Date   

Re: Low cost loop antenna - your thoughts please

Ian
 

Chris, would there be an option to feed the loop with 12v dc ?

Regards Ian


Re: Revised versions of VLF/LF/HF Vertical and HF Active Vee antennas

Robert, VA3ROM
 

Will you be offering just the based unit for sale for those of us with the older antenna unit, Chris?

In my case, the antenna isn't that old ;)

73,
Robert


Re: HF Preselector revised

WA8LMF
 

On 9/29/2019 3:40 PM, Chris Moulding wrote:
We have recently been building a small batch of HF Preselectors and found that the variable capacitor we use in them is no longer available. I couldn't source an alternative.

As a result it has now been redesigned to use varactor diodes for tuning. It now uses an array of four diodes that cancel out any IP3 and IP2 effects from high RF voltages on the DC tuning voltage applied to the varactors.

 

What effect has the varactor diodes had on the selectivity/bandwith of the preselector?    Are the pics on the web page of the selectivity sweeps of the old air variable version, or the new varicap version?      [I would assume the varactor caps are lower-Q  than traditional air variables -- or am I wrong?]


Stephen H. Smith    wa8lmf (at) aol.com
Skype:        WA8LMF
EchoLink:  Node #  14400  [Think bottom of the 2-meter band]
Home Page:          http://wa8lmf.net

Live Off-The-Air APRS Activity Maps
   <http://wa8lmf.net/map>

Long-Range APRS on 30 Meters HF
   <http://wa8lmf.net/aprs/HF_APRS_Notes.htm>



Re: HF Preselector revised

Chris Moulding
 

Hi Nicolas,

Yes you will get the revised version.

Regards,

Chris

--
Chris Moulding
Cross Country Wireless
Unit 24562, PO Box 4336, Manchester, M61 0BW, UK
Cell/Workshop: +44(0)7752 391908
Fax: +44(0)1204 410626
Secure email: g4hyg@protonmail.com
Website: http://www.crosscountrywireless.net
Groups.io: https://groups.io/g/CrossCountryWireless

On 29/09/2019 20:46, Nicolas Kulaga wrote:
Hi Chris.
I just ordered a preselector some days ago.
Will I get the revised version ?
Le dim. 29 sept. 2019 à 21:40, Chris Moulding <chrism@crosscountrywireless.net <mailto:chrism@crosscountrywireless.net>> a écrit :
We have recently been building a small batch of HF Preselectors and
found that the variable capacitor we use in them is no longer
available. I couldn't source an alternative.
As a result it has now been redesigned to use varactor diodes for
tuning. It now uses an array of four diodes that cancel out any IP3
and IP2 effects from high RF voltages on the DC tuning voltage
applied to the varactors.
It now has a 2.1mm DC socket on the rear so that 12 -15 V DC can be
applied. It takes 1.2 mA.
One interesting possibility is that if the tuning control (variable
resistor) is set fully clockwise the DC input could be a variable
voltage between 15V and zero allowing the Preselector tuning to be
remotely controlled.
The text on the web page has been updated, I'll add a revised
photograph of the rear of the Preselector soon.
The web page is:
http://www.crosscountrywireless.net/preselector.htm
Regards,
Chris


Re: HF Preselector revised

Nicolas Kulaga
 

Hi Chris.

I just ordered a preselector some days ago. 

Will I get the revised version ?



Le dim. 29 sept. 2019 à 21:40, Chris Moulding <chrism@...> a écrit :
We have recently been building a small batch of HF Preselectors and found that the variable capacitor we use in them is no longer available. I couldn't source an alternative.

As a result it has now been redesigned to use varactor diodes for tuning. It now uses an array of four diodes that cancel out any IP3 and IP2 effects from high RF voltages on the DC tuning voltage applied to the varactors.

It now has a 2.1mm DC socket on the rear so that 12 -15 V DC can be applied. It takes 1.2 mA.

One interesting possibility is that if the tuning control (variable resistor) is set fully clockwise the DC input could be a variable voltage between 15V and zero allowing the Preselector tuning to be remotely controlled.

The text on the web page has been updated, I'll add a revised photograph of the rear of the Preselector soon.

The web page is:

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

Regards,

Chris


HF Preselector revised

Chris Moulding
 

We have recently been building a small batch of HF Preselectors and found that the variable capacitor we use in them is no longer available. I couldn't source an alternative.

