Tag: doublet

QRO portable from Cromer North Norfolk

I have always enjoyed operating portable HF as you can put up antenna and work bands not possible at home. This coupled with finding an RF quiet location can make HF portable very enjoyable.

Using a 12m spider beam roach pole, an 80m doublet fed with 300 Ohm ribbon cable and Icom 7100 I parked in a rural country lane surrounded by fields. The doublet was cable tied to the roach pole at around 11m, and the pole secured to a farmers fence.

 

 

The Icom, Expert 1.3KFA linear and ATU was placed in the boot of the car, and power was provided by an EU20 Honda generator. I started operating at 19:26 with the first call in the log G4JXC Bob from Bristol, signals seemed very good with reports usually over s9, sometimes s9+40.

At times I had a pile-up, really hard to pick out any calls, I did try and pull out a few QRP stations some running just 3 and 4w.

The amplifier definitely helped, but getting a large antenna in the air inverted V means a lot of the RF goes up in the air. Over the next couple of hours, I worked 57 stations in 10 countries. As darkness descended the skip did lengthen out a little, with stations calling me from Sweden, Germany, Spain and the Netherlands.

 

I was also able to monitor my own signal on my KiwiSDR located some 100 miles away. It was fun to work some stations that had also used my SDR, and also catch up with some people on twitter.

 

A enjoyable was to spend an evening, thanks to everyone who called.

 

Comparing the Wellbrook Loop to a Doublet Antenna

This evening I decided to complete a test using two different HF setups in an effort to compare the receiver performance of my antennas.

Radio 1, Kenwood TS 990, doublet antenna 10m per leg @ 9m

Billy offers support.

Billy offers support.

Radio 2, Elad SDR, Wellbrook RX loop @ 3m

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I decide the best way to test on receive would be to leave both radios receiving on 7076 KHz for 90 minutes, using WSJT-X. Both receivers had been set to 3 KHz bandwidth, and over the course of the next 90 minutes they each collected over 600 measurement reports.

The test started at 1830 Hrs and continued to 2000 Hrs. The doublet collected 633 measurement reports, and the wellbrook 740. This was the first indication that the Elad coupled with the Wellbrook was out performing the Kenwood / doublet setup. The next stage was to look in detail at the reports, WSJT has an option to write all received data into a text file, this includes time, s/n and decoded text. I used this to select at random some calls that represented a selection of EU (and DX if possible) and compare the relative signals received at the very same time on both radio 1 and 2.

The following table shows a selection of data points

wellbrook v doublet

After reviewing the data it was clear the Wellbrook loop improved the quantity of stations decoded, and in many cases also improved the s/n received.

This is by no means a definitive test, but it does indicate the Wellbrook loop (as many others have reported) work well in somewhat noisy urban environments.  The wellbrook loop can be reviewed online at the Wellbrook communications website, the version I used for the tests was ALA1530  its 1m and designed for medium and shortwave 50 KHz to 30 MHz. Steve Nichols G0KYA completed a review in January 2012 Radcom You can see the Eznec plot as photo 3 in the review.

The other factor to consider is the loop antenna has some directivity, I didn’t rotate the antenna at any point during my tests. In many cases rotation will improve / reduce signals as the antenna has directional properties.

The Welbrook performed well on 7 MHz, I suspect it would be even better on 1.9 and 3.5 MHz… to be continued….

Dave M0TAZ