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Thread: Aerial telemetry antenna for Cubs

  1. #1
    Acry's Avatar
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    Aerial telemetry antenna for Cubs

    Hello to all,
    I am a wildlife biologist/pilot doing telemetry flights for mammal and bird surveys in the Swiss alps using a self-built VFR antenna fixed on the foot step of Mr. Pipers Indian tribe (mainly Archers and Cherokees). Now I may switch to Super Cubs (or a 172), and I plan to use H type yagi antennas from either ATS or Telonics. It took me a veery long long time to get my Archer antenna approved by the Aviation Authorities, and it will be at least as difficult to get a Super Cub strut-mounted antenna accepted, if at all. But it would probably help if they were already approved elsewhere.
    After some internet research I found that FAA inspection standards vary depending on how individual FAA inspectors classify the bracket and regional FAA practices and policies. In some parts of the US, aircraft brackets are considered a "minor alteration" and a simple logbook sign off can be completed by a certified A&P to achieve full compliance with FAA rules, in other areas of the country inspectors have asked for a Supplemental Type Certificate (STC). However, the only STC I found - thanks to a member of the IANRP - is SA182CH for Cessna by Ohio Dept. of Transportation from 1994.
    So, the question goes out to you: are wildlife telemetry H type antennas for PA-18s somewhere officially approved by FAA or TCCA (Google didn’t answered conclusively)? I’d really appreciate your help.

    Fly safe,

    RYAN

  2. #2
    wireweinie's Avatar
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    Never heard of any official approval. Most of the operators that I've worked with here, just mount the antenna on a tube (sometimes, literally a broom handle) and clamp them to the struts right at the jury strut attach point (PA 18's).

    Web
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  3. #3
    frequent_flyer's Avatar
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    Don't know if these antennas are suitable for your telemetry frequency but they do list a PA-18 strut mount. No idea what approval they have.

    https://www.telonics.com/literature/aircraft/

  4. #4
    BC12D-4-85's Avatar
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    This is generally what Acry is asking about: https://www.telonics.com/literature/aircraft/ For fish we pointed them forward and used dual up to 4 element yagis with a phasing box and harness to add gain. No inflight effects were noted. At speed the elements can depart the aircraft after long use.

    Alaska has this external load permit document that may be of some help: https://www.faa.gov/documentlibrary/...er_8400.34.pdf

    Gary
    Last edited by BC12D-4-85; 06-24-2022 at 10:18 PM.
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  5. #5
    spinner2's Avatar
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    I have the paperwork for this type of tracking for a C-172 (T41B) from the days this plane was owned by the state of Idaho. I bought it from Idaho in 1998. It’s been a while since I looked at it but I think there is a separate restricted category airworthiness certificate that applies when used this way.
    "Fast is fine, but accuracy is everything." Wyatt Earp

  6. #6
    Mikey's Avatar
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    Was about 15yrs ago, but Seattle FSDO made me go RESTRICTED when the brackets and antennas were installed on my PA-12. Returned to NORMAL when removed. Was able to sign off the switch as "Pilot"

  7. #7

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    Quote Originally Posted by Mikey View Post
    Was about 15yrs ago, but Seattle FSDO made me go RESTRICTED when the brackets and antennas were installed on my PA-12. Returned to NORMAL when removed. Was able to sign off the switch as "Pilot"
    That would be the correct way to do it.


    Sent from my iPad using Tapatalk

  8. #8
    mvivion's Avatar
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    The methodology for “approving” telemetry antennas is so variable, depending on where you operate that it is not funny. I used telemetry tracking antennas mounted on a variety of aircraft for almost forty years in Alaska and Minnesota, both of those states authorized antenna installations commonly with minimal fuss…..in Alaska, the FAA policy on external loads on fixed wing aircraft specifically discusses approval of tracking antennas, inspection and signature by a certificated mechanic.

    In Minnesota, FAA required us to get a field approval. Next door, North Dakota FAA claimed the plane had to go into restricted category, which in our case, invalidated insurance. Since our antennas were approved by a FAA Inspector, we didn’t worry about state lines.

    There are no approvals I’m aware of for Super Cub aircraft for these type antennas.

    I can tell you, however, that all the telemetry antennas that I flew with caused absolutely no problems, and some of those were four element yagis. In fact, I just left the antennas on the planes when doing other things…….saved a bit of wear and tear installing and removing.

