5
$\begingroup$

Since I got my HF radio a year and change ago, I've been able to hear very little except noise and the WWV time station on 10MHz. Noise seems to vary by band, but not how I'd expect:

  • 80m: S7-S9
  • 40m: S9+10-20
  • 20m: S2
  • 15m: S3
  • 10m: S9
  • 6m: S5

My setup currently looks like this: enter image description here

My antenna is fairly low above my house, but even killing mains power didn't reduce my noise level by any noticeable amount. I tried plugging in my 2m J-pole and it - being basically deaf on all of these frequencies - had predictable low noise on all bands, with none above S3.

  • The feedline for my 2m antenna has a similar-but-physically-separate path to my transceiver than the HF dipole does.
  • The dipole is only about 15 feet in the air on the low side and 25 on the high side.
  • The dipole, transceiver, and tuner aren't grounded, but any ground nearby would be ~20' from short 5kV power lines that run along one edge of my property. The power lines are parallel to the dipole and the dipole is currently in the only place that I can put it on my property. I've heard that putting ground rods in our soil is miserable and haven't done it yet.
  • I live in a suburban environment.

Does my conclusion that the noise is likely to be coming in through the antenna make sense? Should grounding make a difference? What steps can I take to try to mitigate the noise?

Suggestions so far are basically:

  • Classic foxhunt with a small AM radio
  • Hitting powerpoles with a stick/mallet/sledgehammer (seriously) and seeing if this affects the received noise.
Improve this question
$\endgroup$
10
  • 1
    $\begingroup$ When I set up parallel dipoles I usually put up only 80 and 20 on one balun. Not sure if that matters here. As for grounding, are your transceiver and tuner grounded? Also, are you sure you are getting clean power? $\endgroup$
    – SDsolar
    Commented Sep 2, 2017 at 0:32
  • 1
    $\begingroup$ Have you checked that the antenna is at least a good match on every band? If you have a fan dipole with an element for each band, you shouldn't need the tuner. $\endgroup$
    – Phil Frost - W8II
    Commented Sep 2, 2017 at 2:39
  • $\begingroup$ @SDsolar - I only have room for one big antenna, so it had to cover the bands I thought I could use reasonably. I think it's fair to assume that either my linear PSU or battery would provide clean power. Maybe it's not? $\endgroup$
    – William
    Commented Sep 2, 2017 at 19:55
  • 1
    $\begingroup$ @PhilFrost-W8II - It's not a good match yet. I cut it long on each band with an intent to trim it later, so I'm using a tuner in the interim. It gets to about 3:1 on 40m and 2:1 on 20m. $\endgroup$
    – William
    Commented Sep 2, 2017 at 20:02
  • 1
    $\begingroup$ @SDsolar - Okay, I've connected my tuner ground to my transceiver ground. Thanks for the tip. $\endgroup$
    – William
    Commented Sep 3, 2017 at 1:59

5 Answers 5

Reset to default
6
$\begingroup$

Some troubleshooting ideas:

  • Check your radio's power supply for noise by substituting a battery and disconnecting the PS from the wall.

  • Run your receiver on a battery and turn off your main breaker. Make sure any battery powered computers/tablets are fully powered off. If the noise reduces, turn off all branch breakers, turn the main breaker back on, and one by one turn on the branch breakers noting any change in noise.

  • Install an additional 1:1 balun close to your radio. This sometimes helps prevent local noise pickup on the coax outer shield.

  • Check your coax for any open or marginal connections - especially the shield connections. Try substituting other coax.

  • Eliminate the tuner and short patch coax and note any change in noise levels.

  • Take your transceiver to a location in the country with a portable antenna and running off batteries to eliminate receiver problems. Alternatively take it to another ham's QTH that isn't suffering from noise to check it.

  • Borrow or rent a battery powered spectrum analyzer and walk your QTH and the neighborhood sniffing for RFI with a small dipole or loop.

  • After eliminating all other possibilities, call the power company and let them know you suspect a cracked insulator or bad transformer is causing RFI. They have techs that specialize in these sorts of problems.

