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Author Topic: Unknown, IDed as probably Arecibo, 5125 kHz, May 21, 22, and 23, 2017.  (Read 4280 times)

Offline linkz

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Here are some pictures from Arecibo, where the HF cross dipoles can be viewed from a pretty close position.

http://www.yeagley.net/Arecibo%20trip/Arecibo%20.html

linkz
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Offline Josh

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Wonder what the gain is on hf for that thing.
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Offline Token

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Wonder what the gain is on hf for that thing.

If we assume 65% efficiency (a good middle of the road number, could be slightly higher or lower, at a bet lower is more likely) it would be about 26.5 dBi on 8175 kHz, and 22.4 dBi on 5125 kHz.  If the antenna is very efficient you might add as much as 2 dB to each of those.

(edit)  Found this paper here :  http://www.naic.edu/~astro/ao50/Arecibo_50th_Paper_Breakall_revised_Oct_23_2013.pdf  which calls the gain on 8175 kHz as 25.5 dBi and the gain at 5125 kHz as 22.2 dBi.  That comes out to about 52% on 8175 kHz and 62% on 5125 kHz.

(edit 2)  Looking at that paper it describes the transmitter as 6x 100 kW transmitters repurposed from a former HF OTHR, and the lower freq of 5100 kHz selected because the OTHR was not designed to go below that freq.  I wonder which OTHR that was?  The power and frequency limits are correct for the FPS-118 (5 to 28 MHz, 100 kW per transmitter module, either 6 or 12 transmitter modules per site).  However I thought the FPS-118's were not scrapped until after the new HF transmitter was added to Arecibo?  I guess it could the FPS-112 transmitter, but I did not think that one did CW.

T!
« Last Edit: May 27, 2017, 0209 UTC by Token »
T!
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Offline Josh

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Lol thanks for the info, I assume they can get a lot more power out of them in burst mode?













"Hang on, gonna turn the dish towards your qth"
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Offline Chanter

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After the Arecibo ID, all I can think is, "Epsilon solar, epsilon solar, thank you for your message..." 

If anyone gets that, I know there's more than one fan of reasonably obscure radio drama around here. 

Seriously though, that's a sharding cool catch.  :) 
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Offline ChrisSmolinski

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I received this sorta verification from Arecibo for the transmission via email:

Quote
Hello Chris,
I was forwarded this email from a staff member. My name is Angel WP3R and am
the president of the Arecibo Observatory ARC KP4AO. The transmissions you
heard were not made from an amateur radio station so a QSL cannot be sent,
but I can confirm that we were transmitting those frequencies during and
Ionosphere experiment. Different modes were used and one of them was the
timing sequence you mentioned. It seems you know a good deal of the
observatory and I congratulate your listening skills.. Hope to hear you on
the bands.
GL & 73,
Angel WP3R
President KP4AO
Arecibo Observatory Amateur Radio Club

Angel M. Vazquez     
Head of Telescope Operations - Spectrum Manager
Arecibo Observatory - SRI International
National Astronomy and Ionosphere Center
Chris Smolinski
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eQSLs appreciated! csmolinski@blackcatsystems.com
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Offline MDK2

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So only hams can get QSL cards from them? Laaaaaaaaaaame.
Denver, CO.
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eQSLs appreciated wickerjennie at gmail

Offline ChrisSmolinski

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So only hams can get QSL cards from them? Laaaaaaaaaaame.

No, they only QSL ham transmissions from the site.
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft horizontal loop / 500 ft northeast beverage / 58 ft T2FD / 120 ft T2FD/ 300 ft south beverage / 43m / 20m / 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline MDK2

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Weird. There's still much for me to learn about this QSL business. Thanks for clarifying.
Denver, CO.
SDRPlay RSP2pro, Icom IC-7100, Grundig Satellit 750, Realistic DX-300, Tecsun PL-600.
W6LVP active loop, G5RV, 20m dipole, homebrewed mag loops.
eQSLs appreciated wickerjennie at gmail