Antenna amplifier for Beverage and large cardioid loop antennas


Chris Moulding
 

Recently on the forum there has been a discussion on building large (2m or 6 foot side) cardioid loops for 160m DX operation. This needs a loop amplifier with an input impedance around 450 ohms.

Today I've been asked if the Loop Antenna Amplifier + can be used with a Beverage antenna.

I've built a prototype amplifier based on the Loop Antenna Amplifier + PCB with a input transformer to match the 450 ohm load presented by a Beverage or a large cardioid loop antenna.

To test it I've built a quick lash to make a 2m (6' 6'') square cardioid loop antenna out of wire fastened around a wooden fence panel with a temporary ground using a screwdriver pushed into the soil. The bottom of the loop is only about 0.3m (1 ') above the ground. I fitted a 470 ohm resistor in the top of the loop to make it into a cardioid loop.

As expected this works well on VLF, medium wave and 160m but I was surprised by the performance on the 20m amateur band.

At the workshop for testing transmitters I have a wire up a tree which forms a 5/8 wave vertical on 20m. This is situated close to a large metal clad building which acts as a reflector towards Europe. As you will expect it's a good antenna with lots of big signals coming in!

I've attached an image with two screenshots taken using a RspDX SDR receiver 5 minutes apart to show the whole 20m band. This is taken on a Wednesday afternoon, no contests filling the band. The top one is the cardioid loop with the prototype amplifier, the bottom one is the 5/8 wave vertical. Here's a link in case the image doesn't show up on the daily digest:

www.crosscountrywireless.net/Cardioid_v_5_8_vertical_on_20m.jpg

There isn't much difference between the two, maybe some signals are stronger on the cardioid loop.

This week I'm building a batch of the new amplifier called the Beverage Antenna Amplifier. The price will be the same as the existing Loop Antenna Amplifier +.

I will be adding it to the web pages but if any one wants one immediately just order a Loop Antenna Amplifier + and let me know that you want the Beverage Antenna Amplifier.

Regards,

Chris


Chris Moulding
 

The first batch of the Beverage Antenna Amplifier are now built and tested and the first orders will be shipped early next week.

The amplifier can also be used with large cardioid loops, the Loop on the Ground and receive only versions of the Terminated Inverted U.

I've added information on the Beverage Antenna Amplifier to the web page below:

http://www.crosscountrywireless.net/beverage_antenna_amplifier.htm

Regards, Chris


David Wilkins
 

Hi Chris - good job !
I’ve just ordered one :) 

Regards,
David.

On 30 Jan 2021, at 19:12, Chris Moulding <chrism@...> wrote:

The first batch of the Beverage Antenna Amplifier are now built and tested and the first orders will be shipped early next week.

The amplifier can also be used with large cardioid loops, the Loop on the Ground and receive only versions of the Terminated Inverted U.

I've added information on the Beverage Antenna Amplifier to the web page below:

http://www.crosscountrywireless.net/beverage_antenna_amplifier.htm

Regards, Chris


Jim Smith G0OFE
 

Would the amplifier be any good for this: http://www.kk5jy.net/LoG/  ?


Jim, Bournemouth, Dorset. IO90BR.
Elad FDM-S2, Airspy HF+, SDRPlay and Funcube Dongle SDR Recievers
8-element OP-DES for Band 2, 8-element LFA for 2m, 3-element LFA for 6m, 20m Windom for HF,. Wellbrook 1530 Loop for LF


On 30/01/2021 19:12, Chris Moulding wrote:
The first batch of the Beverage Antenna Amplifier are now built and tested and the first orders will be shipped early next week.

The amplifier can also be used with large cardioid loops, the Loop on the Ground and receive only versions of the Terminated Inverted U.

I've added information on the Beverage Antenna Amplifier to the web page below:

http://www.crosscountrywireless.net/beverage_antenna_amplifier.htm

Regards, Chris


Tim Makins
 

That webpage mentions 'a Multicoupler to feed five receivers from one Beverage antenna'. Is this a separate product?

73s Tim EI8IC


Chris Moulding
 

Yes the amplifier works well with the Loop on the Ground antenna.

I did most of the original testing with a Loop on the Ground antenna.

An interesting point I discovered is that the background noise floor of the Loop on the Ground and Beverage antennas is very low often below the noise floor of a sensitive receiver.

Having the amplifier with an isolation transformer and a common mode choke filter built into the amplifier allows the very low signals to be amplified to a useful level.

Regards,

Chris


Chris Moulding
 

Hi Tim,

We can supply a Multicoupler to work with the Beverage Antenna Amplifier.

It's our standard HF Multicoupler with a bias-tee added to power the amplifier.

Anyone who wants one just order a HF Multicoupler and send me a note or email to request it with a bias-tee.

Regards,

Chris


Jim Smith G0OFE
 

OK, thanks.. interesting. My back garden is about 6m x 6m. Might be worth trying a LoG. Might also be worth trying a ~20m Bog on the path between here and next door, though I'd be restricted to 330°


Jim, Bournemouth, Dorset. IO90BR.
Elad FDM-S2, Airspy HF+, SDRPlay and Funcube Dongle SDR Recievers
8-element OP-DES for Band 2, 8-element LFA for 2m, 3-element LFA for 6m, 20m Windom for HF,. Wellbrook 1530 Loop for LF


On 31/01/2021 11:57, Chris Moulding wrote:
Yes the amplifier works well with the Loop on the Ground antenna.

I did most of the original testing with a Loop on the Ground antenna.

An interesting point I discovered is that the background noise floor of the Loop on the Ground and Beverage antennas is very low often below the noise floor of a sensitive receiver.