As a result it has now been redesigned to use varactor diodes for tuning. It now uses an array of four diodes that cancel out any IP3 and IP2 effects from high RF voltages on the DC tuning voltage applied to the varactors.

It now has a 2.1mm DC socket on the rear so that 12 -15 V DC can be applied. It takes 1.2 mA.

One interesting possibility is that if the tuning control (variable resistor) is set fully clockwise the DC input could be a variable voltage between 15V and zero allowing the Preselector tuning to be remotely controlled.

The text on the web page has been updated, I'll add a revised photograph of the rear of the Preselector soon.

The web page is:

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

Regards,

Chris


Re: Low cost loop antenna - your thoughts please

D R
 

Hi Chris,

There's nothing in my Junk folders from you, so I think the messages never actually got sent by your provider.  Funnily enough, I've got exactly the same problem with one of my email accounts handled by Heart Internet.  They've just changed the outgoing port number and, although I've made the necessary changes in my account settings, nothing now gets sent out from it.  Have you checked your Outbox to see if the messages are still sitting there?  Thanks for the info about my order, anyway - I'm looking forward to receiving it.

Regards,
Dave


On Wednesday, 25 September 2019, 14:17:29 GMT+1, Chris Moulding <chrism@...> wrote:


Hi Dave,

I've sent two emails to you already. The first was the order acknowledgement and the second was a reply to your email request.

Your Multicoupler is being built over the next few days and will be shipped on Monday.

We've recently changed our SMTP email provider so I wonder if our emails are being blocked or are in your junk mail.

Regards,

Chris


Re: Low cost loop antenna - your thoughts please

Chris Moulding
 

Hi Dave,

I've sent two emails to you already. The first was the order acknowledgement and the second was a reply to your email request.

Your Multicoupler is being built over the next few days and will be shipped on Monday.

We've recently changed our SMTP email provider so I wonder if our emails are being blocked or are in your junk mail.

Regards,

Chris


Re: Low cost loop antenna - your thoughts please

D R
 

Hi Chris,

Can you please let me know what's happening with my order for an HF Multicoupler which I placed on 17 September, as I've had no acknowledgement from you.  Two messages sent to your "info@" address have not been answered so far.

Regards,
Dave


On Wednesday, 25 September 2019, 10:48:15 GMT+1, Chris Moulding <chrism@...> wrote:


The PCBs for the Loop Antenna Amplifier are now being manufactured by our PCB supplier.

Working from their delivery schedule we should have the first batch built, tested and ready to ship by Friday 11th October.

I've added a new web page to the web site and we can now take orders for the first batch.

The web page is:
http://www.crosscountrywireless.net/loop_antenna_amplifier.htm

Thanks for all the helpful suggestions and comments both here on the forum and by email.

Regards,

Chris


Re: Low cost loop antenna - your thoughts please

Chris Moulding
 

The PCBs for the Loop Antenna Amplifier are now being manufactured by our PCB supplier.

Working from their delivery schedule we should have the first batch built, tested and ready to ship by Friday 11th October.

I've added a new web page to the web site and we can now take orders for the first batch.

The web page is:
http://www.crosscountrywireless.net/loop_antenna_amplifier.htm

Thanks for all the helpful suggestions and comments both here on the forum and by email.

Regards,

Chris


Re: Revised versions of VLF/LF/HF Vertical and HF Active Vee antennas

David Cutter
 

This makes  remote access more tempting, eg from the far end of a field (well beyond practical cables) back to the house using an Arduino and WiFi; not that I'm an expert but it adds to my desire list.

David G3UNA

 

From: CrossCountryWireless@groups.io [mailto:CrossCountryWireless@groups.io] On Behalf Of Chris Moulding
Sent: 23 September 2019 21:11
To: CrossCountryWireless@groups.io
Subject: [CrossCountryWireless] Revised versions of VLF/LF/HF Vertical and HF Active Vee antennas

 

Recently I was asked by a customer if it was possible to reduce the DC current consumption of the VLF/LF/HF Active Vertical antenna as he wanted to use a solar panel and small battery to power it and a receiver at a remote location.

The original amplifier design used a JFET amplifier followed by a bipolar transistor output stage to match to 50 ohm coax cable. This used over 100 mA so it would take a high drain from a solar power battery system especially overnight..

I've redesigned the amplifier to use a transformer after the JFET amplifier to match directly into 50 ohm coax and to reduce losses in the base unit replaced the Owen splitter with a hybrid transformer. Other minor resistor value changes to reduce current drain from the green Power LED were also made.

