Topics

40m Delta Loop

John VA3KOT
 

Thanks for the tip Pat!


On Mon, Mar 25, 2019, 12:22 N5VMO Pat <n5vmo00@...> wrote:
Use a counterpoise wire on the ground in the opposite direction of the signal direction will be a BIG help in those =)   I have used those during Summer FD and they work great in pointing a signal where you want it =)

On Mon, Mar 25, 2019 at 10:26 AM John Corby <va3kot@...> wrote:
Of course the downside, as Tom pointed out, is that a Delta Loop takes longer to erect than, for example, an End-Fed wire. That could make it less suitable for a RaDAR exercise. I am also experimenting with other antennas involving a full wavelength of wire. 137ft is about 5% long for a full-wave on 40m but that is the recommended length for a delta loop. I also plan to setup the same wire as an End Fed Wave antenna. That's an interesting concept inspired by the US Marine Corps who used wires one or more wavelengths long, hung in a straight line, close to the ground, for HF comms in the Vietnam era. A signal along the wire interacts with its image in the ground to produce vertically polarized propagation off the end of the wire. EZNEC modeling suggests a height of about 8ft produces a lossless antenna with a takeoff angle around 55deg. If the wire is any lower (e.g. on the ground) the losses are considerable but the takeoff angle is even lower. If the wire is too high it becomes an NVIS antenna. Another variant is the End Fed Half Rhombic antenna which uses the same length of wire supported in the middle by a 30ft pole.

The purpose of the exercise is to find antennas that will keep QRP field operations alive during the solar minimum. Two or three years ago I worked DX with just a homebrew buddistick but the bands are getting a bit tricky as we pass through the solar minimum for the next couple of years.



--
73's Pat  N5VMO


N5VMO Pat
 

Use a counterpoise wire on the ground in the opposite direction of the signal direction will be a BIG help in those =)   I have used those during Summer FD and they work great in pointing a signal where you want it =)


On Mon, Mar 25, 2019 at 10:26 AM John Corby <va3kot@...> wrote:
Of course the downside, as Tom pointed out, is that a Delta Loop takes longer to erect than, for example, an End-Fed wire. That could make it less suitable for a RaDAR exercise. I am also experimenting with other antennas involving a full wavelength of wire. 137ft is about 5% long for a full-wave on 40m but that is the recommended length for a delta loop. I also plan to setup the same wire as an End Fed Wave antenna. That's an interesting concept inspired by the US Marine Corps who used wires one or more wavelengths long, hung in a straight line, close to the ground, for HF comms in the Vietnam era. A signal along the wire interacts with its image in the ground to produce vertically polarized propagation off the end of the wire. EZNEC modeling suggests a height of about 8ft produces a lossless antenna with a takeoff angle around 55deg. If the wire is any lower (e.g. on the ground) the losses are considerable but the takeoff angle is even lower. If the wire is too high it becomes an NVIS antenna. Another variant is the End Fed Half Rhombic antenna which uses the same length of wire supported in the middle by a 30ft pole.

The purpose of the exercise is to find antennas that will keep QRP field operations alive during the solar minimum. Two or three years ago I worked DX with just a homebrew buddistick but the bands are getting a bit tricky as we pass through the solar minimum for the next couple of years.



--
73's Pat  N5VMO


John VA3KOT
 

Of course the downside, as Tom pointed out, is that a Delta Loop takes longer to erect than, for example, an End-Fed wire. That could make it less suitable for a RaDAR exercise. I am also experimenting with other antennas involving a full wavelength of wire. 137ft is about 5% long for a full-wave on 40m but that is the recommended length for a delta loop. I also plan to setup the same wire as an End Fed Wave antenna. That's an interesting concept inspired by the US Marine Corps who used wires one or more wavelengths long, hung in a straight line, close to the ground, for HF comms in the Vietnam era. A signal along the wire interacts with its image in the ground to produce vertically polarized propagation off the end of the wire. EZNEC modeling suggests a height of about 8ft produces a lossless antenna with a takeoff angle around 55deg. If the wire is any lower (e.g. on the ground) the losses are considerable but the takeoff angle is even lower. If the wire is too high it becomes an NVIS antenna. Another variant is the End Fed Half Rhombic antenna which uses the same length of wire supported in the middle by a 30ft pole.

The purpose of the exercise is to find antennas that will keep QRP field operations alive during the solar minimum. Two or three years ago I worked DX with just a homebrew buddistick but the bands are getting a bit tricky as we pass through the solar minimum for the next couple of years.

