Re: File /AG5RT/LZ1AQ amplifier noise reduction.pdf uploaded
#file-notice
Dear Fred
Please send both papers to me directly.? thanks in advance.
best Paul? VE3PVB
On Thursday, March 20, 2025 at 09:09:20 a.m. EDT, Fred M via groups.io <dl4zao@...> wrote:
Tell me, what you need, i have both papers available.
?
regards, Fred
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Re: File /AG5RT/LZ1AQ amplifier noise reduction.pdf uploaded
#file-notice
Tell me, what you need, i have both papers available.
?
regards, Fred
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Re: File /AG5RT/LZ1AQ amplifier noise reduction.pdf uploaded
#file-notice
On Thu, Mar 20, 2025 at 05:15 AM, Paul V Birke wrote:
can you send me the reference directly to me
Hi Paul,
?
Is the link not working?? If not, you can search on the German word "aktiv" in the files section.? If that does not work, you can contact me directly:? mark-whittington@...?
Mark
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Re: File /AG5RT/LZ1AQ amplifier noise reduction.pdf uploaded
#file-notice
Dear Mark
can you send me the reference directly to me
thanks
Paul? VE3PVB
On Thursday, March 20, 2025 at 07:39:27 a.m. EDT, Mark Whittington AG5RT <mark-whittington@...> wrote:
On Thu, Mar 20, 2025 at 04:10 AM, Paul V Birke wrote:
Maybe that is why the original East German design had a suitable inductor in the same place
There is also this German design that uses the inductors:? ?"Aktiv empangen mit neuen Ideen" (new ideas for active reception)?
?
This may have been the inspiration for the LZ1AQ design.
?
Mark
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Re: File /AG5RT/LZ1AQ amplifier noise reduction.pdf uploaded
#file-notice
On Thu, Mar 20, 2025 at 04:10 AM, Paul V Birke wrote:
Maybe that is why the original East German design had a suitable inductor in the same place
There is also this German design that uses the inductors:? ?"Aktiv empangen mit neuen Ideen" (new ideas for active reception)?
?
This may have been the inspiration for the LZ1AQ design.
?
Mark
|
Re: File /AG5RT/LZ1AQ amplifier noise reduction.pdf uploaded
#file-notice
Complementary Push-Pull
Amplifiers for Active Antennas:
A Critical Review
by
Chris Trask / N7ZWY
Sonoran Radio Research
P.O. Box 25240
Tempe, AZ 85285-5240
Dan, this paper contains the East German KA-1000 design...please download
Paul?? VE3PVB
On Thursday, March 20, 2025 at 01:58:00 a.m. EDT, Dan Clementi <dan@...> wrote:
On Thu, Mar 20, 2025 at 12:28 AM, Paul V Birke wrote:
Maybe that is why the original East German design had a suitable inductor in the same place
East German???? To what are you referring?
As far as I am aware, the LZ1AQ loop amplifier is this one:
?
Dan - K3GMQ
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Re: File /AG5RT/LZ1AQ amplifier noise reduction.pdf uploaded
#file-notice
On Thursday, March 20, 2025 at 01:58:00 a.m. EDT, Dan Clementi <dan@...> wrote:
On Thu, Mar 20, 2025 at 12:28 AM, Paul V Birke wrote:
Maybe that is why the original East German design had a suitable inductor in the same place
East German???? To what are you referring?
As far as I am aware, the LZ1AQ loop amplifier is this one:
?
Dan - K3GMQ
|
Re: "active antenna preamplifiers" in ham radio May 1986
Thank you, Martin.
73 Andrea IN3IWZ?
Il gio 20 mar 2025, 09:06 Martin - Southwest UK via <martin_ehrenfried= [email protected]> ha scritto: Yes, that's the default setting in this group, attachments are removed.
?
Dave, can you add it in the files section please.
?
Regards,
?
Martin
?
?
?
On Thu, Mar 20, 2025 at 06:47 AM, Andrea Dalbagno wrote:
It seems that the attachment has been removed from your email.
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Re: "active antenna preamplifiers" in ham radio May 1986
Yes, that's the default setting in this group, attachments are removed.
?
Dave, can you add it in the files section please.
?
Regards,
?
Martin
?
?
?
On Thu, Mar 20, 2025 at 06:47 AM, Andrea Dalbagno wrote:
It seems that the attachment has been removed from your email.
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Re: "active antenna preamplifiers" in ham radio May 1986
Hi Dave
It seems that the attachment has been removed from your email.
Thanks for all your contributes!
73 Andrea IN3IWZ?
Since the last email I read on this loop antenna group addressed an E-Field probe preamp and I've read a number of high-Z preamps on this group, I'll contribute in that thread: high-Z input preamps.
I've recently completed the 4-JFET preamp.? I'll include the schematic as an attachment to this email.? I've used four J-310 N-Channel JEFTs as the active devices instead of the noted devices (2SK932).? While the completed preamp isn't the epitome of neatness, it is proving to be a stellar performer for high-Z E-Field probes at LF and MF (depends on the ferrite material used in the chokes)!!? Just sitting on the bench and powered up with nothing but power leads connected, all the BCB stations are present and accounted for.? I should also add that with the exception of two AM stations, I am not in a strong-signal area.? Just holding a single finger within 1.5-inches of my input disc ceramic blocking capacitor increases the signals displayed on my spectrum analyzer by some 8 to 10 dB.? I'd recommend it to anyone considering the requirement for a high impedance input to a preamp!!
ADDITIONAL COMMENT:? The use of a CMC for the output and isolating DC from the RF should be adopted in many other preamps.? I will certainly use this trick in future builds that require power over coax (new acronym:? POC ?)).? This trick can also be used in the shack to do the same thing.? No need for a multi-component bias tee...
And, yes, the transformers/chokes are wound on 75 material ferrite.? Fortunately, I had a few.? Each has 20 bifilar turns on a 120-75 (1.2-inches OD of 75? material ferrite).?
Also note the output connector (I used BNCs) must be isolated from the main circuit ground plane.? The schematic clearly reflects this requirement.
One last note:? Once the proper bias current is established with the potentiometer, it can be removed, its value measured, and a fixed resistor of the same value can be installed in its place (I had to search a bit deep in my potentiometer collection to locate a 50k pot.).
Dave - W?LEV
Hi Martin
?
Have you tried the G4COL design with? transformer in the FET circuit?. Its simple and is supposed to have better large signal handling characteristics?
?
?
I have taken some snippets as pictures.
?
I was going to try it to see if it was superior to the Miniwhip design for broadcast band overload.
?
Its from a RSGB publication.
?
Henry
--
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Re: File /AG5RT/LZ1AQ amplifier noise reduction.pdf uploaded
#file-notice
On Thu, Mar 20, 2025 at 12:28 AM, Paul V Birke wrote:
Maybe that is why the original East German design had a suitable inductor in the same place
East German???? To what are you referring?
As far as I am aware, the LZ1AQ loop amplifier is this one:
?
Dan - K3GMQ
|
Re: File /AG5RT/LZ1AQ amplifier noise reduction.pdf uploaded
#file-notice
Maybe that is why the original East German design had a suitable inductor in the same place
Paul VE3PVB
On Wednesday, March 19, 2025 at 10:12:17 p.m. EDT, Group Notification < [email protected]> wrote:
The following items have been added to the Files area of the [email protected] group.
By: Mark Whittington AG5RT <mark-whittington@...>
Description:
LZ1AQ loop amplifier noise reduction
I ran an LTSPICE noise analysis of the original LZ1AQ circuit connected to a 3.3 uH loop. I also performed some bench measurements to verify the SPICE results. The analysis and measurements both indicate placing 47 uH inductors in series with the 51 Ohm input emitter bias resistors cuts input referred noise by 2 to 3 dB. This is a substantial reduction. Gain is little effected. Loop diameter can be reduced while maintaining the same input-referred noise level as the original setup.
The LTSPICE listings share this directory.
Mark
AG5RT
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File /AG5RT/LZ1AQ amplifier noise reduction.pdf uploaded
#file-notice
The following items have been added to the Files area of the [email protected] group.
By: Mark Whittington AG5RT <mark-whittington@...>
Description:
LZ1AQ loop amplifier noise reduction
I ran an LTSPICE noise analysis of the original LZ1AQ circuit connected to a 3.3 uH loop. I also performed some bench measurements to verify the SPICE results. The analysis and measurements both indicate placing 47 uH inductors in series with the 51 Ohm input emitter bias resistors cuts input referred noise by 2 to 3 dB. This is a substantial reduction. Gain is little effected. Loop diameter can be reduced while maintaining the same input-referred noise level as the original setup.
The LTSPICE listings share this directory.
Mark
AG5RT
|
After talking with Dave Evans, he noticed that my load resistance slider was at minimum and thought that my radials were too long.? He suggested that I raise and shorten them.? I raised them from on the ground to 18 inches high and shortened them to 15 feet.? That did it!? Thanks to Dave!??
I am satisfied with the antenna and will be able to do better with it after spending more time with it.
| FX |
QTH |
CALL |
DATE |
TIME |
AZ |
K9AY |
LOAD |
AZ |
LOOP |
COMMENTS |
| 363 |
NJ |
RNB |
3 19 |
1330 |
330 |
92-73=19 |
450 |
225 |
87-69-18 |
30 miles |
| 860 |
PA |
WWDB |
3 19 |
1330 |
310 |
90-68=22 |
300 |
000 |
80-65=15 |
|
| 990 |
PHL |
WNTP |
3 19 |
1330 |
330 |
95-65=30 |
350 |
000 |
84-63=21 |
same tower locatiom |
| 1060 |
PHL |
KYW |
3 19 |
1330 |
320 |
95-60=35 |
350 |
000 |
78-60=17 |
same tower locatiom |
| 1150 |
DE |
WDEL |
3 19 |
1330 |
|
101-86=28 |
650 |
240 |
107-79=28 |
|
| 1210 |
PHL |
WPHT |
3 19 |
1330 |
0 |
106-83=23 |
650 |
010 |
96-78=18 |
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| PERSEUS |
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END |
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Re: "active antenna preamplifiers" in ham radio May 1986
Dave,
I used 36 turns of #32 bifilar turns on a FT75-50 toroid for the 4 JFETs amp. I designed a new board that has a common mode choke on the back side of?the board, which uses a FT84-75 toroid wound with 18 turns of RG178.
On Wednesday, March 19, 2025, 1:01 PM, W0LEV via groups.io <davearea51a@...> wrote: Since the last email I read on this loop antenna group addressed an E-Field probe preamp and I've read a number of high-Z preamps on this group, I'll contribute in that thread: high-Z input preamps.
I've recently completed the 4-JFET preamp.? I'll include the schematic as an attachment to this email.? I've used four J-310 N-Channel JEFTs as the active devices instead of the noted devices (2SK932).? While the completed preamp isn't the epitome of neatness, it is proving to be a stellar performer for high-Z E-Field probes at LF and MF (depends on the ferrite material used in the chokes)!!? Just sitting on the bench and powered up with nothing but power leads connected, all the BCB stations are present and accounted for.? I should also add that with the exception of two AM stations, I am not in a strong-signal area.? Just holding a single finger within 1.5-inches of my input disc ceramic blocking capacitor increases the signals displayed on my spectrum analyzer by some 8 to 10 dB.? I'd recommend it to anyone considering the requirement for a high impedance input to a preamp!!
ADDITIONAL COMMENT:? The use of a CMC for the output and isolating DC from the RF should be adopted in many other preamps.? I will certainly use this trick in future builds that require power over coax (new acronym:? POC ?)).? This trick can also be used in the shack to do the same thing.? No need for a multi-component bias tee...
And, yes, the transformers/chokes are wound on 75 material ferrite.? Fortunately, I had a few.? Each has 20 bifilar turns on a 120-75 (1.2-inches OD of 75? material ferrite).?
Also note the output connector (I used BNCs) must be isolated from the main circuit ground plane.? The schematic clearly reflects this requirement.
One last note:? Once the proper bias current is established with the potentiometer, it can be removed, its value measured, and a fixed resistor of the same value can be installed in its place (I had to search a bit deep in my potentiometer collection to locate a 50k pot.).
Dave - W?LEV Hi Martin
?
Have you tried the G4COL design with? transformer in the FET circuit?. Its simple and is supposed to have better large signal handling characteristics?
?
?
I have taken some snippets as pictures.
?
I was going to try it to see if it was superior to the Miniwhip design for broadcast band overload.
?
Its from a RSGB publication.
?
Henry
--
|
Re: "active antenna preamplifiers" in ham radio May 1986
Since the last email I read on this loop antenna group addressed an E-Field probe preamp and I've read a number of high-Z preamps on this group, I'll contribute in that thread: high-Z input preamps.
I've recently completed the 4-JFET preamp.? I'll include the schematic as an attachment to this email.? I've used four J-310 N-Channel JEFTs as the active devices instead of the noted devices (2SK932).? While the completed preamp isn't the epitome of neatness, it is proving to be a stellar performer for high-Z E-Field probes at LF and MF (depends on the ferrite material used in the chokes)!!? Just sitting on the bench and powered up with nothing but power leads connected, all the BCB stations are present and accounted for.? I should also add that with the exception of two AM stations, I am not in a strong-signal area.? Just holding a single finger within 1.5-inches of my input disc ceramic blocking capacitor increases the signals displayed on my spectrum analyzer by some 8 to 10 dB.? I'd recommend it to anyone considering the requirement for a high impedance input to a preamp!!
ADDITIONAL COMMENT:? The use of a CMC for the output and isolating DC from the RF should be adopted in many other preamps.? I will certainly use this trick in future builds that require power over coax (new acronym:? POC ?)).? This trick can also be used in the shack to do the same thing.? No need for a multi-component bias tee...
And, yes, the transformers/chokes are wound on 75 material ferrite.? Fortunately, I had a few.? Each has 20 bifilar turns on a 120-75 (1.2-inches OD of 75? material ferrite).?
Also note the output connector (I used BNCs) must be isolated from the main circuit ground plane.? The schematic clearly reflects this requirement.
One last note:? Once the proper bias current is established with the potentiometer, it can be removed, its value measured, and a fixed resistor of the same value can be installed in its place (I had to search a bit deep in my potentiometer collection to locate a 50k pot.).
Dave - W?LEV
Hi Martin
?
Have you tried the G4COL design with? transformer in the FET circuit?. Its simple and is supposed to have better large signal handling characteristics?
?
?
I have taken some snippets as pictures.
?
I was going to try it to see if it was superior to the Miniwhip design for broadcast band overload.
?
Its from a RSGB publication.
?
Henry
|
Re: "active antenna preamplifiers" in ham radio May 1986
Hi Martin
?
Have you tried the G4COL design with? transformer in the FET circuit?. Its simple and is supposed to have better large signal handling characteristics?
?
?
I have taken some snippets as pictures.
?
I was going to try it to see if it was superior to the Miniwhip design for broadcast band overload.
?
Its from a RSGB publication.
?
Henry
|
My 160m - 220m beverages are usually about 3dB better in s/n than the K9AY loop on 1.8 and 3.5MHz in their design directions, Thank you John. That is very impressive for the relatively small size. Thanks to the tips here in the group, I am very optimistic that I will be able to erect an AziLoop with the 13.8 metre circumference mentioned in the forthcoming manual - and that this antenna will serve me very well for mediumwave reception. 73 Christoph —
|
Hi Christoph,
re. Loop and Beverage comparisons
My 160m - 220m beverages are usually about 3dB better in s/n than the K9AY loop on 1.8 and 3.5MHz in their design directions, as one would expect from the comparitive RDFs, but there are days and directions where the K9AY or conventional loop is as good, possibly because of steerable direction, nulling noise or favourable pattern. It appears to work comparitively well in disturbed conditions.
73
John
|
Hi Christoph,
Yes I need the (remote) preamp nearly all the time to get sufficient s/n over-ride not helped by feeder length of <200m.. Multi-joined RG6 most over 30 years old with loss about 4dB at 1.8MHz, loop R=10 ohms..
At VLF I find its conventional loop mode better and I did manage to hear the SAQ Xmas transmission on 17.2kHz.. Not as good as other larger antennas because of a 20kHz HPF.
A K9AY does not work as well at VLF. Modelling my loop gives a very low -69.5dBi at 300kHz, and only 5dB better if conventional earth used. Worse at 100kHz. Others may comment on what size (conventional?) loops are best for reception down on VLF frequencies and what sensitivities are needed, I would imagine it has been discussed on this forum before!
73
John
|
Bill Riches
Everett N4CY
Christoph Ratzer