Improve this answer
$\endgroup$
5
  • $\begingroup$ All good suggestions, but I would only add that if a balun is at the radio then ladder line would be best for the feedline, as it would then be balanced - and I would then use a 4:1 balun. $\endgroup$
    – SDsolar
    Commented Sep 3, 2017 at 15:38
  • $\begingroup$ @sdsolar With a proper 1:1 balun at the feedpoint shown by the OP, ladder line has little advantage over coax for a fan dipole. Even with ladderline, asymmetric routing can induce CMC. $\endgroup$
    – Glenn W9IQ
    Commented Sep 3, 2017 at 17:55
  • $\begingroup$ @GlennW9IQ The feedpoint Z on some bands might be in the thousands of ohms. Therefore, ladder line might have an advantage on some bands. $\endgroup$
    – Mike Waters
    Commented Sep 3, 2017 at 20:29
  • 1
    $\begingroup$ @mikewaters Not with a fan dipole on the bands for which their is a dipole element. $\endgroup$
    – Glenn W9IQ
    Commented Sep 3, 2017 at 20:54
  • $\begingroup$ @GlennW9IQ Duh! Thanks for correcting me. $\endgroup$
    – Mike Waters
    Commented Sep 3, 2017 at 20:59
3
$\begingroup$

Just went through the same thing last year.

One hint - does the static level lower when it rains? if the answer is yes, very likely a bad insulator or distribution transformer.

Took my electric company almost 90 days to fix it, but went from +20 static down to S-2 or 3.

Also using a 160-10 fan dipole here. The problem insulator was at least 100 yards from my antenna.

The other advice is all sound as well!

73 es GL Dave - KB3MOW

Improve this answer
$\endgroup$
2
  • $\begingroup$ This is good information! I'm going to accept Glenn's answer because it's a sweet laundry list of troubleshooting goodness, but I'll definitely check this out next time it rains. $\endgroup$
    – William
    Commented Sep 3, 2017 at 1:47
  • $\begingroup$ Good point about the potential intermittent nature of power line RFI! $\endgroup$
    – Glenn W9IQ
    Commented Sep 3, 2017 at 17:59
1
$\begingroup$

You wrote "The power lines are parallel to the dipole " and you allow that to pass "OK" because " the dipole is currently in the only place that I can put it...".

In theory , you are inviting inductive linking between your dipole and the power lines.

To wit: I have used a End-Fed Long-Wire of 188 ft , at a height of 17 ft with power lines on three sides, all within 30 ft of antenna.

Antenna design here at K4KKQ : Long-Wire is 188 ft, odd quarters for 40M and 20M.
Long-Wire is up 17 ft, odd quarter for 20M. Long-Wire is angled like letter "Z" and all sides are angled aprox. 45 degrees from power lines.

Connections : Use a 1:1 current balun. Use 50 Ohm coax directly to balun. Use QRP antenna tuner to coax , from the QRP transmitter. Band Noise is measurable at all times, in low "S" units.

Results: Worked all Europe and all states on ONE Watt CW, 20 Meters. Work 1000 miles to New England each weekend, on 20 Meters.

Conclusion: "power lines are parallel to the dipole" and "Linking" and that is why you are getting into such high Band-Noise.

Glen Ellis, K4KKQ

Improve this answer
$\endgroup$
2
  • 1
    $\begingroup$ There is no such thing as backfed SWR. Common mode currents and SWR have no relationship to one another. A 1:1 common mode choke is to prevent or reduce common mode current. $\endgroup$
    – Glenn W9IQ
    Commented Sep 6, 2017 at 7:19
  • $\begingroup$ Glenn W9IQ yesterday You are technically correct. Thank you for correcting my casual figure-of-speech. Glen Ellis, K4KKQ $\endgroup$
    – Glen Ellis K4KKQ
    Commented Sep 7, 2017 at 13:59
1
$\begingroup$

Can you

  1. Turn off all the power in your house
  2. Plug the radio into a battery source (i.e Car 12V) You only need to Rx so no massive power requirement.

Now listen... is this better or the same.

As there (should) be no noice coming from a 12V DC source, if you have noise there are 2 possibilities

  1. Your Transceiver is broken
  2. Your Ant/Env is faulty

Following the House 12V ... can you move the radio to some place like a park/countryside and listen again only connected to 12V (if in a car - this means turning off the Engine). You will need a simple antenna.

