AMRAD LW Active whip antenna

[N4LTA]

Has anyone built the AMRAD active whip receiving antenna? It description in QST (September 2002) seems amazing but some things in the article seem a little cheezy. I need a good LW antenna and am considering a amplified rotated loop, a bevererage (but I just have 480 feet) or possible the AMRAD antenna. I have the CP666 fet already.

I am using a good 80 meter dipole now but the noise is bad on LW.

I am hesitant because all the small antennas that I have ever built ended up with small performance.


Pat

[WA1GFZ]

Check out Clifton Labs. Jack Smith is a good guy. I bought 4 amplifier board kits from him to build a 4 square receive system. Very nice quality. He sells the complete antenna but I have all that hardware and only needed the amplifier board. I plan to homebrew the phaseing system which is a no brainer using a few relays and coax delay lines.

[Steve - K4HX]

Frank is right. Clifton makes some good stuff. Also look at Hi-Z Antennas.

And remember, if you have noise on your dipole, you'll likely have noise on the small whip, unless you can move it far from the noise sources.

I am using a good 80 meter dipole now but the noise is bad on LW.

[N4LTA]

The noise is probably coming from many sources in the house - it is not bad at 80 meters.

I plan to mount the antenna 300 feet from the house on the edge of a lake at at least 300-400 feet from any neighbors house.  The loop could null noise that is not omnidirectional which the short vertical can't do.

I have contacted Jack and I think I am going to buy his antenna - I could build one but his price is very good and it will be tested on his very good test equipment. I'll probably build the power supply kit. I started to get the parts together and start a PC board but its not worth the trouble to scratch build it and the cost savings would be minimal.

I'll probably also build a shielded octoloop later.

Pat

[WA1GFZ]

Yup, it makes even more sense when you want 4 matched antennas. I have all the metal so only needed the amplifier boards. A proven and tested design makes life simple.

[Steve - K4HX]

Jay, W1VD built a large version of the K9AY for LF reception. You may want to look at that too.

[WA1QHQ]

Check out Clifton Labs. Jack Smith is a good guy. I bought 4 amplifier board kits from him to build a 4 square receive system. Very nice quality. He sells the complete antenna but I have all that hardware and only needed the amplifier board. I plan to homebrew the phaseing system which is a no brainer using a few relays and coax delay lines.

Frank,

I did not see the boards for the active antenna listed on his web site individually. Can you buy these by themselves and if so for how much? It looks like a good design and I have an old Loran-C active whip that I would like to convert to HF.

[VK7ZL]

Pat
I am using an active antenna designed by PA0RDT. You will find all the construction details on the internet. I use it primarily on the LF band but they do work up to about 15Mhz.

Bob

[WA1GFZ]

Mark,
I just sent Jack an email and asked if he would sell me the board kits. I think it was around $60 each with parts included. He usually builds and tests the FET stage to set the current for best performance. I told don't bother. BTW he has not posted his new design with a modern dual gate MOS FET. Also has a built in voltage regulator. He said the performance is more stable with a local regulator and the dual gate FET is actually a little better than the J310. fc

[N4LTA]

Bob, Thanks for the tip. I looked it up and it is very interesting. Does it REALLY perform as advertized?

I guess I'll find out as I put together a board this morning. It seems to good too be true.  It's hard to believe that the square of PCB copper is all the antenna element that there is.

Here's my board and I hope to test it this weekend.

[WU2D]

Back when I was doing LF I wanted an antenna that I could use to listen to my 187 kHz beacon. I ended up using a minibox and the top section of a an old CB whip and its base mag mount. All I had in the box was an MPF102 driving a PNP transistor and an NPN emitter follower and a low pass filter. I could pick up my beacon over 30 miles away going 65 MPH and I know that my ERP was only a milliWatt or two...

I sent DC up the coax. The whip was perhaps 3 feet long and I stuck it on my trunk. This simple active whip worked fantastic, outperforming loops and longwires of every sort I could come up with. The Voltage probe is an excellent antenna on longwave.

Here is a crude Frankendrawing of the approach.

 Mike M WU2D

[N4LTA]

First test on the little PA0 active antenna is interesting. With it sitting in the shop next to the receiver it picked up most of the beacons that I hear with the dipole. I just got a new broadband noise source show up since yesterday  morning though and it is a screacher about S9 from 10 Khz to 200 Khz.


I need to move the antenna outside.


Pat

[N4LTA]

I installed the test antenna outside away from the house but the results were poor -more noise than my 80 meter dipole - much worse in fact. I installed a makeshift common mode choke near the antenna and another at the receive converter but they were not optimum. More work needed.

Pat

[Steve - K4HX]

I just came across a mod on the AMRAD circuit by Jay, W1VD.

http://w1vd.com/modifiedeprobe.pdf

Has anyone built the AMRAD active whip receiving antenna? It description in QST (September 2002) seems amazing but some things in the article seem a little cheezy. I need a good LW antenna and am considering a amplified rotated loop, a bevererage (but I just have 480 feet) or possible the AMRAD antenna. I have the CP666 fet already.

I am using a good 80 meter dipole now but the noise is bad on LW.

I am hesitant because all the small antennas that I have ever built ended up with small performance.


Pat

[WA1GFZ]

maybe you are closer to the noise source?

[N4LTA]

Not sure what is going on. I have some large #31 ferrites coming and I am going to make some chokes and do a better job with the feedline. Jack Smiths antenna should be here later his week and I am hoping to put it on a pole at the edge of a small pond about 400 feet from my house  and at least that far from any other houses or power lines. I have 1000' of cable coming also. Been doing a lot of research on common mode noise and how the newer ferrites have helped improve things with regard to common mode noise problems.

Steve - That's a big change - it gets rid of the $20 fet (CP666) - Did he indicate why it was changed?


Pat

[Steve - K4HX]

No. It's just a schematic. Jay shows up here from time to time, so maybe he will post an explanation.

[N4LTA]

I built a copy of Jack Smiths common mode choke this weekend and installed it on my 80 meter dipole. All that I can say is "Wow" .  The noise is much reduced on 80 meters and on LF - at least 3 S units  - which I would never have believed. After installing the choke - and seeing how well that worked - I wrapped the 120 VAC power lead in a core as well as the 12 volt leads to the R75 and the LF receive converter and the network cable and computer 120 volt power lead. After doing it all - I had the quietest antenna noise that I have ever seen with that dipole - in 25 years. I am a believer in type 31 ferrite now.

Jack's active antenna should arrive today or tomarrow so I have something else to do in my spare time.

I copied 14 NDF beacons yesterday all audible (not requiring ARGO) and a mystery 137 KHz beacon

I sure do wish we could get a LF or 500 Khz ham band.

It worked so well that I ordered some more type 31 ferrite cores. They aren't cheap - about 8 buck each.


Pat
N4LTA

[Steve - K4HX]

Very good on the noise reduction. That sounds like quite a dramatic improvement.


Listen for some fellow hams (manny of them AMers) around 500 kHz.

WD2XSH
http://www.500kc.com/

WD2XNS
http://www.w1vd.com/

Here's a recording I made of WF9XIH on 472.5 kHz in Forest, VA, 28 December 2011. Too bad the static was so bad. The warm WX we had around Christmas made RX more noisy than it normally would have been.

[Fred k2dx]

There is an update on Clifton Lab's website indicating the Pixel shielded loop amplifier is his design. http://www.cliftonlaboratories.com/Updates.htm