Antenna Recommendation for L.E.O LRPT

Useful information regarding antennas for SDR products.
FleetingGlimpse
Posts: 21
Joined: Wed Nov 08, 2017 3:04 am

Antenna Recommendation for L.E.O LRPT

Postby FleetingGlimpse » Thu Feb 01, 2018 5:48 pm

Greetings,
I am presently narrowing down which design(s) i ought to use for my Weather Satellite and Earth Observation projects.
I have been reading quite a few design notes published on the Internet.There seems to be a lot going for the QFH .

a)Compared to the other designs such as Turnstile/crossed Dipole, EggBeater,is it worth all the time and effort to construct a QFH?

There seems to be a considerable amount of work involved in the construction,is it worth all that effort?
I would appreciate any suggestions.

Thanks, Norm

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Mike2459
Posts: 103
Joined: Mon Jul 24, 2017 8:24 pm

Re: Antenna Recommendation for L.E.O LRPT

Postby Mike2459 » Fri Feb 02, 2018 1:12 am

About 15 (or more) years ago I built a QFH for the 137 MHz band from a broomstick, some plastic rods, 75 ohm coax and a few cable ties to hold the coax in place. The hardest part was soldering the steel coax shield. I had to use acid core solder. Used an inline TV signal booster as an LNA. It's mounted in the attic. It still works very well. It works even better with an SDR. On occasion I can acquire NOAA wx sats down to a 3 degree elevation. But 5 to 6 degrees is more common. I can also get pretty good images from the Russian Meteor but it's digital (QPSK) requires a stronger signal to decode than the NOAA sats. Local noise levels (which vary), and space weather have the greatest impact on reception, in my case.

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FleetingGlimpse
Posts: 21
Joined: Wed Nov 08, 2017 3:04 am

Re: Antenna Recommendation for L.E.O LRPT

Postby FleetingGlimpse » Fri Feb 02, 2018 9:25 pm

Mike2459 wrote:About 15 (or more) years ago I built a QFH for the 137 MHz band from a broomstick, some plastic rods, 75 ohm coax and a few cable ties to hold the coax in place. The hardest part was soldering the steel coax shield. I had to use acid core solder. Used an inline TV signal booster as an LNA. It's mounted in the attic. It still works very well. It works even better with an SDR. On occasion I can acquire NOAA wx sats down to a 3 degree elevation. But 5 to 6 degrees is more common. I can also get pretty good images from the Russian Meteor but it's digital (QPSK) requires a stronger signal to decode than the NOAA sats. Local noise levels (which vary), and space weather have the greatest impact on reception, in my case.


Ok Mike thanks for the nfo. Someone said “Simplicity is a compromise medium between too little and too much. “ — Joshua Reynold “

I always try and reduce the 'complexity' of any project as much as it is feasibly possible..Reduces the 'stress' level and also the 'hollerations' etc/ etc.

Anyway should in case you or any other Forum member feels "Ambitious" here is a website that i found whilst doing my online research about the QFH.

A Complete step-by-step manual in the construction of a Quadrifilar Antenna to receive 137 MHz signal from NOAA weather satellites.One of the most detailed set of construction notes on the matter..Full of practical 'Hints and Kinks' (no pun intended)

http://hobitus.com/en/equipment/antenna/

Best Regards, Norm

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Mike2459
Posts: 103
Joined: Mon Jul 24, 2017 8:24 pm

Re: Antenna Recommendation for L.E.O LRPT

Postby Mike2459 » Sat Feb 03, 2018 9:07 am

Thanks Norm, that's a link I missed.
I have been considering this double crossed dipole design: http://www.qsl.net/py4zbz/DCA.pdf

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N0BGS
Posts: 5
Joined: Mon Dec 28, 2015 10:54 pm

Re: Antenna Recommendation for L.E.O LRPT

Postby N0BGS » Sun Feb 11, 2018 6:30 pm

Norm,

How about a Moxon pair? Considerably easier to build than a QFH, IMO.

Here's one by L.B. Cebik, W7RNL, who was a real antenna expert.

http://www.oocities.org/w9bci/VHFUHFSatelite.pdf

Of course you'll need to scale those measurements to 137 Mhz. You can do that very easily using MoxGen.

Here: http://www.moxonantennaproject.com/design.htm

I have collected all the parts but haven't built one yet. :roll:

Good luck!

73,

--Kurt

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FleetingGlimpse
Posts: 21
Joined: Wed Nov 08, 2017 3:04 am

Re: Antenna Recommendation for L.E.O LRPT

Postby FleetingGlimpse » Tue Feb 27, 2018 6:41 am

Greetings.
Thanks comrades Mike2459 and NOBGS for the recommendations. Yes i have read about all those designs, actually i have compiled quite an extensive list of construction articles related to Weather satellite reception. The Double cross Antenna is definitely among my picks and have started to procure the parts needed for construction.
Here is a link to one such construction which i have decided to implement https://w9fe.blogspot.com/2017/10/the-d ... llite.html Seems as if he has done the 'grunt' work and has kindly posted a set of complete plans..Ought to be fun and No Hassle.
Will post outcome of that construction project.