    I have some papers that may or may not help with approvals that are in electronic form, assuming I can find them….. They don’t concern approvals, but attachment, etc.

    im pretty sure there are some helicopter approvals to install tracking antennas, but don’t know where you’d find them.
    Send me a pm with your email, and I’ll send a copy of the Alaska external loads policy and some other papers. I also have some photos if that’ll help.

    MTV
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  9. #9
    frequent_flyer's Avatar
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    With the proliferation of all sorts of cameras and camera mounts with, apparently, no approval at all I'm surprised that a small Yagi (yes, it's a capital Y) would draw any attention at all.

    If joining SuperCub.org has taught me anything it's that going EAB was a good choice for me. Still need to part with the PA-28 though before some over-zealous inspector decides some of my maintenance was not properly supervised.

  10. #10

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    Aerial telemetry antenna for Cubs

    Quote Originally Posted by frequent_flyer View Post
    With the proliferation of all sorts of cameras and camera mounts with, apparently, no approval at all I'm surprised that a small Yagi (yes, it's a capital Y) would draw any attention at all.

    If joining SuperCub.org has taught me anything it's that going EAB was a good choice for me. Still need to part with the PA-28 though before some over-zealous inspector decides some of my maintenance was not properly supervised.
    But E-AB would not work for the mission described in this thread. 91.319 says you can only use the aircraft for the PURPOSE for which it is certified. Tracking stuff with external antennas doesn’t qualify as Operating Amateur Built Aircraft.


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  11. #11
    BC12D-4-85's Avatar
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    Actually some enterprising inventor could build a 4-square vertically polarized phased array mounted to a common groundplane. And/or attach same to the belly (metal ideal). They can be phased in four directions with the right harness and switching mechanism. This is for the Ham Bands but could be sized for 150 Mhz +-. They do work well.

    Gary
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  12. #12
    mvivion's Avatar
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    Quote Originally Posted by frequent_flyer View Post
    With the proliferation of all sorts of cameras and camera mounts with, apparently, no approval at all I'm surprised that a small Yagi (yes, it's a capital Y) would draw any attention at all.

    If joining SuperCub.org has taught me anything it's that going EAB was a good choice for me. Still need to part with the PA-28 though before some over-zealous inspector decides some of my maintenance was not properly supervised.
    You’re speaking of the US. He’s in the Swiss Alps. Do they even have an “EAB” type program, and, would as DGA notes, this qualify in that category in that country?

    I suspect, like it or not, I would document at least to some extent, the literally hundreds of thousands of hours these types of antennas have been flown in wildlife research all over the world, and I don’t know if a single accident in the US that one of these antenna systems was listed even as a contributing factor.

    I personally have flown nine or ten thousand hours with these antennas, and I know of others with a lot of time flying with them.

    Then, go to your regulatory agency and overwhelm them with data.

    Or, strap em on and go fly.

    MTV
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  13. #13
    wireweinie's Avatar
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    Quote Originally Posted by BC12D-4-85 View Post
    Actually some enterprising inventor could build a 4-square vertically polarized phased array mounted to a common groundplane. And/or attach same to the belly (metal ideal). They can be phased in four directions with the right harness and switching mechanism. This is for the Ham Bands but could be sized for 150 Mhz +-. They do work well.

    Gary
    Not sure I follow. You want to mount it horizontal on the belly?

    Web
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  14. #14
    BC12D-4-85's Avatar
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    Quote Originally Posted by wireweinie View Post
    Not sure I follow. You want to mount it horizontal on the belly?

    Web
    Probably on the belly of the tracking aircraft with the ants projecting down...it would likely work at distance on top but might be shielded by a metal fuselage underneath when close. Just a thought as an alternative to Yagis which may be more difficult to approve for some than four vertical antennas attached to proper ground plane like the fuselage. Some with simple BNC connectors to allow attachment. The antennas need not be physically 1/4 WL just electrically an impedance match. They could be shortened and helically wound like hand held radios, or base or mid-antenna coil loaded but also shortened. In most 4-sq/3-sq/or 2-sq antenna setups there's an omni direction reception or transmit mode that then can be later selected for four directions once a signal is detected.

