you have described has very high Q, I believe I could do
> better with a two or three resonator filter running at lower Q, since
> the slope of the attenuation versus frequency is much greater.
I will receive QRSS at all. And I think that it would be best way is
using
narrow-band antenna -> filter -> synchronous detector.
> there was some especially strong signal in the band, I would at least
> consider a fixed-tuned bandpass filter that covered my band of
> interest, assuming that band is fairly narrow such as 7.0-7.1MHz.
>
> Can you tell that you are getting the expected antenna bandwidth,
> about 3kHz at the 3dB points at 7MHz?
I'm just testing. I will purchase RF generator in next week and test.
Now I have only self-oscillation frequency.
Antenna looks like working. I'm receiving a lots of Morse signals at
7.000 - 7050 Mhz. But I cant recognize any voice signal.
This is receiving signal. Looks like narrow-band enough. This is not
self oscillation. In self oscillation voltage a few volts.
http://img148.imageshack.us/my.php?image=ds0000bu6.png
This is schematics. I'm not sure that I'm correct use gual gate
transistors.
http://img210.imageshack.us/my.php?image=schbr1.jpg
I'm not sure that using shielded cable and ferrite chocks is good
idea.
http://img171.imageshack.us/my.php?image=hwak2.jpg
np0 caps.
http://img370.imageshack.us/my.php?image=capsnf8.jpg
Richard Clark
wrote:
>Antenna looks like working. I'm receiving a lots of Morse signals at
>7.000 - 7050 Mhz. But I cant recognize any voice signal.
Side Band?
>I'm not sure that using shielded cable and ferrite chocks is good
>idea.
Not enough choking and needs to be repeated a quarter wave down the
choked wire(s).
Artem
Artem
> On Sun, 23 Mar 2008 12:39:35 -0700 (PDT), Artem <artem.b...@gmail.com>
> wrote:
>
> >Antenna looks like working. I'm receiving a lots of Morse signals at
> >7.000 - 7050 Mhz. But I cant recognize any voice signal.
>
> Side Band?
No. Out of band. I'm now add varicaps and all working! Antenna really
very narrow.
>
> >I'm not sure that using shielded cable and ferrite chocks is good
> >idea.
>
> Not enough choking and needs to be repeated a quarter wave down the
> choked wire(s).
It's 7Mhz. quarter wave is 10 miters.
I'm use choking:
between amplifier and antenna
between transformer and coax cable.
For amplifier power wires and gain control.
Richard Clark
wrote:
>> >I'm not sure that using shielded cable and ferrite chocks is good
>> >idea.
>>
>> Not enough choking and needs to be repeated a quarter wave down the
>> choked wire(s).
>
>It's 7Mhz. quarter wave is 10 miters.
Then again at the far end of the wire(s).
>I'm use choking:
>between amplifier and antenna
>between transformer and coax cable.
>For amplifier power wires and gain control.
I've observed that, and I have observed it is not enough from your
photo - if you still have self-oscillation. Your pictures do not
reveal any choking of the RF Out cable.
As for the diagonal arm for "ground." This is fine insofar as it
being placed in the electrical middle of the antenna loop (a ground),
but all this rat's nest of wiring throws the concept of balance out
the window. I see in earlier pictures where you clean that up with
careful routing, but it seems much too busy. This leads me into the
comments following:
On another note, the AGC seems overly elaborate, especially when all
that wire could be introducing the self-oscillation. Further, wiring
in power seems another invitation to problems when a 9V battery would
solve that too. Local power would discard the need for the ground
coming from the loop's perimeter, eliminate unnecessary AGC, reduce
the complexity of choking, lower gain (it obviously has too much), and
give you only one coax coming from the antenna.
You need to solve the self-oscillation through removing complexity.
When you accomplish that, THEN that is the time to add it back in, one
thing at a time. You will probably discover all those features and
design gimmicks are not worth it.
Richard Clark
wrote:
>COOL! All worked!
It would seem no further advice is necessary, much less my last bit of
wisdom on the topic.
It would help if you were to elaborate as to what actually killed the
oscillation.
Artem
> On Sun, 23 Mar 2008 14:42:22 -0700 (PDT), Artem <artem.b...@gmail.com>
> wrote:
>
> >> >I'm not sure that using shielded cable and ferrite chocks is good
> >> >idea.
>
> >> Not enough choking and needs to be repeated a quarter wave down the
> >> choked wire(s).
>
> >It's 7Mhz. quarter wave is 10 miters.
>
> Then again at the far end of the wire(s).
>
> >I'm use choking:
> >between amplifier and antenna
> >between transformer and coax cable.
> >For amplifier power wires and gain control.