Yes i do agree that the QFH Is somewhat of a labor intense build..i know, i just got done buidling my version of the design,I opted for the Tall and Narrow layout....http://perso.wanadoo.es/dimoni/ant_qha.htm

Presently i am performing a set of tests just to verify a few parameters,I have not yet connected it to any SDR to see how well it performs on capturing any signals from the Various POES - Polar Orbiting Environmental Satellites
I would like to be able to compare results from two different set of antennas.
I am excited, will definitely post a few results.

I gotta admit that i have been 'smitten' by the QFH Antenna construction sense of accomplishment..No doubt that i shall be 'rolling' out more than one QFH..For now,it is test time to verify if all the Hype is really worth it.

Many of the existing published QFH designs i researched featured difficult to build designs and loaded with too much unnecessary technical jargon.

Here are a few links that i have Bookmarked dealing with the Topic of QFH

http://orbanmicrowave.com/wp-content/up ... tennas.pdf
http://www.rish.kyoto-u.ac.jp/digitalbe ... _Guide.pdf
http://www.aribra.it/autocostruzione/qfh/qfh.pdf
https://www.jcoppens.com/ant/qfh/versions.en.php
Can't wait to tryout my Tall & Narrow QFH design.

Best Regards, Storminorm

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FleetingGlimpse
Posts: 21
Joined: Wed Nov 08, 2017 3:04 am

Re: Antenna Recommendation for L.E.O LRPT

Postby FleetingGlimpse » Tue Feb 27, 2018 7:25 am

We have been taught the Theory of Reciprocity which states that the receive and transmit properties of an antenna are identical.
I was fortunate to have been provided the opportunity to construct quite a few Circular Polarized Aerial systems for FM Broadcast

Curious how such a circular design radiation pattern design would work for POES reception?

https://twitter.com/fearlesslyloyal/sta ... 4464513026 & https://twitter.com/fearlesslyloyal/sta ... 4464513026

Go ahead muse yourselves, Don't be a prude 8-) :D Antenna construction can and ought to bea fun experience

Best Regards, Storminorm

"And kind old King George
Sent mother a note
When he heard that father was gone"...From "The Final cut" When the Tigers Broke Free..Lyrics By Roger Waters

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FleetingGlimpse
Posts: 21
Joined: Wed Nov 08, 2017 3:04 am

Re: Antenna Recommendation for L.E.O LRPT

Postby FleetingGlimpse » Tue Feb 27, 2018 8:05 pm

Greetings.
After wireing the connections to the QFH i performed a set of active RF test to determine the resonant frequency of the Build.

https://twitter.com/fearlesslyloyal/sta ... 4672429057

I was surprised when i found that the unit resonated at 128Mhz https://twitter.com/fearlesslyloyal/sta ... 0813149184

During the construction, i decided to change the tubing to that of solid copper wire, due physical restraints on my cervical neck column (Chronic Pain and discomforts) So maybe the change from tubing to solid copper might have resulted in a 9Mhz frequency difference from 137Mhz.The copper wire was a lot easier to bend and twist into a helix form factor. https://twitter.com/fearlesslyloyal/sta ... 8245060610

From a Transmitter base station perspective i would be appalled if any design resulted in a VSWR Greater than 1.5 to 1...Most antenna construction afficionados strive for a perfect match of 1 t0 1 VSWR Or no greater than 1.5 to 1 at the design frequency or range of frequencies.

Even though i will not be using the QFH for TX Transmitting purposes, i can imagine the Torture the final PA stages would be going thru feeding power into an Aerial system with a 3 to 1 VSWR..SWEAT :x

I also subjected the QFH to a series of SNR test using my VSWR Analyzer as a signal source,and connected the SDR Unit to the QFH to get a basic quantify of the SNR..So the next tests will be the QFH in actual real world POES signal Acquisition...Can't wait. :D

Best Regards, Norm

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AussieSusan
Posts: 25
Joined: Wed Aug 16, 2017 6:50 am

Re: Antenna Recommendation for L.E.O LRPT

Postby AussieSusan » Wed Feb 28, 2018 2:21 am

*In Theory* at the frequencies in question, all of the signal is at the surface of the conductor (skin effect) so how thick the conductor is should not matter.
Going from a tube to a solid wire might make a difference as it be considered there were 2 'skins' in the tube but that is a bit beyond my thought-experiment-constrained brain.
In my experience, a QFH is more sensitive to the lengths of the wires (not just those outside the main part) and quality of joints etc..
However, when all is said and done, you should get as good a signal from your QFH as from one that is "perfectly tuned".
(And the reason most people go for a low SWR is for the Tx side where they want to get as much signal out as possible and not get it sent back to the final amplifiers - that was fine when they were valves but solid state devices can be a bit more sensitive. The Rx side is far more forgiving.)
Susan

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RSP2user
Posts: 82
Joined: Mon Oct 09, 2017 7:11 am

Re: Antenna Recommendation for L.E.O LRPT

Postby RSP2user » Sun Sep 30, 2018 11:18 pm

There is an excellent article on the SDRPlay forum here for building a nice QFH antenna for APT and LRPT image reception. You can tell how well this antenna works from the images posted, which are quite good.

https://www.sdrplay.com/community/viewt ... f=5&t=2529

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