As a result the DC current consumption is now down to 15 mA and the RF output and IP3 performance is identical to the original version.

All new VLF/LF/HF Active Vertical and HF Active Vee antennas will now use the revised amplifier. Amplifier and base unit PCBs will be marked with the number 2.

Regards,

Chris

_._,_._,_


Virus-free. www.avast.com


Revised versions of VLF/LF/HF Vertical and HF Active Vee antennas

Chris Moulding
 

Recently I was asked by a customer if it was possible to reduce the DC current consumption of the VLF/LF/HF Active Vertical antenna as he wanted to use a solar panel and small battery to power it and a receiver at a remote location.

The original amplifier design used a JFET amplifier followed by a bipolar transistor output stage to match to 50 ohm coax cable. This used over 100 mA so it would take a high drain from a solar power battery system especially overnight..

I've redesigned the amplifier to use a transformer after the JFET amplifier to match directly into 50 ohm coax and to reduce losses in the base unit replaced the Owen splitter with a hybrid transformer. Other minor resistor value changes to reduce current drain from the green Power LED were also made.

As a result the DC current consumption is now down to 15 mA and the RF output and IP3 performance is identical to the original version.

All new VLF/LF/HF Active Vertical and HF Active Vee antennas will now use the revised amplifier. Amplifier and base unit PCBs will be marked with the number 2.

Regards,

Chris


Re: Low cost loop antenna - your thoughts please

Greg_2e1gw
 

I would definitely be interested in seeing this developed.  Especially now the loop has been stopped.

Best wishes
Greg
2E1GW


From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> on behalf of Oene Spoelstra <spoelstraoene@...>
Sent: 20 September 2019 19:59
To: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io>
Subject: Re: [CrossCountryWireless] Low cost loop antenna - your thoughts please
 
Nice !

Op vr 20 sep. 2019 14:02 schreef Chris Moulding <chrism@...>:
The test this morning was to try and destroy the loop antenna amplifier with RF.

!00W over all HF bands from a transmit antenna 3m (10 ft) from the loop antenna using the 1m diameter coax loop did not damage the amplifier.

I can now finish the PCB design this evening.

Regards,

Chris


Re: Low cost loop antenna - your thoughts please

Oene Spoelstra <spoelstraoene@...>
 

Nice !

Op vr 20 sep. 2019 14:02 schreef Chris Moulding <chrism@...>:

The test this morning was to try and destroy the loop antenna amplifier with RF.

!00W over all HF bands from a transmit antenna 3m (10 ft) from the loop antenna using the 1m diameter coax loop did not damage the amplifier.

I can now finish the PCB design this evening.

Regards,

Chris


Re: Low cost loop antenna - your thoughts please

WA8LMF
 

On 9/20/2019 11:55 AM, Chris Moulding wrote:
Here's a link to a photo of the test loop used in the tests so far.

www.crosscountrywireless.net/Loop_amplifier_test_loop.JPG

It's a 1m diameter loop of LDF4-50 coax cable with short wire tails added to connect to the loop amplifier.

Its cable tied to a 4.5m carbon fibre mast which is a secondhand wind surfer mast. Very light and easy to handle as a temporary mast for testing.

It might give some idea of what can be used to make a loop for the antenna.

Regards,

Chris
_._,_._,_


How much effect does the diameter of the loop conductor have on it's performance?    I was thinking of using something thin and "springy" like piano wire, that could be coiled up into a very compact coil for storage for portable use.  And then pop-out into a perfect circle when unpacked.



Tomorrow (Saturday 21 Sept) is the next test of my big "Kite Loop" at the General Motors ARC Trunk Swap event in metro Detroit.    More details and location on my APRS UI-Webserver at

    <http://WA8LMF.net/map>   Click on the black link for "Special Events Webserver".

Hope to get some better and more detailed pictures of the loop assembly.

If the weather holds, there will be another test on Sunday at the "Flying Beers International" hamfest in Ferndale, MI. (Also metro Detroit area.)


Stephen H. Smith    wa8lmf (at) aol.com
Skype:        WA8LMF
EchoLink:  Node #  14400  [Think bottom of the 2-meter band]
Home Page:          http://wa8lmf.net

Live Off-The-Air APRS Activity Maps
   <http://wa8lmf.net/map>

Long-Range APRS on 30 Meters HF
   <http://wa8lmf.net/aprs/HF_APRS_Notes.htm>


Re: Low cost loop antenna - your thoughts please

Chris Moulding
 

Here's a link to a photo of the test loop used in the tests so far.

www.crosscountrywireless.net/Loop_amplifier_test_loop.JPG

It's a 1m diameter loop of LDF4-50 coax cable with short wire tails added to connect to the loop amplifier.