>
> I've observed that, and I have observed it is not enough from your
> photo - if you still have self-oscillation. Your pictures do not
> reveal any choking of the RF Out cable.
It's inside. Nearby BNC socket.
>
> As for the diagonal arm for "ground." This is fine insofar as it
> being placed in the electrical middle of the antenna loop (a ground),
> but all this rat's nest of wiring throws the concept of balance out
> the window.
I think that some disbalance should compensate differencial amplifier
on transistors.
> I see in earlier pictures where you clean that up with
> careful routing, but it seems much too busy. This leads me into the
> comments following:
>
> On another note, the AGC seems overly elaborate, especially when all
> that wire could be introducing the self-oscillation. Further, wiring
> in power seems another invitation to problems when a 9V battery would
> solve that too. Local power would discard the need for the ground
Yes. But FETs draw more that 10ma each.
> coming from the loop's perimeter, eliminate unnecessary AGC, reduce
> the complexity of choking, lower gain (it obviously has too much), and
> give you only one coax coming from the antenna.
Cable length is not problem. I'm living in apartment. I can put
antenna outside the window. But not on the roof.
I can make power supply over coax cable. I can put Atmega8 (en
example) to amplifier and add DACs for operate varicaps, AGC. I can
add rectifier and filter for detect self-oscillation and automatics
reduce AGC. But it's not necessary.
Richard Clark
wrote:
>> I've observed that, and I have observed it is not enough from your
>> photo - if you still have self-oscillation. Your pictures do not
>> reveal any choking of the RF Out cable.
>
>It's inside. Nearby BNC socket.
Which defeats the choking.
>> As for the diagonal arm for "ground." This is fine insofar as it
>> being placed in the electrical middle of the antenna loop (a ground),
>> but all this rat's nest of wiring throws the concept of balance out
>> the window.
>
>I think that some disbalance should compensate differencial amplifier
>on transistors.
That makes no sense whatever.
>>another invitation to problems when a 9V battery would
>> solve that too. Local power would discard the need for the ground
>
>Yes. But FETs draw more that 10ma each.
That is trivial. However, you can bias for less because you don't
need that much drain current.
>> coming from the loop's perimeter, eliminate unnecessary AGC, reduce
>> the complexity of choking, lower gain (it obviously has too much), and
>> give you only one coax coming from the antenna.
>
>Cable length is not problem. I'm living in apartment. I can put
>antenna outside the window. But not on the roof.
>
>I can make power supply over coax cable. I can put Atmega8 (en
>example) to amplifier and add DACs for operate varicaps, AGC. I can
>add rectifier and filter for detect self-oscillation and automatics
>reduce AGC. But it's not necessary.
Sounds like a lot of unnecessary complexity. The one thing you repeat
is varicaps, but I don't see them.
Artem
>> As for the diagonal arm for "ground." This is fine insofar as it
> >> being placed in the electrical middle of the antenna loop (a ground),
> >> but all this rat's nest of wiring throws the concept of balance out
> >> the window.
>
> >I think that some disbalance should compensate differencial amplifier
> >on transistors.
>
> That makes no sense whatever.
Disbalance mean in-phase signal on gate 1 FETs. differencial will not
amplify this signal.
> Sounds like a lot of unnecessary complexity. The one thing you repeat
> is varicaps, but I don't see them.
I have. I just did now how them because this is trivial.
Artem
>> As for the diagonal arm for "ground." This is fine insofar as it
> >> being placed in the electrical middle of the antenna loop (a ground),
> >> but all this rat's nest of wiring throws the concept of balance out
> >> the window.
>
> >I think that some disbalance should compensate differencial amplifier
> >on transistors.
>
> That makes no sense whatever.
Disbalance mean in-phase signal on gate 1 FETs. differencial will not
amplify this signal.
> Sounds like a lot of unnecessary complexity. The one thing you repeat
> is varicaps, but I don't see them.
I have. I just did now how them because this is trivial.
Artem
>I just did now how them because this is trivial.
Sorry.
Artem
Artem
Richard Clark
wrote:
>> >I think that some disbalance should compensate differencial amplifier
>> >on transistors.
>>
>> That makes no sense whatever.
>
>Disbalance mean in-phase signal on gate 1 FETs. differencial will not
>amplify this signal.
This is still a strain in language as you have done nothing to
describe what the "compensation" is for. The circuit of your
schematic is fully differential in a bridge configuration, so saying
it will not amplify still makes no sense. To offer a deliberate
imbalance to a balanced circuit gives rise to astability which is the
first hallmark of oscillation - especially in an amplifier with too
much gain, and too much current drain - or a lockdown.
