[bars] WRKO RFI on 14.280 MHz
Christopher Lennon
kwaj.speedo at gmail.com
Sat Feb 11 21:41:44 EST 2023
The radio I have is a SDRPlay RSPdx. It is a receive only SDR but it
has good coverage even below the AM band. I occasionally look at 60 kHz
to see if I can see WWVB. When I go down that low the radio displays a
two sided spectrum. This evening I could not see WWVB, but at 0 Hz
there was a signal that looked like AM. So I clicked on that using AM
to demod and I heard an intelligible voice. I tuned to 680 kHz. Hmmm
was it the same? Back and forth a few times and, yes, what I was
hearing at 680 kHz I was also hearing at baseband on the SDR.
I don't see it at 14280 kHz. But I that radio station is sneaking into
my radio at baseband. I haven't studied up on the SDRPlay to understand
the frequency plan. I have mostly been using the ham bands laid out in
the software. I think if select a low enough frequency you get a direct
digital sampling. The SDRPlay RSP dx is supposed to have a low pass
filter to take out the AM Broadcast bands when you select a lower
frequency. I don't see a switch to turn that on. But it was clearly
not on when I went to 60 kHz because I could see the AM broadcast band
in the two sided spectrum.
I guess I will have to RTFM.
Chris W2BPL
On 2/11/2023 7:32 PM, Craig Davidson via bars wrote:
> Wow - thanks Art - great field work haha.
>
> Simonds park is close to my QTH. I'll bet the sensitivity on my rigs
> might be better than the Grundig, but can't be sure by how much.
>
> As power falls off I believe as a function of distance squared, the
> probability of seeing the harmonics after a few miles is pretty low.
>
> Appreciate you taking the time to capture this data - will have to
> think about this some more.
>
> -Craig
>
> On Saturday, February 11, 2023 at 06:27:25 PM EST, apizer at comcast.net
> <apizer at comcast.net> wrote:
>
>
> And here is the data form Simmonds park overlooking the common. No
> issues there, I was able to copy some dx even on 14280 ssb.
>
> -Art
>
> NF1A
>
> *From:* bars <bars-bounces at w1hh.org> *On Behalf Of *apizer at comcast.net
> *Sent:* Saturday, February 11, 2023 5:19 PM
> *To:* 'wo1n' <wo1n at comcast.net>; 'Craig Davidson'
> <cwdavidson1 at yahoo.com>; 'BARS Reflector' <bars at w1hh.org>
> *Subject:* Re: [bars] WRKO RFI on 14.280 MHz
>
> Got the data before sunset. Will send something out later.
>
> -Art
>
> *From:* bars <bars-bounces at w1hh.org> *On Behalf Of *wo1n
> *Sent:* Saturday, February 11, 2023 4:52 PM
> *To:* apizer at comcast.net; 'Craig Davidson' <cwdavidson1 at yahoo.com>;
> 'BARS Reflector' <bars at w1hh.org>
> *Subject:* Re: [bars] WRKO RFI on 14.280 MHz
>
> Don’t forget they reduce power and change the pattern on the array
> precisely at local sunset.
>
> Ken
>
> *From:* bars <bars-bounces at w1hh.org> *On Behalf Of *apizer at comcast.net
> *Sent:* Saturday, February 11, 2023 3:46 PM
> *To:* 'Craig Davidson' <cwdavidson1 at yahoo.com>; 'BARS Reflector'
> <bars at w1hh.org>
> *Subject:* Re: [bars] WRKO RFI on 14.280 MHz
>
> OK you guys really got me going . . .literally . . . I am heading out
> now with my Grundig to the Network Drive/ Middlesex Pike construction
> site.
>
> Art
>
> NF1A
>
> *From:* bars <bars-bounces at w1hh.org> *On Behalf Of *Craig Davidson via
> bars
> *Sent:* Saturday, February 11, 2023 1:03 PM
> *To:* 'BARS Reflector' <bars at w1hh.org>
> *Subject:* Re: [bars] WRKO RFI on 14.280 MHz
>
> Thanks Tom,
>
> I first assumed an overload case, but using the input attenuators, or
> using a terrible antenna (a two foot piece of coax) I think would
> eliminate the cause as being a front end overload.
>
> The other concerning clue is this just started happening a few days
> ago. It could be that WRKO increased transmitter power at that point,
> but not being familiar with broadcast operations I'm not sure it
> that's even reasonable to consider.
>
> I do see this on two receivers, and both receivers are direct
> conversion front ends (IC-7300 and ANAN 7000 DLE), so don't know if
> that is a factor.
>
> If this was ongoing from when I first set up my shack a few months ago
> I would be less suspicious of some change at WRKO.
>
> I did see that they have a night antenna pattern, so that's a good
> reminder to check out the interference level tonight.
>
> I have attached a video of the interference while using a two foot
> piece of unterminated coax. The signal level is at around a S5-S7
>
> 73, Craig
>
> On Saturday, February 11, 2023 at 12:40:46 PM EST, Tom Walsh
> <k1tw at comcast.net> wrote:
>
> Hi Folks,
>
> I am a mere 2-3 miles from WRKO’s transmitter site and there is no
> detectable signal at my QTH on 14.280 even with my beam pointed at
> their transmitter site. I will try listening again after dark when
> they shift to a night antenna pattern.
