New amplifier design for HF Active and Active Vee antennas


Chris Moulding
 

The amplifier design for both these antennas has remained the same since launch as the HF Active antenna was the reference receive antenna for the RSGB Noise Measurement project.

As that project is now completed it's allowed me to look again at the amplifier design to see what improvements could be made after receiving a lot of customer feedback and learning what customers do with our antennas.

We are now launching a new version of each antenna with a re-designed amplifier. It's a push pull design with 20 dB more output that the original version with higher common mode rejection and IP3 performance.

The base unit has two RF outputs one at full level suitable for use with long feeder runs up to 305m and the second with a 20 dB attenuator for short cable runs including the 20m cable supplied with the antenna.

The amplifier in the head unit has a voltage regulator so we recommend that with short feeder runs a 12 to 15V power supply is used and with long runs a 24V supply is used.

The improved common mode rejection is very useful when used close to other electrical equipment in an urban or suburban environment.

The prototype Vee antenna using the new amplifier is now set up as part of a WebSDR server on the 160m amateur band using a SDR-4+ Special Edition receiver. The local ADSL/VDSLnoise has been nulled out by rotating the antenna for the position of minimum noise. The capacitive coupled local noise sources have been canceled out in the amplifier. The background noise is now S6 making it usable again.

The 160m WebSDR server is at: http://g4hyg.ddns.net:8901/

Regards,

Chris


David Cutter
 


Listening in to TB and a station around 1942 is very clear with no typical local noises.  How do I get it to tune down to cw portion?  I've tried typing in and dragging but neither are working for me, perhaps there's a trick I'm missing
 
David
G3UNA

----- Original Message -----
Sent: Tuesday, February 27, 2018 6:10 PM
Subject: [CrossCountryWireless] New amplifier design for HF Active and Active Vee antennas

The amplifier design for both these antennas has remained the same since launch as the HF Active antenna was the reference receive antenna for the RSGB Noise Measurement project.

As that project is now completed it's allowed me to look again at the amplifier design to see what improvements could be made after receiving a lot of customer feedback and learning what customers do with our antennas.

We are now launching a new version of each antenna with a re-designed amplifier. It's a push pull design with 20 dB more output that the original version with higher common mode rejection and IP3 performance.

The base unit has two RF outputs one at full level suitable for use with long feeder runs up to 305m and the second with a 20 dB attenuator for short cable runs including the 20m cable supplied with the antenna.

The amplifier in the head unit has a voltage regulator so we recommend that with short feeder runs a 12 to 15V power supply is used and with long runs a 24V supply is used.

The improved common mode rejection is very useful when used close to other electrical equipment in an urban or suburban environment.

The prototype Vee antenna using the new amplifier is now set up as part of a WebSDR server on the 160m amateur band using a SDR-4+ Special Edition receiver. The local ADSL/VDSLnoise has been nulled out by rotating the antenna for the position of minimum noise. The capacitive coupled local noise sources have been canceled out in the amplifier. The background noise is now S6 making it usable again.

The 160m WebSDR server is at: http://g4hyg.ddns.net:8901/

Regards,

Chris


Chris Moulding
 

The 160m receiver used for the WebSDR server is usually fixed at 1953 kHz, the frequency of the Bolton Wireless Club net. Users can then listen +/- 24 kHz either side.

For this evening I've retuned the receiver so that it's centre frequency is 1834 kHz so that users can tune from the band edge 1810 kHz up to 1858 kHz.

Try it again, David...

Regards,

Chris


David Cutter
 


EA5byp on 1823.6 clear as day with no snap, crackle and pop!  Can't remember the last time I heard a quiet band
 
David
G3UNA

----- Original Message -----
Sent: Tuesday, February 27, 2018 8:50 PM
Subject: Re: [CrossCountryWireless] New amplifier design for HF Active and Active Vee antennas

The 160m receiver used for the WebSDR server is usually fixed at 1953 kHz, the frequency of the Bolton Wireless Club net. Users can then listen +/- 24 kHz either side.

For this evening I've retuned the receiver so that it's centre frequency is 1834 kHz so that users can tune from the band edge 1810 kHz up to 1858 kHz.

Try it again, David...

Regards,

Chris


Angel M0HDF
 

Hi Chris

Thanks for the update. Better common mode rejection and higher output / IP3 sounds great.
I have here the first active loop (1m wing span) on a feed of 50m of UTP Feedline and the output is low as I mentioned before.

At 14Mhz, the antenna noise floor is just 6dB above the SDR noise floor at max gain (SDRplay) in an urban environment .
I have also done some other comparisons with Verticals and dipoles. I will email some observations directly.

73 Angel
M0HDF


Chris Moulding
 

You have the early smaller version of the loop antenna. The later current version is almost double the size so the signal level at the input to the amplifier is higher. This change was made for greater sensitivity at rural and beach locations.

The levels you quote show that even with the smaller loop you are still limited by the external noise at your location and you will have nearly the maximum dynamic range available from your receiver.

Regards,

Chris