• Effective immediately we will be deleting, without notice, any negative threads or posts that deal with the use of encryption and streaming of scanner audio.

    We've noticed a huge increase in rants and negative posts that revolve around agencies going to encryption due to the broadcasting of scanner audio on the internet. It's now worn out and continues to be the same recycled rants. These rants hijack the threads and derail the conversation. They no longer have a place anywhere on this forum other than in the designated threads in the Rants forum in the Tavern.

    If you violate these guidelines your post will be deleted without notice and an infraction will be issued. We are not against discussion of this issue. You just need to do it in the right place. For example:
    https://forums.radioreference.com/rants/224104-official-thread-live-audio-feeds-scanners-wait-encryption.html

What is this?

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pinkfish457

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#1
I received this today using a SDR dongle and a Ham-It-Up upconverter. As you can see it's in the 20m Ham Band, but doesn't look like anything I've seen before.


On another topic. Can anyone explain why I'm getting "ghost signals". As an example, when I tune to WWV on 15 Mhz, and then tune to 14Mhz on 20 meters, there is the "ghost signal" of WWV. It's just as loud and clean as the original one at 15Mhz.

Thx
 

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#2
That's what you get with cheap receivers and cheap up-converters - false signals, cross modulation, image interference, etc, etc, the whole nine yards.
 
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#3
SDRs are nice to work with, but they are not without issues. Some of the problems with SDRs is poor shielding and RF overload. Users report all kinds of artifacts that aren't really there.

Some time ago I heard two hams talking from relatively close locations (200-300 miles). One ham was operating mobile and running about 50 watts. The other ham was using a SDR and proceeded to berate the other ham saying that his signal was 20KHz wide with spurs running up and down the band. Yet, I couldn't hear anything wrong with his signal and there were QSOs on either side of the mobile ham that had no interference at all. The ham with the SDR just needed to learn how to use a attenuator. Then he would have gotten a better idea of the other hams signal.

Martin - K7MEM
 

vagrant

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#4
I turn the knob on my washing machine, press the button, and it starts. What is this detergent you speak of ?

My house is bombarded by RFI from nearby AM, FM, and various service related stuff. While my HF rig moves right along, the wideband scanners, receivers, and even VHF/UHF radios are loaded with bandpass and notch filters on the lines to clean things up. Oh yeah, ferrite beads a-plenty on things plugged into the computer. When Radio Shack closed their doors on locations, I was in there harvesting ferrite cores. Even when working portable, I have ferrite beads on a cable that connects to a tablet PC.

Still, I enjoy playing with those USB dongles from time to time. Actually, I have seen metal enclosures available for those USB dongles.
 
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Token

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#5
SDRs are nice to work with, but they are not without issues. Some of the problems with SDRs is poor shielding and RF overload. Users report all kinds of artifacts that aren't really there.
Depends on the SDR, some SDRs have more dynamic range than a top of the line traditional receiver. However, once you get the ADC clipping you have issues. Still, this is NOT a hard condition to detect, or correct.

Unfortunately, when you say “SDR” today many people automatically jump to the conclusion you are talking about one of the 8 bit RTL dongles, totally forgetting that there are much better SDRs out there. An 8 bit RTL SDR might have a dynamic range of only 45 to 50 dB, and an MDS of -110 dBm or better, meaning that without front end attenuation an honest S9 signal might be putting the SDR in clipping or overload. By the same token a good 16+ bit SDR might have an instantaneous dynamic range in excess of 95 dB (for example the Perseus is measured at 99 dB).

RTL dongles and associated upconverters are a mixed blessing. For under $100 they bring some capabilities that you could not touch for under $10000 just a few years ago. However, they ARE cheap devices, and they have several issues. There is a reason that “good” SDRs cost a lot more than these kinds of setups, unfortunately people forget that in general you do get what you pay for, and expecting a $100 receiver to perform on a level with a $1000 receiver is a pipe dream.

Some time ago I heard two hams talking from relatively close locations (200-300 miles). One ham was operating mobile and running about 50 watts. The other ham was using a SDR and proceeded to berate the other ham saying that his signal was 20KHz wide with spurs running up and down the band. Yet, I couldn't hear anything wrong with his signal and there were QSOs on either side of the mobile ham that had no interference at all. The ham with the SDR just needed to learn how to use a attenuator. Then he would have gotten a better idea of the other hams signal.
You are absolutely correct, if you have a big booming signal that looks dirty knock a little attenuation in the front end and see if the signal cleans up some. It might be that the signal is indeed dirty…or you might be getting some serious issues on your end. Learning the limitations and how to use your equipment is an important factor, everything is not a “turn it on and tells you everything, 100% correct” device.

But also people can be surprised by how wide a signal might be, I have seen the same issue with people the first time they use a station monitor or a spectrum analyzer. Some people do not understand that it is possible for a ham signal to be 20 kHz wide, even without major problems…if you are looking 80 or 90 dB down. And a signal that is 40 dB over S9 might be 100 dB above the noise floor, so you can easily look 80+ dB down. Bandwidth without a relative power measurement is sometimes meaningless.

T!
 

pinkfish457

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#6
I turn the knob on my washing machine, press the button, and it starts. What is this detergent you speak of ?

My house is bombarded by RFI from nearby AM, FM, and various service related stuff. While my HF rig moves right along, the wideband scanners, receivers, and even VHF/UHF radios are loaded with bandpass and notch filters on the lines to clean things up. Oh yeah, ferrite beads a-plenty on things plugged into the computer. When Radio Shack closed their doors on locations, I was in there harvesting ferrite cores. Even when working portable, I have ferrite beads on a cable that connects to a tablet PC.

Still, I enjoy playing with those USB dongles from time to time. Actually, I have seen metal enclosures available for those USB dongles.
I have ferrite beads but don't know exactly where to put them. I also have the latest V3 dongle in a double metal housing. Most of the time I can get a clean/er signal, but when it get noisy I just shut it down!
 

vagrant

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#7
If the USB dongle is plugged directly into the computer, try using a USB extension cable to get it away from the computer. On that line you could put a ferrite bead or two. On the antenna line coming into the dongle, try putting a bead on that as well, but the beads are mainly for localized RFI that you or your neighbors are causing.

The beads can also be placed on the offending devices/cords. I had a Nokia phone charger that wiped out multiple bands with RFI. It had to go as the beads could not resolve it. They are band-aids and not really a cure.

* Your original post identifies a WWV ghost signal. The earlier recommendation of attenuation may certainly help if what you are tuning is close to that ghost or various harmonic signals. I use notch and bandpass filters as well for various devices, but if what you want to listen to is on the same band as another signal that is blasting through, that is a tough nut to beat with inexpensive gear. You can have custom filters made, but they will typically cost more than a USB dongle. You would be better served with an improved receiver $$, or just learn to live with it.

The other day I was dialing around on my HF rig and when on a particular frequency, either my scanner or VHF/UHF radio was scanning through freq's and it locked onto white noise but no voice audio was coming over. I turned the HF radio dial off of the freq and the other device began to scan again. I turned it back and it locked again, and then off when I changed the frequency. (Welcome to RFI)

Also, some people utilize splitters when distributing the receive from one antenna to multiple devices. I use one but it does not over amplify the signal beyond the attenuation the device causes, as that would overload my wide band receivers connected to it. Some may perceive attenuation as counterintuitive, but it can be your friend.

Have fun!
 
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