CB radio scanning wierdness

[cj5]

Today, I was scanning through all the CB channels, and in a few of the channels I keep picking up what sounds like multiple foreign radio station broadcasts (i.e. Spanish or Italian, or some European language). So far I have logged the broadcasts on frequencies 27.265, 27.105, 27.155, 27.275, and 27.335. There are maybe 3 or so transmissions coming over at once. What is this, and why is it coming over the CB channels (26.965 - 27.405 MHz)?

My setup is an Icom R-20, connected to an HF active gain antenna that is mounted to a tripod outside on my exterior, covered stairwell landing.

CJ...

 

[nd5y]

Probably intermod

 

[Highlander_821]

IF images.

 

[cj5]

Probably intermod

Intermod on CB frequencies! Really!? Huh! Funny how much trouble I have picking up HF from long distances, yet on CB I get intermod. Do these radio waves just wash across the ionosphere, coming and going at random times? This seems to happen once or twice a day, some days it never happens. I am not a pro here, so elaborate answers are welcomed.

 

[wesct]

did you try turning on the attenuator on the radio?

My setup is an Icom R-20, connected to an HF active gain antenna that is mounted to a tripod outside on my exterior, covered stairwell landing.

does the active antenna have a gain control? if it does, try turning it down.

wesct

 

[MarkWestin]

Hello,

Could this have anything to do with the "major" solar flares that we are having at the moment?

I have heard solar flares blamed for many things in the past including disruptions in radio communications and power blackouts.

Mark

 

[cj5]

The attenuator kills everything (nothing comes in). Nope, the gain antenna has no gain control just an on/off switch. Before I started using the gain antenna, signals were horrible, and hardly anything came in (except real nearby CB operators). Now, I guess, that the antenna draws in more, it REALLY draws in more. I am picking up more truckers, but can't tell where they're coming from. I-93 is about 30 miles from me, and I-95 is about 45 miles from me. Is it possible for the R20 and the antenna to perform that well?

 

[cj5]

Hello,

Could this have anything to do with the "major" solar flares that we are having at the moment?

I have heard solar flares blamed for many things in the past including disruptions in radio communications and power blackouts.

Mark

Don't know. Would like to find out if it does, and if it doesn't, what kind of effects does solar flare have on radio comms?

 

[nd5y]

When I put my PRO-95 on my HF antenna it got lots of intermod, images, mixing products,
whatever you want to call them from HF broadcast stations all over VHF low band.

HF broadcasters use different frequencies at different times of the day and different times of
the year depending on the location of their target audience. Signal strength on HF varies a lot
depending on the ionospheric conditions. That is why you won't get the same signals mixing in
your receiver or acive antenna all the time.

Different types of radiation and solar flares and other stuff that the sun pukes on us can have
different effects at different frequency ranges. Search for HF propagation
or ionospheric propagation there are a lot of web pages that explain it better
than I can.

One of the best places to start is here http://www.sec.noaa.gov/Education

 

[cj5]

Thanks Tom,

That's the answer I needed. It seems to me that learning how to learn the art of scanning HF is going to be a long difficult road, but a fun one at that.

 

[LarrySC]

Devide 27MHz by 2 = 13.5 This freq range is full of Broadcast stations. Poor dynamics. This is a common problem with many receivers because a good antenna will hear those 13.5's much stronger. Botton line. They pop up like a harmonic.

 

[cj5]

Devide 27MHz by 2 = 13.5 This freq range is full of Broadcast stations. Poor dynamics. This is a common problem with many receivers because a good antenna will hear those 13.5's much stronger. Botton line. They pop up like a harmonic.

Interesting. So why do we divide by 2? Is it based on the 'n' of gain? Does work like chords in music notes C-E-G make C?

 

[N5RLR]

Interesting. So why do we divide by 2? Is it based on the 'n' of gain? Does work like chords in music notes C-E-G make C?

Kinda sorta. In music, the fundemental and harmonics of such blend to the resulting notes. Radio frequencies, being essentially "vibrations" taken higher [i.e., 14.68 MHz is 14 million, 680 thousand cycles or "vibrations" per second] behave virtually identical in this respect. They have harmonics [multiples of the fundemental frequency], and can be mixed and filtered.

RF harmonics can be 2x, 3x, 4x, etc. of the fundamental, usually decreasing in strength the higher the multiple. To cut to the chase, if your active antenna has a preselector [input tuner] built in, try tweaking it to the band that you're listening to. If not, then you might consider buying or building a small tuner to connect between the active antenna and the receiver. [I'm assuming that your active antenna has a built-in whip that cannot be removed; it'd be better to place the preselector between the whip/antenna and it's amplifier, but barring that, putting it between the amplifier and receiver will have to do.] The active antenna's amplifier is probably broadband, boosting everything that it hears; not differentiating between what you're wanting to listen to and not.