N5VMO Pat
 

I to like loops Tom =)    When I had a house I had a 80 meter horizontal loop about 10 meters off the ground fed with 20 meters of ladder line directly into the back of my manual tuner balanced line port =)   It worked GREAT on any band 10 to 80 meters  WARP bands where a bit to tune but worked =)   I built a 10 meter vertical delta loop for a new tech ( my first Delta Loop ) that worked and tuned by changing the feed point at the top by sliding down the feed point ( RG-58 ) a bit one side to a perfect tune all across the band =)   So I will have to make a 40 and 30 meter band Delta Loop for camping =)


On Sun, Mar 24, 2019 at 6:57 PM Thomas Robinson via Groups.Io <g0sbw=btinternet.com@groups.io> wrote:
I am very fond of delta loops. My home QTH antenna is a horizontal loop for 80m. This is fed by an auto tuner quite some distance away from the shack. The antenna is fed from the atu by open wire feeder and tunes up on all bands 80 thro 10. However I have delta loops available for 20m and 17m. These are deployed in upside down pyramid and are fed by a quarter wave of 75 ohm coax. Normal 50 ohm coax from the rig to the quarter wave.  The deltas can be horizontally or vertically polarised depending on how the are deployed. I normally use them vertically polarised as dx antennas.  They perform well in this mode. Without any salt water amplifier effect I have worked Antarctica on 17m. I have not tried them portable as yet.  But I will give them a go on the salt marsh this summer.  They should work well. Bit more work to deploy compared to an end fed half wave though.



--
73's Pat  N5VMO


Thomas Robinson
 

I am very fond of delta loops. My home QTH antenna is a horizontal loop for 80m. This is fed by an auto tuner quite some distance away from the shack. The antenna is fed from the atu by open wire feeder and tunes up on all bands 80 thro 10. However I have delta loops available for 20m and 17m. These are deployed in upside down pyramid and are fed by a quarter wave of 75 ohm coax. Normal 50 ohm coax from the rig to the quarter wave.  The deltas can be horizontally or vertically polarised depending on how the are deployed. I normally use them vertically polarised as dx antennas.  They perform well in this mode. Without any salt water amplifier effect I have worked Antarctica on 17m. I have not tried them portable as yet.  But I will give them a go on the salt marsh this summer.  They should work well. Bit more work to deploy compared to an end fed half wave though.

N5VMO Pat
 

John that looks like a great antenna to use =)   I have seen in the past Greg using one and I may give it a try as well =)    Hmmm .... a 30 foot push-up pole now with tent rain-fly spreaders =)


On Sun, Mar 24, 2019 at 2:58 PM John Corby <va3kot@...> wrote:
Finally got some mild weather in southern Ontario today so I put up an antenna I've been waiting to try out. It is a vertically polarized Delta loop for 40m. It uses 137ft of wire supported on a 30ft pole at the peak with the low, horizontal section just 4ft above ground. EZNEC modeling showed promising expectations so I was excited to test it outside as a possible RaDAR antenna.

I fired off some CW CQs at 5 watts using my Hendricks PFR3 radio and received an immediate spot on RBN from a station in Wisconsin 400 miles away. My signal was reported at a very strong 21dB so this antenna may be doing its job! Unfortunately I didn't get any QSOs but that has become all too common the way the bands have been lately.

Now I'm looking forward to a new RaDAR operating season with some new antenna designs. Hope to catch you all on the bands this summer.

John, VA3KOT
EN93XX67



--
73's Pat  N5VMO


John VA3KOT
 

Finally got some mild weather in southern Ontario today so I put up an antenna I've been waiting to try out. It is a vertically polarized Delta loop for 40m. It uses 137ft of wire supported on a 30ft pole at the peak with the low, horizontal section just 4ft above ground. EZNEC modeling showed promising expectations so I was excited to test it outside as a possible RaDAR antenna.

I fired off some CW CQs at 5 watts using my Hendricks PFR3 radio and received an immediate spot on RBN from a station in Wisconsin 400 miles away. My signal was reported at a very strong 21dB so this antenna may be doing its job! Unfortunately I didn't get any QSOs but that has become all too common the way the bands have been lately.

Now I'm looking forward to a new RaDAR operating season with some new antenna designs. Hope to catch you all on the bands this summer.

John, VA3KOT
EN93XX67