Its cable tied to a 4.5m carbon fibre mast which is a secondhand wind surfer mast. Very light and easy to handle as a temporary mast for testing.

It might give some idea of what can be used to make a loop for the antenna.

Regards,

Chris


Re: Low cost loop antenna - your thoughts please

Chris Moulding
 

To try and see if it would work next to an antenna with a kilowatt going through it I ran two extra tests this afternoon.

In the first test I reduced the spacing between the antennas to 1m (3ft 3 in) without any damage.

I then reduced it to 10 cm (4 in) again without any damage after transmitting a 100W carrier on all the HF bands.

A kilowatt at 3m will be fine.

Just to finish the tests I ran 100W carrier on all HF bands into the output connector for 1 second on each band to simulate the "Oops!" moment with a transceiver. It survived OK.

It has similar RF overpower protection to our other products so it's good to see that it works!

Regards,

Chris


Re: Low cost loop antenna - your thoughts please

Edward Feustel, AI1R
 

Will you be able to determine the limit of power at 3 meters for safety for those of us with kilowatt
amplifiers. Is there a possible relay connection to ground the input of the amplifier using a PTT grounded line?

73,
Ed, N5EI
WORD FOR THE DAY for 2019/9/9

Pay attention. Be astonished. Tell about it.

Mary Oliver
On 19/09/20 08:02, Chris Moulding wrote:

The test this morning was to try and destroy the loop antenna amplifier with RF.

!00W over all HF bands from a transmit antenna 3m (10 ft) from the loop antenna using the 1m diameter coax loop did not damage the amplifier.

I can now finish the PCB design this evening.

Regards,

Chris


Re: Low cost loop antenna - your thoughts please

Chris Moulding
 

The test this morning was to try and destroy the loop antenna amplifier with RF.

!00W over all HF bands from a transmit antenna 3m (10 ft) from the loop antenna using the 1m diameter coax loop did not damage the amplifier.

I can now finish the PCB design this evening.

Regards,

Chris


Re: Low cost loop antenna - your thoughts please

Tom Crosbie G6PZZ
 

Good news Chris.

I’m presuming the performance at 14kHz extends to cover NDB, LW and MW. If so, you’ve got another great antenna product on the way. I know there is great interest in these bands in the US. (I keep forgetting to re-join our own Medium Wave Circle). You will have developed a product that allows the end user to experiment with the size and shape of loop and the materials used. For me, the difficulty would have been producing the electronic and fitting into a waterproof box.

 

Tom G6PZZ

 

From: CrossCountryWireless@groups.io <CrossCountryWireless@groups.io> On Behalf Of Chris Moulding
Sent: 19 September 2019 18:44
To: CrossCountryWireless@groups.io
Subject: Re: [CrossCountryWireless] Low cost loop antenna - your thoughts please

 

I've finished and tested the design today.

To test it I've used a 1m (3ft 3 in) loop of LDF4-50 coax. I expect that this will be a typical size of loop users will try, using the outer braid or shield of the larger sizes of coax as a loop reduces the loop inductance and increases performance. The loop was mounted 4.5m (14 ft 9 in) above ground at the highest point of the loop.

From measurements made at VLF with a Sentinel 4 receiver the antenna will work well down to 14 kHz. I saw lightning spikes from 14 kHz up and the lowest frequency VLF station I could identify at midday was JXN in Norway on 16.4 kHz. (This is from north west England).

On HF the performance was excellent. Despite very poor HF conditions on 20m FT8 I heard a station in Malawi with what appeared to the whole of Europe calling him!

The directivity of the antenna is as expected. Think of a dipole with two sharp nulls.

To increase the overall gain I've added an amplifier stage in the base unit. The external noise is higher than the loop amplifier noise.

I tried a common mode filter before the loop amplifier input but it was unstable at certain frequencies due to the very low impedance (0.25 ohms). Instead I added the common mode filter on the output of the loop amplifier. This reduced VHF FM broadcast stations by 20 dB and everything above 200 MHz by greater than 40 dB.

I can keep the same target price with the extra components.

The next stage is to start the PCB design and get a small batch produced for testing and production.

Regards,

Chris

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