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Author Topic: Static on HF bands  (Read 18233 times)
K5LXP
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« Reply #15 on: February 16, 2015, 06:10:33 AM »

I unplugged everything in my apartment except for the radio, noise level did not drop.[

This may sound like rearranging the deck chairs on the titanic, but the only way to really know for sure there are not emitters in your residence is to flip the main breaker(s) and run your radio off of a battery.  There are devices that are wired directly to the mains you may not be able to unplug like HVAC controls, alarms and some appliances with computer controls.  It only takes one to cause problems, so until you kill power to the *entire* residence you will never know for sure if there still isn't a problem within your residence and within your means to mitigate. 

It's actually much quicker and simpler to flip the breaker than it is going around an unplugging stuff.  If there is more than one source you may not detect a difference when you unplug just one thing with the rest still buzzing away.  It's a 30 second test and it can tell you a lot.


Mark K5LXP
Albuquerque, NM
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SHORTWIRE
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Posts: 47




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« Reply #16 on: February 16, 2015, 04:46:58 PM »

The value of a separate receive antenna cannot be overestimated!

A broadband active loop is usually best in terms of convenience(needs no constant tuning), where as a narrowband magnetic loop may give the lowest noise overall.

The theory is that you place the small loop where the noise is lowest, and you place the transmit antenna where it has the best radiation "out of the house"

In this way, you are not forced to find a compromise between the two(RX SNR and TX), but can optimise both, to which ever level is possible.
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K1DA
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« Reply #17 on: February 21, 2015, 08:07:43 AM »

Placing a choke on the shield of the coax will only help if the coax runs close to  a noise source.  If your antenna is in the midst of this noise it will pick up the noise  anyway. 
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KK5DR
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« Reply #18 on: February 23, 2015, 05:03:41 PM »

I once lived in an apartment, third floor at the top. I hung an antenna off the balcony rail. It was very difficult to run HF there. The noise levels were very high most of the time. This made it very hard to hear any stations that were not thunderously loud to begin with. I stuck with vhf/UHF until I moved out.
Next I lived in a small house in a crowded neighborhood next to an interstate hwy and lots of commercial buildings. It was better, but still very noisy.
Finally I moved out to the country on acreage.
The noise was nearly all gone on HF. I can put up what ever I want, run any band I want, at any power level, no problems. It's radio paradise.
Save up, move out, way out. The drive to work will be longer, but radio will be heavenly.
Rule number 1, no HOA, EVER ! Do not accept any form of HOA where you plan to live.
Rule 2, buy land, as much as you can afford.
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VE3TMT
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« Reply #19 on: February 25, 2015, 08:45:20 AM »

The apartment I lived in, although the largest in the building was also right next to the main transformer room where the line drop came in. You talk about noise. About the only antenna that worked was a homemade 3' loop.

Good luck with resolving your issue.
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KC2QYM
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Posts: 367




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« Reply #20 on: February 25, 2015, 12:30:57 PM »

You're in a noise trap and that's the reality. Unless you can get an antenna high up and away from your building complex it may never abate.  Your other alternative is to go mobile.  Since you're already using a compromised antenna in your apartment why drop more money on trying to abate something which will always haunt you.  At least if you go mobile with a screwdriver antenna let's say, you are not locked into a noisy environment.  You can park at different locations and engage in nice QSOs with decent reception.  We speak to mobile stations all the time and some of those guys are mobile simply because they live in antenna restricted areas and/or electrically noisy locations.
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W2UIS
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« Reply #21 on: March 05, 2015, 05:55:10 AM »

Look into DStar.
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SHORTWIRE
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Posts: 47




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« Reply #22 on: April 09, 2015, 02:08:51 PM »

You might consider a Magnetic Loop antenna, or possibly an Active Loop for receive.

See my posting elsewhere in this forum.

