[altusmetrum] Coax connecter/cable/antenna confusion

Joe Zawodny jmzawodny at gmail.com
Sat Jun 1 13:53:51 MDT 2013


I suspect your rocket is too small to for a patch antenna at the frequency
these use.
http://linux.students.engr.scu.edu/~bhorwath/presentations/Microstrip%20Patch%20Antenna%20Design.pdf

Joe


On Fri, May 31, 2013 at 7:45 PM, Peter Hackett <
peter.hackett at cal.berkeley.edu> wrote:

> RE copper tape patch antenna:
>
> "Tell me more" :-)
>
> Specifically, how do you attach (say) a sma cable to the the copper tape?
> And would I just tape 7" of the copper tape to the inside of the altimeter
> bay?
>
> I guess I can figure this out with a bit of web surfing, but ...
>
> Is "Copper tape" something that is sticky like masking, er I mean rocket
> tape
> or is it more like cassette tape (copper on some sort of plastic film?)
>
> BTW love the pics of "Behemoth Bertha" rocket on your Google+ page
>
> Peter "A 'real' rocket would be fun" Hackett
>
>
> On Fri, May 31, 2013 at 1:53 PM, Joe Zawodny <jmzawodny at gmail.com> wrote:
>
>> Why not consider building a patch antenna out of the copper tape that
>> hobbyists use in making stained glass.  Patch antennae are what they use on
>> "real" rockets.
>>
>> Joe Z
>>
>>
>> On Fri, May 31, 2013 at 4:42 PM, Peter Hackett <
>> peter.hackett at cal.berkeley.edu> wrote:
>>
>>> Casey and Bdale, thanks for the info!
>>>
>>> RE " ... when another newbie ham asked a similar question"
>>> :-) you!
>>>
>>> Ok, I think I understand most everything.
>>>
>>> I did some more poking around (Casey's thread and a little Googling)
>>>
>>> Which got me to thinking about moving the altimeter from rocket to
>>> rocket.
>>>
>>> I found a web page which seemed to suggest I could strip off (in my
>>> case)  ~ 7"
>>> of the outer casing and outer conduct of a coax cable to form the
>>> equivalent of
>>> a 7" wire antenna. Does that sound right?
>>>
>>> Give that it is true (works reasonably well) I was thinking I could buy
>>> a (say) 5ft
>>> sma male to <anyConnector> coax cable cut off the <anyConnector> end,
>>> drill a cable diameter hole in the "main" side of the altimeter bay
>>> thread the cable
>>> through leaving enough slack to easily connect the sma male connector to
>>> the
>>> TeleMetrum. I would then epoxy the cable as it passes from the inside to
>>> the
>>> outside of altimeter bay. Then I would cut the cable to (say) 8" long on
>>> the outside
>>> of the altimeter bay and strip 7" of the outer case and out conductor to
>>> form the
>>> wire antenna.
>>>
>>> *Seems* like it should work. Thoughts?
>>>
>>> This seems like it would be a good solution because I could install a
>>> cable/antenna
>>> in each rocket for the price of a sma male to xx cable (~$10)
>>>
>>>
>>>
>>> On Thu, May 30, 2013 at 9:30 PM, Bdale Garbee <bdale at gag.com> wrote:
>>>
>>>> Peter Hackett <peter.hackett at cal.berkeley.edu> writes:
>>>>
>>>> > Can I just bend the whip antenna into a horse-shoe shape to get it to
>>>> fit
>>>> > into the altimeter bay? (I guess the really question is "Will this
>>>> > significantly compromise the performance of the antenna?") And if it
>>>> > is "a bad idea" what should I do?
>>>>
>>>> It's a bad idea for two reasons.  One is that it'll dramatically impact
>>>> the radiation pattern, as you surmise.  The second is that doing that
>>>> will put strain on the SMA connector's attachment to the board, which
>>>> isn't a good idea.  I've had to repair boards that had the SMA damaged
>>>> or sheared off because of loads put on the connector by such an antenna
>>>> setup... sadly, one was one of my own boards that I stuffed in a 54mm
>>>> airframe in a hurry at a launch a couple of years ago .. /o\
>>>>
>>>> > My first thought was to find a short SMA male to SMA female cable so
>>>> that
>>>> > the whip antenna can be straight. Is this "a good idea"? (necessary?,
>>>> > etc)
>>>>
>>>> That's a better plan.
>>>>
>>>> > Next: in poking around the Altus Metrum and gag.com web sites while
>>>> > researching about my altimeter question, I saw a link to a "SMA To BNC
>>>> > adapter" on the Teledongle page.
>>>> >
>>>> > I bought an Arrow II Hand Held Portable Antenna 440-3 and in looking
>>>> more
>>>> > closely at the product description page, it looks like it has a BNC
>>>> > connector.
>>>> >
>>>> > So it looks like I'll need to get either the SMA to BNC adapter or
>>>> get a
>>>> > coax cable with a male SMA connector on one end and a male BNC
>>>> > connector on the other. Have I got that right?
>>>>
>>>> Yes.
>>>>
>>>> > If so, any recommendations?
>>>>
>>>> Ok.  The SMA-BNC adapter is the optimal way to attach a TeleDongle to an
>>>> Arrow antenna.  It puts the receiver as close to the antenna feed point
>>>> as possible, which minimizes the loss between the antenna and the
>>>> receiver, giving you the best possible system noise temperature.
>>>>
>>>> On the rocket end, I really prefer the wire whip.  The only reason to
>>>> use an SMA is if you're installing the board in something like an
>>>> aluminum or carbon fiber airframe section (both are more or less opaque
>>>> to RF signals) where you need to remote mount the antenna(s).
>>>>
>>>> Given that you have the SMA connector on the board, the two most
>>>> plausible choices are to use a short SMA male to female cable to remote
>>>> the whip, or to make up a simple wire whip with an SMA on it to use as
>>>> an antenna.
>>>>
>>>> > Peter "I just got my ham radio technical license, so *clearly* I'm an
>>>> > expert on all things RF" Hackett
>>>>
>>>> ;-)
>>>>
>>>> No worries, we all started somewhere!
>>>>
>>>> 73 - Bdale, KB0G
>>>>
>>>
>>>
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