Having the amplifier with an isolation transformer and a common mode choke filter built into the amplifier allows the very low signals to be amplified to a useful level.

Regards,

Chris


Chris Moulding
 

Hi Jim,

You will be surprised by the Loop on the Ground, I was.

Most radio amateurs think Beverage antennas are only for LF work on 160 and 80m. This is because Beverage's original QST article in 1922 only covers those bands.

It will work well up to 30 MHz. The optimum length is 2 wavelengths but lengths down to 1/4 wavelengths give good results as shown on the web page with a 40m long Beverage on 80m.

A 20m long Beverage running at 330 degrees will give excellent results to North America on 20m and above.

Regards,

Chris


Simon
 

Jim

Let me know how the log goes if you try one.
I have and it was a total failure..but that may have been due to over many many meters of radials laid out in the side garden..( which it was directly over.) Or i just got it wrong..( probably was late and dark...to keep neighbours off the scent.was a while ago, don’t remember now.)

Considering trying again as so easy to implement..i have a spare ccw loop amp and suitable ferrite ring to wind a matching transformer. Though will be more squashed than ideal..( thin side garden.)

Ideal rx antenna though if can get to work for the nosey neighbour issues..

One wonders what the gnd needs to be to make it work? ( log.) Poor ie like a beverage needs or good like a vertical? My earth is very good..thames basin, always wet clay type soil.( even in mid summer at 2 inches down.)

Simon


Chris Moulding
 

The Loop on the Ground and the Beverage antennas work the same way.

It relies on the incoming wavefront interacting with the ground to tilt the wavefront . This is how a vertically polarised wave can induce a current into a horizontal wire.

Having the wire so close to ground cancels out the horizontally polarised signals leaving weak vertically polarised signals with a very low noise background.

If it's installed over a radial field, seawater or ground with very good conductivity it doesn't work well because there is no or little tilt to the incoming wavefront.

Simon, this is probably why your transmit loop antenna works so well on 160m. With normal ground it would have severe ground losses due to the penetration into the soil. Over saltwater or ground with very good conductivity it will not penetrate the ground so the losses are minimal.

Regards,

Chris


Simon
 

Hi Chris

yes radials..when we moved in we had no neighbours to the left of us..infact both houses were being sold, also the side garden was very empty, plus our rear yarden ( spelt that correctly!) was just  the sand left from an old patio.
i enlisted my daughter at midnight for 3 days  and laid down about 600m plus of radials going from where the loop was to be.( well 1/4 vertical for 40 then.) all bolted to a copper plate...dont tell my current neighbours but their gardens have alot of copper under them!
more went down when we got the patio done..
9 inch disc to cut the ground followed by daughter laying the copper wires!! There are at least  40 plus radials..
each wire 10-20m long..also into side garden..they bend they are straight whatever..
disappears  into the grass very quickly!!tricky to get under the fences though!!

when run against a 1/4 40m vertical ( tx excellent!!! Rx terrible.) mfj259 said 25r ( or so.) ..so a good earth!! Plus the gnd here is sodden clay 12 months a year..

dont tell anyone lol  Simon


Kev Haworth
 

Can someone confirm that Beverage antennas aren't good over saltwater/beaches?


Chris Moulding
 

Beverage antennas don't really work over salt water or beaches.

They rely on the incoming radio wavefront penetrating the ground. Due to the change in the speed of light (radio) in a dielectric (soil) the wavefront tiltsno tilting occurs.

This allows a horizontal wire on or very close to the ground to receive the signal.

Over saltwater or beaches the wavefront doesn't penetrate the ground or water so no tilting occurs for the Beverage antenna to work.

Depending on your location it might be worth trying one on sand dunes near a beach. Relatively dry sand will act as a dielectric allowing a Beverage antenna to work.

Regards,

Chris


Kev Haworth
 

Challenge accepted!

Will e-meither you over next few days.

Kev


Tom Crosbie G6PZZ
 

I don’t want to rub salt water into wounds (pun intended – shoot me!) but there are few people on the IRCA group who may argue with the effectiveness of a Beachfront Beverage. Have a listen to the Masset Kiwi which I think has a Beverage on the beachfront. You’ll find it at http://209.53.83.138:8073

 

Tom G6PZZ

 

From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of Chris Moulding
Sent: 04 February 2021 20:06
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Antenna amplifier for Beverage and large cardioid loop antennas

 

Beverage antennas don't really work over salt water or beaches.

They rely on the incoming radio wavefront penetrating the ground. Due to the change in the speed of light (radio) in a dielectric (soil) the wavefront tiltsno tilting occurs.

This allows a horizontal wire on or very close to the ground to receive the signal.

Over saltwater or beaches the wavefront doesn't penetrate the ground or water so no tilting occurs for the Beverage antenna to work.

Depending on your location it might be worth trying one on sand dunes near a beach. Relatively dry sand will act as a dielectric allowing a Beverage antenna to work.

Regards,

Chris


Simon
 

If you can..and its rf quiet a vertical over salt water will be stunning..( and easy to put to to check.)


Kev Haworth
 

Simon, oh yes, my favourite antenna is a vertical over salt. 

We used them on the GB0HI and GB2HI activations and to hear JA/VK coming over the top of local stations on 40M in the morning was something I won't forget in a hurry. I've used kite antennas for 160 too over salt, probably at the wrong time of year though as we were working stateside/EU stations only. When I buy my next transceiver, I will be portable from a local beach and will be out in the wintertime with the kites.

Just sorting some ideas out now as how to power / feed from the car to test the beverages over the same beaches,  will take a loop with me as well to switch to and from.


Simon
 

Sounds like you need a van!! Lol

Or ex mil signals vehicle??