In my apartment it makes the difference between at least being able to receive moderate to strong signals, as opposed to only VERY strong ones. Undecided
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AA4PB
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« Reply #23 on: April 09, 2015, 03:48:06 PM »

Door bell transformers are one thing that runs continuously and can cause RFI. They have over-temp sensors whose contacts can begin arcing when the transformer needs to be replaced. Cutting off the main breaker will remove power from the transformer.
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KB0RDL
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Posts: 33




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« Reply #24 on: April 10, 2015, 02:56:46 PM »

I'm wondering if anyone has had a bad experience with the fluorescent lightbulbs we all have to use now?  Do the emit significant RFI?

Also, do dimmers still emit RFI when the switch is in an "off" position?  I assume the dimmer unit is in the switch, so can it be removed by replacing it with a conventional on/off switch?

I live in the center unit of a single-level condo.  I got a provision put in the deed when we brought it that allowed me to have a 2 meter vertical because I'm a county storm spotter.  Also, there are several dish antennas in the condo subdivision so they really couldn't say too much anyway without shutting down a lot of satellite TVs.  HF, however, is another issue.

The only place I could have an outside antenna was on the roof, on the deck or in a small front yard.  The only one that’s practical is the deck.   I put a vertical VHF/UHF antenna on the deck.  It sticks up about 15 ft. over the roof line.  We live in a depression so I needed the extra height to reach all over the county if I run the net at home. 

After I moved here I haven’t bother to upgrade to general class because I wouldn't be able to put up a sufficient transmit antenna and I'm more interested in just listening anyway.  Besides, I have a lot of friends on 2 meter to talk with.

I have an Icom R75 receiver, which is a very good radio.  I tried a number of wire antennas on the deck and they all worked about the same.  The last was an end-fed SWR antenna that was really too long for the deck at 45 ft. and still brought in strong RF except from very strong stations.  With an additional digital speaker (the R75 has digital built in) I was able to reduce some RF enough to the radio listenable, plus a bunch of ferrite beads here and there, but the digital processing made the audio too growly to be entirely pleasant.

Finally, I bought a Pixel RF Pro-1B magnetic loop antenna for $500 plus 50 ft. of quad-shield coax with N connectors.  I stuck a 4 ft. mast on a corner of the deck, cut another 2 ft. section of mast with the reduced diameter end nesting in it so I could turn it easily and attached the loop antenna to that.  It's easy to turn and I don't plan to get a rotor.   The loop does not need to be elevated more than a few feet off the ground.  In fact, higher than 8 or 10 feet degrades from its signal.  I’m not sure why but I’ve seen it demonstrated on YouTube.

When I experimented with the loop I found the null (side) area needed to be pointed directly at the center of the house -- directly through the deck door at my wife's computer, a diming light switch and probably the doorbell transformer.  At that point all of the hash the loop picked up was gone because it was nulled out, but I can't turn the loop in any other direction to pick up stations without bringing it back.  More than 5 degrees either side of a fixed roughly north-south direction on the loop and I begin getting RF again.  The null is very good but I'm stuck in one direction until I eliminate the RF source(s).  On the other hand, the non-null receiving lobes are pretty wide, I would say at least 90 degrees both north and south and probably wider.  I've only had it a week so I'm still playing around with it.

The magnetic loop works wonderful with certain limitations.  Pointed in the right direction (assuming most of the RF comes from a single or very close together sources), it's all you can hope for.  Even though it works on a different principle than conventional RF antennas, it will still get some RF hash if it's nearby and strong enough unless you rotate the antenna to null it out.  Also, some RF could be getting into the radio in the shack, too.  I notice when my laptop is charging I get light hash but it goes away when I run it on batteries.  A bunch of ferrites helped but only about 30%.  Ferrites can be helpful but they are not magic.  I still have RF hash issues to work on nevertheless.

