[evlatests] New (to me) L-band RFI

[Rick Perley]

Unlikely in this case.  The signal appears to be about the same strength in all antennas, and we're in the A configuration — so an enormous range of distances from the cell tower.  I would expect much worse behavior at the end of the east arm, but this is not the case.

________________________________
From: evlatests <evlatests-bounces at listmgr.nrao.edu> on behalf of Paul Demorest via evlatests <evlatests at listmgr.nrao.edu>
Sent: Thursday, April 16, 2026 1:33 PM
To: evlatests at listmgr.nrao.edu <evlatests at listmgr.nrao.edu>
Subject: Re: [evlatests] New (to me) L-band RFI

I've heard recent suggestion in RFI discussions that this freq range is now being handled by our favorite cell tower (T-Mobile @ gray hill) either instead of or in addition to SpaceX.  Maybe someone with actual knowledge about this could confirm/deny.

If this is true, then this signal would not mitigated by ODS, but I would expect to see a noticeable antenna dependence with East-arm antennas more strongly affected (similar to what we see at 2150 MHz).

-Paul

________________________________________
From: evlatests <evlatests-bounces at listmgr.nrao.edu> on behalf of Lorant Sjouwerman via evlatests <evlatests at listmgr.nrao.edu>
Sent: Thursday, April 16, 2026 12:46 PM
To: evlatests at listmgr.nrao.edu
Subject: Re: [evlatests] New (to me) L-band RFI

Does ODS take into account the wide extent of the sidelobes or only the primary beam?


On 4/16/26 11:33, Ylva Pihlstrom via evlatests wrote:
Then indeed ODS should have been active and reporting to SpaceX.

Ylva


From: Rick Perley <rperley at nrao.edu><mailto:rperley at nrao.edu>
Date: Thursday, April 16, 2026 at 11:22
To: Ylva Pihlstrom <ypihlstr at nrao.edu><mailto:ypihlstr at nrao.edu>, evlatests <evlatests at nrao.edu><mailto:evlatests at nrao.edu>
Subject: Re: New (to me) L-band RFI

Ylva:

The RFI was seen with the L-band receiver, in the 16th spectral window.  The RIF wasn't strong enough to cause problems to any other SPW — and indeed, the portion of the 16th SPW lying outside that frequency range looked fine.

Rick

________________________________
From: Ylva Pihlstrom <ypihlstr at nrao.edu><mailto:ypihlstr at nrao.edu>
Sent: Thursday, April 16, 2026 11:17 AM
To: Rick Perley <rperley at nrao.edu><mailto:rperley at nrao.edu>; evlatests <evlatests at nrao.edu><mailto:evlatests at nrao.edu>
Subject: Re: New (to me) L-band RFI

That band is exactly the one of SpaceX’s downlinks.  If the L-band receiver was used, the ODS may or may not have been active depending on the frequencies used in the setup: https://obs.vla.nrao.edu/ods/index.html/nrao_ods_status.html).

Ylva


From: evlatests <evlatests-bounces at listmgr.nrao.edu><mailto:evlatests-bounces at listmgr.nrao.edu> on behalf of Rick Perley via evlatests <evlatests at listmgr.nrao.edu><mailto:evlatests at listmgr.nrao.edu>
Date: Thursday, April 16, 2026 at 11:11
To: evlatests <evlatests at nrao.edu><mailto:evlatests at nrao.edu>
Subject: [evlatests] New (to me) L-band RFI

>From data taken two nights ago, a strong RFI source at L-band is seen — on all antennas.  It spans 1.990 to 1.995 GHz.

Rick



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--
-

Regards,

Lorant Sjouwerman - Scientific Services - lsjouwerman at nrao.edu<mailto:lsjouwerman at nrao.edu>
 (he, him, his) ----------------------------------------------
c/o NRAO Array Operations Center       Phone:  +1-575-835-7332
    P.O. Box O (1011 Lopezville Rd)    Switch: +1-575-835-7000
    Socorro NM 87801                   Fax:    +1-575-835-7027
Also a PandA Adjunct Professor at the University of New Mexico

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