It could be that the amplifier is overloading the "front end" [input] of your R-20. This can be bad, in that the input RF amp and maybe mixer can be "desensed" [desensitized, essentially deafened, permanently damaged] by continous use of the external amplifier. Try using a simple wire antenna, maybe a loop of small-gauge wire thumbtacked on the wall at the ceiling all around the room [use white wire and white thumbtacks for "stealth" ], and see what happens. You may be surprised, if the Icom R-20's front end is as "hot" as that in my Yaesu VR-500.

Speaking if which, here is my take on the VR-500: In Defense Of The Yaesu VR-500 [click]

And, it's interesting that you mention the musical notes C-E-G. G-E-C [above middle C, I think] is the infamous "NBC Chime." "Bonng, Binng, Bunnnng..." :lol:

 

[cj5]

To cut to the chase, if your active antenna has a preselector [input tuner] built in, try tweaking it to the band that you're listening to. If not, then you might consider buying or building a small tuner to connect between the active antenna and the receiver.

Any suggestions on what to get or where I can go to build a tuner. The gain antenna is the LF Engineering H-900. It came with a simple switch amplifier (no tuning option).

It could be that the amplifier is overloading the "front end" [input] of your R-20. This can be bad, in that the input RF amp and maybe mixer can be "desensed" [desensitized, essentially deafened, permanently damaged] by continous use of the external amplifier.

OMG, really?! How do you know that the radio has been desensed? What are the symptoms? I have been forced to reduce the RF gain a lot lately on the R20, or I basically just turn the antenna's amp off. I don't know why, but I am just getting way too much RFI, with the gain antenna, and/or the whips. Will give the wire loop antenna you suggested a try though.

I gather you highly recommend the Yaesu VR-500. I will definitely look into that model. I am very very happy with the R20 overall. It just blows my mind that such a small unit, could do so much. I am also looking into purchasing a base unit for doing HF scanning. Any suggestions?

Oh, and about the NBC jingle, yeah I knoew that. Funny! I studied music theory for two years, and I remember one of my instructors telling me about those tones. I remember him saying that they had some kind of technical siginificance????

Thanks for the feedback, N5RLR

 

[N5RLR]

Any suggestions on what to get or where I can go to build a tuner. The gain antenna is the LF Engineering H-900. It came with a simple switch amplifier (no tuning option).

Some ideas that I've found on-the-fly:

Buy:

MFJ Enterprises #MFJ-956 Preselector [click], $49.95

MFJ Enterprises #MFJ-1046 Preselector [click], $99.95

Miracle Antenna "Miracle Whip" [click], $119.95

Miracle Antenna "Miracle Ducker IL" [click], $128.95


Build:

G4FON Variarion On "Miracle Whip" Antenna [click] [My suggestion: Substitute an input jack for the whip antenna.]

Carpet Loop Tunable Antenna [PM me with your E-Mail address if you'd like this -- I've a PDF file that's too large to attach to this post.]

How do you know that the radio has been desensed? What are the symptoms? I have been forced to reduce the RF gain a lot lately on the R20, or I basically just turn the antenna's amp off. I don't know why, but I am just getting way too much RFI, with the gain antenna, and/or the whips. Will give the wire loop antenna you suggested a try though.

If you've had to throttle back the RF gain just to make listening tolerable, then it's a good chance that the front hasn't been desensed. The symptoms of desense are much like that of hearing loss -- you hear less and less.

I gather you highly recommend the Yaesu VR-500. I will definitely look into that model. I am very very happy with the R20 overall. It just blows my mind that such a small unit, could do so much. I am also looking into purchasing a base unit for doing HF scanning. Any suggestions?

For a good travel portable, yes. But it isn't exactly cheap, at just under $300.00 when I bought it. I was looking at several "DC-to-daylight" portables at the time, and the Yaesu struck my fancy, as well as being the least expensive of the lot. It sounds as if your R20 will do just as well, especially when you solve the overloading dilemma.

For base HF receivers, I'll suggest Universal Radio [click]. The have a bit of a selection of tabletop receivers, and of course portables. [Note: They also have Icom's CS-R20 programming software for the R20, [click].]