At this point the situation is acceptable and I can live with the limitations.  If you really want to eliminate a lot of RF, perhaps nearly all of it depending upon your circumstances, the magnetic loop is the way to go. Some people have even used them inside and gotten good results.  There's quite a bit on the web about them so check it out.  Go to:  https://www.youtube.com/watch?v=wV_BakwEG8M

As for the RF Pro 1B magnetic loop, it's very light, made very well, not flimsy at all, the only delicate part appears to be amplifier which remains outside attached to the antenna and it's encased in metal.  The whole setup is easy to assemble if you follow the simple directions that mostly have to do with attaching the amplifier.  They could easily sent it attached but for some reason they don't.  I've called the manufacturer once with a question and they were very helpful.  At $500 it is a bunch of money, but far less than a tower and beams, and not a whole lot more than some high class verticals -- none of which are possible in apartments.  It is a receive-only antenna, however, and you would need another antenna to transmit on!   Transmit on it and the amplifier is toast.  However, I am able to transmit on my 2-meter vertical antenna about 15 ft. away from the loop without issue, however.   I checked with the manufacturer before I even tried.  It doesn’t effect it at all.
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AA4PB
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Posts: 13245




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« Reply #25 on: April 10, 2015, 05:56:37 PM »

I haven't had any RFI problems with the florescent tubes or CFL bulbs that I have. I even tried an AM broadcast band portable radio near the bulbs with no RFI after a foot away.

Dimmers shouldn't generate any RFI with they are either full on or full off. Anywhere in between they are switching the current on and off to reduce the average (thus dimming the bulb) which creates a square wave which causes the RFI.
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N8CMQ
Member

Posts: 460




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« Reply #26 on: April 11, 2015, 08:45:30 AM »

I once lived in an apartment, third floor at the top. I hung an antenna off the balcony rail. It was very difficult to run HF there. The noise levels were very high most of the time. This made it very hard to hear any stations that were not thunderously loud to begin with. I stuck with vhf/UHF until I moved out.
Next I lived in a small house in a crowded neighborhood next to an interstate hwy and lots of commercial buildings. It was better, but still very noisy.
Finally I moved out to the country on acreage.
The noise was nearly all gone on HF. I can put up what ever I want, run any band I want, at any power level, no problems. It's radio paradise.
Save up, move out, way out. The drive to work will be longer, but radio will be heavenly.
Rule number 1, no HOA, EVER ! Do not accept any form of HOA where you plan to live.
Rule 2, buy land, as much as you can afford.


I agree 100%!

I live next door to site condos that have HOAs, they moved into the
'country' 10 years after I bought my property. I can hunt, farm, build
antennas and have as much fun as I want. My neighbor can't even have
chickens on his 'country' property. I am kind and let him have chickens
on my property, drives the HOA nazi nuts!
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N8CMQ   Jeff
AD5TD
Member

Posts: 123




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« Reply #27 on: April 19, 2015, 07:37:30 AM »

If he lives in a apartment complex it is a exercise in futility. He is in a noise rich environment.

That may be the case. But please don't make it sound like there is zero chance of lowering his noise level. Wouldn't you try if you lived there? He should too.

Strange how you left suggested work arounds from my quote.

"Disable preamp on rig and/or reduce RF gain a good bit. Many even use a attenuator too. It will quiet receiver some yet signals strong enough to overcome noise will still be heard and it will be more pleasant to listen too"

Ok, John, let's address your suggested workarounds.

I have a question first: it sounds like you are saying that if the OP's preamp is off and/or he backs down the RF gain --and maybe adds some attenuation-- that can improve his signal-to noise ratio help him hear signals that he couldn't hear before he did those things you suggested?

I work almost exclusively mobile, one of THE noisiest environments,  if it were not for the attenuator and the RF gain control, I would have given up a long time ago.  I worked without them for years, thinking I needed to receive the MOST signal I could, but boy was I wrong.  Those two controls brought back the fun. 

AD5TD
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K1DA
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Posts: 618




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« Reply #28 on: April 23, 2015, 05:44:58 PM »

If you like deep sea fishing, living in the desert is not a good choice.
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KB0RDL
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Posts: 33




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« Reply #29 on: Today at 01:52:27 AM »

It's interesting to note that 18,033 people have viewed this request for help but only 20 replied.  EHAM readers are looking for answers but when they have solved their own problem they disappear.  This isn't exactly as useful to hams as it could be, you think?
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