MT magazine UHF Satcom antenna project

[SCPD]

Ok..did some outdoor field testing today with the X-wing which rendered some impressive results. Moving the antenna outdoors improved the signals dramatically.I was picking up the usual pirates operating on 255.550 well above the static with a clear signal. I did notice when I angled the antenna a bit down toward the south east the signal improved even more. Im impressed with its performance thus far and now moving to test phase three. Installing it to the roof of my house!

 

[prcguy]

Your quite a ways north and almost in between the CONUS and Atlantic orbital slots, so you might want to tilt slightly south instead of south east. I thought the 255.550 pirates were on the CONUS satellite which is south west of you.

Nice work on the antenna!
prcguy


QUOTE=N1RGR;1449035]Ok..did some outdoor field testing today with the X-wing which rendered some impressive results. Moving the antenna outdoors improved the signals dramatically.I was picking up the usual pirates operating on 255.550 well above the static with a clear signal. I did notice when I angled the antenna a bit down toward the south east the signal improved even more. Im impressed with its performance thus far and now moving to test phase three. Installing it to the roof of my house![/QUOTE]

 

[SCPD]

Your quite a ways north and almost in between the CONUS and Atlantic orbital slots, so you might want to tilt slightly south instead of south east. I thought the 255.550 pirates were on the CONUS satellite which is south west of you.

Nice work on the antenna!
prcguy

Thanks prcguy. It was a nice little winter project. I will try it pointed more to the south next time during testing. I think Im going to use a spare dish network bracket I have laying around to mount the antenna on. Im also thinking of constructing a swivel bracket that will attach the x-wing reflector to the dish bracket arm so that I can adjust the angle if needed to but will most likely just leave it pointed straight up as prescribed.

Thanks again for all your help.

 

[prcguy]

The two orbital slots that you can see from RI are both fixed south of you and they don't move, so the antenna would not require any movement once its installed.

If you have a way to accurately measure signal strength you can try raising the dipoles above the reflector screen a little with the screen parallel to the ground. This should lower the pattern toward the horizon and might benefit your location.
prcguy

Thanks prcguy. It was a nice little winter project. I will try it pointed more to the south next time during testing. I think Im going to use a spare dish network bracket I have laying around to mount the antenna on. Im also thinking of constructing a swivel bracket that will attach the x-wing reflector to the dish bracket arm so that I can adjust the angle if needed to but will most likely just leave it pointed straight up as prescribed.

Thanks again for all your help.

 

[SCPD]

Ok..got the home made bracket together and attatched the sucker to the roof today. I found an adjustable angled bracket that I have attached to the reflector. So far the best results are with the antenna directed south west and angled down a bit towards the horizon as it is in the picture.

In this position I am picking up pirates on 262.200,265.4500 (UFO CONUS) and 253.500 which I think is the Milstar Sat all with reasonably good signals. If I point the antenna straight up the signals degrade a bit.

However with the antenna fixed to the CONUS position Im not receiving a good signal on 255.550. It only improves with the antenna pointed more towards the east a bit.

Could this be because 255.550 is on Fltsatcom-8 which is at the 15 deg.west slot?

 

[prcguy]

The 15deg orbital slot is about a 16 deg look angle from RI and the antenna was optomised for 20 to 60 deg elevation, so I can see why it improves when you angle it SE.

It would be interesting to see how it works with the refllector parallel to the ground and the dipole support raised to pull the pattern lower.
prcguy

Ok..got the home made bracket together and attatched the sucker to the roof today. I found an adjustable angled bracket that I have attached to the reflector. So far the best results are with the antenna directed south west and angled down a bit towards the horizon as it is in the picture.

In this position I am picking up pirates on 262.200,265.4500 (UFO CONUS) and 253.500 which I think is the Milstar Sat all with a reasonably good signals. If I point the antenna straight up the signals degrade a bit.

However with the antenna fixed at the CONUS position Im not receiving a good signal on 255.550. It only improves with the antenna pointed more towards the east a bit.

Could this be because 255.550 is on Fltsatcom-8 which is at the 15 deg.west slot?

 

[Ozi]

Hi guys,

Interesting antenna, thanks for posting the plans and Info to build it.

Just an observation N1RGR, If you Intend to point it as you are other than vertical, maybe a reflector/driven spacing of 3/8 wave might work a little better opposed to 1/2 wave. At 3/8 it'll narrow the antennas beamwidth (slightly more gain towards where your pointing it) but then again you guys have a few more sats up there to play with so maybe 1/2 spacing might work best

I know.... just build a couple more


regards
Darren

 

[prcguy]

If you change the dipole spacing above the reflector everything goes out of whack. The dipole impedance changes, affecting the phasing harness and it pulls the resonant frequency around a bit.

Its very time consuming to analyze the needed changes with EZNEC and then tweaking the hardware requires an antenna analyzer and a way to accurately measure minute signal strength changes.
prcguy

Hi guys,

Interesting antenna, thanks for posting the plans and Info to build it.

Just an observation N1RGR, If you Intend to point it as you are other than vertical, maybe a reflector/driven spacing of 3/8 wave might work a little better opposed to 1/2 wave. At 3/8 it'll narrow the antennas beamwidth (slightly more gain towards where your pointing it) but then again you guys have a few more sats up there to play with so maybe 1/2 spacing might work best

I know.... just build a couple more


regards
Darren

 

[Ozi]

Agreed on the above with the described phasing harness thats in the pdf instructions.. so yeah stick to the plan dimensions.