>
> Craig, if you are an ARRL member, you can also reach out to their Lab
> folks in Newington for advice.
>
> Please look at this web page from ARRL
> http://www.arrl.org/broadcast-station.
>
> This may explain what is probably occurring at Craig’s QTH which is
> very close to the WRKO transmitter site in Burlington. It also
> suggest remedies such as reducing the receiver input sensitivity.
>
> From the ARRL page and I quote:
>
> “In ARRL’s experience, however, the majority of broadcast interference
> reports arise because the fundamental signal overloads sensitive
> amateur receivers. In that case, the additional filtering or
> attenuation necessary to protect the receiver must be installed by the
> amateur operator.”
>
> 73,
>
> Tom K1TW
>
> *From:*bars <bars-bounces at w1hh.org> *On Behalf Of *Craig Davidson via bars
> *Sent:* Saturday, February 11, 2023 10:48 AM
> *To:* Christopher Lennon <kwaj.speedo at gmail.com>; ARTHUR PIZER
> <apizer at comcast.net>; n1hts at comcast.net
> *Cc:* Craig Davidson via bars <bars at w1hh.org>
> *Subject:* Re: [bars] WRKO RFI on 14.280 MHz
>
> Hi Jim,
>
> I think If it's actually a spur from the station then a filter wont help.
>
> This morning, I am able to see the 680 KHz station at 21.280 MHz using
> *NO* antenna, but just a short two foot piece of coax connected to the
> rig. I see it on both of my receivers.
>
> From Art - NF1A
>
> "I could not hear it at my home station on 14280 tried 4 antennas
> various polarizations including hex beam at 40 ft pointed south. I
> live just north of the Billerica Country Club golf course. Let me
> know if it still persists. I may throw my Grundig G6 in the car and
> drive around and monitor the next time I run errands in Burlington.
>
> Art
>
> NF1A"
>
> Thanks for your report Art.
>
> Since I have the signal with a terrible antenna (short piece of coax),
> and it responds like a normal signal to attenuation, can I assume my
> digital front-ends are not overloaded? Is it more likely I'm seeing
> the 21'st harmonic spur from a station a few miles away? Also - this
> just started a few days ago - no real change to my setup.
>
> -Craig, K1CWD
>
> On Saturday, February 11, 2023 at 10:32:06 AM EST, n1hts at comcast.net
> <mailto:n1hts at comcast.net><n1hts at comcast.net
> <mailto:n1hts at comcast.net>> wrote:
>
> If AM stations are bleeding in, buy a filter.
>
> Morgan Filters (kf7p.com) <https://kf7p.com/KF7P/Morgan_Filters.html>
>
> jim
>
> On 02/10/2023 7:19 PM Christopher Lennon <kwaj.speedo at gmail.com
> <mailto:kwaj.speedo at gmail.com>> wrote:
>
> I live in Bedford. I hear 680kHz loud and clear, but that is WBEZ.
>
> I only have an SDR receiver with a simple wire antenna set up at
> the moment. I didn't hear anything on 14.280.
>
> Chris W2BPL
>
> On Fri, Feb 10, 2023, 12:32 PM ARTHUR PIZER <apizer at comcast.net
> <mailto:apizer at comcast.net>> wrote:
>
> Hi all I’ve been sending these replies from my iPhone voice to
> text feature from my cafeteria during lunch at work so I
> apologize for any typographical errors or that is to say
> transcription errors when I get home I will give a listen for
> my shack tonight 73 Art
>
> On 02/10/2023 12:27 PM Craig Davidson via bars
> <bars at w1hh.org <mailto:bars at w1hh.org>> wrote:
>
> Thanks for all the replies from everyone. I'm not sure if
> everyone sees the replies through the reflector, but
> wanted to add some additional info:
>
> I have two rigs, an ANAN 7000 and an IC-7300. Both rigs
> see the AM signal at 14.280.
>
> I can tell it's WRKO because I switch to the AM band and
> hear the same dialog on their station. Of course, their
> station is booming because I'm only a few miles away.
>
> There is no overload condition on the front-ends of either
> receiver that I can tell. I can reduce the input
> attenuation and the signal is still there, although
> reduced somewhat with the attenuation, which is to be
> expected I think if it's actually interference being
> picked up by the antenna, as opposed to an RFI path after
> the front-end.
>
> I have two wire antennas with two separate feedlines, and
> have the interference on both antenna's.
>
> This just started recently, and can't correlate it to any
> change I made in my station.
>
> Thanks,
>
> Craig
>
> On Friday, February 10, 2023 at 11:32:10 AM EST, Craig
> Davidson via bars <bars at w1hh.org <mailto:bars at w1hh.org>>
> wrote:
>
> Good Morning,
>
> Has anybody else noticed interference at 14.280 from the
> WRKO station broadcasting at 680 KHz?
>
> This seems to have started a few days ago.
>
> I'm pretty sure it's not receiver overload on my end, but
> actual out-of-band stuff generated by the station (granted
> that my QTH is very close to the transmitter in Burlington).
>
> I tried calling the station numbers I had available but
> just get voicemail.
>
> Anybody deal with this before, or have good contact info
> for the station engineer?
>
> Thanks,
>
> Craig, K1CWD
>
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