[amsat-bb] NASA Helical Antenna Question

[Nico Janssen]

Correction:
VHF 2 on 130.165 MHz is the secundary downlink from ISS.
The Soyuz downlink frequency is 121.750 MHz.

73,
Nico PA0DLO

On 08-05-18 14:51, Nico Janssen wrote:
>
> 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
>>>> _______________________________________________
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>>>
>>> -- 
>>> -----------------------------------------------------------------------
>>> 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"
>>>
>>>
>
> _______________________________________________
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> to all interested persons worldwide without requiring membership. 
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