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

[Ken Sowinski]

On Thu, 16 Apr 2026, Paul Demorest via evlatests wrote:

> 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).

When this was discussed in the test meeting last week someone talked
about which 'sector' the L band transmitter would use.  Was it one
directed toward the center of the VLA or away?

Ken


> -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) ----------------------------------------------
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>    Socorro NM 87801                   Fax:    +1-575-835-7027
> Also a PandA Adjunct Professor at the University of New Mexico
>
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