[amsat-bb] NASA Helical Antenna Question

[Nico Janssen]

VHF 1 is 143.625 MHz (the standard Russian ISS downlink frequency) and
VHF 2 is 130.165 MHz (the Soyuz downlink frequency).

The gain of this 8 turn helix should be about 13 dBic.

I once built a 9 turn helix for 2 m. Worked very well.

73,
Nico PA0DLO

On 08-05-18 06:30, Wendy and Terry Osborne wrote:
> Hi,
>
> Yes, it's an 8 turn helix with a Gamma match (50 ohms to 120 ohms).
> The advantages of ring reflector are in an IEEE Transactions paper 
> somewhere. (about 25 years ago?).
> Not sure what the VHF 1 and VHF 2 frequencies are but if they are more 
> than a few MHz apart, that would explain the use of a helix
> rather than a crossed yagi antenna.
>
> The other picture (existingvhf.jpg) on the web page shows a 4 crossed 
> yagi array with rotators.
>
> 73,
> Terry Osborne ZL2BAC
>
>
> -----Original Message----- From: John Mac
> Sent: Tuesday, May 08, 2018 1:51 PM
> To: Glenn Little WB4UIV
> Cc: amsat-bb at amsat.org
> Subject: Re: [amsat-bb] NASA Helical Antenna Question
>
> Hi.
>
> Not sure its a standard 8 turn helix, the feed looks totally different 
> and
> looks like it has a ring reflector..
>
> John
>
> On Tue, May 8, 2018 at 9:39 AM, Glenn Little WB4UIV <
> glennmaillist at bellsouth.net> wrote:
>
>> Looks like a standard 8 turn, axial mode, helix to me.
>>
>> see https://en.wikipedia.org/wiki/Helical_antenna#Axial-mode_helical
>>
>> Looks like about 8 dBi gain.
>>
>> 73
>> Glenn
>> WB4UIV
>>
>>
>>
>> On 5/7/2018 6:57 PM, Steve Bossert via AMSAT-BB wrote:
>>
>>> I am curious about the helical antenna in the article just released 
>>> late
>>> last month:
>>> https://www.nasa.gov/feature/goddard/2018/nasa-upgrades-spac
>>> e-station-emergency-communications-ground-stations
>>>
>>> This one:
>>> https://www.nasa.gov/sites/default/files/thumbnails/image/
>>> upgradedvhf-antenna.jpg
>>>
>>> While I await a reply from the article author, I wonder if anyone may
>>> have some details on this antenna.
>>> Looks like a good candidate as a functional lawn ornament that is not
>>> another QFH for more garden modern art satellite installation.  I would
>>> like to author a construction and theory article for the HVDN.org 
>>> website
>>> in the "notebook" section.
>>>
>>> Thanks,
>>> Steve
>>> Steve Bossert K2GOG at yahoo.com 914-573-1799
>>> _______________________________________________
>>> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
>>> to all interested persons worldwide without requiring membership.
>>> Opinions expressed
>>> are solely those of the author, and do not reflect the official 
>>> views of
>>> AMSAT-NA.
>>> Not an AMSAT-NA member? Join now to support the amateur satellite 
>>> program!
>>> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
>>>
>>
>> -- 
>> -----------------------------------------------------------------------
>> Glenn Little                ARRL Technical Specialist   QCWA  LM 28417
>> Amateur Callsign:  WB4UIV            wb4uiv at arrl.net    AMSAT LM 2178
>> QTH:  Goose Creek, SC USA (EM92xx)  USSVI LM   NRA LM   SBE ARRL TAPR
>> "It is not the class of license that the Amateur holds but the class
>> of the Amateur that holds the license"
>>
>>