I get every impression that this bridge configuration arrived from
some sense of "ground" that then drove the need for the cross piece to
the midpoint of the loop. That point is "ground", but only as an
electrical neutral to the loop. It carries no other "ground"
distinction and you could have as easily built a single MOSFET
amplifier rather than a bridge configuration. A split shield around
the loop (or integrating it into the design) would have simplified AGC
and control lines too.
You tried to incorporate some of the split shield design into this
when you enclosed the amplifier and made a socket connection, but you
defeated the benefit of the choke at the same time with a zero net
gain (the choke, as built, has no use).
>> Sounds like a lot of unnecessary complexity. The one thing you repeat
>> is varicaps, but I don't see them.
>
>I have. I just did now how them because this is trivial.
They are not shown in your schematic. I don't see them in your
photos. Making them operational is adding yet more lines, although I
can see they would be necessary for your purposes.
Providing the decoupled varicap bias into a balanced circuit is not
trivial at all, and offers the prospects of returning to that self
oscillation. There will be something like half a dozen components for
that alone.
HOWEVER, this is all beside the point unless your design breaks into
oscillation again. You haven't informed us how you cured that since
you announced you had solve all your problems.
Artem
> On Mon, 24 Mar 2008 07:59:50 -0700 (PDT), Artem <artem.b...@gmail.com>
> wrote:
>
> >> >I think that some disbalance should compensate differencial amplifier
> >> >on transistors.
>
> >> That makes no sense whatever.
>
> >Disbalance mean in-phase signal on gate 1 FETs. differencial will not
> >amplify this signal.
>
> This is still a strain in language as you have done nothing to
> describe what the "compensation" is for. The circuit of your
> schematic is fully differential in a bridge configuration, so saying
> it will not amplify still makes no sense. To offer a deliberate
It will not amplify signal in-phase signal. It's same like
differential amplifier.
> I get every impression that this bridge configuration arrived from
> some sense of "ground" that then drove the need for the cross piece to
> the midpoint of the loop. That point is "ground", but only as an
> electrical neutral to the loop. It carries no other "ground"
Yes. It's "Ground" only for bridge amplifier.
> distinction and you could have as easily built a single MOSFET
> amplifier rather than a bridge configuration. A split shield around
It's more difficult for me. It's looks more simply for me to build
fully symmetrical amplifier.
> the loop (or integrating it into the design) would have simplified AGC
> and control lines too.
>
> You tried to incorporate some of the split shield design into this
> when you enclosed the amplifier and made a socket connection, but you
> defeated the benefit of the choke at the same time with a zero net
> gain (the choke, as built, has no use).
I have.
>
> >> Sounds like a lot of unnecessary complexity. The one thing you repeat
> >> is varicaps, but I don't see them.
>
> >I have. I just did now how them because this is trivial.
>
> They are not shown in your schematic. I don't see them in your
> photos. Making them operational is adding yet more lines, although I
> can see they would be necessary for your purposes.
JosephKK
wrote:
>On Mar 22, 8:48 pm, K7ITM <k7...@msn.com> wrote:
Please see the US ARRL frequency chart here:
http://www.arrl.org/FandES/field/regulations/Hambands_color.pdf
7000 to 7050 MHz is RTTY and Morse code only. If you want voice,
probably SSB try 7125 to 7300 MHz.
Artem
> Please see the US ARRL frequency chart here:
>
> http://www.arrl.org/FandES/field/regulations/Hambands_color.pdf
>
> 7000 to 7050 MHz is RTTY and Morse code only. If you want voice,
> probably SSB try 7125 to 7300 MHz.
I'm in Europe. We have only 7000....7100.
Richard Clark
wrote:
>> This is still a strain in language as you have done nothing to
>> describe what the "compensation" is for. The circuit of your
>> schematic is fully differential in a bridge configuration, so saying
>> it will not amplify still makes no sense. To offer a deliberate
>
>It will not amplify signal in-phase signal. It's same like
>differential amplifier.
This still makes no sense. You have not described what you are
"compensating" for, and differential amplifiers amplify without
distinction to "in-phase" or "out-of-phase." If it did, you are not
using the right topology because you are using operational amplifier
terminology - the circuit is not an operational amplifier, even by
discrete components.
>> They are not shown in your schematic. I don't see them in your
>> photos. Making them operational is adding yet more lines, although I
>> can see they would be necessary for your purposes.
>
>http://img245.imageshack.us/my.php?image=d3du5.jpg
Nice close-up. Choking of some of the lines seems OK, but not the
coax. So, now where is the schematic of the biasing for these
varicaps? If those two clear insulation lines are going to the loop,
it is going to be hard to apply DC to a dead short - or does that
black shroud cover more than the varicaps?