For other spacings a simple matching stub with additional phasing stub (90° delay for rhcp) will work. Ive analyzed an alternative feed at diff. λ spacings for this antenna and the original dimensions are pretty close.

 

[prcguy]

The original X-wing antenna project started out much different than what you see and would have been a "plumbers delight" to construct from 1/2" copper pipe. The two sets of dipoles were of different lengths to force a delay in one set to create CP and one long and short element of each pair shared a common feed point.

The dipoles sat on top of a balanced feedline 1/2 wavelength long made of 1/2 copper pipe and shorted to ground at the reflector side. A 300 ohm TV transformer was attached to the balanced line and moved up and down to obtain a match.

It needed a lot of tweaking and we ran out of time for the article deadline so the version you see was put together quickly using more conventional ideas. I think it turned out well and is easy to reproduce.

I like to encourage experimentation and hopefully someone will make a version that's easier to build without loosing any performance.
prcguy

Agreed on the above with the described phasing harness thats in the pdf instructions.. so yeah stick to the plan dimensions.

For other spacings a simple matching stub with additional phasing stub (90° delay for rhcp) will work. Ive analyzed an alternative feed at diff. λ spacings for this antenna and the original dimensions are pretty close.

 

[SCPD]

Wow..what a bummer....I think? Today my x-wing collapsed from two feet of snow build up on the reflector during a blizzard today. The bracket totally failed and the antenna is now resting completely on its side pointing south down at the horizon. The amazing thing is that Im receiving the Fltsat 100%better now with a very clean and strong signal. This has me scratching my head. I may just leave it like this. Im going to try and get a picture of this thing tomorrow.

 

[mikelib]

X-wing

Just came across this thread, I had built the antenna last June, it works well and I was able to receive the Brazilian Pirates;

 

[prcguy]

Looks great, I made one too!
prcguy

Just came across this thread, I had built the antenna last June, it works well and I was able to receive the Brazilian Pirates;

 

[kb1qzh]

Great write-up!! I hope to build one of these next month. by then, my funcube dongle should be here. I've got a question, kinda longshot but here goes: how hard would it be to adapt this design for use with a magnetic antenna mount? the goal would be to use the car roof as the reflector.

most of my radio enjoyment (ham and monitoring) is split between home and on the road (first HF contact was made at the office parking lot)

thanks

 

[prcguy]

If you look at the first part of the article, a magnetic mount military antenna was the inspiration for the design. The military antenna has a main lobe that points straight up which is ok for some parts of the world but the magazine article version is tailored for the US and several other areas with a look angle of about 20 to 60 degrees.

For vehicular use I would use 1/8" thick stock for the elements to keep then from singing in the wind and maybe a large mount with four 5" magnets. You just need to keep the element spacing above the car at whatever the article says. The thicker elements will detune the antenna slightly but hopefully not too much. If you have an antenna analyzer that covers these freqs you could fine tune it with thicker elements.

If you make one send in a pic!
prcguy

Great write-up!! I hope to build one of these next month. by then, my funcube dongle should be here. I've got a question, kinda longshot but here goes: how hard would it be to adapt this design for use with a magnetic antenna mount? the goal would be to use the car roof as the reflector.

most of my radio enjoyment (ham and monitoring) is split between home and on the road (first HF contact was made at the office parking lot)

thanks

 

[mikelib]

Mike Frye quites Monitoring Times

Page 74 of February's 2011 MT,

"We are sorry to report Mike, (Mike Frye) who made a very promising beginning as our quarterly VHF/UHF antenna columnist,will not be able to continue, due to increase in work load on his demanding "day job."

There seems to be someone in the wings to take Mike's place he will be introduced in March 2011 issue.

I e-mailed Mike in July 2010, a picture of my x-wing and asked him if it was possible to stack another x-wing on top of the existing one. He responded with a nice e-mail and told me he was very busy on the job and he just about making his writing deadlines. He also said that him and his day job boss were discussing how to stack the antenna's and he might include it in a future article.

I guess now that not going to happen.

de Mikelib

 

[kb1qzh]

Will do!! I may make up two sets of elements, one at the specified thickness and another at 1/8th". The test will be how well it holds from south western CT to Deerfield, NH and back for Nearfest!!

i'll keep everyone posted
kb1qzh

If you look at the first part of the article, a magnetic mount military antenna was the inspiration for the design. The military antenna has a main lobe that points straight up which is ok for some parts of the world but the magazine article version is tailored for the US and several other areas with a look angle of about 20 to 60 degrees.

For vehicular use I would use 1/8" thick stock for the elements to keep then from singing in the wind and maybe a large mount with four 5" magnets. You just need to keep the element spacing above the car at whatever the article says. The thicker elements will detune the antenna slightly but hopefully not too much. If you have an antenna analyzer that covers these freqs you could fine tune it with thicker elements.

If you make one send in a pic!
prcguy

 

[KA5QYR]

Here ya go.
prcguy

Thank you PCGUY for posting the full article for the antenna.

John

 

[prcguy]

Your welcome and if you really want to show extra thanks you can subscribe to Monitoring Times magazine who first published the article.
prcguy

Thank you PCGUY for posting the full article for the antenna.

John

 

[18D]

When I was on a mission Thailand I had to point satellite antenna parallel to the earth to hit the satellite it caused a lot of problems for me US Army