If there is still S9+18 it is time to visit the radio repair shop.

Improve this answer
$\endgroup$
3
  • $\begingroup$ As addressed in the question, I've already tried killing my mains power and running my radio off the battery and it didn't make any difference. I know it's not my radio broken because I've been able to confirm the noise level with an RTL-SDR and an upconverter. $\endgroup$
    – William
    Commented Nov 2, 2017 at 18:27
  • $\begingroup$ William - sorry I overlooked that. Then as others have posted your Dipole is too close to the 5Kv power lines. You may want to measure the EMF from this emfields-solutions.com/detectors/pf5-emf.asp would be one tool (I have never used this). Where do you live ? And could you simply call the power line company to see if there is something they can do/assist you with. The ARRL has some info arrl.org/power-line-noise I am not sure how applicable this is too you. $\endgroup$
    – Tim Seed
    Commented Nov 2, 2017 at 21:45
  • $\begingroup$ I've worried about this, and am thinking to purchase a multi-band vertical once the wallet can stand it. I don't see any other way to get around the power lines being so close. $\endgroup$
    – William
    Commented Nov 3, 2017 at 3:00
0
$\begingroup$

I have an OCF dipole fed with dual coax. This method of feeding will drop the noise --in some cases-- by 5 S-units. I used RG-6 for the parallel conductors, 78 feet long. This antenna is 140 feet long.

I have a common-mode choke made from 25' of RG-e coiled, wound onto a one gallon paint can, for a CMC on other antennas.

Improve this answer
$\endgroup$
6
  • $\begingroup$ Hi Rich, kindly use lower-case in the future. Upper case is considered shouting, and is more difficult to read. And please edit your question to indicate what type of coax you mean. RG-E isn't coax. :-) $\endgroup$
    – Mike Waters
    Commented Oct 31, 2017 at 23:19
  • $\begingroup$ I got "lucky" only once when using an air-wound choke. But since I read G3TXQ's CM choke page, I switched to ferrite and never looked back. Also, see K9YC's excellent PDF on common-mode chokes. It contains absolutely the finest how-to for making good CM chokes anywhere, either online or in print! $\endgroup$
    – Mike Waters
    Commented Nov 1, 2017 at 1:50
  • 1
    $\begingroup$ I've never heard of using two lines of coax in parallel. Does that give you... 37.5ohm characteristic impedance? $\endgroup$
    – William
    Commented Nov 1, 2017 at 2:20
  • $\begingroup$ WILLIAM: NO/ TWO 75 OHM COAXES IN PARALLEL GIVES YOU 150 OHMS[hamuniverse.com/kf9focfdipole.html] I BUILT THIS THING FROM AN ARTICLE IN W1ICP'[SK]. SENT PLANS TO BRAZIL, INDONESIA, MANY STATES HR IN U.S. ALL VY PLEASED W/ THE THING. THE GUYS IN BRAZIL WANTED TO WORK 160 [WITH A MATCHBOX IT CAN BE DONE] - BTW THERES NO SUCH THING AS AN ANTENNA "TUNER". WHEN YOU CUT A DRIVEN ELT. DIPOLE, YAGI, BEVERAGE, RHOMBIC YOU HAVE "TUNED" IT FOR THE FREQ. OF OP. THE BOX ON YOUR DESK DOES NOTHING BUT MATCH THE ANTENNA - "SYSTEM" - GL, KF9F $\endgroup$
    – Rich Morgan - KF9F
    Commented Nov 2, 2017 at 1:31
  • $\begingroup$ I AGREE G3TXQ AND K9AY, AS WELL W4RNL [SK], AND RICK DJ0IP ALL HAVE GOOD VIEWS ON COMMON MODE CURRENT EFFECTS. ON CAPS: I WILL BE TOTALLTY BLIND IN A COUPLE. I TAUGHT ELECTRONICS I USED ALL UPPER CASE FOR THEE BENEFIT OF MY STUDENTS. $\endgroup$
    – Rich Morgan - KF9F
    Commented Nov 2, 2017 at 1:37

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .