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Re: "active antenna preamplifiers" in ham radio May 1986

 

Hi Everett,
?
I think if you do this, you will have to spell out that a separate "ground" reference for the antenna and PCB needs to be provided, as the coax performs this function by default in most other designs.
?
I know it seems obvious, but many end users don't understand this significant point.
?
Regards,
?
Martin
?
?
On Wed, Mar 19, 2025 at 06:24 PM, Everett N4CY wrote:

I designed a new board that has a common mode choke on the back side of?the board,
Re: "active antenna preamplifiers" in ham radio May 1986

 

Hi Dave,
?
The free versions of IO groups, have limitations on storage. These limitations depend on the T&C's of when the group was established, the older groups have more free storage than younger groups. It was offered as an incentive to early adopters.
?
If folks include images or files in the body of their posts, it automatically gets included and stored, which counts towards the overall limit.
?
IO also reduces the resolution of images included in posts, but not when uploaded to images, and any messages that include previous posts with files or images can end up being copied multiple times.
?
By getting folks to deliberately upload to the files and photos area, only items that are likely to be of long term use get to be stored, and the more trivial items are excluded.
?
I hope this helps provide a bit of the background as to why the rules on various groups sometimes differ.
?
Regards,
?
Martin
?
On Thu, Mar 20, 2025 at 04:12 PM, W0LEV wrote:

So we can not do attachments OR embedded graphics in the body of an email???
Re: "active antenna preamplifiers" in ham radio May 1986

 

So we can not do attachments OR embedded graphics in the body of an email??? A picture is worth 1k words.? But I understand the cost when archived in storage.? These days, storage is the least expensive of digital options.? But I still understand.?

Today I will be attempting to make a frequency sweep of my unit.? I'll wait to upload to the files until that is complete. ?

Dave - W?LEV

On Thu, Mar 20, 2025 at 8:06?AM Martin - Southwest UK via <martin_ehrenfried=[email protected]> wrote:

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.



--
Dave - W?LEV
File /Modified AMRAD eProbe Antenna.pdf uploaded #file-notice

Group Notification
 

The following items have been added to the Files area of the [email protected] group.

By: Everett N4CY <everettsharp@...>

Description:
Active eProbe antenna
Re: "active antenna preamplifiers" in ham radio May 1986

 

Mike,
?
I just uploaded it.
?
Everett N4CY

In a message dated 3/20/2025 10:44:13 AM Central Daylight Time, amdx@... writes:
?

Has the 4 FET input High Z amp schematic been posted to the files section, if so under what heading?
??????????????????? Thanks, Mikek
Re: "active antenna preamplifiers" in ham radio May 1986

 

Has the 4 FET input High Z amp schematic been posted to the files section, if so under what heading?
??????????????????? Thanks, Mikek
Re: "active antenna preamplifiers" in ham radio May 1986

 

Hi Henry,
?
I just quickly built one up.
?
The gain seems quite low and the IMD performance isn't that good. Current draw is about 10mA, which is quite low.
?
I need to experiment to see if I can further optimise the circuit, but it's not looking too promising.
?
When folks state things like "good strong signal handling" without providing any figures, or other parameters as evidence, it's difficult to know if a circuit is performing as expected.
?
Regards,
?
Martin
?
?
On Wed, Mar 19, 2025 at 02:30 AM, <tardivat@...> wrote:

Have you tried the G4COL design with? transformer in the FET circuit?
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
Re: File /AG5RT/LZ1AQ amplifier noise reduction.pdf uploaded #file-notice

 

Tell me, what you need, i have both papers available.
?
regards, Fred
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
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
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
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.
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.
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?



Il mer 19 mar 2025, 19:01 W0LEV via <davearea51a=[email protected]> ha scritto:
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

On Wed, Mar 19, 2025 at 2:30?AM tardivat via <tardivat=[email protected]> wrote:
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



--
Dave - W?LEV
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
File /AG5RT/LZ1AQ amplifier noise reduction.pdf uploaded #file-notice

Group Notification
 

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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