My "base" HF shortwave receiver is a Realistic DX-440 [built by Sangean and marketed as their ATS-803A, identical except for labeling and 5-pin DIN tape-out jack]. If you can find one of these, it'd be a good choice, providing that it's been taken care of.

Overall, a choice of receiver and/or accessories is about what you want it to be capable of, ease of operation, audio quality, price, and any number of other factors. At the end of the day, if you're satisfied with a particular piece of gear or setup, that is all that is required.

Oh, and about the NBC jingle, yeah I knew that. Funny! I studied music theory for two years, and I remember one of my instructors telling me about those tones. I remember him saying that they had some kind of technical siginificance????

I'd read that in addition to being a nifty "interval signal," the NBC Chime indicated a switchover between the NBC Red and NBC Blue networks, which existed before 1943. That year, a court mandated that NBC divest itself of one of its networks, and so NBC Blue was sold, to become the American Broadcasting Company, yes, ABC.

There was also a fourth chime, an extra C I believe, that was rarely used but in the most extreme circimstances. It was a signal for news correspondents to contact the network or their local affiliate, for instructions or assignments. One such instance was the announcement of the Japanese surrender at the end of WWII.

Some have believed that the "G-E-C" sequence stood for General Electric Corporation, which owned NBC until the 1990s. It's been said that this wasn't the case...but it makes for a good story.

You're welcome...anything I can do to help.

 

[cj5]

Wow! You are a wealth of information. The infamous red and blue. Now the interval signal I remember, but the fourth chime, I had no idea. Sounds like the precursor to emergency tones used for the public safety repeaters.

As for the IC R-20. I spoke with the company today, and since I have a full year warranty on it, the rep. said it wouldn't hurt to send it in for a potential repair or replacement. I don't know what I am going to do without my shortwave receiver. I highly suspect it's been desensitized, because since I started using the active gain antenna, RF is way up, but things that I used to pick up on a daily basis have not been coming in clearly, and all of the sidebands are very, very low. Almost unbearable. The static is all there, and when I do hear something the squelch bearly kicks in, and the voice transmissions are overwhelmed by the static, or stray intermods. We'll see.

I did read your comments on the Yaesu VR-500, and was fairly impressed (I also read the reviews on eham.net). It sounds like a great unit, but I want to focus on getting a base model instead, since I am very pleased with the R-20. The one shortcoming of the R-20 is the volume in the sidebands. It's extremely low. My fix was building a small external audio amplifier, and adding that between the receiver, and a Radio Shack external speaker, and that boosted the audio way up.

And finally, I am going to look into constructing my own version of that "Miracle Ducker". For $130! Thanks, but no thanks. I'll wait and brush up on my electroinics skills. I am getting there, just need to focus more on the math, so I don't go overloading anything again.

 

[Al42]

it's been desensitized, because since I started using the active gain antenna, RF is way up, but things that I used to pick up on a daily basis have not been coming in clearly, and all of the sidebands are very, very low. Almost unbearable. The static is all there, and when I do hear something the squelch bearly kicks in, and the voice transmissions are overwhelmed by the static, or stray intermods. We'll see.

Remember, there's still one heck of a solar flare problem, which could be causing all of that on those frequencies.

BTW, unless the amplifier is very poorly designed, it won't damage the receiver. No matter how much you increase the signal going into the amplifier, unless it has infinite gain (this is the real world - only the universe is infinite), the output stops going up at some point - and that point is usually just 2 or 3 times the signal needed to be "the strongest signal" your receiver can indicate - which is well below the damage point. (Most HF receivers will consider a 1,000 Uv signal to be "all there can be", but can handle a 1 volt signal [1,000 times as strong] without damage.)

The problem is that the amplifiers in the receiver also don't have infinite gain. If there's a 1,000 uv signal getting into the receiver, the amplifiers will "top out" and not amplify the little 2 uv signal you're listening to as much as they should. That's "desense". As soon as that big signal goes away, everything works again. (Drive past a tower with a dozen two-way radio antennas on it while you're on a cell phone, in an area in which there's no close cell tower. You might get choppy reception. You might even lose the call.)

 

[cj5]

AI42,

Thanks for the reply. I am not really near any major towers (out in the sticks of NH). I am going to stick with N5RLR' s suggestions, because the radio just simply does receive like it did right after I took it out of the box. The higher frequencies in FM (i.e. anything above 150 MHz) come in fine, and have a lot of clarity, but AM, anything in USB, LSB, or anything below 60 MHz seems dead or inaudible. So, the receiver is going back to Icom for repair or replacement. The question is should I panic, and go through with sending back the receiver, or just blame it on some noise in and around my place, or lousy propagation?