    But...how about an amplified compact loop antenna plus sense wire as used by ADF's? They're frequency of interest is NDB through HF...but the tech of wound core detection and sense antenna supplied resolution is known. Gain with weak signals or false paths of propagation could be a challenge.

    Yagis are simple and effective for adding gain and directional sensing. But surely today modern aircraft deserve a better method of geolocation...I suspect it exists for those that need it and are well funded by tax.

    Gary

  15. #15
    wireweinie's Avatar
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    I like the idea of using the ADF style system. The antennas would need to be wound to match the frequency used but putting a small 'cake pan' antenna on the belly would be sweet.

    Web
    Life's tough . . . wear a cup.

  16. #16
    mvivion's Avatar
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    That system MIGHT work…….. But, as Gary is well aware, what you’re searching for, and trying to DF are infinitely low power signals in a very large world. I suspect that might be the challenge using that style system.

    And, of course, that sort of limitation may or may not be an issue DEPENDING on what sort of creatures the transmitters are attached to, and what kind of terrain they live in. The “Swiss Alps” could offer some interesting challenges.

    Ive run those H antennas (they are technically not true yagis) on a bunch of different planes, and they don’t have quite the range (reach) that a true three or four element yagi has, but they seem to have a very acceptable range.

    I always mounted them vertically polarized vs horizontally polarized as Telonics’ mounts put them in. Vertically polarized gives them the tightest directionality, due to the shape of their reception pattern. Makes it easier to DF.

    MTV

  17. #17
    BC12D-4-85's Avatar
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    Well there is one of those ADF style setups available. Civil Air Patrol and others have it. Someone already figured it out.
    https://www.rhotheta.com/products
    https://www.gocivilairpatrol.com/med...B48891840B.pdf
    https://www.rhotheta.com/products/rt-600?locale=en
    https://rhothetaint.com/airborne/
    https://rhothetaint.com/product/rt-600/

    Gary
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  18. #18
    JWE's Avatar
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    Our aircraft was previously owned by the government and had an antenna installed. Attached is a copy of the sample 337 that came with the antenna installation as well as an article about the bracket used. This information is several years old and may not be applicable now.

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  19. #19
    Acry's Avatar
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    Thank you all for the good points and inputs you have mentioned! And thank you for sharing your experiences and knowledge. Too bad there are no official permits, but I'll discuss with the authorities and see if I can convince them with good data. And if all else fails, I'll do as MTV suggested, strap them on and go flying, preferably in the early morning


    The range of the H antennas is not so much the problem in the Alps. First, I use an amplifier, which increases the range, and second, I have to fly up and down the valleys and gorges anyway to be sure I don't miss a weak signal, like when a transmitter is in an avalanche. Having worked with lynx for 20 years, I mainly look for those, but also deer, or sometimes birds or bats.


    By the way, we do have an "EAB" type program (EAS, Experimental aircraft of Switzerland), but the aviation authorities are as strict with them as with other aircrafts. With the advent of external cameras, the authorities have become even more sensitive...


    I'll keep you posted from this corner of the world.

    All the best and fly safe,

    ACRY

  20. #20
    mvivion's Avatar
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    Quote Originally Posted by Acry View Post
    Thank you all for the good points and inputs you have mentioned! And thank you for sharing your experiences and knowledge. Too bad there are no official permits, but I'll discuss with the authorities and see if I can convince them with good data. And if all else fails, I'll do as MTV suggested, strap them on and go flying, preferably in the early morning


    The range of the H antennas is not so much the problem in the Alps. First, I use an amplifier, which increases the range, and second, I have to fly up and down the valleys and gorges anyway to be sure I don't miss a weak signal, like when a transmitter is in an avalanche. Having worked with lynx for 20 years, I mainly look for those, but also deer, or sometimes birds or bats.


    By the way, we do have an "EAB" type program (EAS, Experimental aircraft of Switzerland), but the aviation authorities are as strict with them as with other aircrafts. With the advent of external cameras, the authorities have become even more sensitive...


    I'll keep you posted from this corner of the world.

    All the best and fly safe,

    ACRY
    Please send me an email address via private message, and I'll send you some paperwork I have that MAY be of assistance. And, I can sympathize, the situation in the US can be just as daunting. I had a Super Cub hung with a yellow tag (this aircraft is not airworthy) by an FAA Inspector once due to the antennas, which were field approved.....

    MTV

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