Artem
> On Mon, 24 Mar 2008 15:40:53 -0700 (PDT), Artem <artem.b...@gmail.com>
> wrote:
>
> >> This is still a strain in language as you have done nothing to
> >> describe what the "compensation" is for. The circuit of your
> >> schematic is fully differential in a bridge configuration, so saying
> >> it will not amplify still makes no sense. To offer a deliberate
>
> >It will not amplify signal in-phase signal. It's same like
> >differential amplifier.
>
> This still makes no sense. You have not described what you are
> "compensating" for, and differential amplifiers amplify without
> distinction to "in-phase" or "out-of-phase." If it did, you are not
> using the right topology because you are using operational amplifier
> terminology - the circuit is not an operational amplifier, even by
> discrete components.
>
> >> They are not shown in your schematic. I don't see them in your
> >> photos. Making them operational is adding yet more lines, although I
> >> can see they would be necessary for your purposes.
>
> >http://img245.imageshack.us/my.php?image=d3du5.jpg
>
> Nice close-up. Choking of some of the lines seems OK, but not the
> coax.
Could you find in this picture choke?
> So, now where is the schematic of the biasing for these
> varicaps? If those two clear insulation lines are going to the loop,
It's lines from resonance loop to amplifier.
> it is going to be hard to apply DC to a dead short - or does that
> black shroud cover more than the varicaps?
Now my Antenna in broken. I will fix my antenna mad make a web for
schematics, software for calculation? etc.
PS: Could anyone know, What I can receive in QRSS, 7 MHz in Europe on
this
http://www.radiointel.com/review-degende1103.htm
receiver?
Richard Clark
wrote:
>> Nice close-up. Choking of some of the lines seems OK, but not the
>> coax.
>http://img370.imageshack.us/my.php?image=d2eb0.jpg
>
>Could you find in this picture choke?
What material is used in the ferrite?
>> So, now where is the schematic of the biasing for these
>> varicaps? If those two clear insulation lines are going to the loop,
>
>It's lines from resonance loop to amplifier.
Does this mean the varicaps are across the loop?
If so:
>> it is going to be hard to apply DC to a dead short - or does that
>> black shroud cover more than the varicaps?
>
>Now my Antenna in broken. I will fix my antenna mad make a web for
>schematics, software for calculation? etc.
You've done it by parts already, so, sure.
Benj
> Hello all.
> I'm looking how to make narrow band active antenna for 7 or 10.1mzh.
> My idea: I will use magnetic antenna with one loop. A one-turn loop of
> 3.14m cupper pipe with diameter 15mm has 2.687uH. With Varicaps of
> 192pf it will have resonance frequency of 7MHz. I will load this LC
> tank directly to Gate one of dual gate
The most effective antenna for size and gain in this range would be
the DDRR or variations of it such as the normal mode helix. They both
are single loops of copper pipe tuned at the end with a capacitor
(probably a "real" capacitor rather than a varicap would work
better.) The Helix is basically the DDRR with the ground plane
removed and the image side constructed. For more information go look
at my article in a VERY old issue of QST (May 76) and somewhere about
that time you'll also find two articles on the DDRR which are very
detailed and excellent! Note that these are often called "hula hoop"
antennas. They are basically transmission line antennas.
Artem
> On Tue, 25 Mar 2008 13:55:16 -0700 (PDT), Artem <artem.b...@gmail.com>
> wrote:
>
> >> Nice close-up. Choking of some of the lines seems OK, but not the
> >> coax.
> >http://img370.imageshack.us/my.php?image=d2eb0.jpg
>
> >Could you find in this picture choke?
>
> What material is used in the ferrite?
For transformer - low magnetic permeability (50) for chokes - high.
>
> >> So, now where is the schematic of the biasing for these
> >> varicaps? If those two clear insulation lines are going to the loop,
>
> >It's lines from resonance loop to amplifier.
>
> Does this mean the varicaps are across the loop?
Richard Clark
wrote:
>> What material is used in the ferrite?
>
>For transformer - low magnetic permeability (50) for chokes - high.
Unless you can be more specific, this sounds like the wrong material
(which you have not specified - do you know what you used?).
Artem
> On Wed, 26 Mar 2008 04:15:20 -0700 (PDT), Artem <artem.b...@gmail.com>
> wrote:
>
> >> What material is used in the ferrite?
>
> >For transformer - low magnetic permeability (50) for chokes - high.
>
> Unless you can be more specific, this sounds like the wrong material
> (which you have not specified - do you know what you used?).
I'm use USSR ferrite 50HH.
Richard Clark
wrote:
>I'm use USSR ferrite 50HH.
Google reveals all of one page in the entire Web that responds to that
as a search term - and that page refuses to load.